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Title: Heroes of Science: Physicists

Author: William Garnett

Release date: January 15, 2012 [eBook #38583]

Language: English

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Produced by Albert László, P. G. Máté, Matthew Wheaton and
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    HEROES OF SCIENCE.




    HEROES OF SCIENCE.

    PHYSICISTS.

    BY

    WILLIAM GARNETT, M.A., D.C.L.,


    FORMERLY FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE; PRINCIPAL OF
    THE DURHAM COLLEGE OF SCIENCE, NEWCASTLE-UPON-TYNE; HON. MEMBER
    OF THE NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL
    ENGINEERS.

    PUBLISHED UNDER THE DIRECTION OF THE COMMITTEE OF GENERAL
    LITERATURE AND EDUCATION APPOINTED BY THE SOCIETY FOR PROMOTING
    CHRISTIAN KNOWLEDGE.

    LONDON:
    SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE,
    NORTHUMBERLAND AVENUE, CHARING CROSS, W.C.;

    43, QUEEN VICTORIA STREET, E.C.;
    26, ST. GEORGE'S PLACE, HYDE PARK CORNER, S.W.
    BRIGHTON: 135, NORTH STREET.

    NEW YORK: E. & J. B. YOUNG AND CO.




PREFACE.


The following pages claim no originality, and no merits beyond that of
bringing within reach of every boy and girl material which would
otherwise be available only to those who had extensive libraries at
their command, and much time at their disposal. In the schools and
colleges in which the principles of physical science are well taught,
the history of the discoveries whereby those principles have been
established has been too much neglected. The series to which the
present volume belongs is intended, in some measure, to meet this
deficiency.

A complete history of physical science would, if it could be written,
form a library of considerable dimensions. The following pages deal
only with the biographies of a few distinguished men, who, by birth,
were British subjects, and incidental allusions only are made to
living philosophers; but, notwithstanding these narrow restrictions,
the foundations of the Royal Society of London, of the American
Philosophical Society, of the great Library of Pennsylvania, and of
the Royal Institution, are events, some account of which comes within
the compass of the volume. The gradual development of our knowledge of
electricity, of the mechanical theory of heat, and of the undulatory
theory of optics, will be found delineated in the biographies
selected, though no continuous history is traced in the case of any
one of these branches of physics.

The sources from which the matter contained in the following pages has
been derived have been, in addition to the published works of the
subjects of the several sketches, the following:--

"The Encyclopædia Britannica."

"Memoir of the Honourable Robert Boyle," by Thomas Birch, M.A.,
prefixed to the folio edition of his works, which was published in
London in 1743.

"Life of Benjamin Franklin," from his own writings, by John Bigelow.

Dr. G. Wilson's "Life of Cavendish," which forms the first volume of
the publications of the Cavendish Society; and the "Electrical
Researches of the Hon. Henry Cavendish, F.R.S.," edited by the late
Professor James Clerk Maxwell.

"The Life of Sir Benjamin Thompson, Count Rumford," by George E.
Ellis, published by the American Academy of Arts and Sciences, in
connection with the complete edition of his works.

"Memoir of Thomas Young," by the late Dean Peacock.

Dr. Bence Jones's "Life of Faraday;" and Professor Tyndall's "Faraday
as a Discoverer."

"Life of James Clerk Maxwell," by Professor Lewis Campbell and William
Garnett.

It is hoped that the perusal of the following sketches may prove as
instructive to the reader as their preparation has been to the writer.

    WM. GARNETT.

    NEWCASTLE-UPON-TYNE,
    _December, 1885_.




CONTENTS.


                     PAGE
INTRODUCTION            1
ROBERT BOYLE            5
BENJAMIN FRANKLIN      38
HENRY CAVENDISH       125
COUNT RUMFORD         148
THOMAS YOUNG          194
MICHAEL FARADAY       237
JAMES CLERK MAXWELL   278
CONCLUSION            309




HEROES OF SCIENCE.




INTRODUCTION.


The dawn of true ideas respecting mechanics has been described in the
volume of this series devoted to astronomers. At the time when the
first of the following biographies opens there were a few men who held
sound views respecting the laws of motion and the principles of
hydrostatics. Considerable advance had been made in the subject of
geometrical optics; the rectilinear propagation of light and the laws
of reflection having been known to the Greeks and Arabians, whilst
Willebrod Snellius, Professor of Mathematics at Leyden, had correctly
enunciated the laws of refraction very early in the seventeenth
century. Pliny mentions the action of a sphere of rock-crystal and of
a glass globe filled with water in bringing light to a focus. Roger
Bacon used segments of a glass sphere as lenses; and in the eleventh
century Alhazen made many measurements of the angles of incidence and
refraction, though he did not succeed in discovering the law. Huyghens
developed to a great extent the undulatory theory; while Newton at the
same time made great contributions to the subject of geometrical
optics, decomposed white light by means of a prism, investigated the
colours of thin plates, and some cases of diffraction, and speculated
on the nature, properties, and functions of the ether, which was
equally necessary to the corpuscular as to the undulatory theory of
light, if any of the phenomena of interference were to be explained.
The velocity of light was first measured by Roemer, in 1676. The
camera obscura was invented by Baptista Porta, a wealthy Neapolitan,
in 1560; and Kepler explained the action of the eye as an optical
instrument, in 1604. Antonio de Dominis, Archbishop of Spalatro,
discovered the fringe of colours produced by sunlight once reflected
from the interior of a globe of water, and this led, in Newton's
hands, to the complete explanation of the rainbow.

The germ of the mechanical theory of heat is to be found in the
writings of Lord Bacon. The first thermometers which were blown in
glass with a bulb and tube hermetically sealed, were made by a
craftsman in Florence, in the time of Torricelli. The graduations on
these thermometers were made by attaching little beads of coloured
glass to their stems, and they were carried about Europe by members of
the Florentine Academy, in order to learn whether ice melted at the
same temperature in all latitudes.

In electricity the attraction of light bodies by amber when rubbed,
was known at least six hundred years before the Christian era, and the
shocks of the torpedo were described by Pliny and by Aristotle; but
the phenomena were not associated in men's minds until recent times.
Dr. Gilbert, of Colchester, Physician to Queen Elizabeth, may be
regarded as the founder of the modern science. He distinguished two
classes of bodies, viz. electrics, or those which would attract light
bodies when rubbed; and non-electrics, or those which could not be so
excited. The first electric machine was constructed by Otto von
Guericke, the inventor of the Magdeburg hemispheres, who mounted a
ball of sulphur so that it could be made rapidly to rotate while it
was excited by the friction of the hand. He observed the repulsion
which generally follows the attraction of a light body by an
electrified object after the two have come in contact. He also noticed
that certain bodies placed near to electrified bodies possessed
similar powers of attraction to those of the electrified bodies
themselves. Newton replaced the sulphur globe of Otto von Guericke by
a globe of glass. Stephen Gray discovered the conduction of
electricity, in 1729, when he succeeded in transmitting a charge to a
distance of 886 feet along a pack-thread suspended by silk strings so
as to insulate it from the earth. Desaguliers showed that Gilbert's
"electrics" were simply those bodies which could not conduct
electricity, while all conductors were "non-electrics;" and Dufay
showed that all bodies could be electrified by friction if supported
on insulating stands. He also showed that there were two kinds of
electrification, and called one _vitreous_, the other _resinous_.
Gray, Hawksbee, and Dr. Wall all noticed the similarity between
lightning and the electric discharge. The prime conductor was first
added to the electric machine by Boze, of Wittenberg; and Winkler, of
Leipsic, employed a cushion instead of the hand to produce friction
against the glass. The accumulation of electricity in the Leyden jar
was discovered accidentally by Cuneus, a pupil of Muschenbroeck, of
Leyden, about 1745, while attempting to electrify water in a bottle
held in his hand. A nail passed through the cork, by which the
electricity was communicated to the water. On touching the nail after
charging the water, he received the shock of the Leyden jar. This
brings the history of electrical discovery down to the time of
Franklin.




ROBERT BOYLE.


Robert Boyle was descended from a family who, in Saxon times, held
land in the county of Hereford, and whose name in the Doomsday Book is
written Biuvile. His father was Richard Boyle, Earl of Cork, to whom
the fortunes of the family were largely due. Richard Boyle was born in
the city of Canterbury, October 3, 1566. He was educated at Bene't
College (now Corpus Christi College), Cambridge, and afterwards became
a member of the Middle Temple. Finding his means insufficient for the
prosecution of his legal studies, he determined to seek his fortune
abroad. In 1595 he married, at Limerick, one of the daughters of
William Apsley, who brought him land of the value of £500 per annum.
In his autobiography the Earl of Cork writes:--

    When first I arrived at Dublin, in Ireland, the 23rd of June
    1588, all my wealth then was twenty-seven pounds three shillings
    in money, and two tokens which my mother had given me, viz. a
    diamond ring, which I have ever since and still do wear, and a
    bracelet of gold worth about ten pounds; a taffety doublet cut
    with and upon taffety, a pair of black velvet breeches laced, a
    new Milan fustian suit laced and cut upon taffety, two cloaks,
    competent linen, and necessaries, with my rapier and dagger. And
    since, the blessing of God, whose heavenly providence guided me
    hither, hath enriched my weak estate, in beginning with such a
    fortune, as I need not envy any of my neighbours, and added no
    care or burthen of my conscience thereunto. And the 23rd of
    June, 1632, I have served my God, Queen Elizabeth, King James,
    and King Charles, full forty-four years, and so long after as it
    shall please God to enable me.

Richard Boyle's property in Ireland increased so rapidly that he was
accused to Queen Elizabeth of receiving pay from some foreign power.
When about to visit England in order to clear himself of this charge,
the rebellion in Munster broke out; his lands were wasted, and his
income for the time destroyed. Reaching London, he returned to his old
chambers in the Middle Temple, until he entered the service of the
Earl of Essex, to whom the government of Ireland had been entrusted.
The charges against him were then resumed, and he was made a prisoner,
and kept in confinement until the Earl of Essex had gone over to
Ireland. At length he obtained a hearing before the queen, who fully
acquitted him of the charges, gave him her hand to kiss, and promised
to employ him in her own service; at the same time she dismissed Sir
Henry Wallop, who was Treasurer for Ireland, and prominent among
Boyle's accusers, from his office.

A few days afterwards, Richard Boyle was appointed by the queen Clerk
to the Council of Munster, and having purchased a ship of Sir Walter
Raleigh, he returned to Ireland with ammunition and provisions.

"Then, as Clerk of the Council, I attended the Lord President in all
his employments, and waited upon him at the siege of Kingsale, and was
employed by his Lordship to her Majesty, with the news of that happy
victory; in which employment I made a speedy expedition to the court;
for I left my Lord President at Shannon Castle, near Corke, on the
Monday morning, about two of the clock, and the next day, being
Tuesday, I delivered my packet, and supped with Sir Robert Cecil,
being then principal Secretary of State, at his house in the Strand;
who, after supper, held me in discourse till two of the clock in the
morning; and by seven that morning called upon me to attend him to the
court, where he presented me to her Majesty in her bed-chamber, who
remembered me, calling me by my name, and giving me her hand to kiss,
telling me that she was glad that I was the happy man to bring the
first news of that glorious victory ... and so I was dismissed with
grace and favour."

In reading of this journey from Cork to London, it is almost necessary
to be reminded that it took place two hundred and fifty years before
the introduction of steam-boats and railways. At the close of the
rebellion, Richard Boyle purchased from Sir Walter Raleigh all his
lands in Munster; and on July 25, 1603, he married his second wife,
Catharine, the only daughter of Sir Geoffrey Fenton, principal
Secretary of State, and Privy Councillor in Ireland, "with whom I
never demanded any marriage portion, neither promise of any, it not
being in my consideration; yet her father, after my marriage, gave me
one thousand pounds in gold with her. But that gift of his daughter
unto me I must ever thankfully acknowledge as the crown of all my
blessings; for she was a most religious, virtuous, loving, and
obedient wife unto me all the days of her life." He was knighted by
the Lord Deputy of Ireland, Sir George Carew, on his wedding-day; was
sworn Privy Councillor of State of the Kingdom of Ireland in 1612;
created Lord Boyle, Baron of Youghall, September 29, 1616; Lord
Viscount of Dungarvon and Earl of Cork, October 26, 1620; one of the
Lords Justices of Ireland, with a salary of £1200 per annum, in 1629;
and Lord High Treasurer of Ireland, November 9, 1631.

Robert Boyle, the seventh son of the Earl of Cork, was born January
25, 1627. His mother died February 16, 1630. The earl lived in
prosperity in Ireland till the breaking out of the rebellion in 1641,
and died at Youghall in September, 1643. It is said that when Cromwell
saw the vast improvements which the earl had made on his estate in
Munster, he declared that "if there had been an Earl of Cork in every
province, it would have been impossible for the Irish to have raised a
rebellion."

At a very early age Robert was sent by his father to a country nurse,
"who, by early inuring him, by slow degrees, to a coarse but cleanly
diet, and to the usual passion of the air, gave him so vigorous a
complexion that both hardships were made easy to him by custom, and
the delights of conveniences and ease were endeared to him by their
rarity." Making the acquaintance of some children who stuttered in
their speech, he, by imitation, acquired the same habit, "so
contagious and catching are men's faults, and so dangerous is the
familiar commerce of those condemnable customs, that, being imitated
but in jest, come to be learned and acquired in earnest." Before going
to school he studied French and Latin, and showed considerable
aptitude for scholarship. He was then sent to Eton, where his master
took much notice of him, and "would sometimes give him unasked
play-days, and oft bestow upon him such balls and tops and other
implements of idleness as he had taken away from others that had
unduly used them."

While at school, in the early morning, a part of the wall of the
bedroom, with the bed, chairs, books, and furniture of the room above,
fell on him and his brother. "His brother had his band torn about his
neck, and his coat upon his back, and his chair crushed and broken
under him; but by a lusty youth, then accidentally in the room, was
snatched from out the ruins, by which [Robert] had, in all
probability, been immediately oppressed, had not his bed been
curtained by a watchful Providence, which kept all heavy things from
falling on it; but the dust of the crumbled rubbish raised was so
thick that he might there have been stifled had not he remembered to
wrap his head in the sheet, which served him as a strainer, through
which none but the purer air could find a passage." At Eton he spent
nearly four years, "in the last of which he forgot much of that Latin
he had got, for he was so addicted to more solid parts of knowledge
that he hated the study of bare words naturally, as something that
relished too much of pedantry to consort with his disposition and
designs." On leaving Eton he joined his father at Stalbridge, in
Dorsetshire, and was sent to reside with "Mr. W. Douch, then parson of
that place," who took the supervision of his studies. Here he renewed
his acquaintance with Latin, and devoted some attention to English
verse, spending some of his idle hours in composing verses, "most of
which, the day he came of age, he sacrificed to Vulcan, with a design
to make the rest perish by the same fate." A little later he returned
to his father's house in Stalbridge, and was placed under the tutelage
of a French gentleman, who had been tutor to two of his brothers.

In October, 1638, Robert Boyle and his brother were sent into France.
After a short stay at Lyons, they reached Geneva, where Robert
remained with his tutor for about a year and three quarters. During
his residence here an incident occurred which he regarded as the most
important event of his life, and which we therefore give in his own
words.

"To frame a right apprehension of this, you must understand that,
though his inclinations were ever virtuous, and his life free from
scandal and inoffensive, yet had the piety he was master of already so
diverted him from aspiring unto more, that Christ, who long had lain
asleep in his conscience (as He once did in the ship), must now, as
then, be waked by a storm. For at a time which (being the very heat of
summer) promised nothing less, about the dead of night, that adds most
terror to such accidents, [he] was suddenly waked in a fright with
such loud claps of thunder (which are oftentimes very terrible in
those hot climes and seasons), that he thought the earth would owe an
ague to the air, and every clap was both preceded and attended with
flashes of lightning, so frequent and so dazzling that [he] began to
imagine them the sallies of that fire that must consume the world. The
long continuance of that dismal tempest, where the winds were so loud
as almost drowned the noise of the very thunder, and the showers so
hideous as almost quenched the lightning ere it could reach his eyes,
confirmed him in his apprehensions of the day of judgment's being at
hand. Whereupon the consideration of his unpreparedness to welcome
it, and the hideousness of being surprised by it in an unfit
condition, made him resolve and vow that, if his fears were that night
disappointed, all his further additions to his life should be more
religiously and watchfully employed. The morning came, and a serene,
cloudless sky returned, when he ratified his determinations so
solemnly, that from that day he dated his conversion, renewing, now he
was past danger, the vow he had made whilst he believed himself to be
in it; and though his fear was (and he blushed it was so) the occasion
of his resolution of amendment, yet at least he might not owe his more
deliberate consecration of himself to piety to any less noble motive
than that of its own excellence."

After leaving Geneva, he crossed the Alps and travelled through
Northern Italy. Here he spent much time in learning Italian; "the rest
of his spare hours he spent in reading the modern history in Italian,
and the new paradoxes of the great stargazer Galileo, whose ingenious
books, perhaps because they could not be so otherwise, were confuted
by a decree from Rome; his highness the Pope, it seems, presuming, and
that justly, that the infallibility of his chair extended equally to
determine points in philosophy as in religion, and loth to have the
stability of that earth questioned in which he had established his
kingdom."

Having visited Rome, he at length returned to France, and was detained
at Marseilles, awaiting a remittance from the earl to enable him to
continue his travels. Through some miscarriage, the money which the
earl sent did not arrive, and Robert and his brother had to depend on
the credit of the tutor to procure the means to enable them to return
home. They reached England in the summer of 1644, "where we found
things in such confusion that, although the manor of Stalbridge were,
by my father's decease, descended unto me, yet it was near four months
before I could get thither." On reaching London, Robert Boyle resided
for some time with his sister, Lady Ranelagh, and was thus prevented
from entering the Royalist Army. Later on he returned for a short time
to France; visited Cambridge in December, 1645, and then took up his
residence at Stalbridge till May, 1650, where he commenced the study
of chemistry and natural philosophy.

It was in October, 1646, that Boyle first made mention of the
"_invisible college_," which afterwards developed into the Royal
Society. Writing to a Fellow of Magdalen College, Cambridge, in
February, 1647, he says, "The corner-stones of the _invisible_, or, as
they term themselves, the _philosophical college_, do now and then
honour me with their company." It appears that a desire to escape from
the troubles of the times had induced several persons to take refuge
in philosophical pursuits, and, meeting together to discuss the
subjects of their study, they formed the "invisible college." Boyle
says, "I will conclude their praises with the recital of their
chiefest fault, which is very incident to almost all good things, and
that is, that there is not enough of them." Dr. Wallis, one of the
first members of the society, states that Mr. Theodore Hooke, a German
of the Palatinate, then resident in London, "gave the first occasion
and first suggested those meetings and many others. These meetings we
held sometimes at Dr. Goddard's lodging, in Wood Street (or some
convenient place near), on occasion of his keeping an operator in his
house, for grinding glasses for telescopes and microscopes, and
sometimes at a convenient place in Cheapside; sometimes at Gresham
College, or some place near adjoining. Our business was (precluding
theology and State affairs) to discourse and consider of philosophical
inquiries, and such as related thereunto; as physic, anatomy,
geometry, astronomy, navigation, statics, magnetics, chemics,
mechanics, and natural experiments, with the state of these studies as
then cultivated at home and abroad. About the year 1648-49 some of us
being removed to Oxford, first Dr. Wilkins, then I, and soon after Dr.
Goddard, our company divided. Those in London continued to meet there
as before, and we with them when we had occasion to be there. And
those of us at Oxford, with Dr. Ward, since Bishop of Salisbury, Dr.
Ralph Bathurst, now President of Trinity College in Oxford, Dr. Petty,
since Sir William Petty, Dr. Willis, then an eminent physician in
Oxford, and divers others, continued such meetings in Oxford, and
brought those studies into fashion there; meeting first at Dr.
Petty's lodgings, in an apothecary's house, because of the convenience
of inspecting drugs and the like, as there was occasion; and after his
remove to Ireland (though not so constantly) at the lodgings of Dr.
Wilkins, then Warden of Wadham College; and after his removal to
Trinity College in Cambridge, at the lodgings of the Honourable Mr.
Robert Boyle, then resident for divers years in Oxford. These meetings
in London continued, and after the king's return, in 1660, were
increased with the accession of divers worthy and honourable persons,
and were afterwards incorporated by the name of the _Royal Society_,
and so continue to this day."

Boyle was only about twenty years of age when he wrote his "Free
Discourse against Swearing;" his "Seraphic Love; or, Some Motives and
Incentives to the Love of God;" and his "Essay on Mistaken Modesty."
"Seraphic Love" was the last of a series of treatises on love, but the
only one of the series that he published, as he considered the others
too trifling to be published alone or in conjunction with it. In a
letter to Lady Ranelagh, he refers to his laboratory as "a kind of
Elysium," and there were few things which gave him so much pleasure as
his furnaces and philosophical experiments. In 1652 he visited
Ireland, returning in the following summer. In the autumn he was again
obliged to visit Ireland, and remained there till the summer of 1654,
though residence in that country was far from agreeable to him. He
styled it "a barbarous country, where chemical spirits were so
misunderstood, and chemical instruments so unprocurable, that it was
hard to have any hermetic thoughts in it." On his return he settled in
Oxford, and there his lodgings soon became the centre of the
scientific life of the university. Boyle and his friends may be
regarded as the pioneers of experimental philosophy in this country.
To Boyle the methods of Aristotle appeared little more than
discussions on words; for a long time he refused to study the
philosophy of Descartes, lest he should be turned aside from reasoning
based strictly on the results of experiment. The method pursued by
these philosophers had been fully discussed by Lord Bacon, but at best
his experimental methods, though most complete and systematic, existed
only upon paper, and it was reserved for Boyle and his friends to put
the Baconian philosophy into actual practice.

It was during his residence at Oxford that he invented the air-pump,
which was afterwards improved for him by Hooke, and with which he
conducted most of those experiments on the "spring" and weight of the
air, which led up to the investigations that have rendered his name
inseparably connected with "the gaseous laws." The experiments of
Galileo and of Torricelli had shown that the pressure of the air was
capable of supporting a column of water about thirty-four feet in
height, or a column of mercury nearly thirty inches high. The younger
Pascal, at the request of Torricelli, had carried a barometer to the
summit of the Puy de Dome, and demonstrated that the height of the
column of mercury supported by the air diminishes as the altitude is
increased. Otto von Guericke had constructed the Magdeburg
hemispheres, and shown that, when exhausted, they could not be
separated by sixteen horses, eight pulling one way and eight the
other. He was aware that the same traction could have been produced by
eight horses if one of the hemispheres had been attached to a fixed
obstacle; but, with the instincts of a popular lecturer, he considered
that the spectacle would thus be rendered less striking, and it was
prepared for the king's entertainment. Boyle wished for an air-pump
with an aperture in the receiver sufficiently large for the
introduction of various objects, and an arrangement for exhausting it
without filling the receiver with water or otherwise interfering with
the objects placed therein. His apparatus consisted of a large glass
globe capable of containing about three gallons or thereabouts,
terminating in an open tube below, and with an aperture of about four
inches diameter at the top. Around this aperture was cemented a turned
brass ring, the inner surface being conical, and into this conical
seat was fitted a brass plate with a thick rim, but drilled with a
small hole in the centre. To this hole, which was also conical, was
fitted a brass stopper, which could be turned round when the receiver
was exhausted. By attaching a string to this stopper, which was so
long as to enter the receiver to the depth of two or three inches, and
turning the stopper in its seat, the string could be wound up, and
thus objects could be moved within the receiver. The tube at the
bottom of the receiver communicated with a stop-cock, and this with
the upper end of the pumpbarrel, which was inverted, so that this
stop-cock, which was at the top of the barrel, took the place of the
foot-valve. The piston was solid, made of wood, and surrounded with
sole leather, which was kept well greased. There being no valve in the
piston, it was necessary to place an exhaust-valve in the upper end of
the cylinder. This consisted of a small brass plug closing a conical
hole so that it could be removed at pleasure. The construction of the
cylinder was, therefore, similar to that of an ordinary force-pump,
except that the valves had to be moved by hand (as in the early forms
of the steam-engine). The piston was raised and depressed by means of
a rack and pinion. The pumps could be used either for exhausting the
receiver or for forcing air into it, according to the order in which
the "valves" were opened. If the stop-cock communicating with the
receiver were open while the piston was being drawn down, and the
brass plug removed so as to open the exhaust-valve when the piston was
being forced up, the receiver would gradually be exhausted. If the
brass plug were removed during the descent of the piston, and the
stop-cock opened during its ascent, air would be forced into the
receiver. In the latter case it was necessary to take special
precautions to prevent the brass plate at the top of the receiver
being raised from its seat. All joints were made air-tight with
"diachylon," and when, through the bursting of a glass bulb within it,
the receiver became cracked, the crack was rendered air-tight by the
same means. Other receivers of smaller capacity were also provided, on
account of the greater readiness with which they could be exhausted.

With this apparatus Boyle carried out a long series of experiments. He
could reduce the pressure in the large receiver to somewhat less than
that corresponding to an inch of mercury, or about a foot of water.
Squeezing a bladder so as to expel nearly all the air, tying the neck,
and then introducing it into the receiver, he found, on working the
pump, that the bladder swelled so that at length it became completely
distended. In order to account for this great expansibility, Boyle
pictured the constitution of the air in the following way. He supposed
the air to consist of separate particles, each resembling a spiral
spring, which became tightly wound when exposed to great pressure, but
which expanded so as to occupy a larger circle when the pressure was
diminished. Each of these little spirals he supposed to rotate about a
diameter so as to exclude every other body from the sphere in which it
moved. Increasing the length of the diameter tenfold would increase
the volume of one of these spheres, and therefore the volume of the
gas, a thousandfold. Possibly this was only intended as a mental
illustration, exhibiting a mechanism by which very great expansion
might conceivably be produced, and scarcely pretending to be
considered a _theory_ of the constitution of the air. Boyle's first
idea seems to have been derived from a lock of wool in which the
elasticity of each fibre caused the lock to expand after it had been
compressed in the hand. In another passage he speaks of the air as
consisting of a number of bodies capable of striking against a surface
exposed to them. He demonstrated the weight of the air by placing a
delicate balance within the receiver, suspending from one arm a
bladder half filled with water, and balancing it with brass weights.
On exhausting the air, the bladder preponderated, and, by repeating
the experiment with additional weights on the other arm until a
balance was effected in the exhausted receiver, he determined the
amount of the preponderance. In another experiment he compressed air
in a bladder by tying a pack-thread round it, balanced it from one arm
of his balance in the open air; then, pricking the bladder so as to
relieve the pressure, he found that with the escape of the compressed
air the weight diminished.

One of the most important of his experiments with the air-pump was the
following. He placed within the receiver the cistern of a mercurial
barometer, the tube of which was made to pass through the central hole
in the brass plate, from which the stopper had been removed. The space
around the tube was filled up with cement, and the receiver
exhausted. At each stroke of the pump the mercury in the barometer
tube descended, but through successively diminishing distances, until
at length it stood only an inch above the mercury in the cistern. The
experiment was then repeated with a tube four feet long and filled
with water. This constituted the nineteenth experiment referred to
later on. A great many strokes of the pump had to be made before the
water began to descend. At length it fell till the surface in the tube
stood only about a foot above that in the tank. Placing vessels of
ordinary spring-water and of distilled rain-water in the receiver, he
found that, after the exhaustion had reached a certain stage, bubbles
of gas were copiously evolved from the spring-water, but not from the
distilled water. On another occasion he caused warm water to boil by a
few strokes of the pump; and, continuing the exhaustion, the water was
made to boil at intervals until it became only lukewarm. The
experiment was repeated with several volatile liquids. He also noticed
the cloud formed in the receiver when the air was allowed rapidly to
expand; but the mechanical theory of heat had not then made sufficient
progress to enable him to account for the condensation by the loss of
heat due to the work done by the expanding air. The very minute
accuracy of his observations is conspicuous in the descriptions of
most of his experiments. That the air is the usual medium for the
conveyance of sound was shown by suspending a watch by a linen thread
within the receiver. On exhausting the air, the ticking of the watch
ceased to be heard. A pretty experiment consisted in placing a bottle
of a certain fuming liquid within the receiver; on exhausting the air,
the fumes fell over the neck of the bottle and poured over the stand
on which it was placed like a stream of water. Another experiment, the
thirty-second, is worthy of mention on account of the use to which it
was afterwards applied in the controversy respecting the cause of
suction. The receiver, having been exhausted, was removed from the
cylinder, the stop-cock being turned off, and a small brass valve, to
which a scale-pan was attached, was placed just under the aperture of
the tube below the stop-cock. On turning the latter, the stream of air
raised the valve, closing the aperture, and the atmospheric pressure
supported it until a considerable weight had been placed in the
scale-pan. Because the receiver could not be exhausted so thoroughly
as the pump-cylinder, Boyle attempted to measure the pressure of the
air by determining what weight could be supported by the piston. He
found first that a weight of twenty-eight pounds suspended directly
from the piston was sufficient to overcome friction when air was
admitted above the piston. When the access of air to the top of the
piston was prevented, more than one hundred pounds additional weight
was required to draw down the piston. The diameter of the cylinder was
about three inches.

Boyle's style of reasoning is well illustrated by the following from
his paper on "The Spring of the Air:"--

"In the next place, these experiments may teach us what to judge of
the vulgar axiom received for so many ages as an undoubted truth in
the peripatetick schools, that Nature abhors and flieth a vacuum, and
that to such a degree that no human power (to go no higher) is able to
make one in the universe; wherein heaven and earth would change
places, and all its other bodies rather act contrary to their own
nature than suffer it.... It will not easily, then, be intelligibly
made out how hatred or aversation, which is a passion of the soul, can
either for a vacuum or any other object be supposed to be in water, or
such like inanimate body, which cannot be presumed to know when a
vacuum would ensue, if they did not bestir themselves to prevent it;
nor to be so generous as to act contrary to what is most conducive to
their own particular preservation for the public good of the universe.
As much, then, of intelligible and probable truth as is contained in
this metaphorical expression seems to amount but to this--that by the
wise Author of nature (who is justly said to have made all things in
number, weight, and measure) the universe, and the parts of it, are so
contrived that it is hard to make a vacuum in it, as if they
studiously conspired to prevent it. And how far this itself may be
granted deserves to be further considered.

"For, in the next place, our experiments seem to teach that the
supposed aversation of Nature to a vacuum is but accidental, or in
consequence, partly of the weight and fluidity, or, at least,
fluxility of the bodies here below; and partly, and perhaps
principally, of the air, whose restless endeavour to expand itself
every way makes it either rush in itself or compel the interposed
bodies into all spaces where it finds no greater resistance than it
can surmount. And that in those motions which are made _ob fugam
vacui_ (as the common phrase is), bodies act without such generosity
and consideration as is wont to be ascribed to them, is apparent
enough in our thirty-second experiment, where the torrent of air, that
seemed to strive to get into the emptied receiver, did plainly prevent
its own design, by so impelling the valve as to make it shut the only
orifice the air was to get [in] at. And if afterwards either Nature or
the internal air had a design the external air should be attracted,
they seemed to prosecute it very unwisely by continuing to suck the
valve so strongly, when they found that by that suction the valve
itself could not be drawn in; whereas, by forbearing to suck, the
valve would, by its own weight, have fallen down and suffered the
excluded air to return freely, and to fill again the exhausted
vessel....

"And as for the care of the public good of the universe ascribed to
dead and stupid bodies, we shall only demand why, in our nineteenth
experiment, upon the exsuction of the ambient air, the water deserted
the upper half of the glass tube, and did not ascend to fill it up
till the external air was let in upon it. Whereas, by its easy and
sudden rejoining that upper part of the tube, it appeared both that
there was then much space devoid of air, and that the water might,
with small or no resistance, have ascended into it, if it could have
done so without the impulsion of the readmitted air; which, it seems,
was necessary to mind the water of its formerly neglected duty to the
universe."

Boyle then goes on to explain the phenomena correctly by the pressure
of the air. Elsewhere he accounts for the diminished pressure on the
top of a mountain by the diminished weight of the superincumbent
column of air.

The treatise on "The Spring of the Air" met with much opposition, and
Boyle considered it necessary to defend his doctrine against the
objections of Franciscus Linus and Hobbes. In this defence he
described the experiment in connection with which he is most generally
remembered. Linus had admitted that the air might possess a certain
small amount of elasticity, but maintained that the force with which
mercury rose in a barometer tube was due mainly to a totally different
action, as though a string were pulling upon it from above. This was
his funicular hypothesis. Boyle undertook to show that the pressure of
the air might be made to support a much higher column of mercury than
that of the barometer. To this end he took a glass tube several feet
in length, and bent so as to form two vertical legs connected below.
The shorter leg was little more than a foot long, and hermetically
closed at the top. The longer leg was nearly eight feet in length, and
open at the top. The tube was suspended by strings upon the staircase,
the bend at the bottom pressing lightly against the bottom of a box
placed to receive the mercury employed in case of accident. Each leg
of the tube was provided with a paper scale. Mercury was poured in at
the open end, the tube being tilted so as to allow some of the air to
escape from the shorter limb until the mercury stood at the same level
in both legs when the tube was vertical. The length of the closed tube
occupied by the air was then just twelve inches. The height of the
barometer was about 29-1/8 inches. Mercury was gently poured into the
open limb by one operator, while another watched its height in the
closed limb. The results of the experiments are given in the table on
the opposite page.

In this table the third column gives the result of adding to the
second column the height of the barometer, which expresses in inches
of mercury the pressure of the air on the free surface of the mercury
in the longer limb. The fourth column gives the total pressure, in
inches of mercury, on the hypothesis that the pressure of the air
varies inversely as the volume. The agreement between the third and
fourth columns is very close, considering the roughness of the
experiment and that no trouble appears to have been taken to
_calibrate_ the shorter limb of the tube, and justified Boyle in
concluding that the hypothesis referred to expresses the relation
between the volume and pressure of a given mass of air.

    +-----------+---------------+----------------+--------------+
    |Length of  |Height of      |Total pressure  |Total pressure|
    |closed tube|mercury in open|on air in inches|according to  |
    |occupied   |tube above that|of mercury.     |Boyle's law.  |
    |by air.    |in closed tube.|                |              |
    +-----------+---------------+----------------+--------------+
    |  12       |     0         |   29-2/16      |   29-2/16    |
    |  11-1/2   |     1-7/16    |   30-9/16      |   30-6/16    |
    |  11       |     2-13/16   |   31-15/16     |   31-12/16   |
    |  10-1/2   |     4-6/16    |   33-8/16      |   33-1/7     |
    |  10       |     6-3/16    |   35-5/16      |   35         |
    |   9-1/2   |     7-14/16   |   37           |   36-15/19   |
    |   9       |    10-1/16    |   39-3/16      |   38-7/8     |
    |   8-1/2   |    12-8/16    |   41-10/16     |   41-2/17    |
    |   8       |    15-1/16    |   44-3/16      |   43-11/16   |
    |   7-1/2   |    17-15/16   |   47-1/16      |   46-3/5     |
    |   7       |    21-3/16    |   50-5/16      |   50         |
    |   6-1/2   |    25-3/16    |   54-5/16      |   53-10/13   |
    |   6       |    29-11/16   |   58-13/16     |   58-2/8     |
    |   5-3/4   |    32-3/16    |   61-5/16      |   60-13/23   |
    |   5-1/2   |    34-15/16   |   64-1/16      |   63-6/11    |
    |   5-1/4   |    37-15/16   |   67-1/16      |   66-4/7     |
    |   5       |    41-9/16    |   70-11/16     |   70         |
    |   4-3/4   |    45         |   74-2/16      |   73-11/19   |
    |   4-1/2   |    48-12/16   |   77-14/16     |   77-2/3     |
    |   4-1/4   |    53-11/16   |   82-13/16     |   82-4/17    |
    |   4       |    58-2/16    |   87-14/16     |   87-1/8     |
    |   3-3/4   |    63-15/16   |   93-1/16      |   93-1/5     |
    |   3-1/2   |    71-5/16    |  100-7/16      |   99-6/7     |
    |   3-1/4   |    78-11/16   |  107-13/16     |  107-7/13    |
    |   3       |    88-7/16    |  117-9/16      |  116-4/8     |
    +-----------+---------------+----------------+--------------+

To extend the investigation so as to include expansion below
atmospheric pressure, a different apparatus was employed. It consisted
of a glass tube about six feet in length, closed at the lower end and
filled with mercury. Into this bath of mercury was plunged a length of
quill tube, and the upper end was sealed with wax. When the wax and
air in the tube had cooled, a hot pin was passed through the wax,
making a small orifice by which the amount of air in the tube was
adjusted so as to occupy exactly one inch of its length as measured by
a paper scale attached thereto, after again sealing the wax. The quill
tube was then raised, and the height of the surface of the mercury in
the tube above that in the bath noticed, together with the length of
the tube occupied by the air. The difference between the height of the
barometer and the height of the mercury in the tube above that in the
bath gave the pressure on the imprisoned air in inches of mercury. The
result showed that the volume varied very nearly in the inverse ratio
of the pressure. A certain amount of air, however, clung to the sides
of the quill tube when immersed in the mercury, and no care was taken
to remove it by boiling the mercury or otherwise; in consequence of
this, as the mercury descended, this air escaped and joined the rest
of the air in the tube. This made the pressure rather greater than it
should have been towards the end of the experiment, and when the tube
was again pressed down into the bath it was found that, when the
surfaces of the mercury within and without the tube were at the same
level, the air occupied nearly 1-1/8 inch instead of one inch of the
tube. These experiments first established the truth of the great law
known as "Boyle's law," which states that _the volume of a given mass
of a perfect gas varies inversely as the pressure to which it is
exposed_.

Another experiment, to show that the pressure of the air was the cause
of suction, Boyle succeeded in carrying out at a later date. Two discs
of marble were carefully polished, so that when a little spirit of
turpentine was placed between them the lower disc, with a pound weight
suspended from it, was supported by the upper one. The apparatus was
introduced into the air-pump, and a considerable amount of shaking
proved insufficient to separate the discs. After sixteen strokes of
the pump, on opening the communication between the receiver and
cylinder, when no mechanical vibration occurred, the discs separated.

Upon the Restoration in 1660, the Earl of Clarendon, who was Lord
Chancellor of England, endeavoured to persuade Boyle to enter holy
orders, urging the interest of the Church as the chief motive for the
proceeding. This made some impression upon Boyle, but he declined for
two reasons--first, because he thought that he would have a greater
influence for good if he had no share in the patrimony of the Church;
and next, because he had never felt "an inward motion to it by the
Holy Ghost."

In 1649 an association was incorporated by Parliament, to be called
"the President and Society for the Propagation of the Gospel in New
England," whose object should be "to receive and dispose of moneys in
such manner as shall best and principally conduce to the preaching and
propagating the gospel among the natives, and for the maintenance of
schools and nurseries of learning for the education of the children of
the natives; for which purpose a general collection was appointed to
be made in and through all the counties, cities, towns, and parishes
of England and Wales, for a charitable contribution, to be as the
foundation of so pious and great an undertaking." The society was
revived by special charter in 1661, and Boyle was appointed president,
an office he continued to hold until shortly before his death. The
society afterwards enlarged its sphere of operations, and became the
Society for the Propagation of the Gospel in Foreign Parts.

In the same year (1661) Boyle published "Some Considerations on the
Usefulness of Experimental Natural Philosophy," etc., and in 1663 an
extremely interesting paper on "Experiments and Considerations
touching Colours." In the course of this paper he describes some very
beautiful experiments with a tincture of _Lignum nephriticum_, wherein
the dichroism of the extract is made apparent. Boyle found that by
transmitted light it appeared of a bright golden colour, but when
viewed from the side from which it was illuminated the light emitted
was sky blue, and in some cases bright green. By arranging experiments
so that some parts of the liquid were seen by the transmitted light
and some by the scattered light, very beautiful effects were produced.
Boyle endeavoured to learn something of the nature of colours by
projecting spectra on differently coloured papers, and observing the
appearance of the papers when illuminated by the several spectral
rays. He also passed sunlight, concentrated by a lens, through plates
of differently coloured glass superposed, allowing the light to fall
on a white paper screen, and observing the tint of the light which
passed through each combination. But the most interesting of these
experiments was the actual mixture of light of different colours by
forming two spectra, one by means of a fixed prism, the other by a
prism held in the hand, and superposing the latter on the former so
that different colours were made to coincide. This experiment was
repeated in a modified form, nearly two hundred years later, by
Helmholtz, who found that the mixture of blue and yellow lights
produced pink. Unfortunately, Boyle's spectra were far from pure, for,
the source of light being of considerable dimensions, the different
colours overlapped one another, as in Newton's experiments, and in
consequence some of his conclusions were inaccurate. Thus blue paper
in the yellow part of the spectrum appeared to Boyle green instead of
black, but this was due to the admixture of green light with the
yellow. He concluded that bodies appear black because they damp the
light so as to reflect very little to the eye, but that the surfaces
of white bodies consist of innumerable little facets which reflect the
light in all directions. In the same year he published some
"Observations on a Diamond, which shines in the Dark;" and an
extensive treatise on "Some Considerations touching the Style of the
Holy Scriptures." Next year appeared several papers from his pen, the
most important being "Occasional Reflections upon Several Subjects,"
the wide scope of which may be gathered from the title. His "New
Experiments and Observations touching Cold" were printed in 1665. In
this paper he discussed the cause of the force exerted by water in
freezing, methods of measuring degrees of cold, the action of
freezing-mixtures, and many other questions. He contended that cold
was probably only privative, and not a positive existence.

Lord Bacon had asserted that the "essential self" of heat was probably
motion and nothing more, and had adduced several experiments and
observations in support of this opinion. In his paper on the
mechanical origin of heat and cold, Boyle maintained that heat was
motion, but motion of the very small particles of bodies, very
intense, and taking place in all directions; and that heat could be
produced by any means whatever by which the particles of bodies could
be agitated. On one occasion he caused two pieces of brass, one convex
and the other concave, to be pressed against each other by a spring,
and then rubbed together in a vacuum by a rotary motion communicated
by a shaft which passed air-tight through the hole in the cover of the
receiver, a little emery being inserted between them. In the second
experiment the brasses became so hot that he "could not endure to hold
[his] hand on either of them." This experiment was intended, like the
rubbing of the blocks of ice in vacuo by Davy, to meet the objection
that the heat developed by friction was due to the action of the air.
The following extract from a paper intended to show that the sense of
touch cannot be relied upon for the estimation of temperature, shows
that Boyle possessed a very clear insight into the question:--"The
account upon which we judge a body to be cold seems to be that we feel
its particles less vehemently agitated than those of our fingers or
other parts of the organ of touching; and, consequently, if the temper
of that organ be changed, the object will appear more or less cold to
us, though itself continue of one and the same temperature." To
determine the expansion of water in freezing, he filled the bulb and
part of the stem of a "bulb tube," or, as it was then generally
called, "a philosophical egg," with water, and applying a
freezing-mixture, at first to the bottom of the bulb, he succeeded in
freezing the water without injury to the glass, and found that 82
volumes of water expanded to 91-1/8 volumes of ice--an expansion of
about 11-1/8 per cent. Probably air-bubbles caused the ice to appear
to have a greater volume than it really possessed, the true expansion
being about nine per cent. of the volume of the water at 4°C. The
expansion of water in freezing he employed in order to compress air to
a greater extent than he had been able otherwise to compress it.
Having nearly filled a tube with water, but left a little air above,
and then having sealed the top of the tube, he froze the water from
the bottom upwards, so that in expanding it compressed the air to
one-tenth of its former volume.

Magnetism and electricity came in for some share of Boyle's attention.
He carried out a number of experiments on magnetic induction, and
found that lodestones, as well as pieces of iron, when heated and
allowed to cool, became magnetized by the induction of the earth. His
later experiments with exhausted receivers were not made with his
first pump, but with a two-barrelled pump, in which the pistons were
connected by a cord passing over a large fixed pulley, so that, when
the receiver was nearly exhausted, the pressure of the air on the
descending piston during the greater part of the stroke nearly
balanced that on the ascending piston. In this respect the pump
differed only from Hawksbee's in having the pulley and cord instead of
the pinion and two racks. It also resembled Hawksbee's pump in having
self-closing valves in the pistons and at the bottom of the cylinders,
which, in this pump, had their open ends at the top. The pistons were
alternately raised and lowered by the feet of the operator, which were
placed in stirrups, of which one was fixed on each piston. The lower
portions of the barrels were filled with water, through which the air
bubbled, and this, occupying the clearance, enabled a much higher
degree of exhaustion to be produced than could be obtained without its
employment.

In 1665 Boyle was nominated Provost of Eton, but declined to accept
the appointment. His "Hydrostatical Paradoxes," published about this
time, contain all the ordinary theorems respecting the pressure of
fluids under the action of gravity demonstrated experimentally.

In 1677 Boyle printed, at his own expense, five hundred copies of the
four Gospels and the Acts of the Apostles in the Malayan tongue. This
was but one of his many contributions towards similar objects.

On November 30, 1680, the Royal Society chose Boyle for President. He,
however, declined to accept the appointment, because he had
conscientious objections to taking the oath required of the President
by the charter of the Society.

It appears that very many of Boyle's manuscripts, which were written
in bound books, were taken away, and others mutilated by "corrosive
liquors." In May, 1688, he made this known to his friends, but, though
these losses put him on his guard, he complained afterwards that all
his care and circumspection had not prevented the loss of "six
centuries of matters of fact in one parcel," besides many other
smaller papers. His works, however, which have been published are so
numerous that it would take several pages for the bare enumeration of
their titles, many of them being devoted to medical subjects. The
edition published in London in 1743 comprises nearly three thousand
pages of folio. Boyle always suffered from weak eyes, and in
consequence he declined to revise his proofs. In the advertisement to
the original edition of his works the publisher mentioned this, and at
the same time pleaded his own business engagements as an excuse for
not revising the proofs himself! It was partly on account of the
injury to his manuscripts, and partly through failing health, that in
1689 he set apart two days in the week, during which he declined to
receive visitors, that he might devote himself to his work, and
especially to the reparation of the injured writings. About this time
he succeeded in procuring the repeal of an Act passed in the fifth
year of Henry IV. to the effect "that none from thenceforth should use
to multiply gold or silver, or use the craft of multiplication; and if
any the same do, they should incur the pain of felony." By this repeal
it was made legal to extract gold and silver from ores, or from their
mixtures with other metals, in this country provided that the gold and
silver so procured should be put to no other use than "the increase of
moneys." It is curious that Boyle seems always to have believed in the
possibility of transmuting other metals into gold.

His sister, Lady Ranelagh, died on December 23, 1691, and Boyle
survived her but a few days, for he died on December 30, and his body
was interred near his sister's grave in the chancel of St.
Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works,
writes, "The men of wit and learning have, in all ages, busied
themselves in explaining nature by words; but it is Mr. Boyle alone
who has wholly laid himself out in showing philosophy in action. The
single point he perpetually keeps in view is to render his reader, not
a talkative or a speculative, but an actual and practical philosopher.
Himself sets the example; he made all the experiments he possibly
could upon natural bodies, and communicated them with all desirable
candour and fidelity." The second part of his treatise on "The
Christian Virtuoso," Boyle concluded with a number of aphorisms, of
which the following well represent his views respecting science:--

"I think it becomes Christian philosophers rather to try whether they
can investigate the final causes of things than, without trial, to
take it for granted that they are undiscoverable."

"The book of Nature is a fine and large piece of tapestry rolled up,
which we are not able to see all at once, but must be content to wait
for the discovery of its beauty and symmetry, little by little, as it
gradually comes to be more unfolded or displayed."




BENJAMIN FRANKLIN.


Among those whose contributions to physics have immortalized their
names in the annals of science, there is none that holds a more
prominent position in the history of the world than Benjamin Franklin.
At one time a journeyman printer, living in obscure lodgings in
London, he became, during the American War of Independence, one of the
most conspicuous figures in Europe, and among Americans his reputation
was probably second to none, General Washington not excepted.

Professor Laboulaye says of Franklin: "No one ever started from a
lower point than the poor apprentice of Boston. No one ever raised
himself higher by his own unaided forces than the inventor of the
lightning-rod. No one has rendered greater service to his country than
the diplomatist who signed the treaty of 1783, and assured the
independence of the United States. Better than the biographies of
Plutarch, this life, so long and so well filled, is a source of
perpetual instruction to all men. Every one can there find counsel and
example."

A great part of the history of his life was written by Franklin
himself, at first for the edification of the members of his own
family, and afterwards at the pressing request of some of his friends
in London and Paris. His autobiography does not, however, comprise
much more than the first fifty years of his life. The first part was
written while he was the guest of the Bishop of St. Asaph, at Twyford;
the second portion at Passy, in the house of M. de Chaumont; and the
last part in Philadelphia, when he was retiring from public life at
the age of eighty-two. The former part of this autobiography was
translated into French, and published in Paris, in 1793, though it is
not known how the manuscript came into the publisher's hands. The
French version was translated into English, and published in England
and America, together with such other of Franklin's works as could be
collected, before the latter part was given to the world by Franklin's
grandson, to whom he had bequeathed his papers, and who first
published them in America in 1817.

For a period of three hundred years at least Franklin's family lived
on a small freehold of about thirty acres, in the village of Ecton, in
Northamptonshire, the eldest son, who inherited the property, being
always brought up to the trade of a smith. Franklin himself "was the
youngest son of the youngest son for five generations back." His
grandfather lived at Ecton till he was too old to follow his business,
when he went to live with his second son, John, who was a dyer at
Banbury. To this business Franklin's father, Josiah, was apprenticed.
The eldest son, Thomas, was brought up a smith, but afterwards became
a solicitor; the other son, Benjamin, was a silk-dyer, and followed
Josiah to America. He was fond of writing poetry and sermons. The
latter he wrote in a shorthand of his own inventing, which he taught
to his nephew and namesake, in order that he might utilize the sermons
if, as was proposed, he became a Presbyterian minister. Franklin's
father, Josiah, took his wife and three children to New England, in
1682, where he practised the trade of a tallow-chandler and
soap-boiler. Franklin was born in Boston on January 6 (O.S.), 1706,
and was the youngest of seventeen children, of whom thirteen grew up
and married.

Benjamin being the youngest of ten sons, his father intended him for
the service of the Church, and sent him to the grammar school when
eight years of age, where he continued only a year, although he made
very rapid progress in the school; for his father concluded that he
could not afford the expense of a college education, and at the end of
the year removed him to a private commercial school. At the age of ten
young Benjamin was taken home to assist in cutting the wicks of
candles, and otherwise to make himself useful in his father's
business. His enterprising character as a boy is shown by the
following story, which is in his own words:--

    There was a salt marsh that bounded part of the mill-pond, on
    the edge of which, at high-water, we used to stand to fish for
    minnows. By much trampling we had made it a mere quagmire. My
    proposal was to build a wharf there fit for us to stand upon,
    and I showed my comrades a large heap of stones, which were
    intended for a new house near the marsh, and which would very
    well suit our purpose. Accordingly, in the evening, when the
    workmen were gone, I assembled a number of my play-fellows, and
    working with them diligently, like so many emmets, sometimes two
    or three to a stone, we brought them all away and built our
    little wharf. The next morning the workmen were surprised at
    missing the stones, which were found in our wharf. Inquiry was
    made after the removers; we were discovered and complained of;
    several of us were corrected by our fathers; and, though I
    pleaded the usefulness of the work, mine convinced me that
    nothing was useful which was not honest.

Until twelve years of age Benjamin continued in his father's business,
but as he manifested a great dislike for it, and his parents feared
that he might one day run away to sea, they set about finding some
trade which would be more congenial to his tastes. With this view his
father took him to see various artificers at their work, that he
might observe the tastes of the boy. This experience was very
valuable to him, as it taught him to do many little jobs for himself
when workmen could not readily be procured. During this time Benjamin
spent most of his pocket-money in purchasing books, some of which he
sold when he had read them, in order to buy others. He read through
most of the books in his father's very limited library. These mainly
consisted of works on theological controversy, which Franklin
afterwards considered to have been not very profitable to him.

"There was another bookish lad in the town, John Collins by name, with
whom I was intimately acquainted. We sometimes disputed, and very fond
we were of argument, and very desirous of confuting one another, which
disputatious turn, by the way, is apt to become a very bad habit,
making people often very disagreeable in company by the contradiction
that is necessary to bring it into practice; and thence, besides
souring and spoiling the conversation, is productive of disgusts and
perhaps enmities when you may have occasion for friendship. I had
caught it by reading my father's books of dispute about religion.
Persons of good sense, I have since observed, seldom fall into it,
except lawyers, university men, and men of all sorts that have been
bred at Edinburgh."

At length Franklin's fondness for books caused his father to decide to
make him a printer. His brother James had already entered that
business, and had set up in Boston with a new press and types which
he had brought from England. He signed his indentures when only twelve
years old, thereby apprenticing himself to his brother until he should
attain the age of twenty-one. The acquaintance which he formed with
booksellers through the printing business enabled him to borrow a
better class of books than he had been accustomed to, and he
frequently sat up the greater part of the night to read a book which
he had to return in the morning.

While working with his brother, the young apprentice wrote two
ballads, which he printed and sold in the streets of Boston. His
father, however, ridiculed the performance; so he "escaped being a
poet." He adopted at this time a somewhat original method to improve
his prose writing. Meeting with an odd volume of the _Spectator_, he
purchased it and read it "over and over," and wished to imitate the
style. "Making short notes of the sentiment in each sentence," he laid
them by, and afterwards tried to write out the papers without looking
at the original. Then on comparison he discovered his faults and
corrected them. Finding his vocabulary deficient, he turned some of
the tales into verse, then retranslated them into prose, believing
that the attempt to make verses would necessitate a search for several
words of the same meaning. "I also sometimes jumbled my collection of
hints into confusion, and after some weeks endeavoured to reduce them
into the best order, before I began to form the full sentence and
complete the paper. This was to teach me method in the arrangement of
my thoughts."

Meeting with a book on vegetarianism, Franklin determined to give the
system a trial. This led to some inconvenience in his brother's
house-keeping, so Franklin proposed to board himself if his brother
would give him half the sum he paid for his board, and out of this he
was able to save a considerable amount for the purpose of buying
books. Moreover, the time required for meals was so short that the
dinner hour afforded considerable leisure for reading. It was on his
journey from Boston to Philadelphia that he first violated vegetarian
principles; for, a large cod having been caught by the sailors, some
small fishes were found in its stomach, whereupon Franklin argued that
if fishes ate one another, there could be no reason against eating
them, so he dined on cod during the rest of the journey.

After reading Xenophon's "Memorabilia," Franklin took up strongly with
the Socratic method of discussion, and became so "artful and expert in
drawing people, even of superior knowledge, into concessions, the
consequence of which they did not foresee," that some time afterwards
one of his employers, before answering the most simple question, would
frequently ask what he intended to infer from the answer. This
practice he gradually gave up, retaining only the habit of expressing
his opinions with "modest diffidence."

In 1720 or 1721 James Franklin began to print a newspaper, the _New
England Courant_. To this paper, which he helped to compose and print,
Benjamin became an anonymous contributor. The members of the staff
spoke highly of his contributions, but when the authorship became
known, James appears to have conceived a jealousy of his younger
brother, which ultimately led to their separation. An article in the
paper having offended the Assembly, James was imprisoned for a month
and forbidden to print the paper. He then freed Benjamin from his
indentures, in order that the paper might be published in his name. At
length, some disagreement arising, Benjamin took advantage of the
cancelling of his indentures to quit his brother's service. As he
could get no employment in Boston, he obtained a passage to New York,
whence he was recommended to go to Philadelphia, which he reached
after a very troublesome journey. His whole stock of cash then
consisted of a Dutch dollar and about a shilling's worth of coppers.
The coppers he gave to the boatmen with whom he came across from
Burlington. His first appearance in Philadelphia, about eight o'clock
on a Sunday morning, was certainly striking. A youth between seventeen
and eighteen years of age, dressed in his working clothes, which were
dirty through his journey, with his pockets stuffed out with stockings
and shirts, his aspect was not calculated to command respect.

"Then I walked up the street, gazing about till near the market-house
I met a boy with bread. I had made many a meal on bread, and,
inquiring where he got it, I went immediately to the baker's he
directed me to, in Second Street, and ask'd for bisket, intending such
as we had in Boston; but they, it seems, were not made in
Philadelphia. Then I asked for a threepenny loaf, and was told they
had none such. So, not considering or knowing the difference of money,
and the greater cheapness, nor the name of his bread, I bad him give
me three-penny-worth of any sort. He gave me, accordingly, three great
puffy rolls. I was surpriz'd at the quantity, but took it, and having
no room in my pockets, walk'd off with a roll under each arm, and
eating the other. Thus I went up Market Street as far as Fourth
Street, passing by the door of Mr. Read, my future wife's father; when
she, standing at the door, saw me, and thought I made, as I certainly
did, a most awkward, ridiculous appearance. Then I turned and went
down Chestnut Street and part of Walnut Street, eating my roll all the
way, and, coming round, found myself again at Market Street Wharf,
near the boat I came in, to which I went for a draught of the river
water; and, being filled out with one of my rolls, gave the other two
to a woman and her child that came down the river in the boat with us,
and were waiting to go further."

In Philadelphia Franklin obtained an introduction, through a gentleman
he had met at New York, to a printer, named Keimer, who had just set
up business with an old press which he appeared not to know how to
use, and one pair of cases of English type. Here Franklin obtained
employment when the business on hand would permit, and he put the
press in order and worked it. Keimer obtained lodgings for him at the
house of Mr. Read, and, by industry and economical living, Franklin
found himself in easy circumstances. Sir William Keith was then
Governor of Pennsylvania, and hearing of Franklin, he called upon him
at Keimer's printing-office, invited him to take wine at a
neighbouring tavern, and promised to obtain for him the Government
printing if he would set up for himself. It was then arranged that
Franklin should return to Boston by the first ship, in order to see
what help his father would give towards setting him up in business. In
the mean while he was frequently invited to dine at the governor's
house. Notwithstanding Sir William Keith's recommendation, Josiah
Franklin thought his son too young to take the responsibility of a
business, and would only promise to assist him if, when he was
twenty-one, he had himself saved sufficient to purchase most of the
requisite plant. On his return to Philadelphia, he delivered his
father's letter to Sir William Keith, whereon the governor, stating
that he was determined to have a good printer there, promised to find
the means of equipping the printing-office himself, and suggested the
desirability of Franklin's making a journey to England in order to
purchase the plant. He promised letters of introduction to various
persons in England, as well as a letter of credit to furnish the
money for the purchase of the printing-plant. These letters Franklin
was to call for, but there was always some excuse for their not being
ready. At last they were to be sent on board the ship, and Franklin,
having gone on board, awaited the letters. When the governor's
despatches came, they were all put into a bag together, and the
captain promised to let Franklin have his letters before landing. On
opening the bag off Plymouth, there were no letters of the kind
promised, and Franklin was left without introductions and almost
without money, to make his own way in the world. In London he learned
that Governor Keith was well known as a man in whom no dependence
could be placed, and as to his giving a letter of credit, "he had no
credit to give."

A friend of Franklin's, named Ralph, accompanied him from America, and
the two took lodgings together in Little Britain at three shillings
and sixpence per week. Franklin immediately obtained employment at
Palmer's printing-office, in Bartholomew Close; but Ralph, who knew no
trade, but aimed at literature, was unable to get any work. He could
not obtain employment, even among the law stationers as a copying
clerk, so for some time the wages which Franklin earned had to support
the two. At Palmer's Franklin was employed in composing Wollaston's
"Religion of Nature." On this he wrote a short critique, which he
printed. it was entitled "A Dissertation on Liberty and Necessity,
Pleasure and Pain." The publication of this he afterwards regretted,
but it obtained for him introductions to some literary persons in
London. Subsequently he left Palmer's and obtained work at Watts's
printing-office, where he remained during the rest of his stay in
London. The beer-drinking capabilities of some of his fellow-workmen
excited his astonishment. He says:--

    We had an alehouse boy who attended always in the house to
    supply the workmen. My companion at the press drank every day a
    pint before breakfast, a pint at breakfast with his bread and
    cheese, a pint between breakfast and dinner, a pint at dinner, a
    pint in the afternoon about six o'clock, and another when he had
    done his day's work. I thought it a detestable custom, but it
    was necessary, he suppos'd, to drink _strong_ beer, that he
    might be _strong_ to labour. I endeavoured to convince him that
    the bodily strength afforded by beer could only be in proportion
    to the grain or flour of the barley dissolved in the water of
    which it was made; that there was more flour in a pennyworth of
    bread; and therefore, if he would eat that with a pint of water,
    it would give him more strength than a quart of beer. He drank
    on, however, and had four or five shillings to pay out of his
    wages every Saturday night for that muddling liquor; an expense
    I was free from. And thus these poor devils keep themselves
    always under.

Afterwards Franklin succeeded in persuading several of the compositors
to give up "their muddling breakfast of beer and bread and cheese,"
for a porringer of hot-water gruel, with pepper, breadcrumbs, and
butter, which they obtained from a neighbouring house at a cost of
three halfpence.

Among Franklin's fellow-passengers from Philadelphia to England was an
American merchant, a Mr. Denham, who had formerly been in business in
Bristol, but failed and compounded with his creditors. He then went to
America, where he soon acquired a fortune, and returned in Franklin's
ship. He invited all his old creditors to dine with him. At the dinner
each guest found under his plate a cheque for the balance which had
been due to him, with interest to date. This gentleman always remained
a firm friend to Franklin, who, during his stay in London, sought his
advice when any important questions arose. When Mr. Denham returned to
Philadelphia with a quantity of merchandise, he offered Franklin an
appointment as clerk, which was afterwards to develop into a
commission agency. The offer was accepted, and, after a voyage of
nearly three months, Franklin reached Philadelphia on October 11,
1726. Here he found Governor Keith had been superseded by Major
Gordon, and, what was of more importance to him, that Miss Read, to
whom he had become engaged before leaving for England, and to whom he
had written only once during his absence, had married. Shortly after
starting in business, Mr. Denham died, and thus left Franklin to
commence life again for himself. Keimer had by this time obtained a
fairly extensive establishment, and employed a number of hands, but
none of them were of much value; and he made overtures to Franklin to
take the management of his printing-office, apparently with the
intention of getting his men taught their business, so that he might
afterwards be able to dispense with the manager. Franklin set the
printing-house in order, started type-founding, made the ink, and,
when necessary, executed engravings. As the other hands improved under
his superintendence, Keimer began to treat his manager less civilly,
and apparently desired to curtail his stipend. At length, through an
outbreak of temper on the part of Keimer, Franklin left, but was
afterwards induced to return in order to prepare copper-plates and a
press for printing paper money for New Jersey.

While working for Keimer, Franklin formed a club, which was destined
to exert considerable influence on American politics. The club met on
Friday evenings, and was called the Junto. It was essentially a
debating society, the subject for each evening's discussion being
proposed at the preceding meeting. One of the rules was that the
existence of the club should remain a secret, and that its members
should be limited to twelve. Afterwards other similar clubs were
formed by its members; but the existence of the Junto was kept a
secret from them. The club lasted for about forty years, and became
the nucleus of the American Philosophical Society, of which Franklin
was the first president. This, and the fact that many of the great
questions that arose previously to the Declaration of Independence
were discussed in the Junto in the first instance, give to the club a
special importance. The following are specimens of subjects discussed
by the club:--

"Is sound an entity or body?"

"How may the phenomena of vapours be explained?"

"Is self-interest the rudder that steers mankind, the universal
monarch to whom all are tributaries?"

"Which is the best form of government? and what was that form which
first prevailed among mankind?"

"Can any one particular form of government suit all mankind?"

"What is the reason that the tides rise higher in the Bay of Fundy
than the Bay of Delaware?"

"Is the emission of paper money safe?"

"What is the reason that men of the greatest knowledge are not the
most happy?"

"How may the possessions of the Lakes be improved to our advantage?"

"Why are tumultuous, uneasy sensations united with our desires?"

"Whether it ought to be the aim of philosophy to eradicate the
passions."

"How may smoky chimneys be best cured?"

"Why does the flame of a candle tend upwards in a spire?"

"Which is least criminal--a bad action joined with a good intention,
or a good action with a bad intention?"

"Is it consistent with the principles of liberty in a free government
to punish a man as a libeller when he speaks the truth?"

On leaving Keimer's, Franklin went into partnership with one of his
fellow-workmen, Hugh Meredith, whose father found the necessary
capital, and a printing-office was started which soon excelled its two
rivals in Philadelphia. Franklin's industry attracted the attention of
the townsfolk, and inspired the merchants with confidence in the
prospects of the new concern. Keimer started a newspaper, which he had
not the ability to carry on; Franklin purchased it from him for a
trifle, remodelled it, and continued it in a very spirited manner
under the title of the _Pennsylvania Gazette_. His political articles
soon attracted the attention of the principal men of the state; the
number of subscribers increased rapidly, and the paper became a source
of considerable profit. Soon after, the printing for the House of
Representatives came into the hands of the firm. Meredith never took
to the business, and was seldom sober, and at length was bought out by
his partner, on July 14, 1730. The discussion in the Junto on paper
currency induced Franklin to publish a paper entitled "The Nature and
Necessity of a Paper Currency." This was a prominent subject before
the House, but the introduction of paper money was opposed by the
capitalists. They were unable, however, to answer Franklin's
arguments; the point was carried in the House, and Franklin was
employed to print the money. The amount of paper money in Pennsylvania
in 1739 amounted to £80,000; during the war it rose to more than
£350,000.

"In order to secure my credit and character as a tradesman, I took
care not only to be in _reality_ industrious and frugal, but to avoid
all appearances to the contrary. I drest plainly; I was seen at no
places of idle diversion. I never went out a-fishing or shooting; a
book, indeed, sometimes debauch'd me from my work, but that was
seldom, snug, and gave no scandal; and, to show that I was not above
my business, I sometimes brought home the paper I purchas'd at the
stores thro' the streets on a wheelbarrow. Thus being esteem'd an
industrious, thriving young man, and paying duly for what I bought,
the merchants who imported stationery solicited my custom; others
proposed supplying me with books, and I went on swimmingly. In the
mean time, Keimer's credit and business declining daily, he was at
last forc'd to sell his printing-house to satisfy his creditors."

On September 1, 1730, Franklin married his former _fiancée_, whose
previous husband had left her and was reported to have died in the
West Indies. The marriage was a very happy one, and continued over
forty years, Mrs. Franklin living until the end of 1774. Industry and
frugality reigned in the household of the young printer. Mrs. Franklin
not only managed the house, but assisted in the business, folding and
stitching pamphlets, and in other ways making herself useful. The
first part of Franklin's autobiography concludes with an account of
the foundation of the first subscription library. By the co-operation
of the members of the Junto, fifty subscribers were obtained, who each
paid in the first instance forty shillings, and afterwards ten
shillings per annum. "We afterwards obtained a charter, the company
being increased to one hundred. This was the mother of all the North
American subscription libraries, now so numerous. It is become a great
thing itself, and continually increasing. These libraries have
improved the general conversation of the Americans, made the common
tradesmen and farmers as intelligent as most gentlemen from other
countries, and perhaps have contributed in some degree to the stand so
generally made throughout the colonies in defence of their
privileges."

Ten years ago this library contained between seventy and eighty
thousand volumes.

Franklin's success in business was attributed by him largely to his
early training. "My circumstances, however, grew daily easier. My
original habits of frugality continuing, and my father having, among
his instructions to me when a boy, frequently repeated a proverb of
Solomon, 'Seest thou a man diligent in his business? he shall stand
before kings; he shall not stand before mean men,' I from thence
considered industry as a means of obtaining wealth and distinction,
which encourag'd me, tho' I did not think that I should ever
literally _stand before kings_, which, however, has since happened;
for I have stood before _five_, and even had the honour of sitting
down with one, the King of Denmark, to dinner."

After his marriage, Franklin conceived the idea of obtaining moral
perfection. He was not altogether satisfied with the result, but
thought his method worthy of imitation. Assuming that he possessed
complete knowledge of what was right or wrong, he saw no reason why he
should not always act in accordance therewith. His principle was to
devote his attention to one virtue only at first for a week, at the
end of which time he expected the practice of that virtue to have
become a habit. He then added another virtue to his list, and devoted
his attention to the same for the next week, and so on, until he had
exhausted his list of virtues. He then commenced again at the
beginning. As his moral code comprised thirteen virtues, it was
possible to go through the complete curriculum four times in a year.
Afterwards he occupied a year in going once through the list, and
subsequently employed several years in one course. A little book was
ruled, with a column for each day and a line for each virtue, and in
this a mark was made for every failure which could be remembered on
examination at the end of the day. It is easy to believe his
statement: "I am surprised to find myself so much fuller of faults
than I had imagined; but I had the satisfaction of seeing them
diminish."

"This my little book had for its motto these lines from Addison's
'Cato':--

    "'Here will I hold. If there's a Power above us
    (And that there is, all Nature cries aloud
    Thro' all her work), He must delight in virtue;
    And that which He delights in must be happy.'

"Another from Cicero:--

"'O vitæ Philosophia dux! O virtutum indagatrix expultrixque vitiorum!
Unus dies ex præceptis tuis actus, peccanti immortalitati est
anteponendus.'

"Another from the Proverbs of Solomon, speaking of wisdom and virtue:--

"'Length of days is in her right hand; and in her left hand riches and
honour. Her ways are ways of pleasantness, and all her paths are
peace.'

"And conceiving God to be the fountain of wisdom, I thought it right
and necessary to solicit His assistance for obtaining it; to this end
I formed the following little prayer, which was prefixed to my tables
of examination, for daily use:--

"'O powerful Goodness! bountiful Father! merciful Guide! increase in
me that wisdom which discovers my truest interest. Strengthen my
resolutions to perform what that wisdom dictates. Accept my kind
offices to Thy other children as the only return in my power for Thy
continual favours to me.'

"I used also sometimes a little prayer which I took from Thomson's
Poems, viz.:--

    "'Father of light and life, Thou Good Supreme!
    Oh teach me what is good; teach me Thyself!
    Save me from folly, vanity, and vice,
    From every low pursuit; and fill my soul
    With knowledge, conscious peace, and virtue pure;
    Sacred, substantial, never-failing bliss!'"

The senses in which Franklin's thirteen virtues were to be understood
were explained by short precepts which followed them in his list. The
list was as follows:--

"1. TEMPERANCE.

"Eat not to dulness; drink not to elevation.

"2. SILENCE.

"Speak not but what may benefit others or yourself; avoid trifling
conversation.

"3. ORDER.

"Let all your things have their places; let each part of your business
have its time.

"4. RESOLUTION.

"Resolve to perform what you ought; perform without fail what you
resolve.

"5. FRUGALITY.

"Make no expense but to do good to others or yourself; _i.e._ waste
nothing.

"6. INDUSTRY.

"Lose no time; be always employed in something useful; cut off all
unnecessary actions.

"7. SINCERITY.

"Use no hurtful deceit; think innocently and justly; and, if you
speak, speak accordingly.

"8. JUSTICE.

"Wrong none by doing injuries, or omitting the benefits that are your
duty.

"9. MODERATION.

"Avoid extremes; forbear resenting injuries so much as you think they
deserve.

"10. CLEANLINESS.

"Tolerate no uncleanness in body, clothes, or habitation.

"11. TRANQUILLITY.

"Be not disturbed at trifles, or accidents common or unavoidable.

"12. CHASTITY.

"13. HUMILITY.

"Imitate Jesus and Socrates."

The last of these was added to the list at the suggestion of a Quaker
friend. Franklin claims to have acquired a good deal of the
_appearance_ of it, but concluded that in reality there was no passion
so hard to subdue as _pride_. "For even if I could conceive that I had
completely overcome it, I should probably be proud of my humility."
The virtue which gave him most trouble, however, was order, and this
he never acquired.

In 1732 appeared the first copy of "Poor Richard's Almanack." This was
prepared, printed, and published by Franklin for about twenty-five
years in succession, and nearly ten thousand copies were sold
annually. Besides the usual astronomical information, it contained a
collection of entertaining anecdotes, verses, jests, etc., while the
"little spaces that occurred between the remarkable events in the
calendar" were filled with proverbial sayings, inculcating industry
and frugality as helps to virtue. These sayings were collected and
prefixed to the almanack of 1757, whence they were copied into the
American newspapers, and afterwards reprinted as a broad-sheet in
England and in France.

In 1733 Franklin commenced studying modern languages, and acquired
sufficient knowledge of French, Italian, and Spanish to be able to
read books in those languages. In 1736 he was chosen Clerk to the
General Assembly, an office to which he was annually re-elected until
he became a member of the Assembly about 1750. There was one member
who, on the second occasion of his election, made a long speech
against him. Franklin determined to secure the friendship of this
member. Accordingly he wrote to him to request the loan of a very
scarce and curious book which was in his library. The book was lent
and returned in about a week, with a note of thanks. The member ever
after manifested a readiness to serve Franklin, and they became great
friends--"Another instance of the truth of an old maxim I had learned,
which says, '_He that has once done you a kindness will be more ready
to do you another than he whom you yourself have obliged_.' And it
shows how much more profitable it is prudently to remove, than to
resent, return, and continue inimical proceedings."

In 1737 Franklin was appointed Deputy-Postmaster-General for
Pennsylvania. He was afterwards made Postmaster-General of the
Colonies. He read a paper in the Junto on the organization of the City
watch, and the propriety of rating the inhabitants on the value of
their premises in order to support the same. The subject was also
discussed in the other clubs which had sprung from the Junto, and thus
the way was prepared for the law which a few years afterwards carried
Franklin's proposals into effect. His next scheme was the formation of
a fire brigade, in which he met with his usual success, and other
clubs followed, until most of the men of property in the city were
members of one club or another. The original brigade, known as the
Union Fire Company, was formed December 7, 1736. It was in active
service in 1791.

Franklin founded the American Philosophical Society in 1743. The
head-quarters of the society were fixed in Philadelphia, where it was
arranged that there should always be at least seven members, viz. a
physician, a botanist, a mathematician, a chemist, a mechanician, a
geographer, and a general natural philosopher, besides a president,
treasurer, and secretary. The other members might be resident in any
part of America. Correspondence was to be kept up with the Royal
Society of London and the Dublin Society, and abstracts of the
communications were to be sent quarterly to all the members. Franklin
became the first secretary.

Spain, having been for some years at war with England, was joined at
length by France. This threatened danger to the American colonies, as
France then held Canada, and no organization for their defence
existed. Franklin published a pamphlet entitled "Plain Truth," setting
forth the unarmed condition of the colonies, and recommending the
formation of a volunteer force for defensive purposes. The pamphlet
excited much attention. A public meeting was held and addressed by
Franklin; at this meeting twelve hundred joined the association. At
length the number of members enrolled exceeded ten thousand. These all
provided themselves with arms, formed regiments and companies, elected
their own officers, and attended once a week for military drill.
Franklin was elected colonel of the Philadelphia Regiment, but
declined the appointment, and served as a private soldier. The
provision of war material was a difficulty with the Assembly, which
consisted largely of Quakers, who, though they appeared privately to
be willing that the country should be put in a state of defence,
hesitated to vote in opposition to their peace principles. Hence it
was that, when the Government of New England asked a grant of
gunpowder from Pennsylvania, the Assembly voted £3000 "for the
purchasing of bread, flour, wheat, or _other grain_." Pebble-powder
was not then in use. When it was proposed to devote £60, which was a
balance in the hands of the Union Fire Company, as a contribution
towards the erection of a battery below the town, Franklin suggested
that it should be proposed that a fire-engine be purchased with the
money, and that the committee should "buy a great gun, which is
certainly a _fire-engine_."

The "Pennsylvania fireplace" was invented in 1742. A patent was
offered to Franklin by the Governor of Pennsylvania, but he declined
it on the principle "_that, as we enjoy great advantages from the
inventions of others, we should be glad of an opportunity to serve
others by any invention of ours; and this we should do freely and
generously_." An ironmonger in London made slight alterations, which
were not improvements, in the design, and took out a patent for the
fireplace, whereby he made a "small fortune." Franklin never contested
the patent, "having no desire of profiting by patents himself," and
"hating disputes." This fireplace was designed to burn wood, but,
unlike the German stoves, it was completely open in front, though
enclosed at the sides and top. An air-chamber was formed in the middle
of the stove, so arranged that, while the burning wood was in contact
with the front of the chamber, the flame passed above and behind it on
its way to the flue. Through this chamber a constant current of air
passed, entering the room heated, but not contaminated, by the
products of combustion. In this way the stove furnished a constant
supply of fresh warm air to the room, while it possessed all the
advantages of an open fireplace. Subsequently Franklin contrived a
special fireplace for the combustion of coal. In the scientific
thought which he devoted to the requirements of the domestic
economist, as in very many other particulars, Franklin strongly
reminds us of Count Rumford.

The next important enterprise which Franklin undertook, partly through
the medium of the Junto, was to establish an academy which soon
developed into the University of Philadelphia. The members of the club
having taken up the subject, the next step was to enlist the sympathy
of a wider constituency, and this Franklin effected, in his usual way,
by the publication of a pamphlet. He then set on foot a subscription,
the payments to extend over five years, and thereby obtained about
£5000. A house was taken and schools opened in 1749. The classes soon
became too large for the house, and the trustees of the academy then
took over a large building, or "tabernacle," which had been erected
for George Whitefield when he was preaching in Philadelphia. The hall
was divided into stories, and at a very small expense adapted to the
requirements of the classes. Franklin, having taken a partner in his
printing business, took the oversight of the work. Afterwards the
funds were increased by English subscriptions, by a grant from the
Assembly, and by gifts of land from the proprietaries; and thus was
established the University of Philadelphia.

Having practically retired from business, Franklin intended to devote
himself to philosophical studies, having commenced his electrical
researches some time before in conjunction with the other members of
the Library Company. Public business, however, crowded upon him. He
was elected a member of the Assembly, a councillor and afterwards an
alderman of the city, and by the governor was made a justice of the
peace. As a member of the Assembly, he was largely concerned in
providing the means for the erection of a hospital, and in arranging
for the paving and cleansing of the streets of the city. In 1753 he
was appointed, in conjunction with Mr. Hunter, Postmaster-General of
America. The post-office of the colonies had previously been conducted
at a loss. In a few years, under Franklin's management, it not only
paid the stipends of himself and Mr. Hunter, but yielded a
considerable revenue to the Crown. But it was not only in the conduct
of public business that Franklin's merits were recognized. By this
time he had secured his reputation as an electrician, and both Yale
College and Cambridge University (New England) conferred on him the
honorary degree of Master of Arts. In the same year that he was made
Postmaster-General of America he was awarded the Copley Medal and
elected a Fellow of the Royal Society of London, the usual fees being
remitted in his case.

Before his election as member, Franklin had for several years held the
appointment of Clerk to the Assembly, and he used to relieve the
dulness of the debates by amusing himself in the construction of magic
circles and squares, and "acquired such a knack at it" that he could
"fill the cells of any magic square of reasonable size with a series
of numbers as fast as" he "could write them." Many years afterwards
Mr. Logan showed Franklin a French folio volume filled with magic
squares, and afterwards a magic "square of 16," which Mr. Logan
thought must have been a work of great labour, though it possessed
only the common properties of making 2056 in every row, horizontal,
vertical, and diagonal. During the evening Franklin made the square
shown on the opposite page. "This I sent to our friend the next
morning, who, after some days, sent it back in a letter, with these
words: 'I return to thee thy astonishing and most stupendous piece of
the magical square, in which----;' but the compliment is too
extravagant, and therefore, for his sake as well as my own, I ought
not to repeat it. Nor is it necessary; for I make no question that you
will readily allow this square of 16 to be the most magically magical
of any magic square ever made by any magician."

The square has the following properties:--Every straight row of
sixteen numbers, whether vertical, horizontal, or diagonal, makes
2056.

Every bent row of sixteen numbers, as shown by the diagonal lines in
the figure, makes 2056.

If a square hole be cut in a piece of paper, so as to show through it
just sixteen of the little squares, and the paper be laid on the magic
square, then, wherever the paper is placed, the sum of the sixteen
numbers visible through the hole will be 2056.

[Illustration:

    200 217 232 249   8  25  40  57  72  89 104 121 136 153 168 185
     58  39  26   7 250 231 218 199 186 167 154 135 122 103  90  71
    198 219 230 251   6  27  38  59  70  91 102 123 134 155 166 187
     60  37  28   5 252 229 220 197 188 165 156 133 124 101  92  69
    201 216 233 248   9  24  41  56  73  88 105 120 137 152 169 184
     55  42  23  10 247 234 215 202 183 170 151 138 119 106  87  74
    203 214 235 246  11  22  43  54  75  86 107 118 139 150 171 182
     53  44  21  12 245 236 213 204 181 172 149 140 117 108  85  76
    205 212 237 244  13  20  45  52  77  84 109 116 141 148 173 180
     51  46  19  14 243 238 211 206 179 174 147 142 115 110  83  78
    207 210 239 242  15  18  47  50  79  82 111 114 143 146 175 178
     49  48  17  16 241 240 209 208 177 176 145 144 113 112  81  80
    196 221 228 253   4  29  36  61  68  93 100 125 132 157 164 189
     62  35  30   3 254 227 222 195 190 163 158 131 126  99  94  67
    194 223 226 255   2  31  34  63  66  95  98 127 130 159 162 191
     64  33  32   1 256 225 224 193 192 161 160 129 128  97  96  65
]

In 1754 war with France appeared to be again imminent, and a Congress
of Commissioners from the several colonies was arranged for. Of
course, Franklin was one of the representatives of Pennsylvania, and
was also one of the members who independently drew up a plan for the
union of all the colonies under one government, for defensive and
other general purposes, and his was the plan finally approved by
Congress for the union, though it was not accepted by the Assemblies
or by the English Government, being regarded by the former as having
too much of the _prerogative_ in it, by the latter as being too
_democratic_. Franklin wrote respecting this scheme: "The different
and contrary reasons of dislike to my plan makes me suspect that it
was really the true medium; and I am still of opinion that it would
have been happy for both sides of the water if it had been adopted. The
colonies, so united, would have been sufficiently strong to have
defended themselves; there would then have been no need of troops from
England; of course, the subsequent pretence for taxing America, and
the bloody contest it occasioned, would have been avoided."

With this war against France began the struggle of the Assemblies and
the proprietaries on the question of taxing the estates of the latter.
The governors received strict instructions to approve no bills for the
raising of money for the purposes of defence, unless the estates of
the proprietaries were specially exempted from the tax. The Assembly
of Pennsylvania resolved to contribute £10,000 to assist the
Government of Massachusetts Bay in an attack upon Crown Point, but the
governor refused his assent to the bill for raising the money. At this
juncture Franklin proposed a scheme by which the money could be raised
without the consent of the governor. His plan was successful, and the
difficulty was surmounted for the time, but was destined to recur
again and again during the progress of the war.

The British Government, not approving of the scheme of union, whereby
the colonies might have defended themselves, sent General Braddock to
Virginia, with two regiments of regular troops. On their arrival they
found it impossible to obtain waggons for the conveyance of their
baggage, and the general commissioned Franklin to provide them in
Pennsylvania. By giving his private bond for their safety, Franklin
succeeded in engaging one hundred and fifty four-horse waggons, and
two hundred and fifty-nine pack-horses. His modest warnings against
Indian ambuscades were disregarded by the general, the little army was
cut to pieces, and the remainder took to flight, sacrificing the whole
of their baggage and stores. Franklin was never fully recouped by the
British Government for the payments he had to make on account of
provisions which the general had instructed him to procure for the use
of the army.

After this, Franklin appeared for some time in a purely military
capacity, having yielded to the governor's persuasions to undertake
the defence of the north-western frontier, to raise troops, and to
build a line of forts. After building and manning three wooden forts,
he was recalled by the Assembly, whose relations with the governor had
become more and more strained. At length the Assembly determined to
send Franklin to England, to present a petition to the king respecting
the conduct of the proprietaries, viz. Richard and Thomas Penn, the
successors of William Penn. A bill had been framed by the House to
provide £60,000 for the king's use in the defence of the province.
This the governor refused to pass, because the proprietary estates
were not exempted from the taxation. The petition to the king was
drawn up, and Franklin's baggage was on board the ship which was to
convey him to England, when General Lord Loudon endeavoured to make an
arrangement between the parties. The governor pleaded his
instructions, and the bond he had given for carrying them out, and the
Assembly was prevailed upon to reconstruct the bill in accordance with
the governor's wishes. This was done under protest; in the mean time
Franklin's ship had sailed, carrying his baggage. After a great deal
of unnecessary delay on account of the general's inability to decide
upon the despatch of the packet-boats, Franklin at last got away from
New York, and, having narrowly escaped shipwreck off Falmouth, he
reached London on July 27, 1757.

On arriving in London, Franklin was introduced to Lord Granville, who
told him that the king's instructions were laws in the colonies.
Franklin replied that he had always understood that the Assemblies
made the laws, which then only required the king's consent. "I
recollected that, about twenty years before, a clause in a bill
brought into Parliament by the Ministry had proposed to make the
king's instructions laws in the colonies, but the clause was thrown
out by the Commons, for which we adored them as our friends and the
friends of liberty, till, by their conduct towards us in 1765, it
seem'd that they had refus'd that point of sovereignty to the king
only that they might reserve it for themselves." A meeting was shortly
afterwards arranged between Franklin and the proprietaries at Mr. T.
Penn's house; but their views were so discordant that, after some
discussion, Franklin was requested to give them in writing the heads
of his complaints, and the whole question was submitted to the opinion
of the attorney- and solicitor-general. It was nearly a year before
this opinion was given. The proprietaries then communicated directly
with the Assembly, but in the mean while Governor Denny had consented
to a bill for raising £100,000 for the king's use, in which it was
provided that the proprietary estates should be taxed with the others.
When this bill reached England, the proprietaries determined to oppose
its receiving the royal assent. Franklin engaged counsel on behalf of
the Assembly, and on his undertaking that the assessment should be
fairly made between the estates of the proprietaries and others, the
bill was allowed to pass.

By this time Franklin's career as a scientific investigator was
practically at an end. Political business almost completely occupied
his attention, and in one sense the diplomatist replaced the
philosopher. His public scientific career was of short duration. It
may be said to have begun in 1746, when Mr. Peter Collinson presented
an "electrical tube" to the Library Company in Philadelphia, which was
some time after followed by a present of a complete set of electrical
apparatus from the proprietaries, but by 1755 Franklin's time was so
much taken up by public business that there was very little
opportunity for experimental work. Throughout his life he frequently
expressed in his letters his strong desire to return to philosophy,
but the opportunity never came, and when, at the age of eighty-two, he
was liberated from public duty, his strength was insufficient to
enable him to complete even his autobiography.

It was on a visit to Boston in 1746 that Franklin met with Dr. Spence,
a Scotchman, who exhibited some electrical experiments. Soon after his
return to Philadelphia the tube arrived from Mr. Collinson, and
Franklin acquired considerable dexterity in its use. His house was
continually full of visitors, who came to see the experiments, and, to
relieve the pressure upon his time, he had a number of similar tubes
blown at the glass-house, and these he distributed to his friends, so
that there were soon a number of "performers" in Philadelphia. One of
these was Mr. Kinnersley, who, having no other employment, was induced
by Franklin to become an itinerant lecturer. Franklin drew up a scheme
for the lectures, and Kinnersley obtained several well-constructed
instruments from Franklin's rough and home-made models. Kinnersley and
Franklin appear to have worked together a good deal, and when
Kinnersley was travelling on his lecture tour, each communicated to
the other the results of his experiments. Franklin sent his papers to
Mr. Collinson, who presented them to the Royal Society, but they were
not at first judged worthy of a place in the "Transactions." The paper
on the identity of lightning and electricity was sent to Dr. Mitchell,
who read it before the Royal Society, when it "was laughed at by the
connoisseurs." The papers were subsequently published in a pamphlet,
but did not at first receive much attention in England. On the
recommendation of Count de Buffon, they were translated into French.
The Abbé Nollet, who had previously published a theory of his own
respecting electricity, wrote and published a volume of letters
defending his theory, and denying the accuracy of some of Franklin's
experimental results. To these letters Franklin made no reply, but
they were answered by M. le Roy. M. de Lor undertook to repeat in
Paris all Franklin's experiments, and they were performed before the
king and court. Not content with the experiments which Franklin had
actually performed, he tried those which had been only suggested, and
so was the first to obtain electricity from the clouds by means of the
pointed rod. This experiment produced a great sensation everywhere,
and was afterwards repeated by Franklin at Philadelphia. Franklin's
papers were translated into Italian, German, and Latin; his theory met
with all but universal acceptance, and great surprise was expressed
that his papers had excited so little interest in England. Dr. Watson
then drew up a summary of all Franklin's papers, and this was
published in the "Philosophical Transactions;" Mr. Canton verified the
experiment of procuring electricity from the clouds by means of a
pointed rod, and the Royal Society awarded to Franklin the Copley
Medal for 1753, which was conveyed to him by Governor Denny.

We must now give a short account of Franklin's contributions to
electrical science.

"The first is the wonderful effect of pointed bodies, both in _drawing
off_ and _throwing off_ the electrical fire."

It will be observed that this statement is made in the language of the
_one_-fluid theory, of which Franklin may be regarded as the author.
This theory will be again referred to presently. Franklin electrified
a cannon-ball so that it repelled a cork. On bringing near it the
point of a bodkin, the repulsion disappeared. A blunt body had to be
brought near enough for a spark to pass in order to produce the same
effect. "To prove that the electrical fire is _drawn off_ by the
point, if you take the blade of the bodkin out of the wooden handle,
and fix it in a stick of sealing-wax, and then present it at the
distance aforesaid, or if you bring it very near, no such effect
follows; but sliding one finger along the wax till you touch the
blade, and the ball flies to the shot immediately. If you present the
point in the dark, you will see, sometimes at a foot distance or more,
a light gather upon it like that of a fire-fly or glow-worm; the less
sharp the point, the nearer you must bring it to observe the light;
and at whatever distance you see the light, you may draw off the
electrical fire, and destroy the repelling."

By laying a needle upon the shot, Franklin showed "that points will
_throw off_ as well as _draw off_ the electrical fire." A candle-flame
was found to be equally efficient with a sharp point in drawing off
the electricity from a charged conductor. The effect of the
candle-flame Franklin accounted for by supposing the particles
separated from the candle to be first "attracted and then repelled,
carrying off the electric matter with them." The effect of points is a
direct consequence of the law of electrical repulsion. When a
conductor is electrified, the density of the electricity is greatest
where the curvature is greatest. Thus, if a number of spheres are
electrified from the same source, the density of the electricity on
the different spheres will vary inversely as their diameters. The
force tending to drive the electricity off a conductor is everywhere
proportional to the density, and hence in the case of the spheres will
be greatest for the smallest sphere. On this principle, the density of
electricity on a perfectly sharp point, if such could exist, on a
charged conductor, would be infinite and the force tending to drive it
off would be infinite also. Hence a moderately sharp point is
sufficient to dissipate the electricity from a highly charged
conductor, or to neutralize it if the point is connected to earth and
brought near the conductor so as to be electrified by induction.

Franklin next found that, if the person rubbing the electric tube
stood upon a cake of resin, and the person taking the charge from the
tube stood also on an insulating stand, a stronger spark would pass
between these two persons than between either of them and the earth;
that, after the spark had passed, neither person was electrified,
though each had appeared electrified before. These experiments
suggested the idea of _positive_ and _negative_ electrification; and
Franklin, regarding the electric fluid as corresponding to positive
electrification, remarked that "you may circulate it as Mr. Watson has
shown; you may also accumulate or subtract it upon or from any body,
as you connect that body with the rubber or with the receiver, the
common stock being cut off." Thus Franklin regarded electricity as a
fluid, of which everything in its normal state possesses a certain
amount; that, by appropriate means, some of the fluid may be removed
from one body and given to another. The former is then electrified
negatively, the latter positively, and all processes by which bodies
are electrified consist in the removal of electricity from one body or
system and giving it to another. He regarded the electric fluid as
repelling itself and attracting matter. Æpinus afterwards added the
supposition that matter, when devoid of electricity, is
self-repulsive, and thus completed the "one-fluid theory," and
accounted for the repulsion observed between negatively electrified
bodies.

It had been usual to employ water for the interior armatures of Leyden
jars, or phials, as they were then generally called. Franklin
substituted granulated lead for the water, thereby improving the
insulation by keeping the glass dry. With these phials he contrived
many ingenious experiments, and imitated lightning by discharging them
through the gilding of a mirror or the gold lines on the cover of a
book. He found that the inner and outer armatures of his Leyden jars
were oppositely electrified. "Here we have a bottle containing at the
same time a _plenum_ of electrical fire and a _vacuum_ of the same
fire; and yet the equilibrium cannot be restored between them but by a
communication _without_! though the plenum presses violently to
expand, and the hungry vacuum seems to attract as violently in order
to be filled." The charging of Leyden jars by cascade, that is by
insulating all the jars except the last, connecting the outer armature
of the first with the inner armature of the second, and so on
throughout the series, was well understood by Franklin, and he knew
too that by this method the extent to which each jar could be charged
from a given source varied inversely as the number of jars. The
discharge of the Leyden jar by alternate contacts was also carried out
by him; and he found that, if the jar is first placed on an insulating
stand, it may be held by the hook (or knob) without discharging it.
Franklin, in fact, appears to have known almost as much about the
Leyden jar as is known to-day. He found that, when the armatures were
removed from a jar, no discharge would pass between them, but when a
fresh pair of armatures were supplied to the glass, the jar could be
discharged. "We are of opinion that there is really no more electrical
fire in the phial after what is called its _charging_ than before, nor
less after its _discharging_; excepting only the small spark that
might be given to and taken from the non-electric matter, if separated
from the bottle, which spark may not be equal to a five-hundredth part
of what is called the explosion.

"The phial will not suffer what is called a _charging_ unless as much
fire can go out of it one way as is thrown in by another.

"When a bottle is charged in the common way, its _inside_ and
_outside_ surfaces stand ready, the one to give fire by the hook, the
other to receive it by the coating; the one is full and ready to throw
out, the other empty and extremely hungry; yet, as the first will not
_give out_ unless the other can at the same time _receive in_, so
neither will the latter receive in unless the first can at the same
time give out. When both can be done at once, it is done with
inconceivable quickness and violence."

Then follows a very beautiful illustration of the condition of the
glass in the Leyden jar.

"So a straight spring (though the comparison does not agree in every
particular), when forcibly bent, must, to restore itself, contract
that side which in the bending was extended, and extend that which was
contracted; if either of these two operations be hindered, the other
cannot be done.

"Glass, in like manner, has, within its substance, always the same
quantity of electrical fire, and that a very great quantity in
proportion to the mass of the glass, as shall be shown hereafter.

"This quantity proportioned to the glass it strongly and obstinately
retains, and will have neither more nor less, though it will suffer a
change to be made in its parts and situation; _i.e._ we may take away
part of it from one of the sides, provided we throw an equal quantity
into the other."

"The whole force of the bottle, and power of giving a shock, is in the
GLASS ITSELF; the non-electrics in contact with the two surfaces
serving only to _give_ and _receive_ to and from the several parts of
the glass, that is, to give on one side and take away from the other."

All these statements were, as far as possible, fully substantiated by
experiment. They are perfectly consistent with the views held by
Cavendish and by Clerk Maxwell, and, though the phraseology is not
that of the modern text-books, the statements themselves can hardly be
improved upon to-day.

One of Franklin's early contrivances was an electro-motor, which was
driven by the alternate electrical attraction and repulsion of leaden
bullets which discharged Leyden jars by alternate contacts. Franklin
concluded his account of these experiments as follows:--

    Chagrined a little that we have been hitherto able to produce
    nothing in this way of use to mankind, and the hot weather
    coming on, when electrical experiments are not so agreeable, it
    is proposed to put an end to them for this season, somewhat
    humorously, in a party of pleasure, on the banks of Skuylkil.
    Spirits, at the same time, are to be fired by a spark sent from
    side to side through the river, without any other conductor than
    the water--an experiment which we some time since performed, to
    the amazement of many. A turkey is to be killed for our dinner
    by the _electrical shock_, and roasted by the _electrical jack_
    before a fire kindled by the _electrified bottle_, when the
    healths of all the famous electricians in England, Holland,
    France, and Germany, are to be drunk in _electrified bumpers_,
    under the discharge of guns from the _electrical battery_.

Franklin's electrical battery consisted of eleven large panes of glass
coated on each side with sheet lead. The electrified bumper was a thin
tumbler nearly filled with wine and electrified as a Leyden jar, so
as to give a shock through the lips.

Franklin's theory of the manner in which thunder-clouds become
electrified he found to be not consistent with his subsequent
experiments. In the paper which he wrote explaining this theory,
however, he shows some knowledge of the effects of bringing conductors
into contact in diminishing their capacity. He states that two
gun-barrels electrified equally and then united, will give a spark at
a greater distance than one alone. Hence he asks, "To what a great
distance may ten thousand acres of electrified cloud strike and give
its fire, and how loud must be that crack?

"An electrical spark, drawn from an irregular body at some distance,
is scarcely ever straight, but shows crooked and waving in the air. So
do the flashes of lightning, the clouds being very irregular bodies.

"As electrified clouds pass over a country, high hills and high trees,
lofty towers, spires, masts of ships, chimneys, etc., as so many
prominences and points, draw the electrical fire, and the whole cloud
discharges there.

"Dangerous, therefore, is it to take shelter under a tree during a
thunder-gust. It has been fatal to many, both men and beasts.

"It is safer to be in the open field for another reason. When the
clothes are wet, if a flash in its way to the ground should strike
your head, it may run in the water over the surface of your body;
whereas, if your clothes were dry, it would go through the body,
because the blood and other humours, containing so much water, are
more ready conductors.

"Hence a wet rat cannot be killed by the exploding electrical bottle
[a quart jar], while a dry rat may."

In the above quotations we see, so to speak, the germ of the
lightning-rod. This was developed in a letter addressed to Mr.
Collinson, and dated July 29, 1750. The following quotations will give
an idea of its contents:--

"The electrical matter consists of particles extremely subtile, since
it can permeate common matter, even the densest metals, with such ease
and freedom as not to receive any perceptible resistance.[1]

[Footnote 1: Franklin was aware of the resistance of conductors (see
p. 96).]

"If any one should doubt whether the electrical matter passes through
the substance of bodies or only over and along their surfaces, a shock
from an electrified large glass jar, taken through his own body, will
probably convince him.

"Common matter is a kind of sponge to the electrical fluid.

"We know that the electrical fluid is _in_ common matter, because we
can pump it _out_ by the globe or tube. We know that common matter has
near as much as it can contain, because when we add a little more to
any portion of it, the additional quantity does not enter, but forms
an electrical atmosphere."

To illustrate the action of a lightning-conductor on a thunder-cloud,
Franklin suspended from the ceiling a pair of scales by a twisted
string so that the beam revolved. Upon the floor, in such a position
that the scale-pans passed over it, he placed a blunt steel punch. The
scale-pans were suspended by silk threads, and one of them
electrified. When this passed over the punch it dipped towards it, and
sometimes discharged into it by a spark. When a needle was placed with
its point uppermost by the side of the punch, no attraction was
apparent, for the needle discharged the scale-pan before it came near.

"Now, if the fire of electricity and that of lightning be the same, as
I have endeavoured to show at large in a former paper ... these scales
may represent electrified clouds.... The horizontal motion of the
scales over the floor may represent the motion of the clouds over the
earth, and the erect iron punch a hill or high building; and then we
see how electrified clouds, passing over hills or high buildings at
too great a height to strike, may be attracted lower till within their
striking distance; and lastly, if a needle fixed on the punch, with
its point upright, or even on the floor below the punch, will draw the
fire from the scale silently at a much greater than the striking
distance, and so prevent its descending towards the punch; or if in
its course it would have come nigh enough to strike, yet, being first
deprived of its fire, it cannot, and the punch is thereby secured from
its stroke;--I say, if these things are so, may not the knowledge of
this power of points be of use to mankind, in preserving houses,
churches, ships, etc., from the stroke of the lightning, by directing
us to fix, on the highest parts of those edifices, upright rods of
iron made sharp as a needle, and gilt to prevent rusting, and from the
foot of those rods a wire down the outside of the building into the
ground, or down round one of the shrouds of a ship, and down her side
till it reaches the water? Would not these pointed rods probably draw
the electrical fire silently out of a cloud before it came nigh enough
to strike, and thereby secure us from that most sudden and terrible
mischief?"

Franklin goes on to suggest the possibility of obtaining electricity
from the clouds by means of a pointed rod fixed on the top of a high
building and insulated. Such a rod he afterwards erected in his own
house. Another rod connected to the earth he brought within six inches
of it, and, attaching a small bell to each rod, he suspended a little
ball or clapper by a silk thread, so that it could strike either bell
when attracted to it. On the approach of a thunder-cloud, and
occasionally when no clouds were near, the bells would ring,
indicating that the rod had become strongly electrified. On one
occasion Franklin was disturbed by a loud noise, and, coming out of
his bedroom, he found an apparently continuous and very luminous
discharge taking place between the bells, forming a stream of fire
about as large as a pencil.

A very pretty experiment of Franklin's was that of the _golden fish_.
A small piece of gold-leaf is cut into a quadrilateral having one of
its angles about 150°, the opposite angle about 30°, and the other two
right angles. "If you take it by the tail, and hold it at a foot or
greater horizontal distance from the prime conductor, it will, when
let go, fly to it with a brisk but wavering motion, like that of an
eel through the water; it will then take place under the prime
conductor, at perhaps a quarter or half an inch distance, and keep a
continual shaking of its tail like a fish, so that it seems animated.
Turn its tail towards the prime conductor, and then it flies to your
finger, and seems to nibble it. And if you hold a [pewter] plate under
it at six or eight inches distance, and cease turning the globe, when
the electrical atmosphere of the conductor grows small it will descend
to the plate and swim back again several times with the same fish-like
motion; greatly to the entertainment of spectators. By a little
practice in blunting or sharpening the heads or tails of these
figures, you may make them take place as desired, nearer or further
from the electrified plate."

By the discharge of the battery, Franklin succeeded in melting and
volatilizing gold-leaf, thin strips of tinfoil, etc. His views on the
nature of light are best given in his own words.

"I am not satisfied with the doctrine that supposes particles of
matter called light, continually driven off from the sun's surface,
with a swiftness so prodigious! Must not the smallest particle
conceivable have, with such a motion, a force exceeding that of a
twenty-four pounder discharged from a cannon?... Yet these particles,
with this amazing motion, will not drive before them, or remove, the
least and lightest dust they meet with.

"May not all the phenomena of light be more conveniently solved by
supposing universal space filled with a subtile elastic fluid, which,
when at rest, is not visible, but whose vibrations affect that fine
sense in the eye, as those of air do the grosser organs of the ear? We
do not, in the case of sound, imagine that any sonorous particles are
thrown off from a bell, for instance, and fly in straight lines to the
ear; why must we believe that luminous particles leave the sun and
proceed to the eye? Some diamonds, if rubbed, shine in the dark
without losing any part of their matter. I can make an electrical
spark as big as the flame of a candle, much brighter, and therefore
visible further; yet this is without fuel; and I am persuaded no part
of the electrical fluid flies off in such case to distant places, but
all goes directly and is to be found in the place to which I destine
it. May not different degrees of the vibration of the abovementioned
universal medium occasion the appearances of different colours? I
think the electric fluid is always the same; yet I find that weaker
and stronger sparks differ in apparent colour, some white, blue,
purple, red: the strongest, white; weak ones, red. Thus different
degrees of vibration given to the air produce the seven different
sounds in music, analogous to the seven colours, yet the medium, air,
is the same."

Mr. Kinnersley having called Franklin's attention to the fact that a
sulphur globe when rubbed produced electrification of an opposite kind
from that produced by a glass globe, Franklin repeated the experiment,
and noticed that the discharge from the end of a wire connected with
the conductor was different in the two cases, being "long, large, and
much diverging when the glass globe is used, and makes a snapping (or
rattling) noise; but when the sulphur one is used it is short, small,
and makes a hissing noise; and just the reverse of both happens when
you hold the same wire in your hand and the globes are worked
alternately.... When the brush is long, large, and much diverging, the
body to which it is joined seems to be throwing the fire out; and when
the contrary appears it seems to be drinking in."

On October 19, 1752, Franklin wrote to Mr. Peter Collinson as
follows:--

    As frequent mention is made in public papers from Europe of the
    success of the Philadelphia experiment for drawing the electric
    fire from clouds by means of pointed rods of iron erected on
    high buildings, etc., it may be agreeable to the curious to be
    informed that the same experiment has succeeded in
    Philadelphia, though made in a different and more easy manner,
    which is as follows:--

    Make a small cross of two light strips of cedar, the arms so
    long as to reach to the four corners of a large thin silk
    handkerchief when extended. Tie the corners of the handkerchief
    to the extremities of the cross, so you have the body of a kite;
    which, being properly accommodated with a tail, loop, and
    string, will rise in the air like those made of paper; but this
    being of silk is fitter to bear the wet and wind of a
    thunder-gust without tearing. To the top of the upright stick of
    the cross is to be fixed a very sharp-pointed wire, rising a
    foot or more above the wood. To the end of the twine, next the
    hand, is to be tied a silk ribbon, and, where the silk and twine
    join, a key may be fastened. This kite is to be raised when a
    thunder-gust appears to be coming on, and the person who holds
    the string must stand within a door or window, or under some
    cover so that the silk ribbon may not be wet, and care must be
    taken that the twine does not touch the frame of the door or
    window. As soon as any of the thunder-clouds come over the kite,
    the pointed wire will draw the electric fire from them, and the
    kite, with all the twine, will be electrified, and the loose
    filaments of the twine will stand out every way, and be
    attracted by an approaching finger. And when the rain has wetted
    the kite and twine so that it can conduct the electric fire
    freely, you will find it stream out plentifully from the key on
    the approach of your knuckle. At this key the phial may be
    charged, and from electric fire there obtained spirits may be
    kindled, and all the other electric experiments be performed
    which are usually done by the help of a rubbed glass globe or
    tube, and thereby the sameness of the electric matter with that
    of lightning completely demonstrated.

Having, in September, 1752, erected the iron rod and bells in his own
house, as previously mentioned, Franklin succeeded, in April, 1753, in
charging a Leyden jar from the rod, and found its charge was negative.
On June 6, however, he obtained a positive charge from a cloud. The
results of his observations led him to the conclusion "_That the
clouds of a thunder-gust are most commonly in a negative state of
electricity, but sometimes in a positive state._"

In order to illustrate a theory respecting the electrification of
clouds, Franklin placed a silver can on a wine-glass. Inside the can
was placed a considerable length of chain, which could be drawn out by
means of a silk thread. He electrified the can from a Leyden jar until
it would receive no more electricity. Then raising the silk thread, he
gradually drew the chain out of the can, and found that the greater
the length of chain drawn out the greater was the charge which the jar
would give to the system, and as the chain was raised, spark after
spark passed from the jar to the silver can, thus showing that the
capacity of the system was increased by increasing the amount of
chain exposed.

In 1755 Franklin observed the effects of induction; for, having
attached to his prime conductor a tassel made of damp threads and
electrified the conductor, he found that the threads repelled each
other and stood out. Bringing an excited glass tube near the other end
of the conductor, the threads were found to diverge more, "because the
atmosphere of the prime conductor is pressed by the atmosphere of the
excited tube, and driven towards the end where the threads are, by
which each thread acquires more atmosphere." When the excited tube was
brought near the threads, they closed a little, "because the
atmosphere of the glass tube repels their atmospheres, and drives part
of them back on the prime conductor." A number of other experiments
illustrating electrical induction were also carried out.

In writing to Dr. Living, of Charlestown, under date March 18, 1755,
Franklin gave the following extracts of the minutes of his experiments
as explaining the train of thought which led him to attempt to obtain
electricity from the clouds:--

"_November 7, 1749._ Electrical fluid agrees with lightning in these
particulars: 1. Giving light. 2. Colour of the light. 3. Crooked
direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or
noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies
it passes through. 9. Destroying animals. 10. Melting metals. 11.
Firing inflammable substances. 12. Sulphureous smell. The electric
fluid is attracted by points. We do not know whether this property is
in lightning. But since they agree in all the particulars wherein we
can already compare them, is it not probable they agree likewise in
this? Let the experiment be made."

Another experiment very important in its bearing on the theory of
electricity was described by Franklin in the same letter to Dr.
Living. It was afterwards repeated in a much more complete form by
Cavendish, who deduced from it the great law that electrical repulsion
varies inversely as the square of the distance between the charges.
The same experiment was repeated in other forms by Faraday, who had no
means of knowing what Cavendish had done. Franklin writes:--

    I electrified a silver fruit-can on an electric stand, and then
    lowered into it a cork ball of about an inch in diameter,
    hanging by a silk string, till the cork touched the bottom of
    the can. The cork was not attracted to the inside of the can, as
    it would have been to the outside, and though it touched the
    bottom, yet, when drawn out, it was not found to be electrified
    by that touch, as it would have been by touching the outside.
    The fact is singular. You require the reason? I do not know it.
    Perhaps you may discover it, and then you will be so good as to
    communicate it to me. I find a frank acknowledgment of one's
    ignorance is not only the easiest way to get rid of a
    difficulty, but the likeliest way to obtain information, and
    therefore I practise it. I think it is an honest policy.

A note appended to this letter runs as follows:--

    Mr. F. has since thought that, possibly, the mutual repulsion of
    the inner opposite sides of the electrized can may prevent the
    accumulating an electric atmosphere upon them, and occasion it
    to stand chiefly on the outside. But recommends it to the
    further examination of the curious.

The explanation in this note is the correct one, and from the fact
that in the case of a completely closed hollow conductor the charge is
not only _chiefly_ but _wholly_ on the outside, the law of inverse
squares above referred to follows as a mathematical consequence.

On writing to M. Dalibard, of Paris, on June 29, 1755, Franklin
complained that, though he always (except once) assigned to
lightning-rods the alternative duty of either _preventing_ a stroke or
of _conducting_ the lightning with safety to the ground, yet in Europe
attention was paid only to the _prevention_ of the stroke, which was
only a _part_ of the duty assigned to the conductors. This is followed
by the description of the effect of a stroke upon a church-steeple at
Newbury, in New England. The spire was split all to pieces, so that
nothing remained above the bell. The lightning then passed down a wire
to the clock, then down the pendulum, without injury to the building.
"From the end of the pendulum, down quite to the ground, the building
was exceedingly rent and damaged, and some stones in the
foundation-wall torn out and thrown to the distance of twenty or
thirty feet." The pendulum-rod was uninjured, but the fine wire
leading from the bell to the clock was vaporized except for about two
inches at each end.

Mr. James Alexander, of New York, having proposed to Franklin that the
velocity of the electric discharge might be measured by discharging a
jar through a long circuit of river-water, Franklin, in his reply,
explained that such an experiment, if successful, would not determine
the actual velocity of electricity in the conductor. He compared the
electricity in conductors to an incompressible fluid, so that when a
little additional fluid is injected at one end of a conductor, an
equal amount must be extruded at the other end--his view apparently
being identical with that of Maxwell, who held that all electric
displacements must take place _in closed circuits_.

"Suppose a tube of any length open at both ends.... If the tube be
filled with water, and I inject an additional inch of water at one
end, I force out an equal quantity at the other in the very same
instant.

"And the water forced out at one end of the tube is not the very same
water that was forced in at the other end at the same time; it was
only one motion at the same time.

"The long wire, made use of in the experiment to discover the velocity
of the electric fluid, is itself filled with what we call its natural
quantity of that fluid, before the hook of the Leyden bottle is
applied at one end of it.

"The outside of the bottle being at the time of such application in
contact with the other end of the wire, the whole quantity of electric
fluid contained in the wire is, probably, put in motion at once.

"For at the instant the hook, connected with the inside of the bottle,
_gives out_, the coating or outside of the bottle _draws in_, a
portion of that fluid....

"So that this experiment only shows the extreme facility with which
the electric fluid moves in metal; it can never determine the
velocity.

"And, therefore, the proposed experiment (though well imagined and
very ingenious) of sending the spark round through a vast length of
space, by the waters of Susquehannah, or Potowmack, and Ohio, would
not afford the satisfaction desired, though we could be sure that the
motion of the electric fluid would be in that tract, and not
underground in the wet earth by the shortest way."

In his investigations of the source of electricity in thunder-clouds,
Franklin tried an experiment which has been frequently repeated with
various modifications. Having insulated a large brass plate which had
been previously heated, he sprinkled water upon it, in order, if
possible, to obtain electricity by the evaporation of the water, but
no trace of electrification could be detected.

During his visit to England, Franklin wrote many letters to Mr.
Kinnersley and others on philosophical questions, but they consisted
mainly of accounts of the work done by other experimenters in England,
his public business occupying too much of his attention to allow him
to conduct investigations for himself. In one of his letters, speaking
of Lord Charles Cavendish, he says:--

    It were to be wished that this noble philosopher would
    communicate more of his experiments to the world, as he makes
    many, and with great accuracy.

When the controversy between the relative merits of points and knobs
for the terminals of lightning-conductors arose, Franklin wrote to Mr.
Kinnersley:--

    Here are some electricians that recommend knobs instead of
    points on the upper end of the rods, from a supposition that the
    points invite the stroke. It is true that points draw
    electricity at greater distances in the gradual silent way; but
    knobs will draw at the greatest distance a stroke. There is an
    experiment which will settle this. Take a crooked wire of the
    thickness of a quill, and of such a length as that, one end of
    it being applied to the lower part of a charged bottle, the
    upper may be brought near the ball on the top of the wire that
    is in the bottle. Let one end of this wire be furnished with a
    knob, and the other may be gradually tapered to a fine point.
    When the point is presented to discharge the bottle, it must be
    brought much nearer before it will receive the stroke than the
    knob requires to be. Points, besides, tend to repel the
    fragments of an electrical cloud; knobs draw them nearer. An
    experiment, which I believe I have shown you, of cotton fleece
    hanging from an electrized body, shows this clearly when a point
    or a knob is presented under it.

The following quotation from Franklin's paper on the method of
securing buildings and persons from the effects of lightning is worthy
of attention, for of late years a good deal of money has been wasted
in providing insulators for lightning-rods. A few years ago the vicar
and churchwardens of a Lincolnshire parish were strongly urged to go
to the expense of insulating the conductor throughout the whole height
of the very lofty tower and spire of their parish church. Happily they
were wise enough to send the lightning-rod man about his business. But
this is not the only case which has come under the writer's notice,
showing that there is still a widespread impression that
lightning-conductors should be carefully insulated. Franklin says:--

"The rod may be fastened to the wall, chimney, etc., with staples of
iron. The lightning will not leave the rod (a good conductor) to pass
into the wall (a bad conductor) through these staples. It would
rather, if any were in the wall, pass out of it into the rod, to get
more readily by that conductor into the earth."[2]

[Footnote 2: See p. 141.]

The conditions to be secured in a lightning-conductor are, firstly, a
sharp point projecting above the highest part of the building, and
gilded to prevent corrosion; secondly, metallic continuity from the
point to the lower end of the conductor; and, thirdly, a good
earth-contact. The last can frequently be secured by soldering the
conductor to iron water-pipes underground. Where these are not
available, a copper plate, two or three feet square, imbedded in clay
or other damp earth, will serve the purpose. The method of securing a
building which is erected on granite or other foundation affording no
good earth-connection, will be referred to in a subsequent
biographical sketch.

The controversy of points _versus_ knobs was again revived in London
when Franklin was in Paris, and the War of Independence had begun.
Franklin was consulted on the subject, the question having arisen in
connection with the conductor at the palace. His reply was
characteristic.

"As to my writing anything on the subject, which you seem to desire, I
think it not necessary, especially as I have nothing to add to what I
have already said upon it in a paper read to the committee who ordered
the conductors at Purfleet, which paper is printed in the last French
edition of my writings.

"I have never entered into any controversy in defence of my
philosophical opinions. I leave them to take their chance in the
world. If they are _right_, truth and experience will support them; if
_wrong_, they ought to be refuted and rejected. Disputes are apt to
sour one's temper and disturb one's quiet. I have no private interest
in the reception of my inventions by the world, having never made, nor
proposed to make, the least profit by any of them. The king's changing
his _pointed_ conductors for _blunt_ ones is, therefore, a matter of
small importance to me. If I had a wish about it, it would be that he
had rejected them altogether as ineffectual. For it is only since he
thought himself and family safe from the thunder of Heaven, that he
dared to use his own thunder in destroying his innocent subjects."

The paper referred to was read before "the committee appointed to
consider the erecting conductors to secure the magazines at Purfleet,"
on August 27, 1772. It described a variety of experiments clearly
demonstrating the effect of points in discharging a conductor. This
was a committee of the Royal Society, to whom the question had been
referred on account of Dr. Wilson's recommendation of a blunt
conductor. The committee decided in favour of Franklin's view, and
when, in 1777, the question was again raised and again referred to a
committee of the Royal Society, the decision of the former committee
was confirmed, "conceiving that the experiments and reasons made and
alleged to the contrary by Mr. Wilson are inconclusive."

Though Franklin's scientific reputation rests mainly on his electrical
researches, he did not leave other branches of science untouched.
Besides his work on atmospheric electricity, he devoted a great deal
of thought to meteorology, especially to the vortical motion of
waterspouts. The Gulf-stream received a share of his attention. His
improvements in fireplaces have already been noticed; the cure of
smoky chimneys was the subject of a long paper addressed to Dr.
Ingenhousz, and of some other letters. One of his experiments on the
absorption of radiant energy has been deservedly remembered.

"My experiment was this: I took a number of little square pieces of
broad-cloth from a tailor's pattern-card, of various colours. There
were black, deep blue, lighter blue, green, purple, red, yellow,
white, and other colours or shades of colours. I laid them all out
upon the snow in a bright, sun-shiny morning. In a few hours (I cannot
now be exact as to the time) the black, being warmed most by the sun,
was sunk so low as to be below the stroke of the sun's rays; the dark
blue almost as low, the lighter blue not quite so much as the dark,
the other colours less as they were lighter; and the quite white
remained on the surface of the snow, not having entered it at all.

"What signifies philosophy that does not apply to some use? May we not
learn from hence that black clothes are not so fit to wear in a hot,
sunny climate or season, as white ones?"

Franklin knew much about electricity, but his knowledge of human
nature was deeper still. This appears in all his transactions. His
political economy was, perhaps, not always sound, but his judgment of
men was seldom at fault.

"Finally, there seem to be but three ways for a nation to acquire
wealth. The first is by _war_, as the Romans did, in plundering their
conquered neighbour: this is _robbery_. The second by _commerce_,
which is generally _cheating_. The third by _agriculture_, the only
_honest way_, wherein man receives a real increase of the seed thrown
into the ground, in a kind of continual miracle wrought by the hand of
God in his favour, as a reward for his innocent life and his virtuous
industry."

When Franklin reached London in 1757 he took up his abode with Mrs.
Margaret Stevenson, in Craven Street, Strand. For Mrs. Stevenson and
her daughter Mary, then a young lady of eighteen, he acquired a
sincere affection, which continued throughout their lives. Miss
Stevenson spent much of her time with an aunt in the country, and some
of Franklin's letters to her respecting the conduct of her "higher
education" are among the most interesting of his writings. Miss
Stevenson treated him as a father, and consulted him on every question
of importance in her life. When she was a widow and Franklin eighty
years of age, he urged upon her to come to Philadelphia, for the sake
of the better prospects which the new country offered her boys. In
coming to England, Franklin brought with him his son William, who
entered the Middle Temple, but he left behind his only daughter,
Sarah, in charge of her mother. To his wife and daughter he
frequently sent presents from London, and his letters to Mrs. Franklin
give a pretty full account of all his doings while in England. During
his visit he received the honorary degrees of D.C.L. from the
University of Oxford, and LL.D. from that of Edinburgh. At Cambridge
he was sumptuously entertained. In August, 1762, he started again for
America, and reached Philadelphia on November 1, after an absence of
five years. His son William had shortly before been appointed Governor
of New Jersey. From this time William Franklin became very much the
servant of the proprietaries and of the English Government, but no
offer of patronage produced any effect on the father.

Franklin's stay in America was of short duration, but while there he
was mainly instrumental in quelling an insurrection in Pennsylvania.
He made a tour of inspection through the northern colonies in the
summer of 1763, to regulate the post-offices. The disorder just
referred to in the province caused the governor, as well as the
Assembly, to determine on the formation of a militia. A committee, of
which Franklin was a member, drew up the necessary bill. The governor
claimed the sole power of appointing officers, and required that
trials should be by court-martial, some offences being punishable with
death. The Assembly refused to agree to these considerations. The ill
feeling was increased by the governor insisting on taxing all
proprietary lands at the same rate as uncultivated land belonging to
other persons, whether the proprietary lands were cultivated or not.
The Assembly, before adjourning, expressed an opinion that peace and
happiness would not be secured until the government was lodged
directly in the Crown. When the Assembly again met, petitions to the
king came in from more than three thousand inhabitants. In the mean
while the British Ministry had proposed the Stamp Act, which was
similar in principle to the English Stamp Act, which requires that all
agreements, receipts, bills of exchange, marriage and birth
certificates, and all other legal documents should be provided with an
inland revenue stamp of a particular value, in order that they might
be valid. As soon as the Assembly was convened, it determined to send
Franklin to England, to take charge of a petition for a change of
government. The merchants subscribed £1100 towards his expenses in a
few hours, and in twelve days he was on his journey, being accompanied
to the ship, a distance of sixteen miles, by a cavalcade of three
hundred of his friends, and in thirty days he reached London. Arrived
in London, he at once took up his abode in his old lodgings with Mrs.
Stevenson. He was a master of satire, equalled only by Swift, and
during the quarrels which preceded the War of Independence, as well as
during the war, he made good use of his powers in this respect.
Articles appeared in some of the English papers tending to raise an
alarm respecting the competition of the colonies with English
manufacturers. Franklin's contribution to the discussion was a
caricature of the English press writers.

"It is objected by superficial readers, who yet pretend to some
knowledge of those countries, that such establishments [manufactories
for woollen goods, etc.] are not only improbable, but impossible, for
that their sheep have but little wool, not in the whole sufficient for
a pair of stockings a year to each inhabitant; that, from the
universal dearness of labour among them, the working of iron and other
materials, except in a few coarse instances, is impracticable to any
advantage.

"Dear sir, do not let us suffer ourselves to be amused with such
groundless objections. The very tails of the American sheep are so
laden with wool that each has a little car or waggon on four little
wheels to support and keep it from trailing on the ground. Would they
caulk their ships, would they even litter their horses with wool, if
it were not both plenty and cheap? And what signifies the dearness of
labour, when an English shilling passes for five and twenty? Their
engaging three hundred silk throwsters here in one week for New York
was treated as a fable, because, forsooth, they have 'no silk there to
throw!' Those who make this objection perhaps do not know that, at the
same time, the agents for the King of Spain were at Quebec, to
contract for one thousand pieces of cannon to be made there for the
fortification of Mexico, and at New York engaging the usual supply of
woollen floor-carpets for their West India houses. Other agents from
the Emperor of China were at Boston, treating about an exchange of raw
silk for wool, to be carried in Chinese junks through the Straits of
Magellan.

"And yet all this is as certainly true as the account said to be from
Quebec in all the papers of last week, that the inhabitants of Canada
are making preparations for a cod and whale fishery this summer in the
upper Lakes. Ignorant people may object that the upper Lakes are
fresh, and that cod and whales are salt-water fish; but let them know,
sir, that cod, like other fish when attacked by their enemies, fly
into any water where they can be safest; that whales, when they have a
mind to eat cod, pursue them wherever they fly; and that the grand
leap of the whale in the chase up the Falls of Niagara is esteemed, by
all who have seen it, as one of the finest spectacles in nature."

One of Franklin's chief objects in coming to England was to prevent
the passing of Mr. Grenville's bill, previously referred to as the
Stamp Act. The colonists urged that they had always been liberal in
their votes, whenever money was required by the Crown, and that
taxation and representation must, in accordance with the British
constitution, go hand-in-hand, so that the English Parliament had no
right to raise taxes in America, so long as the colonists were
unrepresented in Parliament. "Had Mr. Grenville, instead of that act,
applied to the king in Council for such requisitional letters [_i.e._
requests to the Assemblies for voluntary grants], to be circulated by
the Secretary of State, I am sure he would have obtained more money
from the colonies by their voluntary grants than he himself expected
from the sale of stamps. But he chose compulsion rather than
persuasion, and would not receive from their good will what he thought
he could obtain without it." The Stamp Act was passed, stamps were
printed, distributors were appointed, but the colonists would have
nothing to do with the stamps. The distributors were compelled to
resign their commissions, and the captains of vessels were forbidden
to land the stamped paper. The cost of printing and distributing
amounted to £12,000; the whole return was about £1500, from Canada and
the West Indies.

The passing of the Stamp Act was soon followed by a change of
Ministry, when the question again came before Parliament. Franklin
submitted to a long examination before a Committee of the whole House.
The feeling prevalent in America respecting the Stamp Act may be
inferred from some of his answers.

"31. _Q._ Do you think the people of America would submit to pay the
stamp duty if it was moderated?

"_A._ No, never, unless compelled by force of arms.

"36. _Q._ What was the temper of America towards Great Britain before
the year 1763?[3]

[Footnote 3: The date of the Sugar Act.]

"_A._ The best in the world. They submitted willingly to the
government of the Crown, and paid, in their courts, obedience to the
Acts of Parliament. Numerous as the people are in the several old
provinces, they cost you nothing in forts, citadels, garrisons, or
armies to keep them in subjection. They were governed by this country
at the expense only of a little pen, ink, and paper; they were led by
a thread. They had not only a respect, but an affection, for Great
Britain--for its laws, its customs and manners, and even a fondness
for its fashions, that greatly increased the commerce. Natives of
Britain were always treated with particular regard; to be an
_Old-Englandman_ was, of itself, a character of some respect, and gave
a kind of rank among us.

"37. _Q._ And what is their temper now?

"_A._ Oh, very much altered.

"50. _Q._ Was it an opinion in America before 1763 that the Parliament
had no right to lay taxes and duties there?

"_A._ I never heard any objection to the right of laying duties to
regulate commerce; but a right to lay internal taxes was never
supposed to be in Parliament, as we are not represented there.

"59. _Q._ You say the colonies have always submitted to external
taxes, and object to the right of Parliament only in laying internal
taxes; now, can you show that there is any kind of difference between
the two taxes to the colony on which they may be laid?

"_A._ I think the difference is very great. An _external_ tax is a
duty laid on commodities imported; that duty is added to the first
cost and other charges on the commodity, and, when it is offered to
sale, makes a part of the price. If the people do not like it at that
price, they refuse it; they are not obliged to pay it. But an
_internal_ tax is forced upon the people without their consent, if not
laid by their own representatives. The Stamp Act says we shall have no
commerce, make no exchange of property with each other, neither
purchase, nor grant, nor recover debts; we shall neither marry nor
make our wills, unless we pay such and such sums; and thus it is
intended to extort our money from us, or ruin us by the consequences
of refusing to pay it.

"61. _Q._ Don't you think cloth from England absolutely necessary to
them?

"_A._ No, by no means absolutely necessary; with industry and good
management they may very well supply themselves with all they want.

"62. _Q._ Will it not take a long time to establish that manufacture
among them? and must they not in the mean while suffer greatly?

"_A._ I think not. They have made a surprising progress already. And I
am of opinion that, before their old clothes are worn out, they will
have new ones of their own making.

"84. _Q._ If the Act is not repealed, what do you think will be the
consequence?

"_A._ A total loss of the respect and affection the people of America
bear to this country, and of all the commerce that depends on that
respect and affection.

"85. _Q._ How can the commerce be affected?

"_A._ You will find that, if the Act is not repealed, they will take a
very little of your manufactures in a short time.

"86. _Q._ Is it in their power to do without them?

"_A._ I think they may very well do without them.

"87. _Q._ Is it their interest not to take them?

"_A._ The goods they take from Britain are either necessaries, mere
conveniences, or superfluities. The first, as cloth, etc., with a
little industry they can make at home; the second they can do without
till they are able to provide them among themselves; and the last,
which are much the greatest part, they will strike off immediately.
They are mere articles of fashion, purchased and consumed because the
fashion in a respected country; but will now be detested and rejected.
The people have already struck off, by general agreement, the use of
all goods fashionable in mournings, and many thousand pounds' worth
are sent back as unsaleable.

"173. _Q._ What used to be the pride of the Americans?

"_A._ To indulge in the fashions and manufactures of Great Britain.

"174. _Q._ What is now their pride?

"_A._ To wear their old clothes over again till they can make new
ones."

The month following Franklin's examination, the repeal of the Stamp
Act received the royal assent. Thereupon Franklin sent his wife and
daughter new dresses, and a number of other little luxuries (or toilet
necessaries).

In 1767 Franklin visited Paris. In the same year his daughter married
Mr. Richard Bache. Though Parliament had repealed the Stamp Act, it
nevertheless insisted on its right to tax the colonies. The Duty Act
was scarcely less objectionable than its predecessor. On Franklin's
return from the Continent, he heard of the retaliatory measures of the
Boston people, who had assembled in town-meetings, formally resolved
to encourage home manufactures, to abandon superfluities, and, after a
certain time, to give up the use of some articles of foreign
manufacture. These _associations_ afterwards became very general in
the colonies, so that in one year the importations by the colonists of
New York fell from £482,000 to £74,000, and in Pennsylvania from
£432,000 to £119,000.

The effect of the Duty Act was to encourage the Dutch and other
nations to smuggle tea and probably other India produce into America.
The exclusion from the American markets of tea sent from England
placed the East India Company in great difficulties; for while they
were unable to meet their bills, they had in stock two million pounds'
worth of tea and other goods. The balance of the revenue collected
under the Duty Act, after paying salaries, etc., amounted to only £85
for the year, and for this a fleet had to be maintained, to guard the
fifteen hundred miles of American coast; while the fall in East India
Stock deprived the revenue of £400,000 per annum, which the East India
Company would otherwise have paid. At length a licence was granted to
the East India Company to carry tea into America, duty free. This, of
course, excluded all other merchants from the American tea-trade. A
quantity of tea sent by the East India Company to Boston was destroyed
by the people. The British Government then blockaded the port. This
soon led to open hostilities. Franklin worked hard to effect a
reconciliation. He drew up a scheme, setting forth the conditions
under which he conceived a reconciliation might be brought about, and
discussed it fully with Mr. Daniel Barclay and Dr. Fothergill. This
scheme was shown to Lord Howe, and afterwards brought before the
Ministry, but was rejected. Other plans were considered, and Franklin
offered to pay for the tea which had been destroyed at Boston. All his
negotiations were, however, fruitless. At last he addressed a memorial
to the Earl of Dartmouth, Secretary of State, complaining of the
blockade of Boston, which had then continued for nine months, and had
"during every week of its continuance done damage to that town, equal
to what was suffered there by the India Company;" and claiming
reparation for such injury beyond the value of the tea which had been
destroyed. The memorial also complained of the exclusion of the
colonists from the Newfoundland fisheries, for which reparation would
one day be required. This memorial was returned to Franklin by Mr.
Walpole, and Franklin shortly afterwards returned to Philadelphia.

During this visit to England he had lost his wife, who died on
December 19, 1774; and his friend Miss Stevenson had married and been
left a widow.

In April, 1768, Franklin was appointed Agent for Georgia, in the
following year for New Jersey, and in 1770 for Massachusetts, so that
he was then the representative in England of four colonies, with an
income of £1200 per annum.

In 1771 he spent three weeks at Twyford, with the Bishop of St. Asaph,
who remained a fast friend of Franklin's until his death. In 1772 he
was nominated by the King of France as Foreign Associate of the
Academy of Sciences.

During his negotiations with the British Government Franklin wrote two
satirical pieces, setting forth the treatment which the American
colonists were receiving. The first was entitled "Rules for Reducing a
Great Empire to a Small One," the rules being precisely those which,
in Franklin's opinion, had been followed by the British Government in
its dealings with America. The other was "An Edict by the King of
Prussia," in which the king claimed the right of taxing the British
nation; of forbidding English manufacture, and compelling Englishmen
to purchase Prussian goods; of transporting prisoners to Britain, and
generally of exercising all such controls over the English people as
had been claimed over America by various Acts of the English
Parliament, on the ground that England was originally colonized by
emigrants from Prussia.

Before Franklin reached America, the War of Independence, though not
formally declared, had fairly begun. He was appointed a member of the
second Continental Congress, and one of a committee of three to confer
with General Washington respecting the support and regulation of the
Continental Army. This latter office necessitated his spending some
time in the camp. On October 3, 1775, he wrote to Priestley:--

    Tell our dear good friend, Dr. Price, who sometimes has his
    doubts and despondencies about our firmness, that America is
    determined and unanimous; a very few Tories and placemen
    excepted, who will probably soon export themselves. Britain, at
    the expense of three millions, has killed a hundred and fifty
    Yankees this campaign, which is £20,000 a head; and at Bunker's
    Hill she gained a mile of ground, half of which she lost again
    by our taking the post on Ploughed Hill. During the same time
    sixty thousand children have been born in America. From these
    _data_ his mathematical head will easily calculate the time and
    expense necessary to kill us all and conquer our whole
    territory.

In 1776 Franklin, then seventy years old, was appointed one of three
Commissioners to visit Canada, in order, if possible, to promote a
union between it and the States. Finding that only one Canadian in
five hundred could read, and that the state of feeling in Canada was
fatal to the success of the Commissioners, they returned, and Franklin
suggested that the next Commission sent to Canada should consist of
schoolmasters. On the 4th of July Franklin took part in the signing of
the Declaration of Independence. When the document was about to be
signed, Mr. Hancock remarked, "We must be unanimous; there must be no
pulling different ways; we must all hang together." Franklin replied,
"Yes, we must indeed all hang together, or most assuredly we shall all
hang separately."

In the autumn of 1776 Franklin was unanimously chosen a Special
Commissioner to the French Court. He took with him his two grandsons,
William Temple Franklin and Benjamin Franklin Bache, and leaving
Marcus Hook on October 28, crossed the Atlantic in a sloop of sixteen
guns. In Paris he met with an enthusiastic reception. M. de Chaumont
placed at his disposal his house at Passy, then about a mile from
Paris, but now within the city. Here he resided for nine years, being
a constant visitor at the French Court, and certainly one of the most
conspicuous figures in Paris. He was obliged to serve in many
capacities, and was very much burdened with work. Not only were there
his duties as Commissioner at the French Court, but he was also made
Admiralty Judge and Financial Agent, so that all the coupons for the
payment of interest on the money borrowed for the prosecution of the
war, as well as all financial negotiations, either with the French
Government or contractors, had to pass through his hands. Perhaps the
most unpleasant part of his work was his continued applications to the
French Court for monetary advances. The French Government, as is well
known, warmly espoused the cause of the Americans, and to the utmost
of its ability assisted them with money, material, and men. Franklin
was worried a good deal by applications from French officers for
introductions to General Washington, that they might obtain employment
in the American Army. At last he framed a model letter of
recommendation, which may be useful to many in this country in the
present day. It was as follows:--

    SIR,

    The bearer of this, who is going to America, presses me to give
    him a letter of recommendation, though I know nothing of him,
    not even his name. This may seem extraordinary, but I assure you
    it is not uncommon here. Sometimes, indeed, one unknown person
    brings another equally unknown, to recommend him; and sometimes
    they recommend one another! As to this gentleman, I must refer
    you to himself for his character and merits, with which he is
    certainly better acquainted than I can possibly be. I recommend
    him, however, to those civilities which every stranger, of whom
    one knows no harm, has a right to; and I request you will do him
    all the good offices and show him all the favour that, on
    further acquaintance, you shall find him to deserve.

    "I have the honour to be," etc.

Captain Wickes, of the _Refusal_, having taken about a hundred British
seamen prisoners, Franklin and Silas Deane, one of the other
Commissioners, wrote to Lord Stormont, the British ambassador,
respecting an exchange. Receiving no answer, they wrote again, and
ventured to complain of the treatment which the American prisoners
were receiving in the English prisons, and in being compelled to fight
against their own countrymen. To this communication Lord Stormont
replied:--

    The king's ambassador receives no applications from rebels,
    unless they come to implore his Majesty's mercy.

To this the Commissioners rejoined:--

    In answer to a letter, which concerns some of the most material
    interests of humanity, and of the two nations, Great Britain and
    the United States of America, now at war, we received the
    enclosed _indecent_ paper, as coming from your Lordship, which
    we return for your Lordship's more mature consideration.

At first the British Government, regarding the Americans as rebels,
did not treat their prisoners as prisoners of war, but threatened to
try them for high treason. Their sufferings in the English prisons
were very great. Mr. David Hartley did much to relieve them, and
Franklin transmitted money for the purpose. When a treaty had been
formed between France and the States, and France had engaged in the
war, and when fortune began to turn in favour of the united armies,
the American prisoners received better treatment from the English
Government, and exchanges took place freely. In April, 1778, Mr.
Hartley visited Franklin at Passy, apparently for the purpose of
preventing, if possible, the offensive and defensive alliance between
America and France. Very many attempts were made to produce a rupture
between the French Government and the American Commissioners, but
Franklin insisted that no treaty of peace could be made between
England and America in which France was not included. In 1779 the
other Commissioners were recalled, and Franklin was made Minister
Plenipotentiary to the Court of France.

In a letter to Mr. David Hartley, dated February 2, 1780, Franklin
showed something of the feelings of the Americans with respect to the
English at that time:--

    You may have heard that accounts upon oath have been taken in
    America, by order of Congress, of the British barbarities
    committed there. It is expected of me to make a school-book of
    them, and to have thirty-five prints designed here by good
    artists, and engraved, each expressing one or more of the horrid
    facts, in order to impress the minds of children and posterity
    with a deep sense of your bloody and insatiable malice and
    wickedness. Every kindness I hear of done by an Englishman to an
    American prisoner makes me resolve not to proceed in the work.

While at Passy, Franklin addressed to the _Journal of Paris_ a paper
on an economical project for diminishing the cost of light. The
proposal was to utilize the sunlight instead of candles, and thereby
save to the city of Paris the sum of 96,075,000 livres per annum. His
reputation in Paris is shown by the following quotation from a
contemporary writer:--

    I do not often speak of Mr. Franklin, because the gazettes tell
    you enough of him. However, I will say to you that our Parisians
    are no more sensible in their attentions to him than they were
    towards Voltaire, of whom they have not spoken since the day
    following his death. Mr. Franklin is besieged, followed,
    admired, adored, wherever he shows himself, with a fury, a
    fanaticism, capable no doubt of flattering him and of doing him
    honour, but which at the same time proves that we shall never be
    reasonable, and that the virtues and better qualities of our
    nation will always be balanced by a levity, an inconsequence,
    and an enthusiasm too excessive to be durable.

Franklin always advocated free trade, even in time of war. He was of
opinion that the merchant, the agriculturist, and the fisherman were
benefactors to mankind. He condemned privateering in every form, and
endeavoured to bring about an agreement between all the civilized
powers against the fitting out of privateers. He held that no
merchantmen should be interfered with unless carrying war material. He
greatly lamented the horrors of the war, but preferred anything to a
dishonourable peace. To Priestley he wrote:--

    Perhaps as you grow older you may ... repent of having murdered
    in mephitic air so many honest, harmless mice, and wish that, to
    prevent mischief, you had used boys and girls instead of them.
    In what light we are viewed by superior beings may be gathered
    from a piece of late West India news, which possibly has not yet
    reached you. A young angel of distinction, being sent down to
    this world on some business for the first time, had an old
    courier-spirit assigned him as a guide. They arrived over the
    seas of Martinico, in the middle of the long day of obstinate
    fight between the fleets of Rodney and De Grasse. When, through
    the clouds of smoke, he saw the fire of the guns, the decks
    covered with mangled limbs and bodies dead or dying; the ships
    sinking, burning, or blown into the air; and the quantity of
    pain, misery, and destruction the crews yet alive were thus with
    so much eagerness dealing round to one another,--he turned
    angrily to his guide, and said, 'You blundering blockhead, you
    are ignorant of your business; you undertook to conduct me to
    the earth, and you have brought me into hell!' 'No, sir,' says
    the guide, 'I have made no mistake; this is really the earth,
    and these are men. Devils never treat one another in this cruel
    manner; they have more sense and more of what men (vainly) call
    humanity.'

Franklin maintained that it would be far cheaper for a nation to
extend its possessions by purchase from other nations than to pay the
cost of war for the sake of conquest.

Two British armies, under General Burgoyne and Lord Cornwallis, having
been wholly taken prisoners during the war, at last, after two years'
negotiations, a definitive treaty of peace was signed on September 3,
1782, between Great Britain and the United States, Franklin being one
of the Commissioners for the latter, and Mr. Hartley for the former.
On the same day a treaty of peace between Great Britain and France was
signed at Versailles. The United States Treaty was ratified by the
king on April 9, and therewith terminated the seven years' War of
Independence. Franklin celebrated the surrender of the armies of
Burgoyne and Cornwallis by a medal, on which the infant Hercules
appears strangling two serpents.

When peace was at length realized, a scheme was proposed for an
hereditary knighthood of the order of Cincinnatus, to be bestowed upon
the American officers who had distinguished themselves in the war.
Franklin condemned the hereditary principle. He pointed out that, in
the ninth generation, the "young noble" would be only "one five
hundred and twelfth part of the present knight," 1022 men and women
being counted among his ancestors, reckoning only from the foundation
of the knighthood. "Posterity will have much reason to boast of the
noble blood of the then existing set of Chevaliers of Cincinnatus."

On May 2, 1785, Franklin received from Congress permission to return
to America. He was then in his eightieth year. On July 12 he left
Passy for Havre, whence he crossed to Southampton, and there saw for
the last time his old friend, the Bishop of St. Asaph, and his family.
He reached his home in Philadelphia early in September, and the day
after his arrival he received a congratulatory address from the
Assembly of Pennsylvania. In the following month he was elected
President of the State, and was twice re-elected to the same office,
it being contrary to the constitution for any president to be elected
for more than three years in succession.

The following extract from a letter, written most probably to Tom
Paine, is worthy of the attention of some writers:--

    I have read your manuscript with some attention. By the argument
    it contains against a particular Providence, though you allow a
    general Providence, you strike at the foundations of all
    religion. For without the belief of a Providence that takes
    cognizance of, guards, and guides, and may favour particular
    persons, there is no motive to worship a Deity, to fear His
    displeasure, or to pray for His protection. I will not enter
    into any discussion of your principles, though you seem to
    desire it. At present I shall only give you my opinion, that,
    though your reasonings are subtle, and may prevail with some
    readers, you will not succeed so as to change the general
    sentiments of mankind on that subject, and the consequence of
    printing this piece will be a great deal of odium drawn upon
    yourself, mischief to you, and no benefit to others. He that
    spits against the wind spits in his own face.

    But were you to succeed, do you imagine any good would be done
    by it? You yourself may find it easy to live a virtuous life
    without the assistance afforded by religion; you having a clear
    perception of the advantages of virtue and the disadvantages of
    vice, and possessing strength of resolution sufficient to enable
    you to resist common temptations. But think how great a portion
    of mankind consists of weak and ignorant men and women, and of
    inexperienced, inconsiderate youth of both sexes, who have need
    of the motives of religion to restrain them from vice, to
    support their virtue, and retain them in the practice of it till
    it becomes _habitual_, which is the great point for its
    security. And perhaps you are indebted to her originally, that
    is, to your religious education, for the habits of virtue upon
    which you now justly value yourself. You might easily display
    your excellent talents of reasoning upon a less hazardous
    subject, and thereby obtain a rank with our most distinguished
    authors. For among us it is not necessary, as among the
    Hottentots, that a youth, to be raised into the company of men,
    should prove his manhood by beating his mother.

    I would advise you, therefore, not to attempt unchaining the
    tiger, but to burn this piece before it is seen by any other
    person; whereby you will save yourself a great deal of
    mortification by the enemies it may raise against you, and
    perhaps a good deal of regret and repentance. If men are so
    wicked _with religion_, what would they be _if without_ it? I
    intend this letter itself as a _proof_ of my friendship, and
    therefore add no _professions_ to it; but subscribe simply
    yours.

During the last few years of his life Franklin suffered from a painful
disease, which confined him to his bed and seriously interfered with
his literary work, preventing him from completing his biography.
During this time he was cared for by his daughter, Mrs. Bache, who
resided in the same house with him. He died on April 17, 1790, the
immediate cause of death being an affection of the lungs. He was
buried beside his wife in the cemetery of Christ Church, Philadelphia,
the marble slab upon the grave bearing no other inscription than the
name and date of death. In his early days (1728) he had written the
following epitaph for himself:--

    THE BODY

    OF

    BENJAMIN FRANKLIN,

    PRINTER,

    (LIKE THE COVER OF AN OLD BOOK,
    ITS CONTENTS TORN OUT
    AND STRIPT OF ITS LETTERING AND GILDING,)
    LIES HERE, FOOD FOR WORMS.
    BUT THE WORK SHALL NOT BE LOST,
    FOR IT WILL (AS HE BELIEVED) APPEAR ONCE MORE
    IN A NEW AND MORE ELEGANT EDITION,
    REVISED AND CORRECTED
    BY

    THE AUTHOR.

When the news of his death reached the National Assembly of France,
Mirabeau rose and said:--

"Franklin is dead!

"The genius, which gave freedom to America, and scattered torrents of
light upon Europe, is returned to the bosom of the Divinity.

"The sage, whom two worlds claim; the man, disputed by the history of
the sciences and the history of empires, holds, most undoubtedly, an
elevated rank among the human species.

"Political cabinets have but too long notified the death of those who
were never great but in their funeral orations; the etiquette of
courts has but too long sanctioned hypocritical grief. Nations ought
only to mourn for their benefactors; the representatives of free men
ought never to recommend any other than the heroes of humanity to
their homage.

"The Congress hath ordered a general mourning for one month throughout
the fourteen confederated States on account of the death of Franklin;
and America hath thus acquitted her tribute of admiration in behalf of
one of the fathers of her constitution.

"Would it not be worthy of you, fellow-legislators, to unite
yourselves in this religious act, to participate in this homage
rendered in the face of the universe to the rights of man, and to the
philosopher who has so eminently propagated the conquest of them
throughout the world?

"Antiquity would have elevated altars to that mortal who, for the
advantage of the human race, embracing both heaven and earth in his
vast and extensive mind, knew how to subdue thunder and tyranny.

"Enlightened and free, Europe at least owes its remembrance and its
regret to one of the greatest men who has ever served the cause of
philosophy and liberty.

"I propose, therefore, that a decree do now pass, enacting that the
National Assembly shall wear mourning during three days for Benjamin
Franklin."




HENRY CAVENDISH.


It would not be easy to mention two men between whom there was a
greater contrast, both in respect of their characters and lives, than
that which existed between Benjamin Franklin and the Honourable Henry
Cavendish. The former of humble birth, but of great public spirit,
possessed social qualities which were on a par with his scientific
attainments, and toward the close of his life was more renowned as a
statesman than as a philosopher; the latter, a member of one of the
most noble families of England, and possessed of wealth far exceeding
his own capacity for the enjoyment of it, was known to very few, was
intimate with no one, and devoted himself to scientific pursuits
rather for the sake of the satisfaction which his results afforded to
himself than from any hope that they might be useful to mankind, or
from any desire to secure a reputation by making them known, and
passed a long life, the most uneventful that can be imagined.

Though the records of his family may be traced to the Norman
Conquest, the famous Elizabeth Hardwicke, the foundress of two ducal
families and the builder of Hardwicke Hall and of Chatsworth as it was
before the erection of the present mansion, was the most remarkable
person in the genealogy. Her second son, William, was raised to the
peerage by James I., thus becoming Baron Cavendish, and was
subsequently created first Earl of Devonshire by the same monarch. His
great-grandson, the fourth earl, was created first Duke of Devonshire
by William III., to whom he had rendered valuable services. He was
succeeded by his eldest son in 1707, and the third son of the second
duke was Lord Charles Cavendish, the father of Henry and Frederick, of
whom Henry was the elder, having been born at Nice, October 13, 1731.
His mother died when he was two years old, and very little indeed is
known respecting his early life. In 1742 he entered Dr. Newcome's
school at Hackney, where he remained until he entered Peterhouse, in
1749. He remained at Cambridge until February, 1753, when he left the
university without taking his degree, objecting, most probably, to the
religious tests which were then required of all graduates. In this
respect his brother Frederick followed his example. On leaving
Cambridge Cavendish appears to have resided with his father in
Marlborough Street, and to have occasionally assisted him in his
scientific experiments, but the investigations of the son soon
eclipsed those of the father. It is said that the rooms allotted to
Henry Cavendish "were a set of stables, fitted up for his
accommodation," and here he carried out many of his experiments,
including all those electrical investigations in which he forestalled
so much of the work of the present century.

During his father's life, or, at any rate, till within a few years of
its close, Henry Cavendish appears to have enjoyed a very narrow
income. He frequently dined at the Royal Society Club, and on these
occasions would come provided with the five shillings to be paid for
the dinner, but no more. Upon his father's death, which took place in
1783, when Henry was more than fifty years of age, his circumstances
were very much changed, but it seems that the greater part of his
wealth was left him by an uncle who had been an Indian officer, and
this legacy may have come into his possession before his father's
death. He appears to have been very liberal when it was suggested to
him that his assistance would be of service, but it never occurred to
him to offer a contribution towards any scientific or public
undertaking, and though at the time of his death he is said to have
had more money in the funds than any other person in the country,
besides a balance of £50,000 on his current account at his bank, and
various other property, he bequeathed none to scientific societies or
similar institutions. Throughout the latter part of his life he seems
to have been quite careless about money, and to have been satisfied if
he could only avoid the trouble of attending to his own financial
affairs. Hence he would allow enormous sums to accumulate at his
banker's, and on one occasion, being present at a christening, and
hearing that it was customary for guests to give something to the
nurse, he drew from his pocket a handful of guineas, and handed them
to her without counting them. After his father's death, Cavendish
resided in his own house on Clapham Common. Here a few rooms at the
top of the house were made habitable; the rest were filled with
apparatus of all descriptions, among which the most numerous examples
were thermometers of every kind. He seldom entertained visitors, but
when, on rare occasions, a guest had to be entertained, the repast
invariably consisted of a leg of mutton. His extreme shyness caused
him to dislike all kinds of company, and he had a special aversion to
being addressed by a stranger. On one occasion, at a reception given
by Sir Joseph Banks, Dr. Ingenhousz introduced to him a distinguished
Austrian philosopher, who professed that his main object in coming to
England was to obtain a sight of so distinguished a man. Cavendish
listened with his gaze fixed on the floor; then, observing a gap in
the crowd, he made a rush to the door, nor did he pause till he had
reached his carriage. His aversion to women was still greater; his
orders for the day he would write out and leave at a stated time on
the hall-table, where his house-keeper, at another stated time, would
find them. Servants were allowed access to the portion of the house
which he occupied only at fixed times when he was away; and having
once met a servant on the stairs, a back staircase was immediately
erected. His regular walk was down Nightingale Lane to Wandsworth
Common, and home by another route. On one occasion, as he was crossing
a stile, he saw that he was watched, and thenceforth he took his walks
in the evening, but never along the same road. There were only two
occasions on which it is recorded that scientific men were admitted to
Cavendish's laboratory. The first was in 1775, when Hunter, Priestley,
Romayne, Lane, and Nairne were invited to see the experiments with the
artificial torpedo. The second was when his experiment on the
formation of nitric acid by electric sparks in air had been
unsuccessfully attempted by Van Marum, Lavoisier, and Monge, and he
"thought it right to take some measures to authenticate the truth of
it."

Besides his house at Clapham, Cavendish occupied (by his instruments)
a house in Bloomsbury, near the British Museum, while a "mansion" in
Dean Street, Soho, was set apart as a library. To this library a
number of persons were admitted, who could take out the books on
depositing a receipt for them. Cavendish was perfectly methodical in
all his actions, and whenever he borrowed one of his own books he duly
left the receipt in its place. The only relief to his solitary life
was afforded by the meetings of the Royal Society, of which he was
elected a Fellow in 1760; by the occasional receptions at the
residence of Sir Joseph Banks, P.R.S.; and by his not infrequent
dinners with the Royal Society Club at the Crown and Anchor; and he
may sometimes have joined the social gatherings of another club which
met at the Cat and Bagpipes, in Downing Street. It was to his visits
to the Royal Society Club that we are indebted for the only portrait
that exists of him. Alexander, the draughtsman to the China Embassy,
was bent upon procuring a portrait of Cavendish, and induced a friend
to invite him to the club dinner, "where he could easily succeed, by
taking his seat near the end of the table, from whence he could sketch
the peculiar great-coat of a greyish-green colour, and the remarkable
three-cornered hat, invariably worn by Cavendish, and obtain,
unobserved, such an outline of the face as, when inserted between the
hat and coat, would make, he was quite sure, a full-length portrait
that no one could mistake. It was so contrived, and every one who saw
it recognized it at once." Another incident is recorded of the Royal
Society Club which, perhaps, reflects as much credit upon Cavendish as
upon the Society. "One evening we observed a very pretty girl looking
out from an upper window on the opposite side of the street, watching
the philosophers at dinner. She attracted notice, and one by one we
got up and mustered round the window to admire the fair one.
Cavendish, who thought we were looking at the moon, hustled up to us
in his odd way, and when he saw the real object of our study, turned
away with intense disgust, and grunted out, 'Pshaw!'"

In the spring and autumn of 1785, 1786, 1787, and 1793, Cavendish made
tours through most of the southern, midland, and western counties, and
reached as far north as Whitby. The most memorable of these journeys
was that undertaken in 1785, since during its course he visited James
Watt at the Soho Works, and manifested great interest in Watt's
inventions. This was only two years after the great controversy as to
the discovery of the composition of water, but the meeting of the
philosophers was of the most friendly character. On all these journeys
considerable attention was paid to the geology of the country.

Allusion has already been made to the two committees of the Royal
Society to which the questions of the lightning-conductors at
Purfleet, and of points _versus_ knobs for the terminals of
conductors, were referred. Cavendish served on each of these
committees, and supported Franklin's view against the recommendation
of Mr. Wilson. On the first committee he probably came into personal
communication with Franklin himself.

Cavendish's life consisted almost entirely of his philosophical
experiments. In other respects it was nearly without incident. He
appears to have been so constituted that he must subject everything to
accurate measurement. He rarely made experiments which were not
_quantitative_; and he may be regarded as the founder of "quantitative
philosophy." The labour which he expended over some of his
measurements must have been very great, and the accuracy of many of
his results is marvellous considering the appliances he had at
disposal. When he had satisfied himself with the result of an
experiment, he wrote out a full account and preserved it, but very
seldom gave it to the public, and when he did publish accounts of any
of his investigations it was usually a long time after the experiments
had been completed. One of the consequences of his reluctance to
publish anything was the long controversy on the discovery of the
composition of water, which was revived many years afterwards by
Arago's _éloge_ on James Watt; but a much more serious result was the
loss to the world for so many years of discoveries and measurements
which had to be made over again by Faraday, Kohlrausch, and others.
The papers he published appeared in the _Philosophical Transactions of
the Royal Society_, to which he began to communicate them in 1766. On
March 25, 1803, he was elected one of the eight Foreign Associates of
the Institute of France. His _éloge_ was pronounced by Cuvier, in
1812, who said, "His demeanour and the modest tone of his writings
procured him the uncommon distinction of never having his repose
disturbed either by jealousy or by criticism." Dr. Wilson says, "He
was almost passionless. All that needed for its apprehension more than
the pure intellect, or required the exercise of fancy, imagination,
affection, or faith, was distasteful to Cavendish. An intellectual
head thinking, a pair of wonderfully acute eyes observing, and a pair
of very skilful hands experimenting or recording, are all that I
realize in reading his memorials." He appeared to have no eye for
beauty; he cared nothing for natural scenery, and his apparatus,
provided it were efficient, might be clumsy in appearance and of the
cheapest materials; but he was extremely particular about accuracy of
construction in all essential details. He reminds us of one of our
foremost men of science, who, when his attention was directed to the
beautiful lantern tower of a cathedral, behind which the full moon was
shining, remarked, "I see form and colour, but I don't know what you
mean by beauty."

The accounts of Cavendish's death differ to some extent in their
details, but otherwise are very similar. It appears that he requested
his servant, "as he had something particular to engage his thoughts,
and did not wish to be disturbed by any one," to leave him and not to
return until a certain hour. When the servant came back, at the time
appointed, he found his master dead. This was on February 24, 1810,
after an illness of only two or three days.

It is mainly on account of his researches in electricity that the
biography of Cavendish finds a place in this volume. These
investigations took place between the years 1760 and 1783, and, as
already stated, were all conducted in the stables attached to his
father's house in Marlborough Street. It was by these experiments that
electricity was first brought within the domain of measurement, and
many of the numerical results obtained far exceeded in accuracy those
of any other observer until the instruments of Sir W. Thomson rendered
many electrical measurements a comparatively easy matter. The near
agreement of Cavendish's results with those of the best modern
electricians has made them a perpetual monument to the genius of their
author. It was at the request of Sir W. Thomson, Mr. Charles
Tomlinson, and others, that Cavendish's electrical researches might be
given to the public, that the Duke of Devonshire, in 1874, entrusted
the manuscripts to the care of the late Professor Clerk Maxwell. They
had previously been in the hands of Sir William Snow Harris, who
reported upon them, but after his death, in 1867, the report could not
be found. The papers, with an introduction and a number of very
valuable notes by the editor, were published by the Cambridge
University Press, just before the death of Clerk Maxwell, in 1879. Sir
W. Thomson quotes the following illustration of the accuracy of
Cavendish's work:--"I find already that the capacity of a disc was
determined experimentally by Cavendish as 1/1·57 of that of a sphere
of the same radius. Now we have capacity of disc = (2/[pi])_a_ =
_a_/1·571!"

Cavendish adopted Franklin's theory of electricity, treating it as an
incompressible fluid pervading all bodies, and admitting of
displacement only in a closed circuit, unless, indeed, the disturbance
might extend to infinity. This fluid he supposed, with Franklin, to be
self-repulsive, but to attract matter, while matter devoid of
electricity, and therefore in the highest possible condition of
negative electrification, he supposed, with Æpinus, to be, like
electricity, self-repulsive. One of Cavendish's earliest experiments
was the determination of the precise law according to which electrical
action varies with the distance between the charges. Franklin had
shown that there was no sensible amount of electricity on the interior
of a deep hollow vessel, however its exterior surface might be
charged. Cavendish mounted a sphere of 12·1 inches in diameter, so
that it could be completely enclosed (except where its insulating
support passed through) within two hemispheres of 13·3 inches
diameter, which were carried by hinged frames, and could thus be
allowed to close completely over the sphere, or opened and removed
altogether from its neighbourhood. A piece of wire passed through one
of the hemispheres so as to touch the inner sphere, but could be
removed at pleasure by means of a silk string. The hemispheres being
closed with the globe within them, and the wire inserted so as to make
communication between the inner and outer spheres, the whole apparatus
was electrified by a wire from a charged Leyden jar. This wire was
then removed by means of a silken string and "the same motion of the
hand which drew away the wire by which the hemispheres were
electrified, immediately after that was done, drew out the wire which
made the communication between the hemispheres and the inner globe,
and, immediately after that was drawn out, separated the hemispheres
from each other," and applied the electrometer to the inner globe. "It
was also contrived so that the electricity of the hemispheres and of
the wire by which they were electrified was discharged as soon as they
were separated from each other.... The inner globe and hemispheres
were also both coated with tinfoil to make them the more perfect
conductors of electricity." The electrometer consisted of a pair of
pith-balls; but, though the experiment was several times repeated,
they shewed no signs of electrification. From this it was clear that,
as there could have been no communication between the globe and
hemispheres when the connecting wire was withdrawn, there must have
been no electrification on the globe while the hemispheres, though
themselves highly charged, surrounded it. To test the delicacy of the
experiment, a charge was given to the globe less than one-sixtieth of
that previously given to the hemispheres, and this was readily
detected by the electrometer. From the result Cavendish inferred that
there is no reason to think the inner globe to be at all charged
during the experiment. "Hence it follows that the electric attraction
and repulsion must be inversely as the square of the distance, and
that, when a globe is positively electrified, the redundant fluid in
it is lodged entirely on its surface." This conclusion Cavendish
showed to be a mathematical consequence of the absence of
electrification from the inner sphere; for, were the law otherwise,
the inner sphere must be electrified positively or negatively,
according as the inverse power were higher or lower than the second,
and that the accuracy of the experiment showed the law must lie
between the 2-1/50 and the 1-49/50 power of the distance. With his
torsion-balance, Coulomb obtained the same law, but Cavendish's method
is much easier to carry out, and admits of much greater accuracy than
that of Coulomb. Cavendish's experiment was repeated by Dr.
MacAlister, under the superintendence of Clerk Maxwell, in the
Cavendish Laboratory, the absence of electrification being tested by
Thomson's quadrant electrometer, and it was shown that the deviation
from the law of inverse squares could not exceed one in 72,000.

The distinction between _electrical charge_ or _quantity of
electricity_ and "_degree of electrification_" was first clearly made
by Cavendish. The latter phrase was subsequently replaced by
_intensity_, but _electric intensity_ is now used in another sense.
Cavendish's phrase, _degree of electrification_, corresponds precisely
with our notion of electric _potential_, and is measured by the work
done on a unit of electricity by the electric forces in removing it
from the point in question to the earth or to infinity. Along with
this notion Cavendish introduced the further conception of the amount
of electricity required to raise a conductor to a given degree of
electrification, that is, the capacity of the conductor. In modern
language, the _capacity_ of a conductor is defined as "the number of
units of electricity required to raise it to unit potential;" and this
definition is in precise accordance with the notion of Cavendish, who
may be regarded as the founder of the mathematical theory of
electricity. Finding that the capacities of similar conductors are
proportional to their linear dimensions, he adopted a sphere of one
inch diameter as the unit of capacity, and when he speaks of a
capacity of so many "inches of electricity," he means a capacity so
many times that of his one-inch sphere, or equal to that of a sphere
whose diameter is so many inches. The modern unit of capacity in the
electro-static system is that of a sphere of _one centimetre radius_,
and the capacity of any sphere is numerically equal to its radius
expressed in centimetres. Cavendish determined the capacities of
nearly all the pieces of apparatus he employed. For this purpose he
prepared plates of glass, coated on each side with circles of tinfoil,
and arranged in three sets of three, each plate of a set having the
same capacity, but each set having three times the capacity of the
preceding. There was also a tenth plate, having a capacity equal to
the whole of the largest set. The capacity of the ten plates was thus
sixty-six times that of one of the smallest set. With these as
standards of comparison, he measured the capacities of his other
apparatus, and, when possible, modified his conductors so as to make
them equal to one of his standards. His large Leyden battery he found
to have a capacity of about 321,000 "inches of electricity," so that
it was equivalent to a sphere more than five miles in diameter. One of
his instruments employed in the measurement of capacities was a "trial
plate," consisting of a sheet of metal, with a second sheet which
could be made to slide upon it and to lie entirely on the top of the
larger plate, or to rest with any portion of its area extending over
the edge of the former. This was a conductor whose capacity could be
varied at will within certain limits. Finding the capacity of two
plates of tinfoil on glass much greater than his calculations led him
to expect, Cavendish compared them with two equal plates having air
between, and found their capacity very much to exceed that of the air
condenser. The same was the case, though in a less degree, with
condensers having shellac or bee's-wax for their dielectrics, and thus
Cavendish not only discovered the property to which Faraday afterwards
gave the name of "specific inductive capacity," but determined its
measure in these dielectrics. He also discovered that the apparent
capacity of a Leyden jar increases at first for some time after it has
been charged--a phenomenon connected with the so-called residual
charge of the Leyden jar. Another feature on which he laid some
stress, and which was brought to his notice by the comparison of his
coated panes, was the creeping of electricity over the surface of the
glass beyond the edge of the tinfoil, which had the same effect on the
capacity as an increase in the dimensions of the tinfoil. The
electricity appeared to spread to a distance of 0·07 inch all round
the tinfoil on glass plates whose thickness was 0·21 inch, and 0·09
inch in the case of plates 0·08 inch thick.

His paper on the torpedo was read before the Royal Society in 1776.
The experiments were undertaken in order to determine whether the
phenomena observed by Mr. John Walsh in connection with the torpedo
could be so far imitated by electricity as to justify the conclusion
that the shock of the torpedo is an electric discharge. For this
purpose Cavendish constructed a wooden torpedo with electrical organs,
consisting of a pewter plate on each side, covered with leather. The
plates were connected with a charged Leyden battery, by means of wires
carried in glass tubes, and thus the battery was discharged through
the water in which the torpedo was immersed, and which was rendered of
about the same degree of saltness as the sea. Cavendish compared the
shock given through the water with that given by the model fish in
air, and found the difference much greater than in the case of the
real torpedo, but, by increasing the capacity of the battery and
diminishing the potential to which it was charged, this discrepancy
was diminished, and it was found to be very much less in the case of a
second model having a leather, instead of a wooden, body, so that the
body of the fish itself offered less resistance to the discharge. One
of the chief difficulties lay in the fact that no one had succeeded in
obtaining a visible spark from the discharge of the torpedo, which
will not pass through the smallest thickness of air. Cavendish
accounted for this by supposing the quantity of electricity discharged
to be very great, and its potential very small, and showed that the
more the charge was increased and the potential diminished in his
model, the more closely did it imitate the behaviour of the torpedo.

But the main interest in this paper lies in the indications which it
gives that Cavendish was aware of the laws which regulate the flow of
electricity through multiple conductors, and in the comparisons of
electrical resistance which are introduced. It had been formerly
believed that electricity would always select the shortest or best
path, and that the whole of the discharge would take place along that
route. Franklin seems to have assumed this in the passage quoted[4]
respecting the discharge of the lightning down the uninsulated
conductor instead of through the building. The truth, however, is
that, when a number of paths are open to an electric current, it will
divide itself between them in the inverse ratios of their resistances,
or directly as their conductivities, so that, however great the
resistance of one of the conductors, some portion, though it may be a
very small fraction, of the discharge will take place through it. But
this law does not hold in the case of insulators like the air, through
which electricity passes only by disruptive discharges, and which
completely prevent its passage unless the electro-motive force is
sufficient to break through their substance. In the case of the
lightning-conductor, however, its resistance is generally so small in
comparison with that of the building it is used to protect, that
Franklin's conclusion is practically correct.

[Footnote 4: Page 96.]

In his paper on the torpedo Cavendish stated that some experiments had
shown that iron wire conducted 400,000,000 times better than rain or
distilled water, sea-water 100 times, and saturated solution of
sea-salt about 720 times, better than rain-water. Maxwell pointed out
that this comparison of iron wire with sea-water would agree almost
precisely with the measurements of Matthiesen and Kohlrausch at 11°C.
The records of the experiments which led to these results were found
among Cavendish's unpublished papers, and the experiments also showed
that the conductivity of saline solutions was very nearly proportional
to the percentage of salt contained, when this was not very large--a
result also obtained long afterwards by Kohlrausch. In making these
measurements Cavendish was his own galvanometer. The solutions were
contained in glass tubes more than three feet long, and a wire
inserted to different distances into the solution; thus the discharge
could be made to pass through any length of the liquid column less
than that of the tube itself. From the Leyden battery of forty-nine
jars, six jars of nearly equal capacity were selected and charged
together, and the charge of one jar only was employed for each shock.
The discharge passed through the column of liquid contained in the
tube, from a wire inserted at the further end, until it reached the
sliding wire, when nearly the whole current betook itself to the wire
on account of its smaller resistance, and thence passed through the
galvanometer, which was Cavendish himself. Two tubes were generally
compared together, and the jars discharged alternately through the
tubes, and the tube which gave the greatest shock was assumed to
possess the least resistance. The wires were then adjusted till the
shocks were nearly equal, and positions determined which made the
first tube possess a greater and then a less resistance than the
second. From these positions the length of the column of liquid was
estimated which would make the resistances of the two tubes exactly
equal. But the result which has the greatest theoretical interest was
obtained by discharging the Leyden jars through wide and narrow tubes
containing the same solutions. By these experiments Cavendish found
that the resistances of the conductors were independent of the
strengths of the currents flowing in them; that is to say, he
established Ohm's law for electrolytes in a form which carried with it
its full explanation. This was in January, 1781. Ohm's law was first
formally stated in 1827. The physical fact which is expressed by it is
that the ratio of the electro-motive force to the current produced is
the same for the same conductor, otherwise under the same physical
conditions, however great or small that electro-motive force may be.

Cavendish devoted considerable attention to the subject of heat,
especially thermometry. In many of his investigations on latent and
specific heat he worked on the same lines as Black, and at about the
same time; but it is difficult to determine the exact date of some of
Cavendish's work, as he frequently did not publish it for a long time
after its completion, and most of Black's results were made public
only to his lecture audience. Cavendish, however, improved upon Black
in his mode of stating some of his results. The heat, for instance,
which is absorbed by a body in passing from the solid to the liquid,
or from the liquid to the gaseous, condition, Black called "latent
heat," and supposed it to become latent within the substance, ready to
reveal itself when the body returned to its original condition. This
heat Cavendish spoke of as being _destroyed_ or _generated_, and this
is in accordance with what we now know respecting the nature of heat,
for when a body passes from the solid to the liquid, or from the
liquid or solid to the gaseous, condition, a certain amount of work
has to be done, and a corresponding amount of heat is used up in the
doing of it. When the body returns to its original condition, the heat
is restored, as when a heavy body falls to the ground, or a bent
spring returns to its original form. Cavendish's determination of the
so-called latent heat of steam was very slightly in error.

About 1760 very extraordinary beliefs were current respecting the
excessive degree of cold and the rapid variations of temperature which
take place in the Arctic regions. Braun, of St. Petersburg, had
observed that mercury, in solidifying in the tube of a thermometer,
descended through more than four hundred degrees, and it was assumed
that the melting point of mercury was about 400° below Fahrenheit's
zero. It then became necessary to suppose that, while the mercury in a
thermometer was freezing, there was a variation of temperature to this
extent, and thus these wild reports became current. Cavendish and
Black independently explained the anomaly, and each suggested the same
method of determining the freezing point of mercury. Cavendish,
however, had a piece of apparatus prepared which he sent to Governor
Hutchins, at Albany Fort, Hudson's Bay. It consisted of an outer
vessel, in which the mercury was allowed to freeze, but not throughout
the whole of its mass, and the bulb of the thermometer was kept
immersed in the liquid metal in the interior. In this way the mercury
in the thermometer was cooled down to the melting point without
commencing to solidify, and the temperature was found to be between
39° and 40° below Fahrenheit's zero.

As a chemist, Cavendish is renowned for his eudiometric analysis,
whereby he determined the percentage of oxygen in air with an amount
of accuracy that would be creditable to a chemist of to-day, and for
his discovery of the composition of water; but to the world generally
he is perhaps best known by the famous "Cavendish experiment" for
determining the mass, and hence the mean density, of the earth. The
apparatus was originally suggested by the Rev. John Michell, but was
first employed by Cavendish, who thereby determined the mean density
of the earth to be 5·45. At the request of the Astronomical Society,
the investigation was afterwards taken up by Mr. Francis Baily, who,
after much labour, discovered that the principal sources of error were
due to radiation of heat, and consequent variation of temperature of
parts of the apparatus during the experiment. To minimize the
radiation and absorption, he gilded the principal portions of the
apparatus and the interior of the case in which it was contained, and
his results then became consistent. Cavendish had himself suggested
the cause of the discrepancy, but the gilding was proposed by
Principal Forbes. As a mean of many hundreds of experiments, Mr. Baily
deduced for the mean density of the earth 5·6604. Cavendish's
apparatus was a delicate torsion-balance, whereby two leaden balls
were supported upon the extremities of a wooden rod, which was
suspended by a thin wire. These balls were about two inches in
diameter, and the experiment consisted in determining the deflection
of the wooden arm by the attraction of two large solid spheres of lead
brought very near the balls, and so situated that the attraction of
each tended to twist the rod horizontally in the same direction. The
force required to produce the observed deflection was calculated from
the time of swing of the rod and balls when left to themselves. The
force exerted upon either ball by a known spherical mass of metal,
with its centre at a known distance, being thus determined, it was
easy to calculate what mass, having its centre at the centre of the
earth, would be required to attract one of the balls with the force
with which the earth was known to attract it.

Dr. Wilson sums up Cavendish's view of life in these words:--

    His theory of the universe seems to have been that it consisted
    _solely_ of a multitude of objects which could be weighed,
    numbered, and measured; and the vocation to which he considered
    himself called was to weigh, number, and measure as many of
    these objects as his allotted three score years and ten would
    permit. This conviction biased all his doings--alike his great
    scientific enterprises and the petty details of his daily life.
    [Greek: _Panta metrô, kai arithmô, kai stathmô_], was his motto;
    and in the microcosm of his own nature he tried to reflect and
    repeat the subjection to inflexible rule and the necessitated
    harmony which are the appointed conditions of the macrocosm of
    God's universe.




COUNT RUMFORD.


Benjamin Thompson, like Franklin, was a native of Massachusetts, his
ancestors for several generations having been yeomen in that province,
and descendants of the first colonists of the Bay. In the diploma of
arms granted him when he was knighted by George III., he is described
as "son of Benjamin Thompson, late of the province of Massachusetts
Bay, in New England, gent." He was born in the house of his
grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26,
1753. His father died at the age of twenty-six, on November 7, 1754,
leaving the infant Benjamin and his mother to the care of the
grandparents. The widow married Josiah Pierce, junior, in March, 1756,
and with her child, now a boy of three, went to live in a house but a
short distance from her former residence.

Young Thompson appears to have received a sound elementary education
at the village school. From some remarks made by him in after years
to his friend, M. Pictet, it has been inferred that he did not receive
very kind treatment at the hands of his stepfather. It is clear,
however, that the most affectionate relationships always obtained
between him and his mother, and the latter appears to have had no
cause to complain of the treatment she received from her second
husband, with whom she lived to a very good old age. That Thompson in
early boyhood developed some tendencies which did not meet with ready
sympathy from those around him is, however, equally clear. His
guardians destined him for a farmer, like his ancestors, and his
experiments in mechanics, which took up much of his playtime and in
all probability not a few hours which should have been devoted to less
interesting work, were not regarded as tending towards the end in
view. Hence he was probably looked upon as "indolent, flighty, and
unpromising." Later on he was sent to school in Byfield, and in 1764,
at the age of eleven, "was put under the tuition of Mr. Hill, an able
teacher in Medford, a town adjoining Woburn." At length, his friends
having given up all hope of ever making a farmer of the boy, he was
apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an
importer of British goods and dealer in miscellaneous articles. He
lived with his master, and seems to have done his work in a manner
satisfactory on the whole, but there is evidence that he would, during
business hours, occupy his spare moments with mechanical contrivances,
which he used to hide under the counter, and even ventured
occasionally to practise on his fiddle in the store. He stayed with
Mr. Appleton till the autumn of 1769, and during this time he attended
the ministry of the Rev. Thomas Barnard. This gentleman seems to have
taken great interest in the boy, and to have taught him mathematics,
so that at the age of fifteen he was able "to calculate an eclipse,"
and was delighted when the eclipse commenced within six seconds of his
calculated time. Thompson, while an apprentice, showed a great faculty
for drawing and designing, and used to carve devices for his friends
on the handles of their knives or other implements. It was at this
time he constructed an elaborate contrivance to produce perpetual
motion, and on one evening it is said that he walked from Salem to
Woburn, to show it to Loammi Baldwin, who was nine years older than
himself, but his most intimate friend. Like many other devices
designed for the same purpose, it had only one fault--it wouldn't go.

It was in 1769, while preparing fireworks for the illumination on the
abolition of the Stamp Act, that Thompson was injured by a severe
explosion as he was grinding his materials in a mortar. His note-book
contained many directions for the manufacture of fireworks.

During Thompson's apprenticeship those questions were agitating the
public mind which finally had their outcome in the War of
Independence. Mr. Appleton was one of those who signed the agreement
refusing to import British goods, and this so affected the trade of
the store that he had no further need for the apprentice. Hence it was
that, in the autumn of 1769, Thompson went to Boston as
apprentice-clerk in a dry goods store, but had to leave after a few
months, through the depression in trade consequent on the
non-importation agreement.

His note-book, containing the entries made at this time, comprised
several comic sketches very well drawn, and a quantity of business
memoranda which show that he was very systematic in keeping his
accounts. His chief method of earning money, or rather of making up
the "Cr." side of his accounts, was by cutting and cording wood. A
series of entries made in July and August, 1771, show the expense he
incurred in constructing an electrical machine. It is not easy to
determine, from the list of items purchased, the character of the
machine he constructed; but it is interesting to note that the price
in America at that time of nitric acid was _2s. 6d._ per ounce; of
lacquer, _40s._ per pint; of shellac, _5s._ per ounce; brass wire,
_40s._ per pound; and iron wire, _1s. 3d._ per yard. The nature of the
problems which occupied his thoughts during the last year or two of
his business life are apparent in the following letters:--

    Woburn, August 16, 1769.

    Mr. Loammi Baldwin,

    SIR,

    Please to inform me in what manner fire operates upon clay to
    change the colour from the natural colour to red, and from red
    to black, etc.; and how it operates upon silver to change it to
    blue.

    I am your most humble and obedient servant,

    BENJAMIN THOMPSON

    God save the king.


    Woburn, August, 1769.

    Mr. Loammi Baldwin,

    SIR,

    Please to give the nature, essence, beginning of existence, and
    rise of the wind in general, with the whole theory thereof, so
    as to be able to answer all questions relative thereto.

    Yours,

    BENJAMIN THOMPSON.

This was an extensive request, and the reply was probably not
altogether satisfactory to the inquirer. On the back of the above
letter was written:--

    Woburn, August 15, 1769.

    SIR,

    There was but few beings (for inhabitants of this world) created
    before the airy element was; so it has not been transmitted down
    to us how the Great Creator formed the matter thereof. So I
    shall leave it till I am asked only the Natural Cause, and why
    it blows so many ways in so short a time as it does.

Thompson appears now to have given up business and commenced the study
of medicine under Dr. Hay, to whom for a year and a half he paid
forty shillings per week for his board. During this time he paid part
of his expenses by keeping school for a few weeks consecutively at
Wilmington and Bradford, and another part was paid by cords of wood.
His business capacity, as well as his dislike of ordinary work, is
shown by some arrangements which he made for getting wood cut and
corded at prices considerably below those at which he was himself paid
for it. His note-book made at this time contains, besides business
entries, several receipts for medicines and descriptions of surgical
operations, in some cases illustrated by sketches. In his work he was
methodical and industrious, and the life of a medical student suited
his genius far better than that of a clerk in a dry goods store. When
teaching at Wilmington he seems to have attracted attention by the
gymnastic performances with which he exercised both himself and his
pupils. While a student with Dr. Hay, he attended some of the
scientific lectures at Harvard College. The pleasure and profit which
he derived from these lectures are sufficiently indicated by the fact
that forty years afterwards he made the college his residuary legatee.

Thompson won such a reputation as a teacher during the few weeks that
he taught in village schools in the course of his student life, that
he received an invitation from Colonel Timothy Walker to come to
Concord, in New Hampshire, on the Merrimack, and accept a permanent
situation in a higher grade school. It was from this place that he
afterwards took his title, for the early name of Concord was Rumford,
and the name was changed to Concord "to mark the restoration of
harmony after a long period of agitation as to its provincial
jurisdiction and its relation with its neighbours."

The young schoolmaster of Concord was soon on very intimate terms with
the minister of the town, the Rev. Timothy Walker,[5] a man who was so
much respected that he had thrice been sent to Britain on diplomatic
business. Mr. Walker's daughter had been married to Colonel Rolfe, a
man of wealth and position, and, with the exception of the Governor of
Portsmouth, said to have been the first man in New Hampshire to drive
a curricle and pair of horses. Thompson soon married--or, as he told
Pictet, was married to--the young widow. Whatever may have been
implied by this other way of putting the question, there is no doubt
that Thompson always had the greatest possible respect for his
father-in-law, and ever remembered him with sincere gratitude. The
fortunes of the gallant young schoolmaster now appeared to be made;
when the engagement was settled, the carriage and pair were brought
out again, and the youth was attired in his favourite scarlet as a man
of wealth and position. In this garb he drove to Woburn, and
introduced his future wife to his mother, whose surprise can be better
imagined than described.

[Footnote 5: Father of the colonel.]

The exact date of Thompson's marriage is not known. His daughter
Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion
on October 18, 1774. It is needless to say that the engagement to Mrs.
Rolfe terminated the teaching at the school.

Thompson now had a large estate and ample means to improve it. He gave
much attention to gardening, and sent to England for garden seeds. In
some way he attracted the attention of Governor Wentworth, the
Governor of Portsmouth, who invited him to the Government House, and
was so taken with the former apprentice, medical student, and
schoolmaster, that he gave him at once a commission as major. This
appointment was the cause of the misfortunes which almost
immediately began to overtake him. He incurred the jealousy of his
fellow-officers, over whom he had been appointed, and he failed to
secure the confidence of the civilians of Concord.

Public feeling in New England was very much excited against the mother
country. Representations were sent to the British Government, but
appeared to be treated with contempt. Very many of these documents
were found, after the war was over, unopened in drawers at the
Colonial Office. British ministers appeared to know little about the
needs of their American dependencies, and relations rapidly became
more and more strained. The patriots appointed committees to watch
over the patriotism of their fellow-townsmen, and thus the freedom of
a free country was inaugurated by an institution bordering in
character very closely upon the Inquisition; and the Committees of
Correspondence and Safety accepted evidence from every spy or
eavesdropper who came before them with reports of suspected persons.
Thompson was accused of "Toryism;" the only definite charge against
him being that he had secured remission of punishment for some
deserters from Boston who had for some time worked upon his estate. He
was summoned before the Committee of Safety, but refused to make any
confession of acts injurious to his country, on the ground that he had
nothing to confess. His whole after-life shows that his sympathies
were very much on the side of monarchy and centralization, but at this
time there appears to have been no evidence that could be brought
against him. The populace, however, stormed his house, and he owed his
safety to the fact that he had received notice of their intentions,
and had made his escape a few hours before. This was in November,
1774. Thompson then took refuge at Woburn, with his mother, but the
popular ill feeling troubled him here, so that his life was one of
great anxiety.

While at Woburn, his wife and child joined him, and stayed there for
some months. At length he was arrested and confined in the town upon
suspicion of being inimical to the interests of his country. When he
was brought before the Committee of Inquiry, there was no evidence
brought against him. Major Thompson then petitioned to be heard
before the Committee of the Provincial Congress at Washington. This
petition he entrusted to his friend Colonel Baldwin to present. The
petition was referred by the committee to Congress, by whom it was
deferred for the sake of more pressing business. At length he secured
a hearing in his native town, but the result was indecisive, and he
did not obtain the public acquittal that he desired, though the
Committee of Correspondence found that the "said Thompson" had not "in
any one instance shown a disposition unfriendly to American liberty;
but that his general behaviour has evinced the direct contrary; and as
he has now given us the strongest assurances of his good intentions,
we recommend him to the friendship, confidence, and protection of all
good people in this and the neighbouring provinces." This decision,
however, does not appear to have been made public; and Thompson, on
his release, retired to Charlestown, near Boston. When the buildings
of Harvard College were converted into barracks, Major Thompson
assisted in the transfer of the books to Concord. It is said that,
after the battle of Charlestown, Thompson was introduced to General
Washington, and would probably have received a commission under him
but for the opposition of some of the New Hampshire officers. He
afterwards took refuge in Boston, and it does not appear that he ever
again saw his wife or her father. His daughter he did not see again
till 1796, when she was twenty-two years of age. On March 24, 1776,
General Washington obliged the British troops to evacuate Boston;
Thompson was the first official bearer of this intelligence to London.
Of course, his property at Concord was confiscated to the commonwealth
of Massachusetts, and he himself was proscribed in the Alienation Act
of New Hampshire, in 1778.

When Thompson reached London with the intelligence of the evacuation
of Boston, Lord George Germaine, the Secretary for War, saw that he
could afford much information which would be of value to the
Government. An appointment was soon found for him in the Colonial
Office, and afterwards he was made Secretary of the Province of
Georgia, in which latter capacity, however, he had no duties to
fulfil. Throughout his career in the Colonial Office he remained on
very intimate terms with Lord George Germaine, and generally
breakfasted with him. In July, 1778, he was guest of Lord George at
Stoneland Lodge, and here, in company with Mr. Ball, the Rector of
Withyham, he undertook experiments "to determine the most advantageous
situation for the vent in firearms, and to measure the velocities of
bullets and the recoil under various circumstances."

The results of these investigations procured for him the friendship of
Sir Joseph Banks, the President of the Royal Society, and Thompson was
not the man to lose opportunities for want of making use of them. In
1779 he was elected a Fellow of the Royal Society, "as a gentleman
well versed in natural knowledge and many branches of polite
learning." In the same year he went for a cruise in the _Victory_ with
Sir Charles Hardy, in order to pursue his experiments on gunpowder
with heavy guns. Here he studied the principles of naval artillery,
and devised a new code of marine signals. In 1780 he was made
Under-Secretary of State for the Northern Department, and in that
capacity had the oversight of the transport and commissariat
arrangements for the British forces.

On the defeat of Cornwallis, Lord George Germaine and his department
had to bear the brunt of Parliamentary dissatisfaction. Lord George
resigned his position in the Government, and was created Viscount
Sackville. He had, however, previously conferred on Thompson a
commission as lieutenant-colonel in the British army, and Thompson,
probably foreseeing the outcome of events and its effect on the
Ministry, was already in America when Lord George resigned. He had
intended landing at New York, but contrary winds drove him to
Charlestown. It is needless to trace the sad events which preceded the
end of the war. It was to be expected that many bitter statements
would be made by his countrymen respecting Thompson's own actions as
colonel commanding a British garrison, for at length he succeeded in
reaching Long Island, and taking the command of the King's American
Dragoons, who were there awaiting him. The spirit of war always acts
injuriously on those exposed to its influence, and Lieutenant-Colonel
Thompson in Long Island was doubtless a very different man from that
which we find him to have been before and after; nor were the months
so spent very fruitful in scientific work.

In 1783, before the final disbanding of the British forces, Thompson
returned to England, and was promoted to the rank of colonel, with
half-pay for the rest of his life. Still anxious for military service,
he obtained permission to travel on the Continent, in hopes of serving
in the Austrian army against the Turks. He took with him three English
horses, which rendered themselves very objectionable to his
fellow-travellers while crossing the Channel in a small boat. Thompson
went to Strasbourg, where he attracted the attention of the Prince
Maximilian, then Field-Marshal of France, but afterwards Elector of
Bavaria. On leaving Strasbourg, the prince gave him an introduction to
his uncle, the Elector of Bavaria. He stayed some days at Munich, but
on reaching Vienna learned that the war against the Turks would not be
carried on, so he returned to Munich, and thence to England.

M. Pictet gives the following as Rumford's account of the manner in
which he was cured of his passion for war:--

"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I
was cured in season of this martial folly. I met, at the house of the
Prince de Kaunitz, a lady, aged seventy years, of infinite spirit and
full of information. She was the wife of General Bourghausen. The
emperor, Joseph II., came often to pass the evening with her. This
excellent person conceived a regard for me; she gave me the wisest
advice, made my ideas take a new direction, and opened my eyes to
other kinds of glory than that of victory in battle.'"

If the course in life which Colonel Thompson afterwards took was due
to the advice of this lady, she deserves a European reputation. The
Elector of Bavaria, Charles Theodore, gave Thompson a pressing
invitation to enter his service in a sort of semi-military and
semi-civil capacity, to assist in reorganizing his dominions and
removing the abuses which had crept in. Before accepting this
appointment, it was necessary to obtain the permission of George III.
The king not only approved of the arrangement, but on February 23,
1784, conferred on the colonel the honour of knighthood. Sir Benjamin
then returned to Bavaria, and was appointed by the elector colonel of
a regiment of cavalry and general aide-de-camp. A palatial residence
in Munich was furnished for him, and here he lived more as a prince
than a soldier. It was eleven years before he returned, even on a
visit, to England, and these years were spent by him in works of
philanthropy and statesmanship, to which it is difficult to find a
parallel. At one time he is found reorganizing the military system of
the country, arranging a complete system of military police, erecting
arsenals at Mannheim and Munich; at another time he is carrying out
scientific investigations in one of these arsenals; and then he is
cooking cheap dinners for the poor of the country.

One great evil of a standing army is the idleness which it develops in
its members, unfitting them for the business of life when their
military service is ended. Thompson commenced by attacking this evil.
In 1788 he was made major-general of cavalry and Privy Councillor of
State, and was put at the head of the War Department, with
instructions to carry out any schemes which he had developed for the
reform of the army and the removal of mendicity. Four years after his
arrival in Munich he began to put some of his plans into operation.
The pay of the soldiers was only threepence per day, and their
quarters extremely uncomfortable, while their drill and discipline
were unnecessarily irksome. Thompson set to work to make "soldiers
citizens and citizens soldiers." The soldier's pay, uniform, and
quarters were improved; the discipline rendered less irksome; and
schools in which the three R's were taught were connected with all the
regiments,--and here not only the soldiers, but their children as well
as other children, were taught gratuitously. Not only were the
soldiers employed in public works, and thus accustomed to habits of
industry, while they were enlivened in their work by the strains of
their own military bands, but they were supplied with raw material of
various kinds, and allowed, when not on duty, to manufacture various
articles and sell them for their own benefit--an arrangement which in
this country to-day would probably raise a storm of opposition from
the various trades. The garrisons were made permanent, so that
soldiers might all be near their homes and remain there, and in time
of peace only a small portion of the force was required to be in
garrison at any time, so that the great part of his life was spent by
each soldier at home. Each soldier had a small garden appropriated to
his use, and its produce was his sole property. Garden seeds, and
especially seed potatoes, were provided for the men, for at that time
the potato was almost unknown in Bavaria. Under these circumstances a
reform was quickly effected; idle men began to take interest in their
gardens, and all looked on Sir Benjamin as a benefactor.

Having thus secured the co-operation of the army, Thompson determined
to attack the mendicants. The number of beggars may be estimated from
the fact that in Munich, with a population of sixty thousand, no less
than two thousand six hundred beggars were seized in a week. In the
towns, they possessed a complete organization, and positions of
advantage were assigned in regular order, or inherited according to
definite customs. In the country, farm labourers begged of travellers,
and children were brought up to beggary from their infancy. Of course,
the evils did not cease with simple begging. Children were stolen and
ill treated, for the purpose of assisting in enlisting sympathy, and
the people had come to regard these evils as inevitable. Thompson
organized a regular system of military patrol through every village of
the country, four regiments of cavalry being set apart for this work.
Then on January 1, 1790, when the beggars were out in full force to
keep their annual holiday, Thompson, with the other field officers and
the magistrates of the city, gave the signal, and all the beggars in
Munich were seized upon by the three regiments of infantry then in
garrison. The beggars were taken to the town hall, and their names and
addresses entered on lists prepared for the purpose. They were ordered
to present themselves next day at the "military workhouse," and a
committee was appointed to inquire into the condition of each, the
city being divided into sixteen districts for that purpose. Relieved
of an evil which they had regarded as inevitable, the townspeople
readily subscribed for the purpose of affording systematic relief,
while tradesmen sent articles of food and other requisites to "the
relief committee." In the military workhouse the former mendicants
made all the uniforms for the troops, besides a great deal of clothes
for sale in Bavaria and other countries. Thompson himself fitted up
and superintended the kitchen, where food was daily cooked for between
a thousand and fifteen hundred persons; and, under Sir Benjamin's
management, a dinner for a thousand was cooked at a cost for fuel of
fourpence halfpenny--a result which has scarcely been surpassed in
modern times, even at Gateshead.

That Thompson's work was appreciated by those in whose interest it was
undertaken is shown by the fact that when, on one occasion, he was
dangerously ill, the poor of Munich went in public procession to the
cathedral to pray for him, though he was a foreigner and a Protestant.
Perhaps it may appear that his philanthropic work has little to do
with physical science; but with Thompson everything was a scientific
experiment, conducted in a truly scientific manner. For example, the
lighting of the military workhouse afforded matter for a long series
of experiments, described in his papers on photometry, coloured
shadows, etc. The investigations on the best methods of employing fuel
for culinary purposes led to some of his most elaborate essays; and
his essay on food was welcomed alike in London and Bavaria at a time
of great scarcity, and when famine seemed impending.

The Emperor Joseph was succeeded by Leopold II., but during the
interregnum the Elector of Bavaria was Vicar of the Empire, and he
employed the power thus temporarily placed in his hands in raising Sir
Benjamin to the dignity of Count of the Holy Roman Empire, with the
order of the White Eagle, and the title which the new count selected
was the old name of the village in New England where he had spent the
two or three years of his wedded life.

In 1795 Count Rumford returned to England, in order to publish his
essays, and to make known in this country something of the work in
which he had been engaged. Soon after his arrival he was robbed of
most of his manuscripts, the trunk containing them being stolen from
his carriage in St. Paul's Churchyard. On the invitation of Lord
Pelham, he visited Dublin, and carried out some of his improvements in
the hospitals and other institutions of that city. On his return to
London he fitted up the kitchen of the Foundling Hospital.

Lady Thompson lived to hear of her husband's high position in Bavaria,
but died on January 29, 1792. When Rumford came to London in 1795, he
wrote to his daughter, who was then twenty-one years of age, to meet
him there, and on January 29, 1796, she started in the _Charlestown_,
from Boston. She remained with her father for more than three years,
and her autobiography gives much information respecting the count's
doings during this time.

While in London, Count Rumford attained a high reputation as a curer
of smoky chimneys. One firm of builders found full employment in
carrying out work in accordance with his instructions; and in his
hotel at Pall Mall he conducted experiments on fireplaces. He
concluded that the sides of a fireplace ought to make an angle of 135°
with the back, so as to throw the heat straight to the front; and that
the width of the back should be one-third of that of the front
opening, and be carried up perpendicularly till it joins the breast.
The "Rumford roaster" gained a reputation not less than that earned
by his open fireplace.

It was during this stay in London that Rumford presented to the Royal
Society of London, and to the American Academy of Sciences £1000 Three
per Cent. Stock, for the purpose of endowing a medal to be called the
Rumford Medal, and to be given each alternate year for the best work
done during the preceding two years in the subjects of heat and light.
He directed that two medals, one in gold and the other in silver,
should be struck from the same die, the value of the two together to
amount to £60. Whenever no award was made, the interest was to be
added to the principal, and the excess of the income for two years
over £60 was to be presented in cash to the recipient of the medal. At
present the amount thus presented is sufficient to pay the composition
fee for life membership of the Royal Society. The first award of the
medal was made in 1802, to Rumford himself. The other recipients have
been John Leslie, William Murdock, Étienne-Louis Malus, William
Charles Wells, Humphry Davy, David Brewster, Augustin Jean Fresnel,
Macedonio Melloni, James David Forbes, Jean Baptiste Biot, Henry Fox
Talbot, Michael Faraday, M. Regnault, F. J. D. Arago, George Gabriel
Stokes, Neil Arnott, M. Pasteur, M. Jamin, James Clerk Maxwell,
Kirchoff, John Tyndall, A. H. L. Fizeau, Balfour Stewart, A. O. des
Cloiseaux, A. J. Ångström, J. Norman Lockyer, P. J. C. Janssen, W.
Huggins, Captain Abney.

In the summer of 1796 Rumford and his daughter left England to return
to Munich. On account of the war, they were obliged to go by sea to
Hamburg; whence they drove to Munich, where the count was anxiously
expected, political troubles having compelled the elector to leave the
city. After the battle of Friedburg, the Austrians retired to Munich,
and, finding the gates of the city closed, they fortified
themselves on an eminence overlooking the city, and, through some
misunderstanding with the local authorities, the Austrian general
threatened to attack the city if any Frenchman should be allowed to
enter. Rumford took supreme command of the Bavarian forces, and so
gained the respect of the rival generals that neither the French nor
the Austrians made any attempt to enter the city. The large number of
soldiers now in Munich gave Rumford a good opportunity to exercise his
skill in cooking on a large scale, and this he did, adding to the
comfort of the soldiers and reducing the cost of the commissariat. On
the return of the elector, Miss Sarah was made a countess, and
one-half of her father's pension was secured to her, thus providing
her with an income of about £200 per annum for life. Many of the
details of the home life and social intercourse during this period of
residence at Munich are preserved in the autobiography of the
countess, as well as accounts of excursions, including a trip by river
to Salzburg for the purpose of inspecting the salt-mines. After two
years' stay in Munich, the count was appointed Minister
Plenipotentiary from Bavaria to the Court of Great Britain. After an
unpleasant and perilous journey, he reached London, _viâ_ Hamburg, in
September, 1798, but was terribly disappointed on learning that a
British subject could not be accepted as an envoy from a Foreign
Power. As he did not then wish to return to Bavaria, he purchased a
house in Brompton Row. But he had been too much accustomed to great
enterprises to be content with a quiet life, and was bound to have
some important scheme on hand. Pressing invitations were sent him to
return to America, but he preferred residence in London, and devoted
himself to the foundation of the Royal Institution, though the
countess returned to the States in August, 1799. A letter from Colonel
Baldwin to her father shortly after her return contains the following
passage:--

    In the cask of fruit which your daughter and Mr. Rolfe have sent
    you, there is half a dozen apples of the growth of my farm,
    wrapped up in papers, with the name of _Baldwin's apples_
    written upon them.... It is (I believe) a spontaneous production
    of this country; that is, it was not originally engrafted fruit.

The history of the remaining period of Rumford's residence in London
is the early history of the Royal Institution.

For many years Rumford had had at his disposal for his philanthropic
projects all the resources of the electorate of Bavaria, and he had
done everything on a royal scale. His original plan for the Royal
Institution appears to embody to a very great extent the work of the
Science and Art Department, the City and Guilds Institute for the
Advancement of Technical Education, the National School of Cookery,
the London Society for the Extension of University Teaching, and, in
addition to all this, to have comprehended a sort of perpetual
International Health Exhibition, where every device for domestic
purposes, and especially for the improvement of the condition of the
poor, could be inspected. How all this was to be carried out with the
resources which the count expected to be able to devote to the
purpose, does not appear. Foremost among the objects of the
institution was placed the management of fire; for its promoter was
convinced that more than half the fuel consumed in the country might
be saved by proper arrangements.

The philanthropic objects with which the institution was started are
apparent from the fact that it was the Society for Bettering the
Condition of the Poor which appointed a committee to confer with
Rumford, to report on the scheme, and to raise the funds necessary for
starting the project; and one of Rumford's hopes in connection with it
was "to make benevolence fashionable." It was arranged that donors of
fifty guineas each should be perpetual proprietors of the institution;
and that subscribers should be admitted at a subscription of two
guineas per annum, or ten guineas for life. The price of a
proprietor's share was raised to sixty guineas from May 1, 1800, and
afterwards increased by ten guineas per annum up to one hundred
guineas. In a very short time there were fifty-eight fifty-guinea
subscribers, and to them Rumford addressed a pamphlet, setting forth
his scheme in detail. The following are specified as some of the
contents of the future institution:--"Cottage fireplaces and kitchen
utensils for cottagers; a farm-house kitchen with its furnishings; a
complete kitchen, with its utensils, for the house of a gentleman of
fortune; a laundry, including boilers, washing, ironing, and drying
rooms, for a gentleman's house, or for a public hospital; the most
improved German, Swedish, and Russian stoves for heating rooms and
passages." As far as possible all these things were to be seen at
work. There were also to be ornamental open stoves with fires in them;
working models of steam-engines, of brewers' boilers, of distillers'
coppers and condensers, of large boilers for hospital kitchens, and of
ships' coppers with the requisite utensils; models of ventilating
apparatus, spinning-wheels and looms "adapted to the circumstances of
the poor;" models of agricultural machinery and bridges, and "of all
such other machines and useful instruments as the managers of the
institution shall deem worthy of public notice." All articles were to
be provided with proper descriptions, with the name and address of the
maker, and the price.

A lecture-room and laboratory were to be fitted up with all necessary
philosophical apparatus, and the most eminent expounders of science
were to be engaged for the purpose of "teaching the application of
science to the useful purposes of life."

The lectures were to include warming and ventilation, the preservation
of food, agricultural chemistry, the chemistry of digestion, of
tanning, of bleaching and dyeing, "and, in general, of all the
mechanical arts as they apply to the various branches of manufacture."
The institution was to be governed by nine managers, of whom three
were to be elected each year by the proprietors; and there was also to
be a committee of visitors, the members of which should not be the
managers. The king became patron of the institution, and the first set
of officers was nominated by him. The Earl of Winchelsea and
Nottingham was President; the Earls of Morton and of Egremont and Sir
Joseph Banks, Vice-Presidents; the Earls of Bessborough, of Egremont,
and of Morton, and Count Rumford, were among the Managers; the Duke of
Bridgewater, Viscount Palmerston, and Earl Spencer the Visitors; and
Dr. Thomas Garnett was appointed first Professor of Physics and
Chemistry. The royal charter of the institution was sealed on January
13, 1800. The superintendence of the journals of the institution was
entrusted to Rumford's care. For some time the count resided in the
house in Albemarle Street, which had been purchased by the
institution, and while there he superintended the workmen and
servants.

Dr. Thomas Garnett, the first professor at the institution, was highly
respected both as a man and a philosopher, and seems to have been
everywhere well spoken of. But Rumford and he could not work together,
and his connection with the institution was consequently a short one.
Rumford was then authorized to engage Dr. Young as Professor of
Natural Philosophy, editor of the journals, and general superintendent
of the house, at a salary of £300 per annum. Shortly before this the
count's attention had been directed to the experiments on heat, made
by Humphry Davy, and on February 16, 1801, it was "resolved that Mr.
Humphry Davy be engaged in the service of the Royal Institution, in
the capacity of Assistant-Lecturer in Chemistry, Director of the
Chemical Laboratory, and Assistant-Editor of the Journals of the
Institution; and that he be allowed to occupy a room in the house, and
be furnished with coals and candles, and that he be paid a salary of
one hundred guineas _per annum_." In his personal appearance, Davy is
said to have been at first somewhat uncouth, and the count was by no
means charmed with him at their first interview. It was not till he
had heard him lecture in private that Rumford would allow Davy to
lecture in the theatre of the institution; but he afterwards showed
his complete confidence in the young chemist by ordering that all the
resources of the institution should be at his service. Davy dined with
Rumford at the count's house in Auteuil, when he visited Paris with
Lady Davy and Faraday, in 1813. He commenced his duties at the
institution on March 11, 1801. It was on June 15, in the same year,
that the managers having objected to the syllabus of his lectures, Dr.
Garnett's resignation was accepted; and on July 6 Dr. Young was
appointed in his stead. Dr. Young resigned after holding the
appointment only two years, as he found the duties incompatible with
his work as a physician.

Rumford's life in London now became daily more unpleasant to himself.
Accustomed, as he had been in Bavaria, to carry out all his projects
"like an emperor," it was difficult for him to work as one member of a
body of managers. One by one he quarrelled with his colleagues, and at
length left England, in May, 1802, never to return.

When distinguished men of science are placed at the head of an
institution like that which Rumford founded, there is always a
tendency for the _technical_ teaching of the establishment to become
gradually merged into scientific research; and in this case, after
Rumford's departure, the genius of Davy gradually converted the Royal
Institution into the establishment for scientific research which it
has been for more than three quarters of a century. Probably the man
who has come nearest to realizing all that Count Rumford had planned
for his institution is the late Sir Henry Cole; but he succeeded only
through the resources of the Treasury.

On leaving England in May, 1802, Rumford went to Paris, where he
stayed till July or August, when he revisited Bavaria and remained
there till the following year, when he returned to Paris. He was again
at Munich in 1805; but under the new elector, though an old friend of
the count, relationships do not seem to have been all that they were
with his uncle, and at length the elector himself was compelled to
leave Munich, and soon after the Bavarian sovereign became a vassal of
Napoleon. On October 24, 1805, Rumford married Madame Lavoisier, a
lady of brilliant talents and ample fortune. That his position might
be nearly equal to hers, the Elector of Bavaria raised his pension to
£1200 per annum. A house, Rue d'Anjou, No. 39, was purchased for six
thousand guineas, and Rumford expended much thought and energy in
making it, with its garden of two acres, all that he could desire. But
the union was not so happy as he anticipated. The count loved quiet;
Madame de Rumford was fond of company: to the former the pleasure of
the table had no charms; the latter took delight in sumptuous
dinner-parties. As time went on, domestic affairs became more and more
unpleasant, and at length a friendly separation was agreed upon, after
they had lived together for about three years and a half. The count
then retired to a small estate which he hired at Auteuil, about four
miles from Paris. The Elector of Bavaria was crowned king on January
1, 1806, and in 1810 Rumford was again at Munich, for the purpose of
forming, at the king's request, an Academy of Arts and Sciences. At
Auteuil the count was joined by his daughter in December, 1811, her
journey having been much delayed through the capture of the vessel in
which she had taken her passage, off Bordeaux. An engraving of the
house at Auteuil, and the room in which Rumford carried on his
experiments, was published in the _Illustrated London News_ of January
22, 1870.

While resident at Auteuil, Rumford frequently read papers before the
Institute of France, of which he was a member. He complained very much
of the jealousy exhibited by the other members with reference to any
discoveries made by a foreigner. He died in his house at Auteuil, on
August 21, 1814, in the sixty-second year of his age. In 1804 he had
made over, by deed of gift to his mother, the sum of ten thousand
dollars, that she might leave it by will to her younger children. As
before mentioned, Harvard College was his residuary legatee, and the
property so bequeathed founded the Rumford Professorship in that
institution.

Cuvier, as Secretary of the Institute, pronounced the customary eulogy
over its late member. The following passages throw some light on the
reputation in which the count was held:--

    He has constructed two singularly ingenious instruments of his
    own contriving. One is a new calorimeter for measuring the
    amount of heat produced by the combustion of any body. It is a
    receptacle containing a given quantity of water, through which
    passes, by a serpentine tube, the product of the combustion; and
    the heat that is generated is transmitted through the water,
    which, being raised by a fixed number of degrees, serves as the
    basis of the calculations. The manner in which the exterior heat
    is prevented from affecting the experiment is very simple and
    very ingenious. He begins the operation at a certain number of
    degrees below the outside heat, and terminates it at the same
    number of degrees above it. The external air takes back during
    the second half of the experiment exactly what it gave up during
    the first. The other instrument serves for noting the most
    trifling differences in the temperature of bodies, or in the
    rapidity of its changes. It consists of two glass bulbs filled
    with air, united by a tube, in the middle of which is a pellet
    of coloured spirits of wine; the slightest increase of heat in
    one of the bulbs drives the pellet towards the other. This
    instrument, which he called a thermoscope, was of especial
    service in making known to him the varied and powerful influence
    of different surfaces in the transmission of heat, and also for
    indicating a variety of methods for retarding or hastening at
    will the processes of heating and freezing....

    He thought it was not wise or good to entrust to men, in the
    mass, the care of their own well-being. The right, which seems
    so natural to them, of judging whether they are wisely governed,
    appeared to him to be a fictitious fancy born of false notions
    of enlightenment. His views of slavery were nearly the same as
    those of a plantation-owner. He regarded the government of China
    as coming nearest to perfection, because, in giving over the
    people to the absolute control of their only intelligent men,
    and in lifting each of those who belonged to this hierarchy on
    the scale according to the degree of his intelligence, it made,
    so to speak, so many millions of arms the passive organs of the
    will of a few sound heads--a notion which I state without
    pretending in the slightest degree to approve it, and which, as
    we know, would be poorly calculated to find prevalence among
    European nations.

    As for the rest, whatever were the sentiments of M. Rumford for
    men, they in no way lessened his reverence for God. He never
    omitted any opportunity in his works of expressing his religious
    admiration of Providence, and of proposing for that admiration
    by others, the innumerable and varied provisions which are made
    for the preservation of all creatures; indeed, even his
    political views came from his firm persuasion that princes ought
    to imitate Providence in this respect by taking charge of us
    without being amenable to us.

In front of the new Government offices and the National Museum in the
Maximilian Strasse, in Munich, stand, on granite pedestals, four
bronze figures, ten feet in height. These represent General Deroy,
Fraunhofer, Schelling, and Count Rumford. The statue of Rumford was
erected in 1867, at the king's private expense. In the English garden
which Rumford planned and laid out is the monument erected during his
absence in England in 1796, and bearing allegorical figures of Peace
and Plenty, and a medallion of the count.

The bare enumeration of Rumford's published papers would occupy
considerable space, but many of them have more to do with philanthropy
and domestic economy than with physics. We have seen that, when guest
of Lord George Germaine, he was engaged in experiments on gunpowder.
The experiments were made in the usual manner by firing bullets into a
ballistic pendulum, and recording the swing of the pendulum. Thompson
suggested a modification of the ballistic pendulum, attaching the
gun-barrel to the pendulum, and observing the recoil, and making
allowance for the recoil due to the discharge from the gun of the
products of combustion of the powder, the excess enabled the velocity
of the bullet to be calculated. Afterwards he made experiments on the
maximum pressure produced by the explosion of powder, and pointed out
that the value of powder in ordnance does not depend simply on the
whole amount of gas produced, but also on the rapidity of combustion.
While superintending the arsenal at Munich, Rumford exploded small
charges of powder in a specially constructed receiver, which was
closed by a plug of well-greased leather, and on this was placed a
hemisphere of steel pressed down by a 24-pounder brass cannon weighing
8081 pounds. He found that the weight of the gun was lifted by the
explosion of quantities of powder varying from twelve to fifteen
grains, and hence concluded that, if the products of combustion of the
powder were confined to the space actually occupied by the solid
powder, the initial pressure would exceed twenty thousand atmospheres.
Rumford's calculation of the pressure, based upon the bursting of a
barrel, which he had previously constructed, is not satisfactory,
inasmuch as he takes no account of the fact that the inner portions of
the metal would give way long before the outer layers exerted anything
like their maximum tension. When a hollow vessel with thick walls,
such as a gun-barrel or shell, is burst by gaseous pressure from
within, the inner layers of material are stretched to their breaking
tension before they receive much support from the outer layers; a rift
is thus made in the interior, into which the gas enters, and the
surface on which the gas presses being thus increased, the rift
deepens till the fracture is complete. In order to gain the full
strength due to the material employed, every portion of that material
should be stretched simultaneously to the extent of its maximum safe
load. This principle was first practically adopted by Sir W. G.
Armstrong, who, by building up the breech of the gun with cylinders
shrunk on, and so arranged that the tension increased towards the
exterior, availed himself of nearly the whole strength of the metal
employed to resist the explosion. Had Rumford's barrel been
constructed on this principle, he would have obtained a much more
satisfactory result.

These investigations were followed by a very interesting series of
experiments on the conducting power of fluids for heat, and, although
he pushed his conclusions further than his experiments warranted, he
showed conclusively that convection currents are the principal means
by which heat is transferred through the substance of fluids, and
described how, when a vessel of water is heated, there is generally an
ascending current in the centre, and a descending current all round
the periphery. Hence it is only when a liquid expands by increase of
temperature that a large mass can be readily heated from below. Water
below 39° Fahr. contracts when heated. Rumford, in his paper, enlarges
on the bearing of this fact on the economy of the universe, and the
following extracts afford a good specimen of his style, and justify
some of the statements made by Cuvier in his eulogy:--

    I feel the danger to which a mortal exposes himself who has the
    temerity to undertake to explain the designs of Infinite Wisdom.
    The enterprise is adventurous, but it cannot surely be improper.

    The wonderful simplicity of the means employed by the Creator of
    the world to produce the changes of the seasons, with all the
    innumerable advantages to the inhabitants of the earth which
    flow from them, cannot fail to make a very deep and lasting
    impression on every human being whose mind is not degraded and
    quite callous to every ingenuous and noble sentiment; but the
    further we pursue our inquiries respecting the constitution of
    the universe, and the more attentively we examine the effects
    produced by the various modifications of the active powers which
    we perceive, the more we shall be disposed to admire, adore, and
    love that great First Cause which brought all things into
    existence.

    Though winter and summer, spring and autumn, and all the variety
    of the seasons are produced in a manner at the same time the
    most simple and the most stupendous (by the inclination of the
    axis of the earth to the plane of the ecliptic), yet this
    mechanical contrivance alone would not have been sufficient (as
    I shall endeavour to show) to produce that gradual change of
    temperature in the various climates which we find to exist, and
    which doubtless is indispensably necessary to the preservation
    of animal and vegetable life....

    But in very cold countries the ground is frozen and covered with
    snow, and all the lakes and rivers are frozen over in the very
    beginning of winter. The cold then first begins to be extreme,
    and there appears to be no source of heat left which is
    sufficient to moderate it in any sensible degree.

    Let us see what must have happened if things had been left to
    what might be called their natural course--if the condensation
    of water, on being deprived of its heat, had followed the law
    which we find obtains in other fluids, and even in water itself
    in some cases, namely, when it is mixed with certain bodies.

    Had not Providence interfered on this occasion in a manner which
    may well be considered _miraculous_, all the fresh water within
    the polar circle must inevitably have been frozen to a very
    great depth in one winter, and every plant and tree destroyed;
    and it is more than probable that the region of eternal frost
    would have spread on every side from the poles, and, advancing
    towards the equator, would have extended its dreary and solitary
    reign over a great part of what are now the most fertile and
    most inhabited climates of the world!...

    Let us with becoming diffidence and awe endeavour to see what
    the means are which have been employed by an almighty and
    benevolent God to protect His fair creation.

He then goes on to explain how large bodies of water are prevented
from freezing at great depths on account of the expansion which takes
place on cooling below 39° Fahr., and the further expansion which
occurs on freezing, and mentions that in the Lake of Geneva, at a
depth of a thousand feet, M. Pictet found the temperature to be 40°
Fahr.

"We cannot sufficiently admire the simplicity of the contrivance by
which all this heat is saved. It well deserves to be compared with
that by which the seasons are produced; and I must think that every
candid inquirer who will begin by divesting himself of all
unreasonable prejudice will agree with me in attributing them both TO
THE SAME AUTHOR....

"But I must take care not to tire my reader by pursuing these
speculations too far. If I have persisted in them, if I have dwelt on
them with peculiar satisfaction and complacency, it is because I think
them uncommonly interesting, and also because I conceived that they
might be of value in this age of _refinement_ and _scepticism_.

"If, among barbarous nations, the _fear of a God_, and the practice of
religious duties, tend to soften savage dispositions, and to prepare
the mind for all those sweet enjoyments which result from peace,
order, industry, and friendly intercourse; a _belief in the existence
of a Supreme Intelligence_, who rules and governs the universe with
wisdom and goodness, is not less essential to the happiness of those
who, by cultivating their mental powers, HAVE LEARNED TO KNOW HOW
LITTLE CAN BE KNOWN."

Rumford, in connection with his experiments on the conducting power of
liquids, tried the effect of increasing the viscosity of water by the
addition of starch, and of impeding its movements by the introduction
of eider-down, on the rate of diffusion of heat through it. Hence he
explained the inequalities of temperature which may obtain in a mass
of thick soup--inequalities which had once caused him to burn his
mouth--and, applying the same principles to air, he at once turned his
conclusions to practical account in the matter of warm clothing.

After an attempt to determine, if possible, the weight of a definite
quantity of heat--an attempt in which very great precautions were
taken to exclude disturbing causes, while the balance employed was
capable of indicating one-millionth part of the weight of the body
weighed--Rumford, finding no sensible effect on the balance, concluded
that "if the weight of gold is neither augmented nor lessened by
_one-millionth part_, upon being heated from the point of _freezing
water_ to that of a _bright red heat_, I think we may very safely
conclude that ALL ATTEMPTS TO DISCOVER ANY EFFECT OF HEAT UPON THE
APPARENT WEIGHTS OF BODIES WILL BE FRUITLESS." The theoretical
investigations of Principal Hicks, based on the vortex theory of
matter and the dynamical theory of heat, have recently led him to the
conclusion that the attraction of gravitation may depend to some
extent on temperature.

A series of very valuable experiments on the radiating powers of
different surfaces showed how that power varied with the nature of the
surface, and the effect of a coating of lamp-black in increasing the
radiating power of a body. In order to determine the effect of
radiation in the cooling of bodies, Rumford employed the thermoscope
referred to by Cuvier. The following passage is worthy of attention,
as the truth it expounds in the last thirteen words appears to have
been but very imperfectly recognized many years after it was
written:--

"All the heat which a hot body loses when it is exposed in the air to
cool is not given off to the air which comes into contact with it, but
... a large proportion of it escapes in rays, which do not heat the
transparent air through which they pass, but, like light, generate
heat only when and where they are stopped and absorbed."

Rumford then investigated the absorption of heat by different
surfaces, and established the law that good radiators are good
absorbers; and recommended that vessels in which water is to be heated
should be blackened on the outside. In speculating on the use of the
colouring matter in the skin of the negro, he shows his fondness for
experiment:--

"All I will venture to say on the subject is that, were I called to
inhabit a very hot country, nothing should prevent me from making the
experiment of blackening my skin, or at least, of wearing a black
shirt, in the shade, and especially at night, in order to find out if,
by those means, I could contrive to make myself more comfortable."

In his experiments on the conduction of heat, Rumford employed a
cylinder with one end immersed in boiling water and the other in
melting ice, and determined the temperature at different points in the
length of the cylinder. He found the difficulty which has recently
been forcibly pointed out by Sir Wm. Thomson, in the article "Heat,"
in the "Encyclopædia Britannica," viz. that the circulation of the
water was not sufficiently rapid to keep the temperature of the layer
in contact with the metal the same as that of the rest of the water;
and he also called attention to the arbitrary character of
thermometer-scales, and recommended that more attention should be
given to the scale of the air thermometer. It was in his visit to
Edinburgh, in 1800, that, in company with some of the university
professors, the count conducted some experiments in the university
laboratory on the apparent radiation of cold. Rumford's views
respecting _frigorific rays_ have not been generally accepted, and
Prevost's theory of exchanges completely explains the apparent
radiation of cold without supposing that cold is anything else than
the mere absence of heat.

We must pass over Rumford's papers on the use of steam as a vehicle of
heat, on new boilers and stoves for the purpose of economizing fuel,
and all the papers bearing on the nutritive value of different foods.
The calorimeter with which he determined the amount of heat generated
by the combustion, and the latent heat of evaporation, of various
bodies has been already alluded to. Of the four volumes of Rumford's
works published by the American Academy of Arts and Sciences, the
third is taken up entirely with descriptions of fireplaces and of
cooking utensils.

Before deciding on the best way to light the military workhouse at
Munich, Rumford made a series of experiments on the relative economy
of different methods, and for this purpose designed his well-known
shadow-photometer. In the final form of this instrument the shadows
were thrown on a plate of ground glass covered with paper, forming the
back of a small box, from which all extraneous light was excluded. Two
rods were placed in front of this screen, and the lights to be
compared were so situated that the shadow of one rod thrown by the
first light might be just in contact with that of the other rod thrown
by the second light. By introducing coloured glasses in front of the
lights, Rumford compared the illuminating powers of different sources
with respect to light of a particular colour. The complementary tints
exhibited by the shadows caused him to devise his theory of the
harmony of complementary colours. One result is worthy of mention: it
is a conclusion to which public attention has since been called in
connection with "duplex" burners. Rumford found that with wax tapers
the amount of light emitted per grain of wax consumed diminished with
the diminution of the consumption, so that a small taper gave out only
one-sixteenth as much light as an ordinary candle for the same
consumption of wax. He says:--

"This result can be easily explained if we admit the hypothesis which
supposes light to be analogous to sound.... The particles ... were so
rapidly cooled ... that they had hardly time to shine one instant
before they became too cold to be any longer visible."

An argand lamp, when compared with a lamp having a flat wick, gave
more light in the ratio of 100 to 85 for the same consumption of oil.

One of the latest investigations of Rumford was that bearing on the
effect of the width of the wheels on the draught of a carriage. To his
own carriage, weighing, with its passengers, nearly a ton, he fitted a
spring dynamometer by means of a set of pulleys attached to the
under-carriage and the splinter-bar. He used three sets of wheels,
respectively 1-3/4, 2-1/4, and 4 inches wide, and, introducing weights
into the carriage to make up for the difference in the weights of the
wheels, he found a very sensible diminution in the tractive force
required as the width of the wheels was increased, and in a truly
scientific spirit, despising the ridicule cast upon him, he persisted
in riding about Paris in a carriage with four-inch tyres.

But the piece of work by which Rumford will be best known to future
generations is that described in his paper entitled "An Inquiry
concerning the Source of the Heat which is excited by Friction." It
was while superintending the boring of cannon in the arsenal at Munich
that Rumford was struck with the enormous amount of heat generated by
the friction of the boring-bar against the metal. In order to
determine whether the heat had come from the chips of metal
themselves, he took a quantity of the abraded borings and an equal
weight of chips cut from the metal with a fine saw, and, heating them
to the temperature of boiling water, he immersed them in equal
quantities of water at 59-1/2° Fahr. The change of temperature of the
water was the same in both cases, and Rumford found that there was no
change which he could discover _in regard to its capacity for heat_
produced in the metal by the action of the borer.

In order to prevent the honeycombing of the castings by the escaping
gas, the cannon were cast in a vertical position with the breech at
the bottom of the mould and a short cylinder projecting about two feet
beyond the muzzle of the gun, so that any imperfections in the casting
would appear in this projecting cylinder. It was on one of these
pieces of waste metal, while still attached to the gun, that Rumford
conducted his experiments. Having turned the cylinder, he cut away the
metal in front of the muzzle until the projecting piece was connected
with the gun by a narrow cylindrical neck, 2·2 inches in diameter and
3·8 inches long. The external diameter of the cylinder was 7·75
inches, and its length 9·8 inches, and it was bored to a depth of 7·2
inches, the diameter of the bore being 3·7 inches. The cannon was
mounted in the boring-lathe, and a blunt borer pressed by a screw
against the bottom of the bore with a force equal to the weight of
10,000 pounds. A small transverse hole was made in the cylinder near
its base for the introduction of a thermometer. The cylinder weighed
113·13 pounds, and, with the gun, was turned at the rate of thirty-two
revolutions per minute by horse-power. To prevent loss of heat, the
cylinder was covered with flannel. After thirty minutes' work, the
thermometer, when introduced into the cylinder, showed a temperature
of 130° Fahr. The loss of heat during the experiment was estimated
from observations of the rate of cooling of the cylinder. The weight
of metal abraded was 837 grains, while the amount of heat produced was
sufficient to raise nearly five pounds of ice-cold water to the
boiling point.

To exclude the action of the air, the cylinder was closed by an
air-tight piston, but no change was produced in the result. As the air
had access to the metal where it was rubbed by the piston, and Rumford
thought this might possibly affect the result, a deal box was
constructed, with slits at each end closed by sliding shutters, and so
arranged that it could be placed with the boring bar passing through
one slit and the narrow neck connecting the cylinder with the gun
through the other slit, the sliding shutters, with the help of collars
of oiled leather, serving to make the box water-tight. The box was
then filled with water and the lid placed on. After turning for an
hour the temperature was raised from 60° to 107° Fahr., after an hour
and a half it was 142° Fahr., at the end of two hours the temperature
was 178° Fahr., at two hours and twenty minutes it was 200° Fahr., and
at two hours and thirty minutes it ACTUALLY BOILED!

"It would be difficult to describe the surprise and astonishment
expressed in the countenances of the bystanders on seeing so large a
quantity of cold water heated and actually made to boil without any
fire.

"Though there was, in fact, nothing that could justly be considered as
surprising in this event, yet I acknowledge fairly that it afforded me
a degree of childish pleasure which, were I ambitious of the
reputation of a _grave philosopher_, I ought most certainly rather to
hide than to discover."

Rumford estimated the "total quantity of ice-cold water which, with
the heat actually generated by the friction and accumulated in two
hours and thirty minutes, might have been heated 180 degrees, or made
to boil" at 26·58 pounds, and the rate of production he considered
exceeded that of nine wax candles, each consuming ninety-eight grains
of wax per hour, while the work of turning the lathe could easily have
been performed by one horse. This was the first rough attempt ever
made, so far as we know, to determine the mechanical equivalent of
heat.

In his reflections on these experiments, Rumford writes:--

    It is hardly necessary to add that anything which any
    _insulated_ body or system of bodies can continue to furnish
    _without limitation_ cannot possibly be _a material substance_;
    and it appears to me to be extremely difficult, if not quite
    impossible, to form any distinct idea of anything capable of
    being excited and communicated in the manner the heat was
    excited and communicated in these experiments, except it be
    MOTION.

It has been stated that, if Rumford had dissolved in acid the borings
and the sawn strips of metal, the capacity for heat of which he
determined, and had shown that the heat developed in the solution was
the same in the two cases, his chain of argument would have been
absolutely complete. Considering the amount of heat produced in the
experiments, there are few minds whose conviction would be
strengthened by this experiment, and it is only those who look for
faultless logic that will refuse to Rumford the credit of having
established the dynamical nature of heat.

Davy afterwards showed that two pieces of ice could be melted by being
rubbed against one another in a vacuum, but he does not appear to have
made as much as he might of the experiment. Mayer calculated the
mechanical equivalent of heat from the heat developed in the
compression of air, but he _assumed_, what afterwards was shown by
Joule to be nearly true, that the whole of the work done in the
compression was converted into heat. It was Joule, however, who first
showed that heat and mechanical energy are mutually convertible, so
that each may be expressed in terms of the other, a _given_ quantity
of heat always corresponding to the _same amount_ of mechanical
energy, whatever may be the intermediate stages through which it
passes, and that we may therefore define the mechanical equivalent of
heat as _the number of units of energy which, when entirely converted
into heat, will raise unit mass of water one degree from the freezing
point_.




THOMAS YOUNG.


"We here meet with a man altogether beyond the common standard, one in
whom natural endowment and sedulous cultivation rivalled each other in
the production of a true philosopher; nor do we hesitate to state our
belief that, since Newton, Thomas Young stands unrivalled in the
annals of British science." Such was the verdict of Principal Forbes
on one who may not only be regarded as one of the founders of the
undulatory theory of light, but who was among the first to apply the
theory of elasticity to the strength of structures, while it is to him
that we are indebted in the first instance for all we know of Egyptian
hieroglyphics, and for the vast field of antiquarian research which
the interpretation of these symbols has opened up.

Thomas Young was the son of Thomas and Sarah Young, and the eldest of
ten children. His mother was a niece of the well-known physician, Dr.
Richard Brocklesby, and both his father and mother were members of
the Society of Friends, in whose principles all their children were
very carefully trained. It was to the independence of character thus
developed that Dr. Young attributed very much of the success which he
afterwards attained. He was born at Milverton, in Somersetshire, on
June 13, 1773. For the greater part of the first seven years of his
life he lived with his maternal grandfather, Mr. Robert Davis, at
Minehead, in Somersetshire. According to his own account, he could
read with considerable fluency at the age of _two_, and, under the
instructions of his aunt and a village schoolmistress, he had "read
the Bible twice through, and also Watts's Hymns," before he attained
the age of four. It may with reason be thought that both the
schoolmistress and the aunt should have been severely reprimanded, and
it is certain that their example is not to be commended; but Young's
infantile constitution seems to have been proof against over-pressure,
and before he was five years old he could recite the whole of
Goldsmith's "Deserted Village," with scarcely a mistake. He commenced
learning Latin before he was six, under the guidance of a
Nonconformist minister, who also taught him to write. When not quite
seven years of age he went to boarding-school, where he remained a
year and a half; but he appears to have learned more by independent
effort than under the guidance of his master, for privately he "had
mastered the last rules of Walkinghame's 'Tutor's Assistant'" before
reaching the middle of the book under the master's inspection. After
leaving this school, he lived at home for six months, but frequently
visited a neighbour who was a land surveyor, and at whose house he
amused himself with philosophical instruments and scientific books,
especially a "Dictionary of Arts and Sciences." When nearly nine he
went to the school of Mr. Thompson, at Compton, in Dorsetshire, where
he remained nearly four years, and read several Greek and Latin
authors, as well as the elements of natural philosophy--the latter in
books lent him by Mr. Jeffrey, the assistant-master. This Mr. Jeffrey
appears to have been something of a mechanical genius, and he gave
Young lessons in turning, drawing, bookbinding, and the grinding and
preparation of colours. Before leaving this school, at the age of
thirteen, Young had read six chapters of the Hebrew Bible.

During the school holidays the construction of a microscope occupied
considerable time, and the reading of "Priestley on Air" turned
Young's attention to the subject of chemistry. Having learned a little
French, he succeeded, with the help of a schoolfellow, in gaining an
elementary knowledge of Italian. After leaving school, he lived at
home for some time, and devoted his energies mainly to Hebrew and to
turning and telescope-making; but Eastern languages received a share
of attention, and by the time he was fourteen he had read most of Sir
William Jones's "Persian Grammar." He then went to Youngsbury, in
Hertfordshire, and resided at the house of Mr. David Barclay, partly
as companion and partly as classical tutor to Mr. Barclay's grandson,
Hudson Gurney. This was the beginning of a friendship which lasted for
life. Gurney was about a year and a half junior to Young, and for five
years the boys studied together, reading the classical works which
Young had previously studied at school. Before the end of these five
years Young had gained more or less acquaintance with fourteen
languages; but his studies were for a time delayed through a serious
illness when he was little more than sixteen. To this illness his
uncle, Dr. Brocklesby, referred in a letter, of which the following
extract is interesting for several reasons:--

    Recollect that the least slip (as who can be secure against
    error?) would in you, who seem in all things to set yourself
    above ordinary humanity, seem more monstrous or reprehensible
    than it might be in the generality of mankind. Your prudery
    about abstaining from the use of sugar on account of the negro
    trade, in any one else would be altogether ridiculous, but as
    long as the whole of your mind keeps free from spiritual pride
    or too much presumption in your facility of acquiring language,
    which is no more than the dross of knowledge, you may be
    indulged in such whims, till your mind becomes enlightened with
    more reason. My late excellent friend, Mr. Day, the author of
    'Sandford and Merton,' abhorred the base traffic in negroes'
    lives as much as you can do, and even Mr. Granville Sharp, one
    of the earliest writers on the subject, has not done half as
    much service in the business as Mr. Day in the above work. And
    yet Mr. Day devoured daily as much sugar as I do; for he
    reasonably concluded that so great a system as the sugar-culture
    in the West Indies, where sixty millions of British property are
    employed, could never be affected either way by one or one
    hundred in the nation debarring themselves the reasonable use of
    it. Reformation must take its rise elsewhere, if ever there is a
    general mass of public virtue sufficient to resist such private
    interests. Read Locke with care, for he opens the avenues of
    knowledge, though he gives too little himself.

With respect to the sugar, no doubt very much may be said on Young's
side of the question. It appears, however, that in his early manhood
there was a good deal in his conduct which to-day would be regarded as
_priggish_, though it was somewhat more in harmony with the spirit of
his time.

He left Youngsbury at the age of nineteen, having read, besides his
classical authors, the whole of Newton's "Principia" and "Opticks,"
and the systems of chemistry by Lavoisier and Nicholson, besides works
on botany, medicine, mineralogy, and other scientific subjects. One of
Young's peculiarities was the extraordinary neatness of his
handwriting, and a translation in Greek iambics of Wolsey's farewell
to Cromwell, which he sent, written very neatly on vellum, to his
uncle, Dr. Brocklesby, attracted the attention of Mr. Burke, Dr.
Charles Burney, and other classical scholars, so that when, a few
months later, Young went to stay with his uncle in London, and was
thrown into contact with some of the chief literary men of the day, he
found that his fame as a scholar had preceded him. This neatness of
his handwriting and his power of drawing were of great use in his
researches on the Egyptian hieroglyphics. He had little faith in
natural genius, but believed that anything could be accomplished by
persevering application.

    "Thou say'st not only skill is gained,
    But genius too may be obtained,
        By studious imitation."

In the autumn of 1792 Young went to London for the purpose of studying
medicine. He lived in lodgings in Westminster, and attended the
Hunterian School of Anatomy. A year afterwards he entered St.
Bartholomew's Hospital as a medical student. The notes which he took
of the lectures were written sometimes in Latin, interspersed with
Greek quotations, and not unfrequently with mathematical calculations,
which may be assumed to have been made before the lecture commenced.
During his school days he had paid some attention to geometrical
optics, and had constructed a microscope and telescope. Now his
attention was attracted to a far more delicate instrument--the eye
itself. Young had learned how a telescope can be "focussed" so as to
give clear images of objects more or less distant. Some such power of
adjustment must be possessed by the eye, or it could never form
distinct images of objects, whether at a distance of a foot or a
mile. The apparently fibrous structure of the crystalline lens of the
eye had been noticed and described by Leuwenhoeck; and Pemberton, a
century before Young took up the subject, had suggested that the
fibres were muscles, by the action of which the eye was "accommodated"
for near or distant vision. In dissecting the eye of an ox Young
thought he had discovered evidence confirmatory of this view, and the
paper which he wrote on the subject was not only published in the
"Philosophical Transactions," but secured his election as a Fellow of
the Royal Society in June, 1794. This paper was important, not simply
because it led to Young's election to the Royal Society, but mainly
because it was his first published paper on optical subjects. Later on
he showed incontestably, by exact measurements, that it is the
crystalline lens which changes its form during adjustment; but he was
wrong in supposing the fibres of the lens to be muscular. By carefully
measuring the distance between the images of two candles formed by
reflection from the cornea, he showed that the cornea experienced no
change of form. His eyes were very prominent; and turning them so as
to look very obliquely, he measured the length of the eye from back to
front with a pair of compasses whose points were protected, pressing
one point against the cornea, and the other between the back of the
eye and the orbit, and showed that, when the eye was focussed for
different distances, there was no change in the length of the axis.
The crystalline lens was the only resource left whereby the
accommodation could be effected. The accommodation is, in fact,
brought about by the action of the ciliary muscle. The natural form of
the lens is more convex than is consistent with distinct vision,
except for very near objects. The tension of the suspensory ligament,
which is attached to the front of the lens all round its edge, renders
the anterior surface of the lens much less curved than it would
naturally be. The ciliary muscle is a ring of muscular fibre attached
to the ciliary process close to the circumference of the suspensory
ligament. By its contraction it forms a smaller ring, and, diminishing
the external diameter, it releases the tension of the suspensory
ligament, thus allowing the crystalline lens to bulge out and adapt
itself for the diverging rays coming from near objects. It is the
exertion of contracting the ciliary muscle that constitutes the effort
of which we are conscious when looking at very near objects. It was
not, however, till long after the time of Dr. Young that this
complicated action was fully made out, though the change of form of
the anterior surface of the crystalline lens was discovered by the
change in the image of a bright object formed by reflection.

In the spring of 1794 Young took a holiday tour in Cornwall, with
Hudson Gurney, visiting on his way the Duke of Richmond, who was
drinking the waters at Bath, under the advice of Dr. Brocklesby. In
Cornwall, the mining machinery attracted his attention very much more
than the natural beauties of the country. Towards the end of the
summer he visited the Duke of Richmond at Goodwood, when the duke
offered him the appointment of private secretary. He resolved,
however, to continue his medical course, one of the reasons which he
alleged being his regard for the Society of Friends, whose principles
he considered inconsistent with the appointment of Private Secretary
to the Master-General of the Ordnance.

The following winter he spent as a medical student at Edinburgh. Here
he gave up the costume of the Society of Friends, and in many ways
departed from their rules of conduct. He mingled freely with the
university, attended the theatre, took lessons in dancing and playing
the flute, and generally cultivated the habits of what is technically
known as "society." Throughout this change in his life he retained his
high moral principles as a guide of conduct, and appears to have acted
from a firm conviction of what was right. At the same time, it must be
admitted that the breaking down of barriers, however conventional they
may be, is an operation attended in most cases by not a little danger.
With Young, the progress of his scientific education may have been
delayed on account of the new demands on his time; but besides the
study of German, Spanish, and Italian, he appears to have read a
considerable amount of general literature during his winter session in
Edinburgh. The following summer he took a tour on horseback through
the Highlands, taking with him his flute, drawing materials, spirits
for preserving insects, boards for drying plants, paper and twine for
packing up minerals, and a thermometer; but the geological hammer does
not then appear to have been regarded as an essential to the equipment
of a philosopher. At Aberdeen he stayed for three days, and reported
thus on the university:--

    Some of the professors are capable of raising a university to
    celebrity, especially Copeland and Ogilvie; but the division and
    proximity of the two universities (King's College and Marischal
    College) is not favourable to the advancement of learning;
    besides, the lectures are all, or mostly, given at the same
    hour, and the same professor continues to instruct a class for
    four years in the different branches. Were the colleges united,
    and the internal regulations of the system new modelled, the
    cheapness of the place, the number of small bursaries for poor
    or distinguished students, and the merit of the instructors,
    might make this university a very respectable seminary in some
    branches of science. The fee to a professor for a five-months'
    session is only a guinea and a half. I was delighted with the
    inspection of the rich store of mathematical and philosophical
    apparatus belonging to Professor Copeland of Marischal College,
    made in his own house, and partly with his own hands, finished
    with no less care than elegance; and tending to illustrate every
    branch of physics in the course of his lectures, which must be
    equally entertaining and instructive.

Before leaving the Highlands, Young visited Gordon Castle, where he
stayed two days; and appears to have distinguished himself by the
powers of endurance he exhibited in dancing reels. On leaving he
writes: "I could almost have wished to break or dislocate a limb by
chance, that I might be detained against my will; I do not recollect
that I have ever passed my time more agreeably, or with a party that I
thought more congenial to my own dispositions: and what would hardly
be credited by many grave reasoners on life and manners, that a person
who had spent the whole of his earlier years a recluse from the gay
world, and a total stranger to all that was passing in the higher
ranks of society, should feel himself more at home and more at ease in
the most magnificent palace in the country than in the humblest
dwelling with those whose birth was most similar to his own. Without
enlarging on the duke's good sense and sincerity, the duchess's spirit
and powers of conversation, Lady Madeline's liveliness and affability,
Louisa's beauty and sweetness, Georgiana's _naïveté_ and quickness of
parts, young Sandy's good nature, I may say that I was truly sorry to
part with every one of them."

Young seems not to have known at this time that it is an essential
feature of true gentlefolk to dissipate all sense of constraint or
uneasiness from those with whom they are brought into contact and
that in this they can be readily distinguished from those who have
wealth without breeding. The Duchess of Gordon gave Young an
introduction to the Duke of Argyll, so, while travelling through the
Western Highlands, he paid a visit to Inverary Castle, and "galloped
over" the country with the duke's daughters. Speaking of these ladies,
he says, "Lady Charlotte ... is to Lady Augusta what Venus is to
Minerva; I suppose she wishes for no more. Both are goddesses."

On his return to the West of England, he visited the Coalbrook Dale
Iron Works, when Mr. Reynolds told him "that before the war he had
agreed with a man to make a flute a hundred and fifty feet long, and
two and a half in diameter, to be blown by a steam-engine and played
on by barrels."

On the 7th of the following October Young left London, and after
spending six days on the voyage from Yarmouth to Hamburg, he reached
Göttingen on the 27th of the same month; two days afterwards he
matriculated, and on November 3 he commenced his studies as a member
of the university. He continued to take lessons in drawing, dancing,
riding, and music, and commenced learning the clavichord. The English
students at Göttingen, in order to advance their German conversation,
arranged to pay a fine whenever they spoke in English in one another's
company. On Sundays it was usual for the professors to give
entertainments to the students, though they seldom invited them to
dinner or supper. "Indeed, they could not well afford, out of a fee
of a louis or two, to give large entertainments; but the absence of
the hospitality which prevails rather more in Britain, is compensated
by the light in which the students are regarded; they are not the
less, but perhaps the more, respected for being students, and indeed,
they behave in general like gentlemen, much more so than in some other
German universities."

At Göttingen Young attended, in addition to his medical lectures,
Spithler's lectures on the History and Constitution of the European
States, Heyne on the History of the Ancient Arts, and Lichtenberg's
course on Physics. Speaking of Blumenbach's lectures on Natural
History, Young says, "He showed us yesterday a laborious treatise,
with elegant plates, published in the beginning of this century at
Wurzburg, which is a most singular specimen of credulity in affairs of
natural history. Dr. Behringen used to torment the young men of a
large school by obliging them to go out with him collecting
petrifactions; and the young rogues, in revenge, spent a whole winter
in counterfeiting specimens, which they buried in a hill which the
good man meant to explore, and imposed them upon him for most
wonderful _lusus naturæ_. It is interesting in a metaphysical point of
view to observe how the mind attempts to accommodate itself; in one
case, where the boys had made the figure of a plant thick and clumsy,
the doctor remarks the difference, and says that Nature seems to have
restored to the plant in thickness that which she had taken away from
its other dimensions."

On April 30, 1796, Young passed the examination for his medical degree
at Göttingen. The examination appears to have been entirely oral. It
lasted between four and five hours. There were four examiners seated
round a table provided "with cakes, sweetmeats, and wine, which helped
to pass the time agreeably." They "were not very severe in exacting
accurate answers." The subject he selected for his public discussion
was the human voice, and he constructed a universal alphabet
consisting of forty-seven letters, of which, however, very little is
known. This study of sound laid the foundation, according to his own
account, of his subsequent researches in the undulatory theory of
light.

The autumn of 1796 Young spent in travelling in Germany; in the
following February he returned to England, and was admitted a
fellow-commoner of Emmanuel College, Cambridge. It is said that the
Master, in introducing Young to the Tutors and other Fellows, said, "I
have brought you a pupil qualified to read lectures to his tutors."
Young's opinion of Cambridge, as compared with German universities,
was favourable to the former; but as he had complained of the want of
hospitality at Göttingen, so in Cambridge he complained of the want of
social intercourse between the senior members of the university and
persons _in statu pupillari_. At that time there was no system of
medical education in the university, and the statutes required that
six years should elapse between the admission of a medical student and
his taking the degree of M.B. Young appears to have attracted
comparatively little attention as an undergraduate in college. He did
not care to associate with other undergraduates, and had little
opportunity of intercourse with the senior members of the university.
He was still keeping terms at Cambridge when his uncle, Dr.
Brocklesby, died. To Young he left the house in Norfolk Street, Park
Lane, with the furniture, books, pictures, and prints, and about
£10,000. In the summer of 1798 a slight accident at Cambridge
compelled Young to keep to his rooms, and being thus forcibly deprived
of his usual round of social intercourse, he returned to his favourite
studies in physics. The most important result of this study was the
establishment of the principle of interference in sound, which
afforded the explanation of the phenomenon of "beats" in music, and
which afterwards led up to the discovery of the interference of
light--a discovery which Sir John Herschel characterized as "the key
to all the more abstruse and puzzling properties of light, and which
would alone have sufficed to place its author in the highest rank of
scientific immortality, even were his other almost innumerable claims
to such a distinction disregarded."

The principle of interference is briefly this: When two waves meet
each other, it may happen that their crests coincide; in this case a
wave will be formed equal in height (amplitude) to the sum of the
heights of the two. At another point the crest of one wave may
coincide with the hollow of another, and, as the waves pass, the
height of the wave at this point will be the difference of the two
heights, and if the waves are equal the point will remain stationary.
If a rope be hung from the ceiling of a lofty room, and the lower end
receive a jerk from the hand, a wave will travel up the rope, be
reflected and reversed at the ceiling, and then descend. If another
wave be then sent up, the two will meet, and their passing can be
observed. It will then be seen that, if the waves are exactly equal,
the point at which they meet will remain at rest during the whole time
of transit. If a number of waves in succession be sent up the string,
the motions of the hand being properly timed, the string will appear
to be divided into a number of vibrating segments separated by
stationary points, or nodes. These nodes are simply the points which
remain at rest on account of the upward series of waves crossing the
series which have been reflected at the top and are travelling
downwards. The division of a vibrating string into nodes thus affords
a simple example of the principle of interference. When a tuning-fork
is vibrating there are certain hyperbolic lines along which the
disturbance caused by one prong is exactly neutralized by that due to
the other prong. If a large tuning-fork be struck and then held near
the ear and slowly turned round, the positions of comparative silence
will be readily perceived. If two notes are being sounded side by
side, one consisting of two hundred vibrations per second and the
other of two hundred and two, then, at any distant point, it is clear
that the two sets of waves will arrive in the same condition, or
"phase," twice in each second, and twice they will be in opposite
conditions, and, if of the same intensity, will exactly destroy one
another's effects, thus producing silence. Hence twice in the second
there will be silence and twice there will be sound, the waves of
which have double the amplitude due to either source, and hence the
sound will have four times the intensity of either note by itself.
Thus there will be two "beats" per second due to interference. Later
on this principle was applied by Young to very many optical phenomena
of which it afforded a complete explanation.

Young completed his last term of residence at Cambridge in December,
1799, and in the early part of 1800 he commenced practice as a
physician at 48, Welbeck Street. In the following year he accepted the
chair of Natural Philosophy in the Royal Institution, which had
shortly before been founded, and soon afterwards, in conjunction with
Davy, the Professor of Chemistry, he undertook the editing of the
journals of the institution. This circumstance has already been
alluded to in connection with Count Rumford, the founder of the
institution. He lectured at the Royal Institution for two years only,
when he resigned the chair in deference to the popular belief that a
physician should give his attention wholly to his professional
practice, whether he has any or not. This fear lest a scientific
reputation should interfere with his success as a physician haunted
him for many years, and sometimes prevented his undertaking scientific
work, while at other times it led him to publish anonymously the
results he obtained. This anonymous publication of scientific papers
caused him great trouble afterwards in order to establish his claim to
his own discoveries. Many of the articles which he contributed to the
supplement to the fourth, fifth, and sixth editions of the
"Encyclopædia Britannica" were anonymous, although the honorarium he
received for this work was increased by 25 per cent. when he would
allow his name to appear. The practical withdrawal of Young from the
scientific world during sixteen years was a great loss to the progress
of natural philosophy, while the absence of that suavity of manner
when dealing with patients which is so essential to the success of a
physician, prevented him from acquiring a valuable private practice.
In fact, Young was too much of a philosopher in his behaviour to
succeed as a physician; he thought too deeply before giving his
opinion on a diagnosis, instead of appearing to know all about the
subject before he commenced his examination, and this habit, which is
essential to the philosopher, does not inspire confidence in the
practitioner. His fondness for society rendered him unwilling to live
within the means which his uncle had left him, supplemented by what
his scientific work might bring, and it was not until his income had
been considerably increased by an appointment under the Admiralty that
he was willing to forego the possible increase of practice which might
accrue by appearing to devote his whole attention to the subject of
medicine. It was this fear of public opinion which caused him, in
1812, to decline the offer of the appointment of Secretary to the
Royal Society, of which, in 1802, he accepted the office of Foreign
Secretary.

Young's resignation of the chair of Natural Philosophy was, however,
not a great loss to the Royal Institution; for the lecture audience
there was essentially of a popular character, and Young cannot be
considered to have been successful as a popular lecturer. His own
early education had been too much derived from private reading for him
to have become acquainted with the difficulties experienced by
beginners of only average ability, and his lectures, while most
valuable to those who already possessed a fair knowledge of the
subjects, were ill adapted to the requirements of an unscientific
audience. A syllabus of his course of lectures was published by Young
in 1802, but it was not till 1807 that the complete course of sixty
lectures was published in two quarto volumes. They were republished in
1845 in octavo, with references and notes by Professor Kelland. Among
the subjects treated in these lectures are mechanics, including
strength of materials, architecture and carpentry, clocks, drawing and
modelling; hydrostatics and hydraulics; sound and musical instruments;
optics, including vision and the physical nature of light; astronomy;
geography; the essential properties of matter; heat; electricity and
magnetism; climate, winds, and meteorology generally; vegetation and
animal life, and the history of the preceding sciences. The lectures
were followed by a most complete bibliography of the whole subject,
including works in English, French, German, Italian, and Latin. The
following is the syllabus of one lecture, and illustrates the
diversity of the subjects dealt with:--

     "ON DRAWING, WRITING, AND MEASURING.

     "Subjects preliminary to the study of practical mechanics;
     instrumental geometry; statics; passive strength; friction;
     drawing; outline; pen; pencil; chalks; crayons; Indian ink;
     water-colours; body colours; miniature; distemper; fresco; oil;
     encaustic paintings; enamel; mosaic work. Writing; materials
     for writing; pens; inks; use of coloured inks for denoting
     numbers; polygraph; telegraph; geometrical instruments; rulers;
     compasses; flexible rulers; squares; triangular compasses;
     parallel rulers; Marquois's scales; pantograph; proportional
     compasses; sector. Measurement of angles; theodolites;
     quadrants; dividing-engine; vernier; levelling; sines of
     angles; Gunter's scale; Nicholson's circle; dendrometer;
     arithmetical machines; standard measures; quotation from
     Laplace; new measures; decimal divisions; length of the
     pendulum and of the meridian of the earth; measures of time;
     objections; comparison of measures; instruments for measuring;
     micrometrical scales; log-lines."

This represents an extensive area to cover in a lecture of one hour.

When Newton, by means of a prism,

    "Unravelled all the shining robe of day,"

he showed that sunlight is made up of light varying in tint from red,
through orange, yellow, green, and blue, to violet, and that by
recombining all these kinds of light, or certain of them selected in
an indefinite number of ways, white light could be produced.
Subsequently Sir Wm. Herschel showed that rays less refrangible than
the red were to be found among the solar radiation; and other rays
more refrangible than the violet, but, like the ultra-red rays,
incapable of exciting vision, were found by Ritter and Wollaston. In
speaking of Newton's experiments, in his thirty-seventh lecture, Young
says:--

    It is certain that the perfect sensations of yellow and of blue
    are produced respectively by mixtures of red and green and of
    green and violet light, and there is reason to suspect that
    those sensations are always compounded of the separate
    sensations combined; at least, this supposition simplifies the
    theory of colours. It may, therefore, be adopted with advantage,
    until it be found inconsistent with any of the phenomena; and we
    may consider white light as composed of a mixture of red, green,
    and violet only, ... with respect to the quantity or intensity
    of the sensations produced.

It should be noticed that, in the above quotation, Young speaks only
of the sensations produced. Objectively considered, sunlight consists
of an infinite number of differently coloured lights comprising nearly
all the shades from one end of the spectrum to the other, though white
light may have a much simpler constitution, and may, for example,
consist simply of a mixture of homogeneous red, green, and violet
lights, or of homogeneous yellow and blue lights, properly selected.
But considered subjectively, Young implies that the eye perceives
three, and only three, distinct colour-sensations, corresponding to
pure red, green, and violet; that when these three sensations are
excited in a certain proportion, the complex sensation is that of
white light; but if the relative intensities of the separate
sensations differ from these ratios, the perception is that of some
colour. To exhibit the effects of mixing light of different colours,
Young painted differently coloured sectors on circles of cardboard,
and then made the discs rotate rapidly about their centres, when the
effect was the same as though the lights emitted by the sectors were
mixed in proportion to the breadth of the sectors. This contrivance
had been previously employed by Newton, and will be again referred to
in connection with another memoir. The results of these experiments
were embodied by Young in a diagram of colour, consisting of an
equilateral triangle, in which the colours red, green, and violet,
corresponding to the simple sensations, were placed at the angles,
while those produced by mixing the primary colours in any proportions,
were to be found within the triangle or along its sides; the rule
being that the colour formed by the admixture of the primary colours
in any proportions, was to be found at the centre of gravity of three
heavy particles placed at the angular points of the triangle, with
their masses proportioned to the corresponding amounts of light. Thus
the colours produced by the admixture of red and green only, in
different proportions, were placed along one side of the triangle,
these colours corresponding to various tints of scarlet, orange,
yellow, and yellowish green; another side contained the mixtures of
green and violet representing the various shades of bluish green and
blue; and the third side comprised the admixtures of red and violet
constituting crimsons and purples. The interior of the triangle
contained the colours corresponding to the mixture of all three
primary sensations, the centre being neutral grey, which is a pure
white faintly illuminated. If white light of a certain degree of
intensity fall on white paper, the paper appears white, but if a
stronger light fall on another portion of the same sheet, that which
is less strongly illuminated appears grey by contrast. Shadows thrown
on white paper may possess any degree of intensity, corresponding to
varying shades of neutral grey, up to absolute blackness, which
corresponds to a total absence of light. Thus considered,
chromatically black and white are the same, differing only in the
amount of light they reflect. A piece of white paper in moonlight is
darker than black cloth in full sunlight.

It must be remembered that Young's diagram of colours corresponds to
the admixture of coloured lights, not of colouring materials or
pigments. The admixture of blue and yellow lights in proper
proportions may make white or pink, but never green. The admixture of
blue and yellow pigments makes a green, because the blue absorbs
nearly all the light except green, blue, and a little violet, while
the yellow absorbs all except orange, yellow, and green. The green
light is the only light common to the two, and therefore the only
light which escapes absorption when the pigments are mixed. Another
point already noticed must also be carefully borne in mind. Young was
quite aware that, physically, there are an infinite number of
different kinds of light differing continuously in wave-length from
the ultra-red to the ultra-violet, though colour can hardly be
regarded as an attribute of the light considered objectively. The
question of colour is essentially one of perception--a physiological,
not a physical, question--and it is only in this sense that Young
maintained the doctrine of three primary colours. In his paper on the
production of colours, read before the Royal Society on July 1, 1802,
he speaks of "the proportions of the sympathetic fibres of the
retina," corresponding to these primary colour-sensations. According
to this doctrine, white light would always be produced when the three
sensations were affected in certain proportions, whether the exciting
cause were simply two kinds of homogeneous light, corresponding to two
pure tones in music, or an infinite number of different kinds, as in
sunlight; and a particular yellow sensation might be excited by
homogeneous yellow light from one part of the spectrum, or by an
infinite number of rays of different wave-lengths, corresponding to
various shades of red, orange, yellow, and green. Subjectively, the
colours would be the same; objectively, the light producing them would
differ exceedingly.

But Young's greatest service to science was his application of the
principle of interference--of which he had already made good use in
the theory of sound--to the phenomena of light. The results of these
researches were presented to the Royal Society, and two of the papers
were selected as Bakerian lectures in 1801 and 1803 respectively.
Unfavourable criticisms of these papers, which appeared in the
_Edinburgh Review_, and were said to have been written by Mr.
(afterwards Lord) Brougham, seem to have caused their contents to be
neglected by English men of science for many years; and it was to
Arago and Fresnel that we are indebted for recalling public attention
to them. The undulatory theory of light, which maintains that light
consists of waves transmitted through an _ether_, which pervades all
space and all matter, owes its origin to Hooke and Huyghens. Huyghens
showed that this theory explained, in a very beautiful manner, the
laws of reflection and of refraction, if it be allowed that light
travels more slowly the denser the medium. According to the celebrated
principle of Huyghens, every point in the front of a wave at any
instant becomes a centre of disturbance, from which a secondary wave
is propagated. The fronts of these secondary waves all lie on a
surface, which becomes the new surface of the primary wave. When light
enters a denser medium obliquely, the secondary waves which are
propagated within the denser medium extend to a less distance than
those propagated in the rarer medium, and thus the front of the
primary wave becomes bent at the point where it meets the common
surface. Huyghens explained, not only the laws of ordinary refraction
in this manner, but, by supposing the secondary waves to form
spheroids instead of spheres, he obtained the laws of refraction of
the extraordinary ray in Iceland-spar. He did not, however, succeed in
explaining why light should not diverge laterally instead of
proceeding in straight lines. Newton supported the theory that light
consists of particles or corpuscles projected in straight lines from
the luminous body, and sometimes transmitted, sometimes reflected,
when incident on a transparent medium of different density. To account
for the particle being sometimes transmitted and sometimes reflected,
Newton had recourse to the hypothesis of "fits of easy transmission
and of easy reflection," and, to account for the fits themselves, he
supposed the existence of an ether, the vibrations of which affected
the particles. The laws of reflection were readily explained, being
the same as for a perfectly elastic ball; the laws of refraction
admitted of very simple explanation, by supposing that the particles
of the denser medium exert a greater attraction on the particles of
light than those of the rarer medium, but that this attraction acts
only through very short distances, so that when the light-corpuscle is
at a sensible distance from the surface, it is attracted equally all
round, and moves as though there were no force acting upon it. As a
consequence of this hypothesis, it follows that the velocity of light
must be greater the denser the medium, while the undulatory theory
leads to precisely the opposite result. When Foucault directly
measured the velocity of light both in air and water, and found it
less in the denser medium, the result was fatal to the corpuscular
theory.

Dr. Young called attention to another crucial test between the two
theories. When a piece of plate-glass is pressed against a slightly
convex lens, or a watch-glass, a series of coloured rings is formed by
reflected light, with a black spot in the centre. This was accounted
for by Newton by supposing that the light which was reflected in any
ring was in a fit of easy transmission (from glass to air) when it
reached the first surface of the film of air, and in a fit of easy
reflection when it reached the second surface. By measuring the
thickness of a film of air corresponding to the first ring of any
particular colour, the length of path corresponding to the interval
between two fits for that particular kind of light could be
determined. When water instead of air is placed between the glasses,
according to the corpuscular theory the rings should expand; but
according to the undulatory theory they should contract; for the
wave-length corresponds to the distance between successive fits of the
same kind on the corpuscular hypothesis. On trying the experiment, the
rings were seen to contract. This result seemed to favour the
undulatory theory; but the objection urged by Newton that rays of
light do not bend round obstacles, like waves of sound, still held its
ground. This objection Young completely demolished by his principle of
interference. He showed that when light passes through an aperture in
a screen, whatever the shape of the aperture, provided its width is
large in comparison with the length of a wave of light (one
fifty-thousandth of an inch), no sensible amount of light will reach
any point not directly in front of the aperture; for if any point be
taken to the right or left, the disturbances reaching that point from
different points of the aperture will neutralize one another by
interference, and thus no light will be appreciable. When the breadth
of the aperture is only a small multiple of a wave-length, then there
will be some points outside the direct beam at which the disturbances
from different points of the aperture will not completely destroy one
another, and others at which they will destroy one another; and these
points will be different for light of different wave-lengths. In this
way Young not only explained the rectilinear propagation of light, but
accounted for the coloured bands formed when light diverges from a
point through a very narrow aperture. In a similar way he accounted
for the hyperbolic bands of colour observed by Grimaldi within the
shadow of a square near its corners. With a strip of card
one-thirtieth of an inch in width, Young obtained bands of colour
within the shadow which completely disappeared when the light was cut
off from either side of the strip of card, showing that they were
produced by interference of the two portions of light which had
passed, one to the right, the other to the left, of the strip of card.
Professor Stokes has succeeded in showing a bright spot at the centre
of the shadow of a circular disc of the size of a sovereign. The
narrow bands of colour formed near the edge of the shadow of any
object, which Newton supposed to be due to the "inflection" of the
light by the attraction of the object, Young showed to be independent
of the material or thickness of the edge, and completely accounted for
them by the principle of interference. Newton's rings were explained
with equal facility. They were due to the interference of light
reflected from the first and second surfaces of the film of air or
water between the glasses. The black spot at the centre of the
reflected rings was due to the difference between reflection taking
place from the surface of a denser or a rarer medium, half an
undulation being lost when the reflection takes place in glass at the
surface of air. If a little grease or water be placed between two
pieces of glass which are nearly in contact, but the space between be
not filled with the water or grease, but contain air in some parts,
and water or grease in others, a series of rings will be seen by
transmitted light, which have been called "the colours of mixed
plates." Young showed that these colours could be accounted for by
interference between the light that had passed through the air and
that which had passed through the water, and explained the fact that,
to obtain the same colour, the distance between the plates must be
much greater than in the case of Newton's rings.

The bands of colour produced by the interference of light proceeding
from a point and passing on each side of a narrow strip of card, have
already been referred to. The bands are broader the narrower the strip
of card. A fine hair gives very broad bands. When a number of hairs
cross one another in all directions, these bands form circular rings
of colour. If the width of the hairs be very variable, the rings
formed will be of different sizes and overlapping one another, no
distinct series will be visible; but when the hairs are of nearly the
same diameter, a series of well-defined circles of colour, resembling
Newton's rings, will be seen, and if the diameter of a particular ring
be measured, the breadth of the hairs can be inferred. Young
practically employed this method for measuring the diameter of the
fibres of different qualities of wool in order to determine their
commercial value. The instrument employed he called the _eriometer_.
It consisted of a plate of brass pierced with a round hole about
one-thirtieth of an inch in diameter in the centre, and around this a
small circle, about one-third of an inch in diameter, of very fine
holes. The plate was placed in front of a lamp, and the specimen of
wool was held on wires at such a distance in front of the brass plate
that the first green ring appeared to coincide with the circle of
small holes. The eye was placed behind the lock of wool, and the
distance to which the wool had to be removed in front of the brass
plate in order that the first green ring might exactly coincide with
the small circle of fine holes, was proportional to the breadth of the
fibres. The same effect is produced if fine particles, such as
lycopodium powder, or blood-corpuscles, scattered on a piece of glass,
be substituted for the lock of wool, and Young employed the instrument
in order to determine the diameter of blood-corpuscles. He determined
the constant of his apparatus by comparison with some of Dr.
Wollaston's micrometric observations. The coloured halos sometimes
seen around the sun Young referred to the existence of small drops of
water of nearly uniform diameter, and calculated the necessary
diameter for halos of different angular magnitudes.

The same principle of interference afforded explanation of the colours
of striated surfaces, such as mother-of-pearl, which vary with the
direction in which they are seen. Viewed at one angle light of a
particular colour reflected from different ridges will be in a
condition to interfere, and this colour will be absent from the
reflected light. At a different inclination, the light reaching the
eye from all the ridges (within a certain angle) will be in precisely
the same phase, and only then will light of that colour be reflected
in its full intensity. With a micrometer scale engraved on glass by
Coventry, and containing five hundred lines to the inch, Young
obtained interference spectra. Modern gratings, with several thousand
lines to the inch, afford the purest spectra that can be obtained, and
enable the wave-length of any particular kind of light to be measured
with the greatest accuracy.

Young's dislike of mathematical analysis prevented him from applying
exact calculation to the interference phenomena which he observed,
such as subsequently enabled Fresnel to overcome the prejudice of the
French Academy and to establish the principle on an incontrovertible
footing. Young's papers attracted very little attention, and Fresnel
made for himself many of Young's earlier discoveries, but at once gave
Young the full credit of the work when his priority was pointed out.
The phenomena of polarization, however, still remained unexplained.
Both Young and Fresnel had regarded the vibrations of light as similar
to those of sound, and taking place in the direction in which the wave
is propagated. The fact that light which had passed through a crystal
of Iceland-spar, was differently affected by a second crystal,
according to the direction of that crystal with respect to the former,
showed that light which had been so transmitted was not like common
light, symmetrical in all azimuths, but had acquired sides or poles.
Such want of symmetry could not be accounted for on the hypothesis
that the vibrations of light took place at right angles to the
wave-front, that is, in the direction of propagation of the light. The
polarization of light by reflection was discovered by Malus, in 1809.
In a letter written to Arago, in 1817, Young hinted at the possibility
of the existence of a component vibration at right angles to the
direction of propagation, in light which had passed through
Iceland-spar. In the following year Fresnel arrived independently at
the hypothesis of transverse vibrations, not as constituting a small
component of polarized light, but as representing completely the mode
of vibration of all light, and in the hands of Fresnel this hypothesis
of transverse vibrations led to a theory of polarization and double
refraction both in uniaxal and biaxal crystals which, though it can
hardly be regarded as complete from a mechanical point of view, is
nevertheless one of the most beautiful and successful applications of
mathematics to physics that has ever been made. To Young, however,
belongs the credit of suggesting that the spheroidal form of the waves
in Iceland-spar might be accounted for by supposing the elasticity
different in the direction of the optic axis and at right angles to
that direction; and he illustrated his view by reference to certain
experiments of Chladni, in which it had been shown that the velocity
of sound in the wood of the Scotch fir is different along, and
perpendicular to, the fibre in the ratio of 5 to 4. Young was also the
first to explain the colours exhibited by thin plates of crystals in
polarized light, discovered by Arago in 1811, by the interference of
the ordinary and extraordinary rays, and Fresnel afterwards completed
Young's explanation in 1822.

It is for his contributions to the undulatory theory of light that
Young will be most honourably remembered. Hooke, in 1664, referred to
light as a "quick, short, vibrating motion;" Huyghens's "Traité de la
Lumière" was published in 1690. From that time the undulatory theory
lost ground, until it was revived by Young and Fresnel. It soon after
received great support from the establishment, by Joule and others, of
the mechanical theory of heat. One remark of Young's respecting the
ether opens up a question which has attracted much attention of late
years. In a letter addressed to the Secretary of the Royal Society,
and read January 16, 1800, he says:--

    That a medium, resembling in many properties that which has been
    denominated ether, does really exist, is undeniably proved by
    the phenomena of electricity; and the arguments against the
    existence of such an ether throughout the universe have been
    pretty sufficiently answered by Euler. The rapid transmission of
    the electrical shock shows that the electric medium is possessed
    of an elasticity as great as is necessary to be supposed for the
    propagation of light. Whether the electric ether is to be
    considered as the same with the luminous ether--if such a fluid
    exists--may perhaps at some future time be discovered by
    experiment.

Besides his contributions to optics, Young made distinct advances in
connection with elasticity, and with surface-tension, or
"capillarity." It is said that Leonardo da Vinci was the first to
notice the ascent of liquids in fine tubes by so-called capillary
attraction. This, however, is only one of a series of phenomena now
very generally recognized, and all of which are referable to the same
action. The hanging of a drop from the neck of a phial; the pressure
of air required to inflate a soap-bubble; the flotation of a greasy
needle on the surface of water; the manner in which some insects rest
on water, by depressing the surface, without wetting their legs; the
possibility of filling a tumbler with water until the surface stands
above the edge of the glass; the nearly spherical form of rain-drops
and of small drops of mercury, even when they are resting on a
table,--are all examples of the effect of surface-tension. These
phenomena have recently been studied very carefully by Quincke and
Plateau, and they have been explained in accordance with the principle
of energy by Gauss. Hawksbee, however, was the first to notice that
the rise of a liquid in a fine tube did not depend on the thickness of
the walls of the tube, and he therefore inferred that, if the
phenomena were due to the attraction of the glass for the liquid, it
could only be the superficial layers which produced any effect. This
was in 1709. Segner, in 1751, introduced the notion of a
surface-tension; and, according to his view, the surface of a liquid
must be considered as similar to a thin layer of stretched
indiarubber, except that the tension is always the same at the surface
bounding the same media. This idea of surface-tension was taken up by
Young, who showed that it afforded explanation of all the known
phenomena of "capillarity," when combined with the fact, which he was
himself the first to observe, that the angle of contact of the same
liquid-surface with the same solid is constant. This angle he called
the "appropriate angle." But Young went further, and attempted to
explain the existence of surface-tension itself by supposing that the
particles of a liquid not only exert an attractive force on one
another, which is constant, but also a repulsive force which increases
very rapidly when the distance between them is made very small. His
views on this subject were embodied in a paper on the cohesion of
liquids, read before the Royal Society in 1804. He afterwards wrote an
article on the same subject for the supplement of the "Encyclopædia
Britannica."

The changes which solids undergo under the action of external force,
and their tendency to recover their natural forms, were studied by
Hooke and Gravesande. The experimental fact that, for small changes of
form, the extension of a rod or string is proportional to the tension
to which it is exposed, is known as Hooke's law. The compression and
extension of the fibres of a bent beam were noticed by James
Bernoulli, in 1630, by Duhamel and others. The bending of beams was
also studied by Coulomb and Robison, but Young appears to have been
almost the first to apply the theory of elasticity to the statics of
structures. In a letter to the Secretary of the Admiralty, written in
1811, in reply to an invitation to report on Mr. Steppings's
improvements in naval architecture, Young claimed that he was the only
person who had published "any attempts to improve the _theory_ of
carpentry." It may be here mentioned that Young accepted the
invitation of the Admiralty, and sent in a very exhaustive report,
which their Lordships regarded as "too learned" to be of great
practical value. Young's contributions to this subject will be chiefly
remembered in connection with his "modulus of elasticity." This he
originally defined as follows:--

"The modulus of the elasticity of any substance is a column of the
same substance capable of producing a pressure on its base which is to
the weight causing a certain degree of compression as the length of
the substance is to the diminution of its length."

It is not usual now to express Young's modulus of elasticity in terms
of a length of the substance considered. As now usually defined,
Young's modulus of elasticity is the force which would stretch a rod
or string to double its natural length if Hooke's law were true for so
great an extension.

So much of Dr. Young's scientific work has been mentioned here because
it was during his early years of professional practice that his most
original scientific work was accomplished. As already stated, after
two years' tenure of the Natural Philosophy chair at the Royal
Institution, Young resigned it because his friends were of opinion
that its tenure militated against his prospects as a physician. In the
summer of 1802 he escorted the great-nephews of the Duke of Richmond
to Rouen, and took the opportunity of visiting Paris. In March, 1803,
he took his degree of M.B. at Cambridge, and on June 14, 1804, he
married Eliza, second daughter of J. P. Maxwell, Esq., whose country
seat was near Farnborough. For sixteen years after his marriage, Young
resided at Worthing during the summer, where he made a very
respectable practice, returning to London in October or November. In
January, 1811, he was elected one of the physicians of St. George's
Hospital, which appointment he retained for the rest of his life. In
this capacity his practice was considerably in advance of the times,
for he regarded medicine as a science rather than an empirical art,
and his careful methods of induction demanded an amount of attention
which medical students, who preferred the more rough-and-ready methods
then in vogue, were slow to give. The apothecary of the hospital
stated that more of Dr. Young's patients went away cured than of those
who were subjected to the more fashionable treatment; but his private
practice, notwithstanding the sacrifices he had made, never became
very valuable.

In 1816 Young was appointed Secretary to a Commission for determining
the length of the second's pendulum. The reports of this Commission
were drawn up by him, though the experimental work was carried out by
Captain Kater. The result of the work was embodied in an Act of
Parliament, introduced by Sir George Clerk, in 1824, which provided
that if the standard yard should be lost it should "be restored to the
same length," by making it bear to the length of the second's pendulum
at sea-level in London, the ratio of 36 to 39·1393; but before the
standards were destroyed, in 1835, so many sources of possible error
were discovered in the reduction of pendulum observations, that the
Commission appointed to restore the standards recommended that a
material standard yard should be constructed, together with a number
of copies, so that, in the event of the standard being again
destroyed, it might be restored by comparison with its copies. In 1818
Young was appointed Superintendent of the Nautical Almanac and
Secretary of the Board of Longitude. When this Board was dissolved in
1828, its functions were assumed by the Admiralty, and Young, Faraday,
and Colonel Sabine were appointed a Scientific Committee of Reference
to advise the Admiralty in all matters in which their assistance might
be required. The income from these Government appointments rendered
Young more independent of his practice, and he became less careful to
publish his scientific papers anonymously. In 1820 he left Worthing
and gave up his practice there. The following year, in company with
Mrs. Young, he took a tour through France, Switzerland, and Italy, and
at Paris attended a meeting of the Institute, where he met Arago, who
had called on him in Worthing, in 1816. At the same time he made the
acquaintance of Laplace, Cuvier, Humboldt, and others. In 1824 he
visited Spa, and took a tour through Holland. In the same year Young
was appointed Inspector of Calculations and Medical Referee to the
Palladium Insurance Company. This caused him to turn his attention to
the subject of life assurance and bills of mortality. In 1825, as
Foreign Secretary of the Royal Society, he had the satisfaction of
forwarding to Fresnel the Rumford Medal in acknowledgment of his
researches on polarized light. Fresnel died, in his fortieth year, a
few days after receiving the medal.

Dr. Young died on May 10, 1829, in the fifty-sixth year of his age,
his excessive mental exertions in early life having apparently led to
a premature old age. He was buried in the parish church of
Farnborough, and a medallion by Sir Francis Chantrey was erected to
his memory in Westminster Abbey.

But, though Young was essentially a scientific man, his
accomplishments were all but universal, and any memoir of him would be
very incomplete without some sketch of his researches in Egyptian
hieroglyphics. His classical training, his extensive knowledge of
European and Eastern languages, and his neat handwriting and drawing,
have already been referred to. To these attainments must be added his
scientific _method_ and power of careful and systematic observation,
and it will be seen that few persons could come to the task of
deciphering an unknown language with a better chance of success than
Dr. Young.

The Rosetta Stone was found by the French while excavating at Fort St.
Pierre, near Rosetta, in 1799, and was brought to England in 1802. The
stone bore an inscription in three different kinds of character--the
Hieroglyphic, the Enchorial or Demotic, and the ordinary Greek.
Young's attention was first called to the Egyptian characters by a
manuscript which was submitted to him in 1814. He then obtained copies
of the inscriptions on the Rosetta Stone and subjected them to a
careful analysis. The latter part of the Greek inscription was very
much injured, but was restored by the conjectures of Porson and Heyne,
and read as follows:--"What is here decreed shall be inscribed on a
block of hard stone, in sacred, in enchorial, and in Greek characters,
and placed in each temple, of the first, second, and third gods."

This indicated that the three inscriptions contained the same decree,
but, unfortunately, the beginnings of the first and second
inscriptions were lost, so that there were no very definitely fixed
points to start upon. The words "Alexander" and "Alexandria,"
however, occurred in the Greek, and these words, being so much alike,
might be recognized in each of the other inscriptions. The word
"Ptolemy" appeared eleven times in the Greek inscription, and there
was a word which, from its length and position, seemed to correspond
to it, which, however, appeared fourteen times in the hieroglyphic
inscription. This word, whenever it appeared in the hieroglyphics, was
surrounded by a ring forming what Champollion called a _cartouche_,
which was always employed to denote the names of royal persons. These
words were identified by Baron Sylvestre de Sacy and the Swedish
scholar Akerblad. Young appears to have started with the idea, then
generally current, that hieroglyphic symbols were purely ideographic,
each sign representing a word. His knowledge of Chinese, however, led
him to modify this view. In that language native words are represented
by single symbols, but, when it is necessary to write a foreign word,
a group of word-symbols is employed, each of which then assumes a
phonetic character of the same value as the initial letter of the word
which it represents. The phonetic value of these signs is indicated in
Chinese by a line at the side, or by enclosing them in a square. Young
supposed that the ring surrounding the royal names in the hieroglyphic
inscription had the same value as the phonetic mark in Chinese, and
from the symbols in the name of Ptolemy he commenced to construct a
hieroglyphic alphabet. He made an error, however, in supposing that
some of the symbols might be syllabic instead of alphabetic. It is
true that in the older inscriptions single signs have sometimes a
syllabic value, and sometimes are used ideographically, while in other
cases a single sign representing the whole word is employed in
conjunction with the alphabetic signs, probably to distinguish the
word from others spelt in the same way, but in inscriptions of so late
a date as the Rosetta Stone, the symbols were purely alphabetic.
Another important step made by Young was the discovery of the use of
_homophones_, or different symbols to represent the same letter.
Young's work was closely followed up by Champollion, and afterwards by
Lepsius, Birsch, and others. The greater part of his researches he
never published, though he made careful examinations of several
funeral rolls and other documents.

It would occupy too much space to give an adequate account of Young's
researches in this subject; some portion of his work he published in a
popular form in the article "Egypt," in the supplement of the
"Encyclopædia Britannica," to which supplement he contributed about
seventy articles on widely different subjects. Perhaps it is not too
much to say that to Young we owe the foundation of all we now know of
hieroglyphics and the Egyptian history which has been learned from
them; and the obelisk on the Thames Embankment should call to mind the
memory of no one more prominently than that of Thomas Young.




MICHAEL FARADAY.


The work of Michael Faraday introduced a new era in the history of
physical science. Unencumbered by pre-existing theories, and
untrammelled by the methods of the mathematician, he set forth on a
line of his own, and, while engaged in the highest branches of
experimental research, he sought to explain his results by reference
to the most elementary mechanical principles only. Hence it was that
those conclusions which had been obtained by mathematicians only by
the help of advanced analytical methods, and which were expressed by
them only in the language of the integral calculus, Faraday achieved
without any such artificial aids to thought, and expressed in simple
language, having reference to the mechanism which he conceived to be
the means by which such results were brought about. For a long time
Faraday's methods were regarded by mathematicians with something more
than suspicion, and, while they could not but admire his experimental
skill and were compelled to admit the accuracy of his conclusions, his
mode of thought differed too widely from that to which they were
accustomed to command their assent. In Sir William Thomson, and in
Clerk Maxwell, Faraday at length found interpreters between him and
the mathematical world, and to the mathematician perhaps the greatest
monument of the genius of Faraday is the "Electricity and Magnetism"
of Clerk Maxwell.

Michael Faraday was born at Newington, Surrey, on September 22, 1791,
and was the third of four children. His father, James Faraday, was the
son of Robert and Elizabeth Faraday, of Clapham Wood Hall, in the
north-west of Yorkshire, and was brought up as a blacksmith. He was
the third of ten children, and, in 1786, married Margaret Hastwell, a
farmer's daughter. Soon after his marriage he came to London, where
Michael was born. In 1796 James Faraday, with his family, moved from
Newington, and took rooms over a coach-house in Jacob's Well Mews,
Charles Street, Manchester Square. In looking at this humble abode one
can scarcely help thinking that the Yorkshire blacksmith and his
little family would have been far happier in a country "smiddy" near
his native moors than in a crowded London court; but, had he remained
there, it is difficult to see how the genius of young Michael could
have met with the requisites for its development.

James Faraday was far from enjoying good health, and his illness
often necessitated his absence from work, and, as a consequence, his
family were frequently in very straitened circumstances. The early
education of Michael was, therefore, not of a very high order, and
consisted "of little more than the rudiments of reading, writing, and
arithmetic." Like most boys in a similar position in London, he found
his amusement for the most part in the streets, but, except that in
his games at marbles we may assume that he played with other boys, we
have no evidence whether his time was spent mostly by himself, or
whether he was one of a "set" of street companions.

In 1804, when thirteen years of age, Michael Faraday went as
errand-boy to Mr. Geo. Riebau, a bookseller in Blandford Street. Part
of his duty in this capacity was to carry round papers lent on hire by
his master, and in his "Life of Faraday," Dr. Bence Jones tells how
anxious the young errand-boy was to collect his papers on Sunday
morning in time to attend the Sandemanian service with the other
members of his family.

Faraday was apprenticed to Mr. Riebau on October 7, 1805, and learned
the business of a bookbinder. He occasionally occupied his spare time
in reading the scientific books he had to bind, and was particularly
interested in Mrs. Marcet's "Conversations in Chemistry," and in the
article on "Electricity" in the "Encyclopædia Britannica." These were
days before the existence of the London Society for the Extension of
University Teaching, and, though Professor Anderson in Glasgow had
shown how the advantages of a university might be extended to those
whose fortunes prevented them from becoming regular university
students, Professor Stuart had not yet taught the English universities
that they had responsibilities outside their own borders, and that the
national universities of the future must be the teachers of all
classes of the community. But private enterprise supplied in a measure
the neglect of public bodies. Mr. Tatum, of 43, Dorset Street, Fleet
Street, advertised a course of lectures on natural philosophy, to be
delivered at his residence at eight o'clock in the evenings. The price
of admission was high, being a shilling for each lecture, but
Michael's brother Robert frequently supplied him with the money, and
in attending these lectures Faraday made many friendships which were
valuable to him afterwards.

Faraday appears to have been aware of the value of skill in drawing--a
point to which much attention has recently been called by those
interested in technical education--and he spent some portion of his
time in studying perspective, so as to be better able to illustrate
his notes of Mr. Tatum's lectures, as well as of some of Sir Humphry
Davy's, which he was enabled to hear at the Royal Institution through
the kindness of a customer at Mr. Riebau's shop.

In 1812, before the end of his apprenticeship, Faraday was engaged in
experiments with voltaic batteries of his own construction. Having
cut out seven discs of zinc the size of halfpence, and covered them
with seven halfpence, he formed a pile by inserting pieces of paper
soaked in common salt between each pair, and found that the pile so
constructed was capable of decomposing Epsom salts. With a somewhat
larger pile he decomposed copper sulphate and lead acetate, and made
some experiments on the decomposition of water. On July 21, 1812, in
writing to his friend Abbott, he mentions the movements of camphor
when floating on water, and adds, "Science may be illustrated by those
minute actions and effects, almost as much as by more evident and
obvious phenomena.... My knife is so bad that I cannot mend my pen
with it; it is now covered with copper, having been employed to
precipitate that metal from the muriatic acid."

Something of Faraday's disposition, as well as of the results of his
self-education, may be gathered from the following quotations from
letters to Abbott, written at this time:--

    I have again gone over your letter, but am so blinded that I
    cannot see any subject except chlorine to write on; but before
    entering on what I intend shall fill up the letter, I will ask
    your pardon for having maintained an opinion against one who was
    so ready to give his own up. I suspect from that circumstance I
    am wrong.... In the present case I conceive that experiments may
    be divided into three classes: first, those which are for the
    old theory of oxymuriatic acid, and consequently oppose the new
    one; second, those which are for the new one, and oppose the old
    theory; and third, those which can be explained by both
    theories--apparently so only, for in reality a false theory can
    never explain a fact.

    It is not for me to affirm that I am right and you wrong;
    speaking impartially, I can as well say that I am wrong and you
    right, or that we both are wrong and a third right. I am not so
    self-opinionated as to suppose that my judgment and perception
    in this or other matters is better or clearer than that of other
    persons; nor do I mean to affirm that this is the true theory in
    reality, but only that my judgment conceives it to be so.
    Judgments sometimes oppose each other, as in this case; and as
    there cannot be two opposing facts in nature, so there cannot be
    two opposing truths in the intellectual world. Consequently,
    when judgments oppose, one must be wrong--one must be false; and
    mine may be so for aught I can tell. I am not of a superior
    nature to estimate exactly the strength and correctness of my
    own and other men's understanding, and will assure you, dear
    A----, that I am far from being convinced that my own is always
    right. I have given you the theory--not as the true one, but as
    the one which appeared true to me--and when I perceive errors in
    it, I will immediately renounce it, in part or wholly, as my
    judgment may direct. From this, dear friend, you will see that I
    am very open to conviction; and from the manner in which I
    shall answer your letter, you will also perceive that I must be
    convinced before I renounce.

On October 7, 1812, Faraday's apprenticeship terminated, and
immediately afterwards he started life as a journeyman bookbinder. He
now found that he had less time at his disposal for scientific work
than he had enjoyed when an apprentice, and his desire to give up his
trade and enter fully upon scientific pursuits became stronger than
ever. During his apprenticeship he had written to Sir Joseph Banks,
then President of the Royal Society, in the hope of obtaining some
scientific employment; he now applied to Sir Humphry Davy. In a letter
written to Dr. Paris, in 1829, Faraday gave an account of this
application.

"My desire to escape from trade, which I thought vicious and selfish,
and to enter into the service of science, which I imagined made its
pursuers amiable and liberal, induced me at last to take the bold and
simple step of writing to Sir H. Davy, expressing my wishes, and a
hope that, if an opportunity came in his way, he would favour my
views; at the same time, I sent the notes I had taken of his lectures.

"The answer, which makes all the point of my communication, I send you
in the original, requesting you to take great care of it, and to let
me have it back, for you may imagine how much I value it.

"You will observe that this took place at the end of the year 1812;
and early in 1813 he requested to see me, and told me of the situation
of assistant in the laboratory of the Royal Institution, then just
vacant.

"At the same time that he thus gratified my desires as to scientific
employment, he still advised me not to give up the prospects I had
before me, telling me that Science was a harsh mistress, and, in a
pecuniary point of view, but poorly rewarding those who devoted
themselves to her service. He smiled at my notion of the superior
moral feelings of philosophic men, and said he would leave me to the
experience of a few years to set me right on that matter.

"Finally, through his good efforts, I went to the Royal Institution,
early in March of 1813, as assistant in the laboratory; and in October
of the same year went with him abroad, as his assistant in experiments
and in writing. I returned with him in April, 1815, resumed my station
in the Royal Institution, and have, as you know, ever since remained
there."

Sir H. Davy's letter was as follows:--

    "SIR,

     "I am far from displeased with the proof you have given me of
     your confidence, and which displays great zeal, power of
     memory, and attention. I am obliged to go out of town, and
     shall not be settled in town till the end of January; I will
     then see you at any time you wish. It would gratify me to be
     of any service to you; I wish it may be in my power.

    "I am, sir,
    "Your obedient humble servant,
    "H. DAVY."

The minutes of the meeting of managers of the Royal Institution, on
March 1, 1813, contain the following entry:--"Sir Humphry Davy has the
honour to inform the managers that he has found a person who is
desirous to occupy the situation in the institution lately filled by
William Payne. His name is Michael Faraday. He is a youth of
twenty-two years of age. His habits seem good, his disposition active
and cheerful, and his manner intelligent. He is willing to engage
himself on the same terms as those given to Mr. Payne at the time of
quitting the institution.

"Resolved, that Michael Faraday be engaged to fill the situation
lately occupied by Mr. Payne, on the same terms."

About this time Faraday joined the City Philosophical Society, which
had been started at Mr. Tatum's house in 1808. The members met every
Wednesday evening, either for a lecture or discussion; and perhaps the
society did not widely differ from some of the "students'
associations" which have more recently been started in connection with
other educational enterprises. Magrath was secretary of this society,
and from it there sprang a smaller band of students, who, meeting once
a week, either at Magrath's warehouse in Wood Street, or at Faraday's
private rooms in the attics of the Royal Institution, for mutual
improvement, read together, and freely criticized each other's
pronunciation and composition. In a letter to Abbott six weeks after
commencing work at the Royal Institution, Faraday says:--

    A stranger would certainly think you and I were a couple of very
    simple beings, since we find it necessary to write to each
    other, though we so often personally meet; but the stranger
    would, in so judging, only fall into that error which envelops
    all those who decide from the outward appearances of things....
    When writing to you I seek that opportunity of striving to
    describe a circumstance or an experiment clearly; so that you
    will see I am urged on by selfish motives partly to our mutual
    correspondence, but, though selfish, yet not censurable.

During the summer of 1813 Faraday, in his letters to Abbott, gave his
friend the benefit of his experience "on the subject of lectures and
lecturers in general," in a manner that speaks very highly of his
power of observation of men as well as things. He was of opinion that
a lecture should not last more than an hour, and that the subject
should "fit the audience."

"A lecturer may consider his audience as being polite or vulgar (terms
I wish you to understand according to Shuffleton's new dictionary),
learned or unlearned (with respect to the subject), listeners or
gazers. Polite company expect to be entertained, not only by the
subject of the lecture, but by the manner of the lecturer; they look
for respect, for language consonant to their dignity, and ideas on a
level with their own. The vulgar--that is to say, in general, those
who will take the trouble of thinking, and the bees of business--wish
for something that they can comprehend. This may be deep and elaborate
for the learned, but for those who are as yet tyros and unacquainted
with the subject, must be simple and plain. Lastly, listeners expect
reason and sense, whilst gazers only require a succession of words."

In favour of experimental illustration he says:--

"I need not point out ... the difference in the perceptive powers of
the eye and the ear, and the facility and clearness with which the
first of these organs conveys ideas to the mind--ideas which, being
thus gained, are held far more retentively and firmly in the memory
than when introduced by the ear.... Apparatus, therefore, is an
essential part of every lecture in which it can be introduced.... When
... apparatus is to be exhibited, some kind of order should be
observed in the arrangement of them on the lecture-table. Every
particular part illustrative of the lecture should be in view, no one
thing should hide another from the audience, nor should anything stand
in the way of or obstruct the lecturer. They should be so placed, too,
as to produce a kind of uniformity in appearance. No one part should
appear naked and another crowded, unless some particular reason
exists and makes it necessary to be so."

On October 13, 1813, Faraday left the Royal Institution, in order to
accompany Sir Humphry Davy in a tour on the Continent. His journal
gives some interesting details, showing the inconveniences of foreign
travel at that time. Sir Humphry Davy took his carriage with him in
pieces, and these had to be put together after escaping the dangers of
the French custom-house on the quay at Morlaix, two years before the
battle of Waterloo.

One apparently trivial incident somewhat marred Faraday's pleasure
throughout this journey. It was originally intended that the party
should comprise Sir Humphry and Lady Davy, Faraday, and Sir Humphry's
valet, but at the last moment that most important functionary declined
to leave his native shores. Davy then requested Faraday to undertake
such of the duties of valet as were essential to the well-being of the
party, promising to secure the services of a suitable person in Paris.
But no eligible candidate appeared for the appointment, and thus
Faraday had throughout to take charge of domestic affairs as well as
to assist in experiments. Had there been only Sir Humphry and himself,
this would have been no hardship. Sir Humphry had been accustomed to
humble life in his early days; but the case was different with his
lady, and, apparently, Faraday was more than once on the point of
leaving his patron and returning home alone. A circumstance which
occurred at Geneva illustrates the position of affairs. Professor E.
de la Rive invited Sir Humphry and Lady Davy and Faraday to dinner.
Sir Humphry could not go into society with one who, in some respects,
acted as his valet. When this point was represented to the professor,
he replied that he was sorry, as it would necessitate his giving
another dinner-party. Faraday subsequently kept up a correspondence
with De la Rive, and continued it with his son. In writing to the
latter he says, in speaking of Professor E. de la Rive, that he was
"the first who personally at Geneva, and afterwards by correspondence,
encouraged and by that sustained me."

At Paris Faraday met many of the most distinguished men of science of
the time. One morning Ampère, Clément, and Desormes called on Davy, to
show him some iodine, a substance which had been discovered only about
two years before, and Davy, while in Paris, and afterwards at
Montpellier, executed a series of experiments upon it. After three
months' stay, the party left Paris for Italy, _viâ_ Montpellier, Aix,
and Nice, whence they crossed the Col de Tende to Turin. The transfer
of the carriage and baggage across the Alps was effected by a party of
sixty-five men, with sledges and a number of mules. The description of
the journey, as recorded in Faraday's diary, makes us respect the
courage of an Englishman who, in the early part of this century, would
attempt the conveyance of a carriage across the Alps in the winter.

"From Turin we proceeded to Genoa, which place we left afterwards in
an open boat, and proceeded by sea towards Lerici. This place we
reached after a very disagreeable passage, and not without
apprehensions of being overset by the way. As there was nothing there
very enticing, we continued our route to Florence; and, after a stay
of three weeks or a month, left that fine city, and in four days
arrived here at Rome." The foregoing is from Faraday's letter to his
mother. At Florence a good deal of time was spent in the Academia del
Cimento. Here Faraday saw the telescope with which Galileo discovered
Jupiter's satellites, with its tube of wood and paper about three feet
and a half long, and simple object-glass and eye-glass. A red velvet
electric machine with a rubber of gold paper, Leyden jars pierced by
the discharge between their armatures, the first lens constructed by
Galileo, and a number of other objects, were full of interest to the
recently enfranchised bookbinder's apprentice; but it was the great
burning-glass of the grand-duke which was the most serviceable of all
the treasures of the museum. With this glass--which consisted of two
convex lenses about three feet six inches apart, the first lens having
a diameter of about fourteen or fifteen inches, and the second a
diameter of three inches--Davy succeeded in burning several diamonds
in oxygen gas, and in proving that the diamond consists of little else
than carbon. In 1818 Faraday published a paper on this subject in the
_Quarterly Journal of Science_. At Genoa some experiments were made
with the torpedo, but the specimens caught were very small and weak,
and their shocks so feeble that no definite results were obtained. At
Rome Davy attempted to repeat an experiment of Signor Morrichini,
whereby a steel needle was magnetized by causing the concentrated
violet and blue rays from the sun to traverse the needle from the
middle to the north end several times. The experiment did not succeed
in the hands of Davy and Faraday, and it was left to the latter to
discover a relation between magnetism and light. From Rome they
visited Naples and ascended Vesuvius, and shortly afterwards left
Italy for Geneva. In the autumn of 1814 they returned from Switzerland
through Germany, visiting Berne, Zurich, the Tyrol, Padua, Venice, and
Bologne, to Florence, where Davy again carried out some chemical
investigations in the laboratory of the academy. Thence they returned
to Rome, and in the spring went on to Naples, and again visited
Vesuvius, returning to England in April, _viâ_ Rome, the Tyrol,
Stuttgart, Brussels, and Ostend.

A fortnight after his return from the Continent Faraday was again
assistant at the Royal Institution, but with a salary of thirty
shillings a week. His character will be sufficiently evident from the
quotations which have been given from his diary and letters.
Henceforth we must be mainly occupied with the consideration of his
scientific work.

In January, 1816, he gave his first lecture to the City Philosophical
Society. In a lecture delivered shortly afterwards before the same
society, the following passage, which gives an idea of one of the
current beliefs of the time, occurs:--

"The conclusion that is now generally received appears to be that
light consists of minute atoms of matter of an octahedral form,
possessing polarity, and varying in size or in velocity....

"If now we conceive a change as far beyond vaporization as that is
above fluidity, and then take into account also the proportional
increased extent of alteration as the changes rise, we shall, perhaps,
if we can form any conception at all, not fall far short of radiant
matter;[6] and as in the last conversion many qualities were lost, so
here also many more would disappear.

[Footnote 6: Not Crookes's.]

"It was the opinion of Newton, and of many other distinguished
philosophers, that this conversion was possible, and continually going
on in the processes of nature, and they found that the idea would bear
without injury the application of mathematical reasoning--as regards
heat, for instance. If assumed, we must also assume the simplicity of
matter; for it would follow that all the variety of substances with
which we are acquainted could be converted into one of three kinds of
radiant matter, which again may differ from one another only in the
size of their particles or their form. The properties of known bodies
would then be supposed to arise from the varied arrangements of their
ultimate atoms, and belong to substances only as long as their
compound nature existed; and thus variety of matter and variety of
properties would be found co-essential. The simplicity of such a
system is singularly beautiful, the idea grand and worthy of Newton's
approbation. It was what the ancients believed, and it may be what a
future race will realize."

In the closing words of his fifth lecture to the City Philosophical
Society, Faraday said:--

"The philosopher should be a man willing to listen to every
suggestion, but determined to judge for himself. He should not be
biassed by any appearances; have no favourite hypothesis; be of no
school; and in doctrine have no master. He should not be a respecter
of persons, but of things. Truth should be his primary object. If to
these qualities be added industry, he may indeed hope to walk within
the veil of the temple of nature."

Many years afterwards he stated that, of all the suggestions to which
he had patiently listened after his lectures at the Royal Institution,
only one proved on investigation to be of any value, and that led to
the discovery of the "extra current" and the whole subject of
self-induction.

Faraday always kept a note-book, in which he jotted down any thoughts
which occurred to him in reference to his work, as well as extracts
from books or other publications which attracted his attention. He
called it his "commonplace-book." Many of the queries which he here
took note of he subsequently answered by experiment. For example:--

"Query: the nature of sounds produced by flame in tubes."

"Convert magnetism into electricity."

"General effects of compression, either in condensing gases or
producing solutions, or even giving combinations at low temperature."

"Do the pith-balls diverge by the disturbance of electricity through
mutual induction or not?"

Speaking of this book, he says, "I already owe much to these notes,
and think such a collection worth the making by every scientific man.
I am sure none would think the trouble lost after a year's
experience."

In a letter dated May 3, 1818, he writes:--

    I have this evening been busy with an atmospherical electrical
    apparatus. It was a very temporary thing, but answered the
    purpose completely. A wire, with some small brush-wire rolled
    round the top of it, was elevated into the atmosphere by a thin
    wood rod having a glass tube at the end, and tied to a
    chimney-pot on the housetop; and this wire was continued down
    (taking care that it touched nothing in its way) into the
    lecture-room; and we succeeded, at intervals, in getting sparks
    from it nearly a quarter of an inch in length, and in charging a
    Leyden jar, so as to give a strong shock. The electricity was
    positive. Now, I think you could easily make an apparatus of
    this kind, and it would be a constant source of interesting
    matter; only take care you do not kill yourself or knock down
    the house.

On June 12, 1820, he married Miss Sarah Barnard, third daughter of Mr.
Barnard, of Paternoster Row--"an event which," to use his own words,
"more than any other contributed to his earthly happiness and
healthful state of mind." It was his wish that the day should be "just
like any other day"--that there should be "no bustle, no noise, no
hurry occasioned even in one day's proceeding," though in carrying out
this plan he offended some of his relations by not inviting them to
his wedding.

Up to this time Faraday's experimental researches had been for the
most part in the domain of chemistry, and for two years a great part
of his energy had been expended in investigating, in company with Mr.
Stodart, a surgical instrument-maker, the properties of certain alloys
of steel, with a view to improve its manufacture for special purposes.
It was in 1821 that he commenced his great discoveries in electricity.
In the autumn of that year he wrote an historical sketch of
electro-magnetism for the "Annals of Philosophy," and he repeated for
himself most of the experiments which he described. In the course of
these experiments, in September, 1821, he discovered the rotation of a
wire conveying an electric current around the pole of a magnet.
[OE]rsted had discovered, in 1820, the tendency of a magnetic needle
to set itself at right angles to a wire conveying a current. This
action is due to a tendency on the part of the north pole to revolve
in a right-handed direction around the current, while the south pole
tends to revolve in the opposite direction. The principle that action
and reaction are equal and opposite indicates that, if a magnetic pole
tend to rotate around a conductor conveying a current, there must be
an equal tendency for the conductor to rotate around the pole. It was
this rotation that constituted Faraday's first great discovery in
electro-dynamics. On December 21, in the same year, Faraday showed
that the earth's magnetism was capable of exerting a directive action
on a wire conveying a current. Writing to De la Rive on the subject,
he says:--

    I find all the usual attractions and repulsions of the magnetic
    needle by the conjunctive wire are deceptions, the motions
    being, not attractions or repulsions, nor the result of any
    attractive or repulsive forces, but the result of a force in the
    wire, which, instead of bringing the pole of the needle nearer
    to or further from the wire, endeavours to make it move round it
    in a never-ending circle and motion whilst the battery remains
    in action. I have succeeded, not only in showing the existence
    of this motion theoretically, but experimentally, and have been
    able to make the wire revolve round a magnetic pole, or a
    magnetic pole round the wire, at pleasure. The law of
    revolution, and to which all the other motions of the needle are
    reducible, is simple and beautiful.

    Conceive a portion of connecting wire north and south, the north
    end being attached to the positive pole of a battery, the south
    to the negative. A north magnetic pole would then pass round it
    continually in the apparent direction of the sun, from east to
    west above, and from west to east below. Reverse the connections
    with the battery, and the motion of the pole is reversed; or, if
    the south pole be made to revolve, the motions will be in the
    opposite direction, as with the north pole.

    If the wire be made to revolve round the pole, the motions are
    according to those mentioned.... Now, I have been able,
    experimentally, to trace this motion into its various forms, as
    exhibited by Ampère's helices, etc., and in all cases to show
    that the attractions and repulsions are only appearances due to
    this circulation of the pole; to show that dissimilar poles
    repel as well as attract, and that similar poles attract as well
    as repel; and to make, I think, the analogy between the helix
    and common bar magnet far stronger than before. But yet I am by
    no means decided that there are currents of electricity in the
    common magnet. I have no doubt that electricity puts the circles
    of the helix into the same state as those circles are in that
    may be conceived in the bar magnet; but I am not certain that
    this state is directly dependent on the electricity, or that it
    cannot be produced by other agencies; and therefore, until the
    presence of electric currents be proved in the magnet by other
    than magnetical effects, I shall remain in doubt about Ampère's
    theory.

The most convenient rule by which to remember the direction of these
electro-magnetic rotations is probably that given by Clerk Maxwell,
which will be stated in its place.[7] If a circular plate of copper
and another of zinc be connected by a piece (or better, by three
pieces) of insulated wire, so that the zinc is about an inch above the
copper, and the combined plates be suspended by a silk fibre in a
small beaker of dilute sulphuric acid, which is placed on the pole of
a large magnet, the liquid will be seen to rotate about a vertical
axis in one direction, and the two plates with their connecting wires
in the opposite direction. On reversing the polarity of the magnet,
both rotations will be reversed. This is a very simple mode of
exhibiting Faraday's discovery. A little powdered resin renders the
motion of the liquid readily visible.

[Footnote 7: See p. 302.]

In 1823 Faraday published his work on the liquefaction of gases, from
which he concluded that there was no difference in kind between gases
and vapours. In the course of this work he met with more than one
serious explosion. On January 8, 1824, he was elected a Fellow of the
Royal Society, and in 1825, on the recommendation of Sir Humphry Davy,
he was appointed Director of the Laboratory of the Royal Institution,
and in this capacity he instituted the laboratory conferences, which
developed into the Friday evening lectures. For five years after
this, the greater part of Faraday's spare time was occupied in some
investigations in connection with optical glass, made at the request
of the Royal Society, and at the expense of the Government. Mr.
Dollond and Sir John Herschel were associated with him on this
committee, but the results obtained were not of much value to
opticians. The silico-borate of lead which Faraday prepared in the
course of these experiments was, however, the substance with which he
first demonstrated the effect of a magnetic field on the plane of
polarization of light, and with which he discovered diamagnetic
action.

Faraday's experimental researches were generally guided by theoretical
considerations. Frequently these theories were based on very slender
premises, and sometimes were little else than flights of a scientific
imagination, but they served to guide him into fruitful fields of
discovery, and he seldom placed much confidence in his conclusions
till he had succeeded in verifying them experimentally. For many years
he had held the opinion that electric currents should exhibit
phenomena analogous to those of electro-static induction. Again and
again he returned to the investigation, and attempted to obtain an
induced current in one wire through the passage of a powerful current
through a neighbouring conductor; but he looked for a permanent
induced current to be maintained during the whole time that the
primary current was flowing. At length, employing two wires wound
together as a helix on a wooden rod, the first capable of transmitting
a powerful current from a battery, while the second was connected with
a galvanometer, he observed that, when the current started in the
primary, there was a movement of the galvanometer, and when it ceased
there was a movement in the opposite direction, though the
galvanometer remained at zero while the current continued steady.
Hence it was apparent that it is by changes in the primary current
that induced currents may be generated, and not by their steady
continuance; and it was demonstrated that, when a current is started
in a conductor, a temporary current is induced in a neighbouring
conductor in the opposite direction, while a current is induced in the
same direction as the primary when the latter ceases to flow. Before
obtaining this result with the wires on a wooden bobbin, he had
experimented with a wrought-iron ring about six inches in diameter,
and made of 7/8-inch round iron. He wound two sets of coils round it,
one occupying nearly half the ring, and the other filling most of the
other half. One of these he connected with a galvanometer, the other
could be connected at will with a battery. On sending the battery
current through the latter coil, the galvanometer needle swung
completely round four or five times, and a similar action took place,
but in the opposite direction, on stopping the current. Here it was
clearly the magnetism induced in the iron ring which produced so
powerful a current in the galvanometer circuit. Next he wound a
quantity of covered copper wire on a small iron bar, and connecting
the ends to a galvanometer, he placed the little bobbin between the
opposite poles of a pair of bar magnets, whose other ends were in
contact. As soon as the iron core touched the magnets, a current
appeared in the galvanometer. On breaking contact, the current was in
the opposite direction. Then came the experiment above mentioned, in
which no iron was employed. After this, one end of a cylindrical bar
magnet was introduced into a helix of copper wire, and then suddenly
thrust completely in. The galvanometer connected with the coil showed
a transient current. On withdrawing the magnet, the current appeared
in the opposite direction; so that currents were induced merely by the
relative motion of a magnet and a conductor.

A copper disc was mounted so that it could be made to rotate rapidly.
A wire was placed in connection with the centre of the disc, and the
circuit completed by a rubbing contact on the circumference. A
galvanometer was inserted in the circuit, and the large horseshoe
magnet of the Royal Institution so placed that the portion of the disc
between the centre and the rubbing contact passed between the poles of
the magnet. A current flowed through the galvanometer as long as the
disc was kept spinning. Then he found that the mere passage of a
copper wire between the poles of the magnet was sufficient to induce a
current in it, and concluded that the production of the current was
connected with the cutting of the "magnetic curves," or "lines of
magnetic force" which would be depicted by iron filings. Thus in the
course of ten days' experimental work, in the autumn of 1831, Faraday
so completely investigated the phenomena of electro-magnetic induction
as to leave little, except practical applications, to his successors.
A few weeks later he obtained induction currents by means of the
earth's magnetism only, first with a coil of wire wound upon an iron
bar in which a strong current was produced when it was being quickly
placed in the direction of the magnetic dip or being removed from that
position, and afterwards with a coil of wire without an iron core. On
February 8, 1832, he succeeded in obtaining a spark from the induced
current. Unless the electro-motive force is very great, it is not
possible to obtain a spark between two metallic surfaces which are
separated by a sensible thickness of air. If, however, the circuit of
a wire is broken _while_ the current is passing, a little bridge of
metallic vapour is formed, across which for an instant the spark
leaps. The induced current being of such short duration, the
difficulty was to break the circuit while it was flowing. Faraday
wound a considerable length of fine wire around a short bar of iron;
the ends of the wire were crossed so as just to be in contact with one
another, but free to separate if exposed to a slight shock. The ends
of the iron bar projected beyond the coil, and were held just over the
poles of the magnet. On releasing the bar it fell so as to strike the
magnetic poles and close the circuit of the magnet. An induced current
was generated in the wire, but, while this was passing, the shock
caused by the bar striking the magnet separated the ends of the wire,
thus breaking the circuit of the conductor, and a spark appeared at
the gap. In this little spark was the germ of the electric light of
to-day. Subsequently Faraday improved the apparatus, by attaching a
little disc of amalgamated copper to one end of the wire, and bending
over the other end so as just to press lightly against the surface of
the disc. With this apparatus he showed the "magnetic spark" at the
meeting of the British Association at Oxford.

Faraday supposed that when a coil of wire was in the neighbourhood of
a magnet, or near to a conductor conveying a current, the coil was
thrown into a peculiar condition, which he called the _electro-tonic
state_, and that the induced currents appeared whenever this state was
assumed or lost by the coil. He frequently reverted to his conception
of the electro-tonic state, though he saw clearly that, when the
currents were induced by the relative motion of a wire and a magnet,
the current induced depended on the rate at which the lines of
magnetic force had been cut by the wire. Of his conception of lines of
force filling the whole of space, we shall have more to say presently.
It is sufficient to remark here that, in the electro-tonic state of
Faraday, Clerk Maxwell recognized the number of lines of magnetic
force enclosed by the circuit, and showed that the electro-motive
force induced is proportional to the rate of change of the number of
lines of force thus enclosed.

It is seldom that a great discovery is made which has not been
gradually led up to by several observed phenomena which awaited that
discovery for their explanation. In the case of electro-magnetic
induction, however, there appears to have been but one experiment
which had baffled philosophers, and the key to which was found in
Faraday's discovery, while the complete explanation was given by
Faraday himself. Arago had found that, if a copper plate were made
rapidly to rotate beneath a freely suspended magnetic needle, the
needle followed (slowly) the plate in its revolution, though a sheet
of glass were inserted between the two to prevent any air-currents
acting on the magnet. The experiment had been repeated by Sir John
Herschel and Mr. Babbage, but no explanation was forthcoming. Faraday
saw that the revolution of the disc beneath the poles of the magnet
must generate induced currents in the disc, as the different portions
of the metal would be constantly cutting the lines of force of the
magnet. These currents would react upon the magnet, causing a
mechanical stress to act between the two, which, as stated by Lenz,
would be in the direction tending to oppose the _relative_ motion, and
therefore to drag the magnet after the disc in its revolution. In the
above figure the unfledged arrows show the general distribution of the
currents in the disc, while the winged arrows indicate the direction
of the disc's rotation. The currents in the semicircle A will repel
the north pole and attract the south pole. Those in the semicircle B
will produce the opposite effect, and hence there will be a tendency
for the magnet to revolve in the direction of the disc, while the
motion of the disc will be resisted. This resistance to the motion of
a conductor in a magnetic field was noticed by Faraday, and,
independently, by Tyndall, and it is sufficiently obvious in the power
absorbed by dynamos when they are generating large currents.

Faraday's next series of researches was devoted to the experimental
proof of the identity of frictional and voltaic electricity. He showed
that a magnet could be deflected and iodide of potassium decomposed by
the current from his electrical machine, and came to the conclusion
that the amount of electricity required to decompose a grain of water
was equal to 800,000 charges of his large Leyden battery. The current
from the frictional machine also served to deflect the needle of his
galvanometer. These investigations led on to a complete series of
researches on the laws of electrolysis, wherein Faraday demonstrated
the principle that, however the strength of the current may be varied,
the amount of any compound decomposed is proportional to the whole
quantity of electricity which has passed through the electrolyte. When
the same current is sent through different compounds, there is a
constant relation between the amounts of the several compounds
decomposed. In modern language, Faraday's laws may be thus
expressed:--

_If the same current be made to pass through several different
electrolytes, the quantity of each ion produced will be proportional
to its combining weight divided by its valency, and if the current
vary, the quantity of each ion liberated per second will be
proportional to the current._

This is the great law of electro-chemical equivalents. The amount of
hydrogen liberated per second by a current of one ampère is about
·00001038 gramme, or nearly one six-thousandth of a grain. This is the
electro-chemical equivalent of hydrogen. That of any other substance
may be found by Faraday's law.

From Faraday's results it appears that the passage of the same amount
of electricity is required in order to decompose one molecule of any
compound of the same chemical type, but it does not follow that the
same amount of energy is employed in the decomposition. For example,
the combining weights of copper and zinc are nearly equal. Hence it
will require the passage of about the same amount of electricity to
liberate a pound of copper from, say, the copper sulphate as to
liberate a pound of zinc from zinc sulphate; but the work to be done
is much less in the case of the copper. This is made manifest in the
following way:--A battery, which will just decompose the copper salt
slowly, liberating copper, oxygen, and sulphuric acid, will not
decompose the zinc salt at all so as to liberate metallic zinc, but
immediately on sending the current through the electrolyte,
polarization will set in, and the opposing electro-motive force thus
introduced will become equal to that of the battery, and stop the
current before metallic zinc makes its appearance. In the case of the
copper, polarization also sets in, but never attains to equality with
the electro-motive force of the primary battery. In fact, in all cases
of electrolysis, polarization produces an opposing electro-motive
force strictly proportional to the work done in the cell by the
passage of each unit of electricity. If the strength of the battery be
increased, so that it is able to decompose the zinc sulphate, and if
this battery be applied to the copper sulphate solution, the latter
will be _rapidly_ decomposed, and the excess of energy developed by
the battery will be converted into heat in the circuit.

One important point in connection with electrolysis which Faraday
demonstrated is that the decomposition is the result of the passage of
the current, and is not simply due to the attraction of the
electrodes. Thus he showed that potassium iodide could be decomposed
by a stream of electricity coming from a metallic point on the prime
conductor of his electric machine, though the point did not touch the
test-paper on which the iodide was placed.

It was in 1834 that Mr. Wm. Jenkin, after one of the Friday evening
lectures at the Royal Institution, called the attention of Faraday to
a shock which he had experienced in breaking the circuit of an
electro-magnet, though the battery employed consisted of only one pair
of plates. Faraday repeated the experiment, and found that, with a
large magnet in circuit, a strong spark could thus be obtained. On
November 14, 1834, he writes, "The phenomenon of increased spark is
merely a case of the induction of electric currents. If a current be
established in a wire, and another wire forming a complete circuit be
placed parallel to it, at the moment the current in the first is
stopped it induces a current in the same direction in the second,
itself then showing but a feeble spark. But if the second be away, it
induces a current in its own wire in the same direction, producing a
strong spark. The strong spark in the current when alone is therefore
the equivalent of the current it can produce in a neighbouring wire
when in company." The strong spark does, in fact, represent the energy
of the current due to the self-induction of its circuit, which energy
would, in part at least, be expended in inducing a current in a
neighbouring wire if such existed.

His time from 1835 till 1838 was largely taken up with his work on
electro-static induction. Faraday could never be content with any
explanation based on direct action at a distance; he always sought for
the machinery through which the action was communicated. In this
search the lines of magnetic force, which he had so often delineated
in iron filings, came to his aid. Faraday made many pictures in iron
filings of magnetic fields due to various combinations of magnets. He
employed gummed paper, and when the filings were arranged on the hard
gummed surface, he projected a feeble jet of steam on the paper, which
melted the gum and fixed the filings. Several of his diagrams were
exhibited at the Loan Collection at South Kensington. He conceived
electrical action to be transmitted along such lines as these, and to
him the whole electric field was filled with lines passing always from
positive to negative electrification, and in some respects resembling
elastic strings. The action at any place could then be expressed in
terms of the lines of force that existed there, the electrifications
by which these lines were produced being left out of consideration.
The acting bodies were thus replaced by the field of force they
produced. He showed that it was impossible to call into existence a
charge of positive electricity without at the same time producing an
equal negative charge. From every unit of positive electricity he
conceived a line of force to start, and thus, with the origin of the
line, there was created simultaneously a charge of negative
electricity on which the line might terminate. By the famous ice-pail
experiment he showed that, when a charged body is inserted in a closed
or nearly closed hollow conductor, an equal amount of the same kind of
electricity appeared on the outside of the hollow conductor, while an
equal amount of the opposite kind appeared on the interior surface of
the conductor. With the ice-pail and the butterfly-net he showed that
there could be no free electricity on the interior of a conductor.
Lines of force cannot pass through the material of a conductor without
producing electric displacement. Every element of electricity must be
joined to an equal amount of the opposite kind by a line of force.
Such lines cannot pass through the conductor itself; hence the charge
must be entirely on the outside of the conductor, so that every
element of the charge may be associated with an equal amount of the
opposite electricity upon the surfaces of surrounding objects. Thus to
Faraday every electrical action was an exhibition of electric
induction. All this work had been done before by Henry Cavendish, but
neither Faraday nor any one else knew about it at the time. From the
fact that there could be no electricity in the interior of a hollow
conductor, Cavendish deduced, in the best way possible, the truth of
the law of inverse squares as applied to electrical attraction and
repulsion, and thus laid the foundation of the mathematical theory of
electricity. To Cavendish every electrical action was a displacement
of an incompressible fluid which filled the whole of space, producing
no effect in conductors on account of the freedom of its motion, but
producing strains in insulators by displacing the material of the
body. Faraday, in his lines of force, saw, as it were, the lines along
which the displacements of Cavendish's fluid took place.

Faraday thought that, if he could show that electric induction could
take place along curved lines, it would prove that the action took
place through a medium, and not directly at a distance. He succeeded
in experimentally demonstrating the curvature of these lines; but his
conclusions were not warranted, for if we conceive of two or more
centres of force acting directly at a distance according to the law of
inverse squares, the resultant lines of force will generally be
curved. Of course, this does not prove the possibility of direct
action at a distance, but only shows that the curvature of the lines
is as much a consequence of the one hypothesis as of the other.

It soon appeared to Faraday that the nature of the dielectric had very
much to do with electric induction. The capacity of a condenser, for
instance, depends on the nature of the dielectric as well as on the
configuration of the conductors. To express this property, Faraday
employed the term "specific inductive capacity." He compared the
electric capacity of condensers, equal in all other respects, but one
possessing air for its dielectric, and the other having other media,
and thus roughly determined the specific inductive capacities of
several insulators. These results turned out afterwards to be of great
value in connection with the insulation of submarine cables. Even now
the student of electricity is sometimes puzzled by the manner in which
specific inductive capacity is introduced to his notice as modifying
the capacity of condensers, after learning that the capacity of any
system of conductors can be calculated from its geometrical
configuration; but the fact is that the intensity of all electrical
actions depends on the nature of the medium through which they take
place, and it will require more electricity to exert upon an equal
charge a unit force at unit distance when the intervening medium has a
high than when it possesses a low specific inductive capacity.

In 1835 Faraday received a pension from the civil list; in 1836 he was
appointed scientific adviser to the Elder Brethren of the Trinity
House. In the same year he was made a member of the Senate of the
University of London, and in that capacity he has exerted no small
influence on the scientific education of the country, for he was one
of those who drew up the schedules of the various examinations.

In his early years, Faraday thought that all kinds of matter might
ultimately consist of three materials only, and that as gases and
vapours appeared more nearly to resemble one another than the liquids
or solids to which they corresponded, so each might be subject to a
still higher change in the same direction, and the gas or vapour
become radiant matter--either heat, light, or electricity. Later on,
Faraday clearly recognized the dynamical nature of heat and light; but
his work was always guided by his theoretical conceptions of the
"correlation of the physical forces." For a long time he had tried to
discover relations between electricity and light; at length, on
September 13, 1845, after experimenting on a number of other
substances, he placed a piece of silico-borate of lead, or
heavy-glass, in the field of the magnet, and found that, when a beam
of polarized light was transmitted through the glass in the direction
of the lines of magnetic force, there was a rotation of the plane of
polarization. Afterwards it appeared that all the transparent solids
and liquids experimented on were capable of producing this rotation in
a greater or less degree, and in the case of all non-magnetic
substances the rotation was in the direction of the electric current,
which, passing round the substance, would produce the magnetic field
employed. Abandoning the magnet, and using only a coil of wire with
the transparent substance within it, similar effects were obtained.
Thus at length a relation was found between light and electricity.

On November 4, employing a piece of heavy-glass and a new horseshoe
magnet, Faraday noticed that the magnet appeared to have a directive
action upon the glass. Further examination showed that the glass was
repelled by the magnetic poles. Three days afterwards he found that
all sorts of substances, including most metals, were acted upon like
the heavy-glass. Small portions of them were repelled, while elongated
cylinders tended to set with their lengths perpendicular to the lines
of magnetic force. Such actions could be imitated by suspending a
feebly magnetic body in a medium more magnetic than itself. Faraday,
therefore, sought for some medium which would be absolutely neutral to
magnetic action. Filling a glass tube with compressed oxygen, and
suspending it in an atmosphere of oxygen at ordinary pressure, the
compressed gas behaved like iron or other magnetic substances.
Faraday compared the intensity of its action with that of ferrous
sulphate, and this led to an explanation of the diurnal variations of
the compass-needle based on the sun's heat diminishing the magnetic
_permeability_ of the oxygen of the air. Repeating the experiment with
nitrogen, he found that the compressed gas behaved in a perfectly
neutral manner when surrounded by the gas at ordinary pressure. Hence
he inferred that in nitrogen he had found the neutral medium required.
Repeating his experiments in an atmosphere of nitrogen, it still
appeared that most bodies were repelled by the magnetic poles, and set
_equatorially_, or at right angles to the lines of force when
elongated portions were tested. To this action Faraday gave the name
of diamagnetism.

About a month after his marriage, Faraday joined the Sandemanian
Church, to which his family had for several generations belonged, by
confession of sin and profession of faith. Not unfrequently he used to
speak at the meetings of his Church, but in 1840 he was elected an
elder, and then he took his turn regularly in conducting the services.
The notes of his addresses he generally made on small pieces of card.
He had a curious habit of separating his religious belief from his
scientific work, although the spirit of his religion perpetually
pervaded his life. A lecture on mental education, given in 1854, at
the Royal Institution, in the presence of the late Prince Consort, he
commenced as follows:--

"Before entering on this subject, I must make one distinction, which,
however it may appear to others, is to me of the utmost importance.
High as man is placed above the creatures around him, there is a
higher and far more exalted position within his view; and the ways are
infinite in which he occupies his thoughts about the fears, or hopes,
or expectations of a future life. I believe that the truth of that
future cannot be brought to his knowledge by any exertion of his
mental powers, however exalted they may be; that it is made known to
him by other teaching than his own, and is received through simple
belief of the testimony given. Let no one suppose for a moment that
the self-education I am about to commend, in respect of the things of
this life, extends to any considerations of the hope set before us, as
if man by reasoning could find out God. It would be improper here to
enter upon this subject further than to claim an absolute distinction
between religious and ordinary belief. I shall be reproached with the
weakness of refusing to apply those mental operations which I think
good in respect of high things to the very highest. I am content to
bear the reproach. Yet even in earthly matters I believe that 'the
invisible things of Him from the creation of the world are clearly
seen, being understood by the things that are made, even His eternal
power and Godhead;' and I have never seen anything incompatible
between those things of man which can be known by the spirit of man
which is within him, and those higher things concerning his future
which he cannot know by that spirit."

On more than one occasion the late Prince Consort had discussed
physical questions with Faraday, and in 1858 the Queen offered him a
house on Hampton Court Green. This was his home until August 25, 1867.
He saw not only the magnetic spark, which he had first produced,
employed in the lighthouses at the South Foreland and Dungeness, but
he saw also his views respecting lines of electric induction examined
and confirmed by the investigations of Thomson and Clerk Maxwell.

Of the ninety-five distinctions conferred upon him, we need only
mention that of Commandant of the Legion of Honour, which he received
in January, 1856.




JAMES CLERK MAXWELL.


The story of the life of James Clerk Maxwell has been told so recently
by the able pen of his lifelong friend, Professor Lewis Campbell, that
it is unnecessary, in the few pages which now remain to us, to attempt
to give a repetition of the tale which would not only fail to do
justice to its subject, but must of necessity fall far short of the
merits of the (confessedly imperfect) sketch which has recently been
placed within the reach of all. Looking back on the life of Clerk
Maxwell, he seems to have come amongst us as a light from another
world--to have but partly revealed his message to minds too often
incapable of grasping its full meaning, and all too soon to have
returned to the source from whence he came. There was scarcely any
branch of natural philosophy that he did not grapple with, and upon
which his vivid imagination and far-seeing intelligence did not throw
light. He was born a philosopher, and at every step Nature partly drew
aside the veil and revealed that which was hidden from a gaze less
prophetic. A very brief sketch of the principal incidents in his life
may, however, not be out of place.

James Clerk Maxwell was born in Edinburgh, on June 13, 1831. His
father, John Clerk Maxwell, was the second son of James Clerk, of
Penicuik, and took the name of Maxwell on inheriting the estate at
Middlesbie. His mother was the daughter of R. H. Cay, Esq., of North
Charlton, Northumberland. James was the only child who survived
infancy.

Some years before his birth his parents had built a house at Glenlair,
which had been added to their Middlesbie estate, and resided there
during the greater part of the year, though they retained their house
in Edinburgh. Hence it was that James's boyish days were spent almost
entirely in the country, until he entered the Edinburgh Academy in
1841. As a child, he was never content until he had completely
investigated everything which attracted his attention, such as the
hidden courses of bell-wires, water-streams, and the like. His
constant question was "What's the go o' that?" and, if answered in
terms too general for his satisfaction, he would continue, "But what's
the particular go of it?" This desire for the thorough investigation
of every phenomenon was a characteristic of his mind through life.
From a child his knowledge of Scripture was extensive and accurate,
and when eight years old he could repeat the whole of the hundred and
nineteenth psalm. About this time his mother died, and thenceforward
he and his father became constant companions. Together they would
devise all sorts of ingenious mechanical contrivances. Young James was
essentially a child of nature, and free from all conventionality. He
loved every living thing, and took delight in petting young frogs, and
putting them into his mouth to see them jump out. One of his
attainments was to paddle on the duck-pond in a wash-tub, and to make
the vessel go "without spinning"--a recreation which had to be
relinquished on washing-days. He was never without the companionship
of one or two terriers, to whom he taught many tricks, and with whom
he seemed to have complete sympathy.

As a boy, Maxwell was not one to profit much by the ordinary teaching
of the schools, and experience with a private tutor at home did not
lead to very satisfactory results. At the age of ten, therefore, he
was sent to the Edinburgh Academy, under the care of Archdeacon
Williams, who was then rector. On his first appearance in this
fashionable school, he was naturally a source of amusement to his
companions; but he held his ground, and soon gained more respect than
he had previously provoked ridicule. While at school in Edinburgh, he
resided with his father's sister, Mrs. Wedderburn, and devoted a very
considerable share of his time and attention to relieving the solitude
of the old man at Glenlair, by letters written in quaint styles,
sometimes backwards, sometimes in cypher, sometimes in different
colours, so arranged that the characters written in a particular
colour, when placed consecutively, formed another sentence. All the
details of his school and home life, and the special peculiarities of
the masters at the academy, were thus faithfully transmitted to his
father, by whom the letters were religiously preserved. At thirteen he
had evidently made progress in solid geometry, though he had not
commenced Euclid, for he writes to his father, "I have made a
tetrahedron, a dodecahedron, and two other hedrons whose names I don't
know." In these letters to Glenlair he generally signed himself, "Your
most obedient servant." Sometimes his fun found vent even upon the
envelope; for example:--

    "Mr. John Clerk Maxwell,
    "Postyknowswere,
    "Kirkpatrick Durham,
    "Dumfries."

Sometimes he would seal his letters with electrotypes of natural
objects (beetles, etc.), of his own making. In July, 1845, he
writes:--

    I have got the eleventh prize for scholarship, the first for
    English, the prize for English verses, and the mathematical
    medal.

When only fifteen a paper on oval curves was contributed by him to the
_Proceedings of the Royal Society of Edinburgh_. In the spring of 1847
he accompanied his uncle on a visit to Mr. Nicol, the inventor of the
Nicol prism, and on his return he made a polariscope with glass and a
lucifer-match box, and sketched in water-colours the chromatic
appearances presented by pieces of unannealed glass which he himself
prepared. These sketches he sent to Mr. Nicol, who presented him in
return with a pair of prisms of his own construction. The prisms are
now in the Cavendish Laboratory at Cambridge. Maxwell found that, for
unannealed glass, pieces of window-glass placed in bundles of eight or
nine, one on the other, answered the purpose very well. He cut the
figures, triangles, squares, etc., with a diamond, heated the pieces
of glass on an iron plate to redness in the kitchen fire, and then
dropped them into a plate of iron sparks (scales from the smithy) to
cool.

In 1847 Maxwell entered the University of Edinburgh, and during his
course of study there he contributed to the Royal Society of Edinburgh
papers upon rolling curves and on the equilibrium of elastic solids.
His attention was mostly devoted to mathematics, physics, chemistry,
and mental and moral philosophy. In 1850 he went to Cambridge,
entering Peterhouse, but at the end of a year he "migrated" to
Trinity; here he was soon surrounded with a circle of friends who
helped to render his Cambridge life a very happy one. His love of
experiment sometimes extended to his own mode of life, and once he
tried sleeping in the evening and working after midnight, but this was
soon given up at the request of his father. One of his friends writes,
"From 2 to 2.30 a.m. he took exercise by running along the upper
corridor, _down_ the stairs, along the lower corridor, then _up_ the
stairs, and so on until the inhabitants of the rooms along his track
got up and laid _perdus_ behind their sporting-doors, to have shots at
him with boots, hair-brushes, etc., as he passed." His love of fun,
his sharp wit, his extensive knowledge, and above all, his complete
unselfishness, rendered him a universal favourite in spite of the
temporary inconveniences which his experiments may have occasionally
caused to his fellow-students.

An undergraduate friend writes, "Every one who knew him at Trinity can
recall some kindness or some act of his which has left an ineffaceable
impression of his goodness on the memory--for 'good' Maxwell was in
the best sense of the word." The same friend wrote in his diary in
1854, after meeting Maxwell at a social gathering, "Maxwell, as usual,
showing himself acquainted with every subject on which the
conversation turned. I never met a man like him. I do believe there is
not a single subject on which he cannot talk, and talk well too,
displaying always the most curious and out-of-the-way information."
His private tutor, the late well-known Mr. Hopkins, said of him, "It
is not possible for that man to think incorrectly on physical
subjects."

In 1854 Maxwell took his degree at Cambridge as second wrangler, and
was bracketed with the senior wrangler (Mr. E. J. Routh) for the
Smith's prize. During his undergraduate course, he appears to have
done much of the work which formed the basis of his subsequent papers
on electricity, particularly that on Faraday's lines of force. The
colour-top and colour-box appear also to have been gradually
developing during this time, while the principle of the stereoscope
and the "art of squinting" received their due share of attention.
Shortly after his degree, he devoted a considerable amount of time to
the preparation of a manuscript on geometrical optics, which was
intended to form a university text-book, but was never completed. In
the autumn of 1855 he was elected Fellow of Trinity. About this time
the colour-top was in full swing, and he also constructed an
ophthalmoscope. In May, 1855, he writes:--

    The colour trick came off on Monday, 7th. I had the proof-sheets
    of my paper, and was going to read; but I changed my mind and
    talked instead, which was more to the purpose. There were sundry
    men who thought that blue and yellow make green, so I had to
    undeceive them. I have got Hay's book of colours out of the
    University Library, and am working through the specimens,
    matching them with the top.

The "colour trick" came off before the Cambridge Philosophical Society.

While a Bachelor Fellow, Maxwell gave lectures to working men in
Barnwell, besides lecturing in college. His father died in April,
1856, and shortly afterwards he was appointed Professor of Natural
Philosophy in Marischal College, Aberdeen. This appointment he held
until the fusion of the college with King's College in 1860. These
four years were very productive of valuable work. During them the
dynamical top was constructed, which illustrates the motion of a rigid
body about its axis of greatest, least, or mean moment of inertia;
for, by the movement of certain screws, the axis of the top may be
made to coincide with any one at will. The Adams Prize Essay on the
stability of Saturn's rings belongs also to this period. In this essay
Maxwell showed that the phenomena presented by Saturn's rings can only
be explained on the supposition that they consist of innumerable small
bodies--"a flight of brickbats"--each independent of all the others,
and revolving round Saturn as a satellite. He compared them to a siege
of Sebastopol from a battery of guns measuring thirty thousand miles
in one direction, and a hundred miles in the other, the shots never
stopping, but revolving round a circle of a hundred and seventy
thousand miles radius. A solid ring of such dimensions would be
completely crushed by its own weight, though made of the strongest
material of which we have any knowledge. If revolving at such a rate
as to balance the attraction of the planet at one part, the stress in
other parts would be more than sufficient to crush or tear the ring.
Laplace had shown that a narrow ring might revolve about the planet
and be stable if so loaded that its centre of gravity was at a
considerable distance from its centre, and thought that Saturn's
rings might consist of a number of such unsymmetrical rings--a theory
to which some support was given by the many small divisions observable
in the bright rings. Maxwell showed that, for stability, the mass
required to load each of Laplace's rings must be four and a half times
that of the rest of the ring; and the system would then be far too
artificially balanced to be proof against the action of one ring on
another. He further showed that, in liquid rings, waves would be
produced by the mutual action of the rings, and that before long some
of these waves would be sure to acquire such an amplitude as would
cause the rings to break up into small portions. Finally, he concluded
that the only admissible theory is that of the independent satellites,
and that the _average_ density of the rings so found cannot be much
greater than that of air at ordinary pressure and temperature.

While he remained at Aberdeen, Maxwell lectured to working men in the
evenings, on the principles of mechanics. On the whole, it is doubtful
whether Aberdeen society was as congenial to him as that of Cambridge
or Edinburgh. He seems not to have been understood even by his
colleagues. On one occasion he wrote:--

    Gaiety is just beginning here again.... No jokes of any kind are
    understood here. I have not made one for two months, and if I
    feel one coming I shall bite my tongue.

But every cloud has its bright side, and, however Maxwell may have
been regarded by his colleagues, he was not long without congenial
companionships. An honoured guest at the home of the Principal, "in
February, 1858, he announced his betrothal to Katherine Mary Dewar,
and they were married early in the following June." Professor Campbell
speaks of his married life as one of unexampled devotion, and those
who enjoyed the great privilege of seeing him at home could more than
endorse the description.

In 1860 Maxwell accepted the chair of Natural Philosophy at King's
College, London. Here he continued his lectures to working men, and
even kept them up for one session after resigning the chair in 1865.
On May 17, 1861, he gave his first lecture at the Royal Institution,
on "The Theory of the Three Primary Colours." This lecture embodies
many of the results of his work with the colour-top and colour-box, to
be again referred to presently. While at King's College, he was placed
on the Electrical Standards Committee of the British Association, and
most of the work of the committee was carried out in his laboratory.
Here, too, he compared the electro-static repulsion between two discs
of brass with the electro-magnetic attraction of two coils of wire
surrounding them, through which a current of electricity was allowed
to flow, and obtained a result which he afterwards applied to the
electro-magnetic theory of light. The colour-box was perfected, and
his experiments on the viscosity of gases were concluded during his
residence in London. These last were described by him in the Bakerian
Lecture for 1866.

After resigning the professorship at King's College, Maxwell spent
most of his time at Glenlair, having enlarged the house, in accordance
with his father's original plans. Here he completed his great work on
"Electricity and Magnetism," as well as his "Theory of Heat," an
elementary text-book which may be said to be without a parallel.

On March 8, 1871, he accepted the chair of Experimental Physics in the
University of Cambridge. This chair was founded in consequence of an
offer made by the Duke of Devonshire, the Chancellor of the
University, to build and equip a physical laboratory for the use of
the university. In this capacity Maxwell's first duty was to prepare
plans for the laboratory. With this view, he inspected the
laboratories of Sir William Thomson at Glasgow, and of Professor
Clifton at Oxford, and endeavoured to embody the best points of both
in the new building. The result was that, in conjunction with Mr. W.
M. Fawcett, the architect, he secured for the university a laboratory
noble in its exterior, and admirably adapted to the purposes for which
it is required. The ground-floor comprises a large battery-room, which
is also used as a storeroom for chemicals; a workshop; a room for
receiving goods, communicating by a lift with the apparatus-room; a
room for experiments on heat; balance-rooms; a room for pendulum
experiments, and other investigations requiring great stability; and a
magnetic observatory. The last two rooms are furnished with stone
supports for instruments, erected on foundations independent of those
of the building, and preserved from contact with the floor. On the
first floor is a handsome lecture-theatre, capable of accommodating
nearly two hundred students. The lecture-table is carried on a wall,
which passes up through the floor without touching it, the joists
being borne by separate brick piers. The lecture-theatre occupies the
height of the first and second floors; its ceiling is of wood, the
panels of which can be removed, thus affording access to the
roof-principals, from which a load of half a ton or more may be safely
suspended over the lecture-table. The panels of the ceiling, adjoining
the wall which is behind the lecturer, can also be readily removed,
and a "window" in this wall communicates with the large
electrical-room on the second floor. Access to the space above the
ceiling of the lecture-theatre is readily obtained from the tower.
Adjoining the lecture-room is the preparation-room, and communicating
with the latter is the apparatus-room. This room is fitted with
mahogany and plate-glass wall and central cases, and at present
contains, besides the more valuable portions of the apparatus
belonging to the laboratory, the marble bust of James Clerk Maxwell,
and many of the home-made pieces of apparatus and other relics of his
early work. The rest of the first floor is occupied by the
professor's private room and the general students' laboratory.
Throughout the building the brick walls have been left bare for
convenience in attaching slats or shelves for the support of
instruments. The second floor contains a large room for electrical
experiments, a dark room for photography, and a number of private
rooms for original work. Water is laid on to every room, including a
small room in the top of the tower, and all the windows are provided
with broad stone ledges without and within the window, the two
portions being in the same horizontal plane, for the support of
heliostats or other instruments. The building is heated with hot
water, but in the magnetic observatory the pipes are all of copper and
the fittings of gun-metal. Open fireplaces for basket fires are also
provided. Over the principal entrance of the laboratory is placed a
stone statue of the present Duke of Devonshire, together with the arms
of the university and of the Cavendish family, and the Cavendish
motto, "Cavendo Tutus." Maxwell presented to the laboratory, in 1874,
all the apparatus in his possession. He usually gave a course of
lectures on heat and the constitution of bodies in the Michaelmas
term; on electricity in the Lent term; and on electro-magnetism in the
Easter term. The following extract from his inaugural lecture,
delivered in October, 1871, is worthy of the attention of all students
of science:--

    Science appears to us with a very different aspect after we
    have found out that it is not in lecture-rooms only, and by
    means of the electric light projected on a screen, that we may
    witness physical phenomena, but that we may find illustrations
    of the highest doctrines of science in games and gymnastics, in
    travelling by land and by water, in storms of the air and of the
    sea, and wherever there is matter in motion.

    The habit of recognizing principles amid the endless variety of
    their action can never degrade our sense of the sublimity of
    nature, or mar our enjoyment of its beauty. On the contrary, it
    tends to rescue our scientific ideas from that vague condition
    in which we too often leave them, buried among the other
    products of a lazy credulity, and to raise them into their
    proper position among the doctrines in which our faith is so
    assured that we are ready at all times to act on them.
    Experiments of illustration may be of very different kinds. Some
    may be adaptations of the commonest operations of ordinary life;
    others may be carefully arranged exhibitions of some phenomenon
    which occurs only under peculiar conditions. They all, however,
    agree in this, that their aim is to present some phenomenon to
    the senses of the student in such a way that he may associate
    with it some appropriate scientific idea. When he has grasped
    this idea, the experiment which illustrates it has served its
    purpose.

    In an experiment of research, on the other hand, this is not the
    principal aim.... Experiments of this class--those in which
    measurement of some kind is involved--are the proper work of a
    physical laboratory. In every experiment we have first to make
    our senses familiar with the phenomenon; but we must not stop
    here--we must find out which of its features are capable of
    measurement, and what measurements are required in order to make
    a complete specification of the phenomenon. We must then make
    these measurements, and deduce from them the result which we
    require to find.

    This characteristic of modern experiments--that they consist
    principally of measurements--is so prominent that the opinion
    seems to have got abroad that, in a few years, all the great
    physical constants will have been approximately estimated, and
    that the only occupation which will then be left to men of
    science will be to carry these measurements to another place of
    decimals.

    If this is really the state of things to which we are
    approaching, our laboratory may, perhaps, become celebrated as a
    place of conscientious labour and consummate skill; but it will
    be out of place in the university, and ought rather to be
    classed with the other great workshops of our country, where
    equal ability is directed to more useful ends.

    But we have no right to think thus of the unsearchable riches of
    creation, or of the untried fertility of those fresh minds into
    which these riches will continually be poured.... The history
    of Science shows that, even during that phase of her progress
    in which she devotes herself to improving the accuracy of the
    numerical measurement of quantities with which she has long been
    familiar, she is preparing the materials for the subjugation of
    new regions, which would have remained unknown if she had been
    contented with the rough methods of her early pioneers.

Maxwell's "Electricity and Magnetism" was published in 1873. Shortly
afterwards there were placed in his hands, by the Duke of Devonshire,
the Cavendish Manuscripts on Electricity, already alluded to. To these
he devoted much of his spare time for several years, and many of
Cavendish's experiments were repeated in the laboratory by Maxwell
himself, or under his direction by his students. The introductory
matter and notes embodied in "The Electrical Researches of the
Honourable Henry Cavendish, F.R.S.," afford sufficient evidence of the
amount of labour he expended over this work. The volume was published
only a few weeks before his death. Another of Maxwell's publications,
which, as a text-book, is unique and beyond praise, is the little book
on "Matter and Motion," published by the S.P.C.K.

In 1878 Maxwell, at the request of the Vice-Chancellor, delivered the
Rede Lecture in the Senate-House. His subject was the telephone, which
was just then absorbing a considerable amount of public attention.
This was the last lecture which he ever gave to a large public
audience.

It was during his tenure of the Cambridge chair that one of the
cottages on the Glenlair estate was struck by lightning. The discharge
passed down the damp soot and blew out several stones from the base of
the chimney, apparently making its way to some water in a ditch a few
yards distant. The cottage was built on a granite rock, and this event
set Maxwell thinking about the best way to protect, from lightning,
buildings which are erected on granite or other non-conducting
foundations. He decided that the proper course was to place a strip of
metal upon the ground all round the building, to carry another strip
along the ridge-stay, from which one or more pointed rods should
project upwards, and to unite this strip with that upon the ground by
copper strips passing down each corner of the building, which is thus,
as it were, enclosed in a metal cage.

After a brief illness, Maxwell passed away on November 5, 1879. His
intellect and memory remained perfect to the last, and his love of fun
scarcely diminished. During his illness he would frequently repeat
hymns, especially some of George Herbert's, and Richard Baxter's hymn
beginning

    "Lord, it belongs not to my care."

"No man ever met his death more consciously or more calmly."

It has been stated that Thomas Young propounded a theory of
colour-vision which assumes that there exist three separate
colour-sensations, corresponding to red, green, and violet, each
having its own special organs, the excitement of which causes the
perception of the corresponding colour, other colours being due to the
excitement of two or more of these simple sensations in different
proportions. Maxwell adopted blue instead of violet for the third
sensation, and showed that if a particular red, green, and blue were
selected and placed at the angular points of an equilateral triangle,
the colours formed by mixing them being arranged as in Young's
diagram, all the shades of the spectrum would be ranged along the
sides of this triangle, the centre being neutral grey. For the mixing
of coloured lights, he at first employed the colour-top, but, instead
of painting circles with coloured sectors, the angles of which could
not be changed, he used circular discs of coloured paper slit along
one radius. Any number of such discs can be combined so that each
shows a sector at the top, and the angle of each sector can be varied
at will by sliding the corresponding disc between the others. Maxwell
used discs of two different sizes, the small discs being placed above
the larger on the same pivot, so that one set formed a central circle,
and the other set a ring surrounding it. He found that, with discs of
five different colours, of which one might be white and another black,
it was always possible to combine them so that the inner circle and
the outer ring exactly matched. From this he showed that there could
be only three conditions to be satisfied in the eye, for two
conditions were necessitated by the nature of the top, since the
smaller sectors must exactly fill the circle and so must the larger.
Maxwell's experiments, therefore, confirmed, in general, Young's
theory. They showed, however, that the relative delicacy of the
several colour-sensations is different in different eyes, for the
arrangement which produced an exact match in the case of one observer,
had to be modified for another; but this difference of delicacy proved
to be very conspicuous in colour-blind persons, for in most of the
cases of colour-blindness examined by Maxwell the red sensation was
completely absent, so that only two conditions were required by
colour-blind eyes, and a match could therefore always be made in such
cases with four discs only. Holmgren has since discovered cases of
colour-blindness in which the violet sensation is absent. He agrees
with Young in making the third sensation correspond to violet rather
than blue. Maxwell explained the fact that persons colour-blind to the
red divide colours into blues and yellows by the consideration that,
although yellow is a complex sensation corresponding to a mixture of
red and green, yet in nature yellow tints are so much brighter than
greens that they excite the green sensation more than green objects
themselves can do, and hence greens and yellows are called yellow by
such colour-blind persons, though their perception of yellow is really
the same as perception of green by normal eyes. Later on, by a
combination of adjustable slits, prisms, and lenses arranged in a
"colour-box," Maxwell succeeded in mixing, in any desired proportions,
the light from any three portions of the spectrum, so that he could
deal with pure spectral colours instead of the complex combinations of
differently coloured lights afforded by coloured papers. From these
experiments it appears that no ray of the solar spectrum can affect
one colour-sensation alone, so that there are no colours in nature so
pure as to correspond to the pure simple sensations, and the colours
occupying the angular points of Maxwell's diagram affect all three
colour-sensations, though they influence two of them to a much smaller
extent than the third. A particular colour in the spectrum corresponds
to light which, according to the undulatory theory, physically
consists of waves all of the same period, but it may affect all three
of the colour-sensations of a normal eye, though in different
proportions. Thus, yellow light of a given wave-length affects the red
and green sensations considerably and the blue (or violet) slightly,
and the same effect may be produced by various mixtures of red or
orange and green. For his researches on the perception of colour, the
Royal Society awarded to Clerk Maxwell the Rumford Medal in 1860.

Another optical contrivance of Maxwell's was a wheel of life, in which
the usual slits were replaced by concave lenses of such focal length
that the picture on the opposite side of the cylinder appeared, when
seen through a lens, at the centre, and thus remained apparently
fixed in position while the cylinder revolved. The same result has
since been secured by a different contrivance in the praxinoscope.

Another ingenious optical apparatus was a real-image stereoscope, in
which two lenses were placed side by side at a distance apart equal to
half the distance between the pictures on the stereoscopic slide.
These lenses were placed in front of the pictures at a distance equal
to twice their focal length. The real images of the two pictures were
then superposed in front of the lenses at the same distance from them
as the pictures, and these combined images were looked at through a
large convex lens.

The great difference in the sensibility to different colours of the
eyes of dark and fair persons when the light fell upon the _fovea
centralis_, led Maxwell to the discovery of the extreme want of
sensibility of this portion of the retina to blue light. This he made
manifest by looking through a bottle containing solution of chrome
alum, when the central portion of the field of view appears of a light
red colour for the first second or two.

A more important discovery was that of double refraction temporarily
produced in viscous liquids. Maxwell found that a quantity of Canada
balsam, if stirred, acquired double-refracting powers, which it
retained for a short period, until the stress temporarily induced had
disappeared.

But Maxwell's investigations in optics must be regarded as his play;
his real work lay in the domains of electricity and of molecular
physics.

In 1738 Daniel Bernouilli published an explanation of atmospheric
pressure on the hypothesis that air consists of a number of minute
particles moving in all directions, and impinging on any surface
exposed to their action. In 1847 Herapath explained the diffusion of
gases on the hypothesis that they consisted of perfectly hard
molecules impinging on one another and on surfaces exposed to them,
and pointed out the relation between their motion and the temperature
and pressure of a gas. The present condition of the molecular theory
of gases, and of molecular science generally, is due almost entirely
to the work of Joule, Clausius, Boltzmann, and Maxwell. To Maxwell is
due the general method of solving all problems connected with vast
numbers of individuals--a method which he called the statistical
method, and which consists, in the first place, in separating the
individuals into groups, each fulfilling a particular condition, but
paying no attention to the history of any individual, which may pass
from one group to another in any way and as often as it pleases
without attracting attention. Maxwell was the first to estimate the
average distance through which a particle of gas passes without coming
into collision with another particle. He found that, in the case of
hydrogen, at standard pressure and temperature, it is about 1/250000
of an inch; for air, about 1/389000 of an inch. These results he
deduced from his experiments on viscosity, and he gave a complete
explanation of the viscosity of gases, showing it to be due to the
"diffusion of momentum" accompanying the diffusion of material
particles between the passing streams of gas.

One portion of the theory of electricity had been considerably
developed by Cavendish; the application of mathematics to the theory
of attractions, and hence to that of electricity, had been carried to
a great degree of perfection by Laplace, Lagrange, Poisson, Green, and
others. Faraday, however, could not satisfy himself with a
mathematical theory based upon direct action at a distance, and he
filled space, as we have seen, with tubes of force passing from one
body to another whenever there existed any electrical action between
them. These conceptions of Faraday were regarded with suspicion by
mathematicians. Sir William Thomson was the first to look upon them
with favour; and in 1846 he showed that electro-static force might be
treated mathematically in the same way as the flow of heat; so that
there are, at any rate, two methods by which the fundamental formulæ
of electro-statics can be deduced. But it is to Maxwell that
mathematicians are indebted for a complete exposition of Faraday's
views in their own language, and this was given in a paper wherein the
phenomena of electro-statics were deduced as results of a stress in a
medium which, as suggested by Newton and believed by Faraday, might
well be that same medium which serves for the propagation of light;
and "the lines of force" were shown to correspond to an actual
condition of the medium when under electrical stress. Maxwell, in
fact, showed, not only that Faraday's lines formed a consistent system
which would bear the most stringent mathematical analysis, but were
more than a conventional system, and might correspond to a state of
stress actually existing in the medium through which they passed, and
that a tension along these lines, accompanied by an equal pressure in
every direction at right angles to them, would be consistent with the
equilibrium of the medium, and explain, on mechanical principles, the
observed phenomena. The greater part of this work he accomplished
while an undergraduate at Cambridge. He showed, too, that Faraday's
conceptions were equally applicable to the case of electro-magnetism,
and that all the laws of the induction of currents might be concisely
expressed in Faraday's language. Defining the positive direction
through a circuit in which a current flows as the direction in which a
right-handed screw would advance if rotating with the current, and the
positive direction around a wire conveying a current as the direction
in which a right-handed screw would rotate if advancing with the
current, Maxwell pointed out that the lines of magnetic force due to
an electric current always pass round it, or through its circuit, in
the positive direction, and that, _whenever the number of lines of
magnetic force passing through a closed circuit is changed, there is
an electro-motive force round the circuit represented by the rate of
diminution of the number of lines of force which pass through the
circuit in the positive direction_.

The words in italics form a complete statement of the laws regulating
the production of currents by the motion of magnets or of other
currents, or by the variation of other currents in the neighbourhood.
Maxwell showed, too, that Faraday's electro-tonic state, on the
variation of which induced currents depend, corresponds completely
with the number of lines of magnetic force passing through the
circuit.

He also showed that, when a conductor conveying a current is free to
move in a magnetic field, or magnets are free to move in the
neighbourhood of such a conductor, _the system will assume that
condition in which the greatest possible number of lines of magnetic
force pass through the circuit in the positive direction_.

But Maxwell was not content with showing that Faraday's conceptions
were consistent, and had their mathematical equivalents,--he proceeded
to point out how a medium could be imagined so constituted as to be
able to perform all the various duties which were thus thrown upon it.
Assuming a medium to be made up of spherical, or nearly spherical,
cells, and that, when magnetic force is transmitted, these cells are
made to rotate about diameters coinciding in direction with the lines
of force, the tension along those lines, and the pressure at right
angles to them, are accounted for by the tendency of a rotating
elastic sphere to contract along its polar axis and expand
equatorially so as to form an oblate spheroid. By supposing minute
spherical particles to exist between the rotating cells, the motion of
one may be transmitted in the same direction to the next, and these
particles may be supposed to constitute electricity, and roll as
perfectly rough bodies on the cells in contact with them. Maxwell
further imagined the rotating cells, and therefore, _à fortiori_, the
electrical particles, to be extremely small compared with molecules of
matter; and that, in conductors, the electrical particles could pass
from molecule to molecule, though opposed by friction, but that in
insulators no such transference was possible. The machinery was then
complete. If the electric particles were made to flow in a conductor
in one direction, passing between the cells, or _molecular vortices_,
they compelled them to rotate, and the rotation was communicated from
cell to cell in expanding circles by the electric particles, acting as
idle wheels, between them. Thus rings of magnetic force were made to
surround the current, and to continue as long as the current lasted.
If an attempt were made to displace the electric particles in a
dielectric, they would move only within the substance of each
molecule, and not from molecule to molecule, and thus the cells would
be deformed, though no continuous motion would result. The deformation
of the cells would involve elastic stress in the medium. Again, if a
stream of electric particles were started into motion, and if there
were another stream of particles in the neighbourhood free to flow,
though resisted by friction, these particles, instead of at once
transmitting the rotary motion of the cells on one side of them to the
cells on the other side, would at first, on account of the inertia of
the cells, begin to move themselves with a motion of translation
opposite to that of the primary current, and the motion would only
gradually be destroyed by the frictional resistance and the molecular
vortices on the other side made to revolve with their full velocity. A
similar effect, but in the opposite direction, would take place if the
primary current ceased, the vortices not stopping all at once if there
were any possibility of their continuing in motion. The imaginary
medium thus serves for the production of induced currents.

The mechanical forces between currents and magnets and between
currents and currents, as well as between magnets and currents, were
accounted for by the tension and pressure produced by the molecular
vortices. When currents are flowing in the same direction in
neighbouring conductors, the vortices in the space between them are
urged in opposite directions by the two currents, and remain almost at
rest; the lateral pressure exerted by those on the outside of the
conductors is thus unbalanced, and the conductors are pushed together
as though they attracted each other. When the currents flow in
opposite directions in parallel conductors, they conspire to give a
greater velocity to the vortices in the space between them, than to
those outside them, and are thus pushed apart by the pressure due to
the rotation of the vortices, as though they repelled each other. In a
similar way, the actions of magnets on conductors conveying currents
may be explained. The motion of a conductor across a series of lines
of magnetic force may squeeze together and lengthen the threads of
vortices in front, and thus increase their speed of rotation, while
the vortices behind will move more slowly because allowed to contract
axially and expand transversely. The velocity of the vortices thus
being greater on one side of the wire than the other, a current must
be induced in the wire. Thus the current induced by the motion of a
conductor in a magnetic field may be accounted for.

This conception of a medium was given by Maxwell, not as a theory, but
to show that it was possible to devise a _mechanism_ capable, in
imagination at least, of producing all the phenomena of electricity
and magnetism. "According to our theory, the particles which form the
partitions between the cells constitute the matter of electricity. The
motion of these particles constitutes an electric current; the
tangential force with which the particles are pressed by the matter of
the cells is electro-motive force; and the pressure of the particles
on each other corresponds to the tension or potential of the
electricity."

When a current is maintained in a wire, the molecular vortices in the
surrounding space are kept in uniform motion; but if an attempt be
made to stop the current, since this would necessitate the stoppage of
the vortices, it is clear that it cannot take place suddenly, but the
energy of the vortices must be in some way used up. For the same
reason it is impossible for a current to be suddenly started by a
finite force. Thus the phenomena of self-induction are accounted for
by the supposed medium.

The magnetic permeability of a medium Maxwell identified with the
density of the substance composing the rotating cells, and the
specific inductive capacity he showed to be inversely proportional to
its elasticity. He then proved that the ratio of the electro-magnetic
unit to the electro-static unit must be equal to the velocity of
transmission of a transverse vibration in the medium, and consequently
proportional to the square root of the elasticity, and inversely
proportional to the square root of the density. If the medium is the
same as that engaged in the propagation of light, then this ratio
ought to be equal to the velocity of light, and, moreover, in
non-magnetic media, the refractive index should be proportional to the
square root of the specific inductive capacity. The different
measurements which had been made of the ratio of the electrical units
gave a mean very nearly coinciding with the best determinations of the
velocity of light, and thus the truth underlying Maxwell's speculation
was strikingly confirmed, for the velocity of light was determined by
purely electrical measurements. In the case also of bodies whose
chemical structure was not very complicated, the refractive index was
found to agree fairly well with the square root of the specific
inductive capacity; but the phenomenon of "residual charge" rendered
the accurate measurement of the latter quantity a matter of great
difficulty. It therefore appeared highly probable that light is an
electro-magnetic disturbance due to a motion of the electric particles
in an insulating medium producing a strain in the medium, which
becomes propagated from particle to particle to an indefinite
distance. In the case of a conductor, the electric particles so
displaced would pass from molecule to molecule against a frictional
resistance, and thus dissipate the energy of the disturbance, so that
true (_i.e._ metallic) conductors must be nearly impervious to light;
and this also agrees with experience.

Maxwell thus furnished a complete theory of electrical and
electro-magnetic action in which all the effects are due to actions
propagated in a medium, and direct action at a distance is dispensed
with, and exposed his theory successfully to most severe tests. In his
great work on electricity and magnetism, he gives the mathematical
theory of all the above actions, without, however, committing himself
to any particular form of mechanism to represent the constitution of
the medium. "This part of that book," Professor Tait says, "is one of
the most splendid monuments ever raised by the genius of a single
individual.... There seems to be no longer any possibility of doubt
that Maxwell has taken the first grand step towards the discovery of
the true nature of electrical phenomena. Had he done nothing but this,
his fame would have been secured for all time. But, striking as it is,
this forms only one small part of the contents of this marvellous
work."




CONCLUSION.

SOME OF THE RESULTS OF FARADAY'S DISCOVERIES, AND THE PRINCIPLE OF
ENERGY.


In early days, _the spirit of the amber_, when aroused by rubbing,
came forth and took to itself such light objects as it could easily
lift. Later on, and the spirit gave place to the _electric effluvium_,
which proceeded from the excited, or charged, body into the
surrounding space. Still later, and a fluid, or two fluids, acting
directly upon itself, or upon matter, or on one another, through
intervening space without the aid of intermediate mechanism, took the
place of the electric effluvium--a step which in itself was, perhaps,
hardly an advance. Then came the time for accurate measurement. The
simple _observation_ of phenomena and of the results of experiment
must be the first step in science, and its importance cannot be
over-estimated; but before any quantity can be said to be known, we
must have learned how to _measure_ it and to reproduce it in definite
amounts. The great law of electrical action, the same as that of
gravitation--the law of the inverse square--soon followed, as well as
the associated fact that the electrification of a conductor resides
wholly on its surface, and there only in a layer whose thickness is
too small to be discovered. The fundamental laws of electricity having
thus been established, there was no limit to the application of
mathematical methods to the problems of the science, and, in the hands
of the French mathematicians, the theory made rapid advances. George
Green, of Sneinton, Nottingham, introduced the term "potential" in an
essay published by subscription, in Nottingham, in 1828, and to him we
are indebted for some of our most powerful analytical methods of
dealing with the subject; but his work remained unappreciated and
almost unknown until many of his theorems had been rediscovered. But
the idea of a body acting where it is not, and without any conceivable
mechanism to connect it with that upon which it operates, is repulsive
to the minds of most; and, however well such a theory may lend itself
to mathematical treatment and its consequences be borne out by
experiment, we still feel that we have not solved the problem until we
have traced out the hidden mechanism. The pull of the bell-rope is
followed by the tinkling of the distant bell, but the young
philosopher is not satisfied with such knowledge, but must learn "what
is the particular go of that." This universal desire found its
exponent in Faraday, whose imagination beheld "lines" or "tubes of
force" connecting every body with every other body on which it acted.
To his mind these lines or tubes had just as real an existence as the
bell-wire, and were far better adapted to their special purposes.
Maxwell, as we have seen, not only showed that Faraday's system
admitted of the same rigorous mathematical treatment as the older
theory, and stood the test as well, but he gave reality to Faraday's
views by picturing a mechanism capable of doing all that Faraday
required of it, and of transmitting light as well. Thus the problem of
electric, magnetic, and electro-magnetic actions was reduced to that
of strains and stresses in a medium the constitution of which was
pictured to the imagination. Were this theory verified, we might say
that we know at least as much about these actions as we know about the
transmission of pressure or tension through a solid.

With regard to the _nature_ of electricity, it must be admitted that
our knowledge is chiefly negative; but, before deploring this, it is
worth while to inquire what we mean by saying that we know what a
thing is. A definition describes a thing in terms of other things
simpler, or more familiar to us, than itself. If, for instance, we say
that heat is a form of energy, we know at once its relationship to
matter and to motion, and are content; we have described the
constitution of heat in terms of simpler things, which are more
familiar to us, and of which we _think_ we know the nature. But if we
ask what _matter_ is, we are unable to define it in terms of anything
simpler than itself, and can only trust to daily experience to teach
us more and more of its properties; unless, indeed, we accept the
theory of the vortex atoms of Thomson and Helmholtz. This theory,
which has recently been considerably extended by Professor J. J.
Thomson, the present occupier of Clerk Maxwell's chair in the
University of Cambridge, supposes the existence of a perfect fluid,
filling all space, in which minute whirlpools, or vortices, which in a
perfect fluid can be created or destroyed only by superhuman agency,
form material atoms. These are _atoms_, that is to say, they defy any
attempts to sever them, not because they are infinitely hard, but
because they have an infinite capacity for _wriggling_, and thus avoid
direct contact with any other atoms that come in their way. Perhaps a
theory of electricity consistent with this theory of matter may be
developed in the future; but, setting aside these theories, we may
possibly say that we know as much about electricity as we know about
matter; for while we are conversant with many of the properties of
each, we _know_ nothing of the ultimate nature of either.

But while the theory of electricity has scarcely advanced beyond the
point at which it was left by Clerk Maxwell, the practical
applications of the science have experienced great developments of
late years. Less than a century ago the lightning-rod was the only
practical outcome of electrical investigations which could be said to
have any real value. [OE]rsted's discovery, in 1820, of the action of
a current on a magnet, led, in the hands of Wheatstone, Cooke, and
others, to the development of the electric telegraph. Sir William
Thomson's employment of a beam of light reflected from a tiny mirror
attached to the magnet of the galvanometer enabled signals to be read
when only extremely feeble currents were available, and thus rendered
submarine telegraphy possible through very great distances. The
discovery by Arago and Davy, that a current of electricity flowing in
a coil surrounding an iron bar would convert the bar into a magnet, at
once rendered possible a variety of contrivances whereby a current of
electricity could be employed to produce small reciprocating
movements, or even continuous rotation, where not much power was
required, at a distance from the battery. An illustration of the
former is found in the common electric bell; it is only necessary that
the vibrating armature should form part of the circuit of the
electro-magnet, and be so arranged that, while it is held away from
the magnet by a spring, it completes the battery circuit, but breaks
the connection as soon as it moves towards the magnet under the
magnetic attraction. To produce continuous rotation, a number of iron
bars may be attached to a fly-wheel, and pass very close to the poles
of the magnet without touching them; when a bar is near the magnet,
and approaching it, contact should be made in the circuit, but should
be broken, so that the magnet may lose its power, as soon as the bar
has passed the poles; or the continuous rotation may be produced from
an oscillating armature by any of the mechanical contrivances usually
adopted for the conversion of reciprocating into continuous circular
motion. But all such motors are extremely wasteful in their employment
of energy. Faraday's discovery of the rotation of a wire around a
magnetic pole laid the foundation for a great variety of
electro-motors, in some of which the efficiency has attained a very
high standard. About ten years ago, Clerk Maxwell said that the
greatest discovery of recent times was the "reversibility" of the
Gramme machine, that is, the possibility of causing the armature to
rotate between the field-magnets by sending a current through the
coils. The electro-motors of to-day differ but little from dynamos in
the principles of their construction. The copper disc spinning between
the poles of a magnet while an electric current was sent from the
centre to the circumference, or _vice versâ_, formed the simplest
electro-motor. All the later motors are simply modifications of this,
designed to increase the efficiency or power of the machine.
Similarly, the earliest machine for the production of an electric
current at the expense of mechanical power only, but through the
intervention of a permanent magnet, was the rotating disc of Faraday,
described on page 262. This contrivance, however, caused a waste of
nearly all the energy employed, for while there was an electro-motive
force from the centre to the circumference, or in the reverse
direction, in that part of the disc which was passing between the
poles of the magnet, the current so generated found its readiest
return path through the other portions of the disc, and very little
traversed the galvanometer or other external circuit. This source of
waste could be, for the most part, got rid of by cutting the disc into
a number of separate rays, or spokes, and filling up the spaces
between them with insulating material. The current then generated in
the disc would be obliged to complete its circuit through the external
conductor. If we can so arrange matters as to employ at once several
turns of a continuous wire in place of one arm, or ray, of the copper
disc, we may multiply in a corresponding manner the electro-motive
force induced by a given speed of rotation. All magneto-electric
generators are simply contrivances with this object. The iron cores
frequently employed within the coils of the armature tend to
concentrate the lines of force of the magnet, causing a greater number
to pass through the coils in certain positions than would pass through
them were no iron present. The electro-motive force of such a
generator depends on the strength of the magnetic field, the length of
wire employed in cutting the lines of force, and the speed with which
the wire moves across these lines. The point to aim at in constructing
an armature is to make the resistance as small as possible consistent
with the electro-motive force required. As there is a limit to the
strength of the magnetic field, it follows that for strong currents,
where thick wire must be employed, the generator must be made of large
dimensions, or the armature must be driven at very high speed to
enable a shorter length of wire to be used.

The so-called "compound-interest principle," by which a very small
charge of electricity might be employed to develop a very large one by
the help of mechanical power, was first applied about a century ago in
the revolving doubler. Long afterwards, Sir William Thomson availed
himself of the same principle in the construction of the "mouse-mill,"
or replenisher. The Holtz machine, the Voss and Wimshurst machines,
and the other induction-machines of the same class, all work on this
principle. It may be illustrated as follows: Take two canisters, call
them A and B, and place them on glass supports. Let a very small
positive charge be given to A, B remaining uncharged. Now take a brass
ball, supported by a silk string. Place it inside A, and let it touch
its interior surface. The ball will, as shown by Franklin, Cavendish,
and Faraday, remain uncharged. Now raise it near the top of the
canister, and, while there, touch it. The ball will become negatively
electrified, because the small positive charge in A will attract
negative electricity from the earth into the ball. Take the ball, with
its negative charge, still hanging by the silk thread, and lower it
into B till it touches the bottom. It will give all its charge to B,
which will thus acquire a slight negative charge. Raise the ball till
it is near the top of B, and then touch it with the finger or a metal
rod. It will receive a positive charge from the earth because of the
attraction of the negative charge on B. Now remove the ball and let it
again touch the interior of A. It will give up all its charge to A;
and then, repeating the whole cycle of operations, the charge carried
on the ball will be greater than before, and increase in each
successive operation, the electrification increasing in geometrical
progression like compound interest. A Leyden jar having one coating
connected to A and the other to B, may thus be highly charged in
course of time. A pair of carrier balls or plates, or a number of
pairs, may be used instead of one. The carriers, just before leaving A
and B, may be put in contact with one another instead of being put to
earth; they may be mounted on a revolving shaft, and the forms of A
and B modified to admit of the revolution of the carriers, and all the
necessary contacts may be made automatically. We thus get various
forms of the continuous electrophorus, and if the carriers are mounted
on glass plates, and rows of points placed alongside the springs or
brushes used for making the contacts, when the charges on the carriers
become very strong, electricity will be radiated from the points on to
the revolving glass plates, which will thus themselves take the place
of the metal carriers. Such is the action in the Voss and other
similar machines.

But after Faraday had shown how to construct a magneto-electric
machine, the idea of applying the "compound-interest principle," and
thus converting the magneto-electric machine into the "dynamo,"
occurred apparently simultaneously and independently to Siemens,
Varley, and Wheatstone. The first dynamo constructed by Wheatstone is
still in the museum of King's College, London. Wilde employed a
magneto-electric machine to generate a current which was used to
excite the electro-magnet of a similar but larger machine, having an
electro-magnet instead of a permanent steel magnet. The electro-magnet
could be made much larger and stronger than the steel magnet, and from
its armature, when made to revolve by steam power, a correspondingly
stronger current could be maintained. The idea which occurred to
Siemens, Varley, and Wheatstone was to use the whole, or a part, of
the current produced by the armature to excite its own electro-magnet,
and thus to dispense with the magneto-electric machine which served as
the separate exciter. When a part only of the current is thus
employed, and is set apart entirely for this duty, the machine is a
"shunt dynamo;" when the whole of the current traverses the
field-magnet coils as well as the external circuit, it is a "series
dynamo." The apparent difficulty lies in starting the current, but a
mass of iron once magnetized always retains a certain amount of
"residual magnetism," unless special means are taken to get rid of
it, and even then the earth's magnetism would generally induce
sufficient in the iron to start the action. Commencing, then, with a
slight trace of residual magnetism, the revolution of the armature
generates a feeble current, which passing round the magnet coils,
strengthens the magnetism, whereupon a stronger current is generated,
which in turn makes the magnet still stronger, and so on until the
magnet becomes saturated or the limit of power of the engine is
reached, and the speed begins to diminish, or a condition of affairs
is reached at which an increased current in the armature injures the
magnetic field as much as the corresponding increase in the
field-magnet coils strengthens it, and then no further increase of
current will take place without increasing the speed of rotation. In a
true dynamo the whole of the energy, both of the current and of the
electro-magnets, is obtained from the source of power employed in
driving the machine.

But Faraday's discovery of electro-magnetic induction led to practical
developments in other directions. Graham Bell placed a thin iron disc
in front of the pole of a bar magnet, and wound a coil of fine wire
round the bar very near the pole. The ends of the coils of two such
instruments he connected together. When the iron disc of one
instrument approached the pole of the magnet, the lines of force were
disturbed, fewer escaped radially from the bar, and more left it at
the end, so as to go straight to the iron disc; thus the number of
lines of force passing through the coil was altered, and a current was
induced which, passing round the coil of the other instrument,
strengthened or weakened its magnet, and caused the iron disc to
approach it or recede from it, according to the way in which the coils
were coupled. Thus the movements of the first disc were faithfully
repeated by the second, and the minute vibrations set up in the disc
by sound-waves were all faithfully repeated by the second instrument.
This was Graham Bell's telephone, in which the transmitter and
receiver were convertible.

But another and an earlier application of Faraday's discoveries is
found in the induction coil. A short length of thick wire and a very
great length of thin wire are wound upon an iron bar. The ends of the
long thin wire, or secondary coil, form the terminals of the machine;
the short thick wire, or primary coil, is connected with a battery,
but in the circuit is placed an "interrupter." This is generally a
small piece of iron, or hammer, mounted on a steel spring opposite one
end of the iron core, the spring pressing the hammer back against a
screw the end of which, like the back of the hammer, is tipped with
platinum; and this contact completes the battery circuit. When the
current starts, the iron core becomes a magnet, attracts the hammer,
breaks the contact, stops the current, the magnetism dies away, the
hammer is forced back by the spring, and then the cycle of events is
repeated. But the starting of the current in the primary causes a
great many lines of magnetic force to pass through each of the many
thousand turns of wire in the secondary, especially as the iron core
conducts most of the lines of force of each turn of the primary almost
from end to end of the coil, and thus through nearly all the turns of
the secondary. This action might be further increased by connecting
the ends of the iron core with an iron tube or series of longitudinal
bars placed outside the whole coil. When the primary current ceases,
all these lines of force vanish. Thus during the starting of the
primary current, which, on account of self-induction, occupies a
considerable time, there will be an inverse current in the secondary
proportional to the rate of increase of the primary; and while the
primary is dying away, there will be a direct current in the secondary
proportional to its rate of decrease. The primary current cannot be
increased at a faster rate than corresponds to the power of the
battery, but by making a very sharp break it may be stopped very
rapidly. Still, however rapidly the circuit is broken, self-induction
causes a spark to fly across the gap until the energy of the current
is used up. The introduction of the condenser, consisting of a number
of sheets of tinfoil insulated by paper steeped in paraffin wax, and
connected alternately with one end or the other of the primary coil,
serves to increase the rapidity with which the primary current died
away, by rapidly using up its energy in charging the condenser, and
produces a corresponding diminution in the spark at the
contact-breaker. This rapid destruction of the primary current causes
a correspondingly great electro-motive force in the secondary coil,
and thus very long sparks are produced between the terminals of the
secondary coil when the primary current is broken, though no such
sparks are produced when the primary current starts. If the secondary
coil be connected up with a galvanometer, so that there is a metallic
circuit throughout, it will be found that just as much electricity
flows in one direction through the circuit at the break of the primary
as flows in the other direction at the make, the difference being that
the first is a very strong current of great electro-motive force but
lasting a very short time, the second a feebler current lasting a
correspondingly longer time.

       *       *       *       *       *

But though the recent advances in electrical science have been very
great, the grandest triumph of this century is the establishment of
the principle of the conservation of energy, which has settled for
ever the problem of "the perpetual motion," by showing that it has no
solution. This problem was not simply to find a mechanism which should
for ever move, but one from which energy might be continuously derived
for the performance of external work--in fact, an engine which should
require no fuel. But in spite of all that has been proved, numbers of
patents are annually taken out for contrivances to effect this
object.

We have seen how Rumford showed that heat was motion, and how he
approximately determined its mechanical equivalent. Séguin, a nephew
of Montgolfier, endeavoured to show that, when a steam-engine was
working, less heat entered the condenser than when the same amount of
steam was blown idly through the engine. This Hirn succeeded in
showing, thus proving that heat was actually used up in doing work.
Mayer, of Heilbronn, measured the work done in compressing air, and
the heat generated by the compression, and assumed that the whole of
the work done in the compression, and no more, was converted into the
heat developed, which was the same thing as assuming that no work was
done in altering the positions of the particles of gas. From these
measurements he deduced a value of the mechanical equivalent of heat.
The assumption which Mayer made was shown experimentally by Joule to
be nearly correct. Joule proved that, when air expands from a high
pressure into a vacuum, no heat is generated or absorbed on the whole.
This he did by compressing air in an iron bottle, which was connected
with another bottle from which the air had been exhausted, the
connecting tube being closed by a stop-cock. The whole apparatus was
immersed in a bath of water, and on allowing the air to rush from one
vessel into the other, and then stirring the water, the temperature
was found to be the same as before. When the iron bottles were in
separate baths of water, that from which the air rushed was cooled,
and that into which it rushed was heated to the same extent. Joule and
Thomson afterwards showed that a very small amount of heat is absorbed
in this experiment. Joule also showed that the heat generated in a
battery circuit is proportional to the product of the electro-motive
force and the current, or to the product of the resistance and the
square of the current, which, in virtue of Ohm's law, is the same
thing. This relation is often known as Joule's law. He also proved
that, for the same amount of chemical action in the battery, the heat
generated was the same, whether it were all generated within the
battery or part in the battery and part in an external wire; and that
in the latter case, if the wire became so hot as to emit light, the
heat measured was less than before, on account of the energy radiated
as light. With a magneto-electric machine he employed mechanical power
to produce a current, and the energy of the current he converted into
heat. In all cases he found that, _whatever transformations the energy
might undergo in its course, a definite amount of mechanical energy,
if entirely converted into heat, always produced the same amount of
heat_; and he thereby proved, not only that heat is essentially
_motion_, but that it corresponds precisely with that particular
dynamical quantity which is called _energy_; and thus justified the
attempt to find a relation between heat and energy, or to express the
mechanical equivalent of heat as so many foot-pounds.

Joule then set to work to determine, in the most accurate manner
possible, the number of foot-pounds of work which, if entirely
converted into heat, would raise one pound of water through 1° Fahr.
The best known of his experiments is that in which he caused a paddle
to revolve by means of a falling weight, and thereby to churn a
quantity of water contained in a cylindrical vessel, the rotation of
the water being prevented by fixed vanes. In these experiments he
allowed for the work done outside the vessel of water or calorimeter,
for the buoyancy of the air on the descending weight, and for the
energy still retained by the weight when it struck the floor. From the
results obtained he deduced 772 foot-pounds as the mechanical
equivalent of heat. Expressed in terms of the Centigrade scale,
Joule's equivalent, that is, the number of foot-pounds of work in the
latitude of Manchester, which, if entirely converted into heat, will
raise one pound of water 1° C., is 1390.

Joule's experiments show that the same amount of energy always
corresponds to, and can be converted into, the same amount of heat,
and that no transformations, electrical or other, can ever increase or
diminish this quantity. Maxwell expressed this principle as follows:--

_The energy of a system is a quantity which can neither be increased
nor diminished by any actions taking place between the parts of the
system, though it may be transformed into any of the forms of which
energy is susceptible._

This is the great principle of the conservation of energy which is
applicable equally to all branches of science.

Another principle, almost equally general in its applicability, is
that of the dissipation of energy, for which we are indebted in the
first instance to Sir William Thomson. All forms of energy may be
converted into heat, and heat tends so to diffuse itself throughout
all bodies as to bring them to one uniform temperature. This is its
ultimate state of degradation, and from that state no methods with
which we are acquainted can transform any portion of it. When energy
is possessed by a system in consequence of the relative positions or
motions of bodies which we can handle, and whose movements we may
control, the whole of the energy may be employed in doing any work we
please; in fact, it is all _available_ for our purpose, or its
_availability_ may be said to be perfect. Energy in any other form is
limited in its availability by the conditions under which we can place
it. For example, the energy of chemical action in a battery may be
used to produce a current, and this to drive a motor by which
mechanical work is effected, but some of the energy must inevitably be
degraded into the form of heat by the resistance of the battery and of
the conductor, and this portion will be greater as the rate of doing
work is increased. The ratio of the quantity of energy which can be
employed for mechanical purposes with the means at our disposal, to
the whole amount present, is called the _availability_ of the energy.
All forms of energy may be wholly converted into heat, but only a
fraction of any quantity of heat can be transformed into higher forms
of energy, and this depends on the temperature of the source of heat
and of the coldest body which can be employed as a condenser, being
greater the greater the difference between the temperatures of the
source and condenser, and the lower the temperature of the latter. In
every operation which takes place in nature there is a degradation of
energy, and though some portion of the energy may be raised in
availability, another portion is lowered, so that on the whole the
availability is diminished. Thus, in the case of the heat-engine, work
can be obtained from heat only by allowing another portion of the heat
to fall in temperature; and, as originally stated by Sir William
Thomson, "it is impossible, by means of inanimate material agency, to
obtain mechanical effect from any portion of matter by cooling it
below the temperature of the coldest of the surrounding objects," and
to leave the working substance in the same condition in which it was
at the commencement of the operations. Accepting this principle,
Professor James Thomson showed that increase of pressure must lower
the freezing point of water, for otherwise it would be possible to
construct an engine which, working by the expansion of water in
freezing, would continue to do work by cooling a body below the
temperature of any other body available, and he calculated the amount
of pressure necessary to lower the freezing point through one degree.
The conclusion was afterwards experimentally verified by Sir William
Thomson, and served to explain all the phenomena of regelation. Thus,
like the principle of the conservation of energy, the principle of the
dissipation of energy serves as a guide in the search after truth. But
there is this difference between the two principles--no one can
conceive of any method by which to circumvent the conservation of
energy; but Clerk Maxwell showed that the principle of dissipation of
energy might be overridden by the exercise of intelligence on the part
of any creature whose faculties were sufficiently delicate to deal
with individual molecules. In the case of gases, the temperature
depends on the average energy of motion of the individual particles,
and heat consists simply of this motion; but in any mass of gas,
whatever the average energy may be, some of the particles will be
moving with very great, and some with very small, velocities. By
imagining two portions of gas, originally at the same temperature,
separated by a partition containing trap-doors which could be opened
or closed without expenditure of energy, and supposing a "demon"
placed in charge of each door, who would open the door whenever a
particle was approaching very rapidly from one side, or very slowly
from the other, but keep it shut under other circumstances, he showed
that it would be possible to sort the particles, so that those in the
one compartment should have a great velocity, and those in the other a
small one. Hence, out of a mass of gas at uniform temperature, two
portions might be obtained, one at a high temperature and the other at
a low, and, by means of a heat-engine, work could be obtained until
the two portions were again at equal temperatures, when the services
of the "demons" might be again taken advantage of, and the operations
repeated until all the heat was used up.

Any theory which is brought forward to explain a phenomenon, or any
process which is proposed to effect any operation, must in the first
instance submit to the test of the application of these two principles
of conservation and dissipation of energy; and any proposal which
fails to bear these tests may be at once rejected. The essential
feature of the science of to-day is its quantitative character. We
must, for instance, not only know that radiant energy comes to us from
the sun, but we must learn how much energy is annually received by the
earth in this way; and, in the next place, how much energy is radiated
by the sun in all directions in the same time. When we have learned
this, we want to know what is the source of this energy; and no theory
of the sun which does not enable us to explain how this constant
expenditure of energy is maintained can be accepted. Last century it
was possible to believe, with Sir William Herschel, that the greater
part of the sun's mass is comparatively cool, and that it is
surrounded by only a thin sheet of flame. To-day such a theory would
be rejected at once, simply because the thin shell of flame could not
provide energy for the solar radiation for any considerable time. The
contact theory of the galvanic cell, as originally enunciated, fell to
the ground for a similar reason. The simple contact of dissimilar
metals could afford no continuous supply of energy to sustain the
current. Applied to the steam-engine, the doctrine of energy teaches
us, not only that, corresponding to the combustion of a pound of coal,
there is a definite quantity of work which is the mechanical
equivalent of the heat generated, and is such that no engine of which
we can conceive is capable of deriving from the combustion of the
pound of coal a greater amount of work, but it teaches us that there
is a further limitation fixed to the amount of work obtainable. This
limitation depends upon the range of temperature at our command; and,
when the range is known, we can express the amount of energy
realizable by a perfect engine working through that range as a
definite fraction of the whole energy corresponding to the heat of
combustion of the fuel. Thus, if we find that a particular engine
realizes only 15 per cent. of the energy of its fuel in work done, we
must not suppose that mechanical improvements in the engine would
enable us to realize any considerable portion of the other 85 per
cent.; for it may be that a theoretically perfect engine, working with
its boiler and condenser at the same temperatures as those of the
engine considered, could only realize 25 per cent. of the energy of
the fuel, reducing the margin for improvement from 85 to 10 per cent.,
as long as the range of temperature is unaltered. To improve the
efficiency beyond this limit, the range of temperature must be
increased, that is, generally, hotter steam must be used.

The principles of energy are thus guides, not only to the scientific
theorist, but to the practical engineer, and they have been
established only through careful measurement. The simple observation
of phenomena, and of the conditions under which they occur, could
never have led to the establishment of such principles; and, though
the carrying out of experiments which do not involve measurements is
of great value, it is the careful measurement, however simple, which
affords the highest training to the mind and hand, and without which
any course of instruction in experimental physics is of little value.

The Hindoos used to regard the earth as a vast dome carried on the
backs of elephants. The elephants themselves, however, required
support, and were represented as standing on the back of a gigantic
tortoise. It does not, however, appear that any support was provided
for the tortoise. In some respects this figure represents the
apparently perpetual condition of scientific knowledge. Phenomena are
investigated, and are shown to depend upon other actions which appear
simpler or more fundamental than the phenomena at first observed.
These, again, are found to obey laws which are of much wider
application, or appear to be still more fundamental; but it may be
that we are as far off as ever from discovering the great secret of
the universe, the ultimate nature of all things.




INDEX.


    A.

    Abbott, Faraday's letters to, 241, 246.

    Aberdeen University, Maxwell appointed professor in, 284;
      Young's report on, 203.

    Absorption, Rumford's experiments on, 185;
      of sun's rays by cloth of different colours, 99.

    Academy of Sciences, Franklin nominated Foreign Associate of, 111.

    Adjustment of the eye, Young's paper on the, 200.

    Æpinus's completion of Franklin's theory, 77.

    Air, Boyle's conception of the constitution of, 19.

    Air-pump, Boyle's experiments with, 19;
      constructed by Boyle, 27.

    American Independence, Declaration of, 113.

    American Philosophical Society, foundation of, 61.

    Ampère's theory, Faraday's views on, 257.

    Anchor-ring experiment, Faraday's, 260.

    Arago's experiment, 264.

    Argand lamp, efficiency of, 188.

    Armstrong gun, principle of the, 180.

    Atmospheric electricity, Faraday's experiments on, 254;
      obtained by a pointed rod, 84.

    Autobiography of Franklin, 39.

    Availability of energy, 326.


    B.

    Baily, Francis, repetition of the Cavendish experiment by, 146.

    Beats in music, explanation of, 209.

    Beggary in Bavaria banished by Rumford, 164.

    Bernoulli's, Daniel, molecular theory of gases, 299.

    Boston, blockade of, 110.

    =Boyle=, Hon. Robert, birth, 8;
      conversion, 11;
      first air-pump, 17;
      conception of the constitution of the air, 19;
      experiments with the air-pump, 19, _et seq._;
      argument on the cause of a vacuum, 23;
      experiments establishing his law, 25;
      statement of his law, 29;
      observations on cold, 32,
      and on the expansion of water in freezing, 33;
      experiments on induced magnetism, 34;
      the province of experimental science, 37.

    Boyle's law, 29.

    Brocklesby, Dr., death of, 208.

    Brougham's criticisms of Thomas Young, 218.

    Bumper, electrical, 80.


    C.

    Camera obscura, invention of, 2.

    Canada balsam, stresses in, 298.

    Candle-flame, effect of, in discharging electricity, 75.

    Capacity, electrical, 137;
      Franklin's experiments on, 81, 89;
      Cavendish's unit of, 138;
      Cavendish's measures of, 134, 138;
      of disc, measured by Cavendish, 134.

    Capillarity, 228.

    Cascade method of charging Leyden jars, 77.

    =Cavendish=, Hon. Henry, F.R.S., birth and parentage, 126;
      social habits, 127;
      appointed member of the R.S. Committee on Lightning-Conductors,
        131;
      elected Foreign Associate of the French Institute, 132;
      death, 133;
      proof of the law of inverse squares, 135;
      experiment with the spheres repeated by MacAlister, 137;
      experiments on the torpedo, 140;
      experiments on the resistance of conductors, 142;
      discovery of Ohm's law, 143;
      view of latent heat, 144;
      apparatus for determining the melting point of mercury, 145;
      the Cavendish experiment, 146.

    Cavendish experiment, 146;
      Laboratory, 288;
      Manuscripts, 134;
      Maxwell's work on the Manuscripts, 293.

    City Philosophical Society, joined by Faraday, 245;
      Faraday's lectures to, 251.

    Cold, Boyle's observations on, 32.

    Collinson, Peter, present of, to the Library Company, 72.

    Colour-blindness, Maxwell's experiments on, 296.

    Colour-box, Maxwell's, 297.

    Colours, effect of, on absorption of sun's rays, 99, 186.

    Colours of the spectrum mixed by Boyle, 31.

    Colour-top, Maxwell's, 284, 295;
      Young's, 215.

    Colour-vision, Maxwell's theory of, 294;
      Young's theory of, 214.

    Commonplace-book, Faraday's, 253.

    Compound-interest principle, 316.

    Condenser, use of, in induction coils, 321.

    Conduction of heat, Rumford's experiments on, 186.

    Conductors, multiple, flow of electricity through, 141.

    Conductors necessarily opaque, 307.

    Conservation of energy, Maxwell's statement of the principle of,
        325.

    Copley Medal awarded to Franklin, 66, 74.

    Cork, Earl of, autobiography of, 5.

    Creeping of electricity on glass, 139.

    Crystalline lens, fibrous structure of, 200;
      mode of adjustment of, 201.

    Cuneus's discovery of the Leyden jar, 4.


    D.

    Davy, Sir Humphry, appointed professor at the Royal Institution,
        174;
      letter of, to Faraday, 244.

    Declaration of American Independence signed, 113.

    Defence of the American Colonies against France and Spain, 62.

    Degree of electrification, 137.

    De la Rive's invitation to Faraday, 249.

    Density of the earth, determinations of the mean, 146.

    Desaguliers on electrics and non-electrics, 4.

    Diagram of colour, Young's, 215;
      Maxwell's, 295.

    Diamagnetism discovered by Faraday, 274.

    Diamonds burned by Davy, 250.

    Dichroism of _Lignum nephriticum_, 30.

    Discharge, electrical, difference between positive and negative, 87.

    Dissipation of energy, principle of, 326.

    Distilled water, resistance of, 142.

    Double refraction explained by Huyghens, 219.

    Dufay showed that all bodies could be electrified, 4.

    Dynamical nature of heat, suggested by Bacon, 2, 32;
      maintained by Boyle, 32;
      investigated by Rumford, 189;
      established by Joule, 193, 324.

    Dynamical top, Maxwell's, 285.

    Dynamo, constructed by Wheatstone, 318;
      action of, 319;
      essential feature of, 319.


    E.

    Effect of points in discharging electricity, 74.

    Electrical picnic, 80.

    Electrical Standards Committee, 287.

    Electric intensity, 137;
      potential, 137.

    Electricity, first obtained from clouds, 74;
      velocity of, 93.

    Electrics and non-electrics, 3.

    Electrolysis, Faraday's laws of, 266.

    Electro-magnetic induction, discovered by Faraday, 259;
      Maxwell's statement of the laws of, 301.

    Electro-magnetic theory of light, 306.

    Electro-motors, 313.

    Electro-tonic state, conceived by Faraday, 264;
      explained by Maxwell, 302.

    Energy of Leyden jar resident in the glass, 79.

    Eriometer, Young's, 223.

    Ether, Maxwell's illustration of the possible constitution of, 302.

    Expansion of water on freezing, 33.

    Extra current, 268.


    F.

    =Faraday=, Michael, birth, 238;
      life in Jacob's Well Mews, 238;
      becomes an errand-boy, 239;
      apprenticeship, 239;
      attends lectures at Tatum's, 240;
      constructs a voltaic pile, 241;
      letters to Abbott, 241, 246;
      starts as a journeyman, 243;
      application to Davy, 243;
      appointed assistant at the Royal Institution, 245;
      joins the City Philosophical Society, 245;
      opinions respecting lectures, 246, 247;
      journey with Davy, 248;
      acquaintance with De la Rive, 249;
      crosses the Alps, 249;
      at the Academia del Cimento, 250;
      returns from the Continent, 251;
      lectures to the City Philosophical Society, 251;
      commonplace-book, 253;
      atmospheric electricity apparatus, 254;
      marriage, 255;
      discovery of electro-magnetic rotation, 255;
      of the earth's action on a current, 256;
      letter to E. de la Rive, 256;
      views on Ampère's theory, 257;
      elected F.R.S., 258;
      appointed director of the laboratory at the Royal Institution,
        258;
      work on optical glass, 259;
      discovery of induced currents, 259;
      institutes Friday evening lectures, 259;
      anchor-ring experiment, 260;
      magneto-electric machine, 262;
      obtains induced current by action of the earth, 262;
      obtains "magnetic spark," 262;
      explanation of Arago's experiment, 264;
      laws of electrolysis, 266;
      proves the identity of frictional and voltaic electricity, 266;
      experiments on self-induction, 268;
      diagrams of lines of magnetic force, 269;
      conception of lines of electric force, 270;
      ice-pail experiment, 270;
      butterfly-net, 270;
      experiments on specific inductive capacity, 272;
      appointed scientific adviser to Trinity House, 273;
      appointed member of the Senate of the University of London, 273;
      discovery of the electro-magnetic rotation of the plane of
        polarization, 273;
      investigations in diamagnetism, 274;
      joins the Sandemanian Church, 275;
      lectures before the Prince Consort, 275;
      retirement to Hampton Court, 277;
      death, 277;
      lines of force investigated by Thomson and Maxwell, 300.

    Forbes's, Principal, opinion of Young, 194.

    Foucault's measurement of the velocity of light, 220.

    _Fovea centralis_, insensibility of, to blue light, 298.

    Franciscus Linus, funicular hypothesis of, 25.

    =Franklin=, Benjamin, autobiography of, 39;
      birth, 40;
      on the disputatious temper, 42;
      method of learning prose composition, 43;
      tries vegetarianism, 44;
      adopts the Socratic method, 44;
      first voyage to England, 48;
      experience as a journeyman in London, 49;
      views on beer as a food, 49;
      marriage, 54;
      endeavours to attain moral perfection, 56;
      method of reconciling an enemy, 60;
      elected F.R.S., 66;
      second voyage to England, 70;
      begins electrical experiments, 72;
      electrical papers ridiculed by the Royal Society, 73;
      discovers the effect of points, 74;
      one-fluid theory of electricity, 76;
      theory of the Leyden jar, 78;
      invention of the lightning-rod, 83;
      golden fish, 85;
      view of the nature of light, 86;
      kite, 88;
      experiments on capacity, 81, 89;
      experiments on electrical induction, 90;
      proof of the absence of electricity in a hollow conductor, 91;
      third voyage to England, 102;
      examination before the Parliamentary Committee, 105;
      nominated Foreign Associate of the Academy of Sciences, 110;
      signs the Declaration of Independence, 113;
      sent to Paris, 113;
      made Minister Plenipotentiary to the Court of France, 116;
      signs the Treaty of Peace, 119;
      elected President of Pennsylvania, 120;
      death, 122.

    Fresnel, awarded the Rumford Medal, 233.

    Fresnel's repetition of Young's experiments, 225.

    Friction as a source of heat, Rumford's experiments on, 189.

    Friday evening lectures instituted by Faraday, 259.


    G.

    Galileo and Torricelli on the pressure of the air, 16.

    Garnett, Dr. Thomas, professor at the Royal Institution, 173.

    Gilbert, Dr., founder of electrical science, 3.

    Göttingen, Young's university course at, 206.

    Graham Bell's telephone, 319.

    Gray, Stephen, discovers electric conduction, 3.

    Grimaldi's fringes explained by Young, 222.

    Gunpowder, Rumford's experiments on, 179.


    H.

    Halos, coloured, Young's explanation of, 224.

    Hawksbee's observations on capillary attraction, 228.

    Heat, a form of energy, 32;
      generated by friction in vacuum, 32;
      generated by friction, Rumford's experiments on, 189.

    Herapath's explanation of gaseous diffusion, 299.

    Herschel's, Sir John, comments on Young's principle of interference,
        208.

    Hicks's, Principal, investigations on the influence of temperature
        on gravitation, 184.

    Hieroglyphics, Young's work on, 234.

    Hobbes, opposition of, to Boyle, 25.

    Hollow conductor, Franklin's experiments on, 91;
      Cavendish's experiments on, 135;
      Faraday's experiments on, 270.

    Honorary degrees conferred on Franklin, 66, 101.

    Hooke's law, 229.

    Hooke, Theodore, founds the Royal Society, 14.

    Huyghens's explanation of double refraction, 219;
      principle, 218.

    Hydrogen, electro-chemical equivalent of, 267.


    I.

    Ice-pail experiment of Faraday, 270.

    Identity of frictional and voltaic electricity, 266.

    Induced currents, discovered by Faraday, 259;
      explained by structure of ether, 304;
      from earth's action, 262.

    Induction coil, 320.

    Induction, Franklin's experiments on, 90;
      self, 142, 306.

    Induction machines, principle of, 316.

    Insulators for lightning-rods, 96.

    Interference, principle of, discovered by Young, 208;
      spectra of, obtained by Young, 225.

    Invisible college, 13.


    J.

    Jenkin, William, discovery of the "extra current" by, 268.

    Joule and Thomson's determination of the heat absorbed by air in
        expanding, 324.

    Joule, Dr., establishment of mechanical theory of heat by, 193, 324.

    Joule's law, 324;
      proof that heat and energy are equivalent, 324;
      determination of the mechanical equivalent of heat, 325.

    Junto Club, formation of the, 51.


    K.

    Kelland's, Professor, edition of Young's lectures, 212.

    Kinnersley commences lecturing, 73.

    Kite, Franklin's, 88.

    Knobs _versus_ points, 95.


    L.

    Laboulaye's comments on Franklin, 38.

    Laplace's theory of Saturn's rings, 285.

    Latent heat, Black's theory of, 144;
      Cavendish's views on, 144.

    Leonardo da Vinci's observation of capillary attraction, 228.

    Leyden jar, discovery of, 4;
      energy of, resident in the glass, 79.

    Leyden jars charged by cascade, 77.

    Light, Franklin's view of nature of, 86;
      Maxwell's electro-magnetic theory of, 306;
      rotation of the plane of polarization of, 273.

    Lightning, effects of, on Newbury steeple, 92.

    Lightning-protectors, Maxwell's, 294.

    Lightning-rod, illustrations of the, 83.

    _Lignum nephriticum_, dichroism of, 30.

    Lines of force mathematically investigated by Thomson and Maxwell,
        300.

    Lines of magnetic force fixed by Faraday, 269.

    Luminiferous ether, the vehicle of electrical action, 227;
      illustration of the possible constitution of, 302.


    M.

    Magdeburg hemispheres, experiments with, by Otto von Guericke, 17.

    Magic squares, Franklin's proficiency in, 66.

    "Magnetic spark" obtained by Faraday, 262.

    Magnetization by induction, Boyle's experiments on, 34.

    Magneto-electric machine, Faraday's, 262, 314.

    Magneto-electric machines, Wilde's, 318;
      objects to be aimed at in the construction of, 315.

    =Maxwell=, James Clerk, birth and parentage, 279;
      enters Edinburgh Academy, 280;
      letters to his father, 280;
      early papers before the Royal Society of Edinburgh, 281;
      visit to Mr. Nicol, 281;
      experiments with unannealed glass, 282;
      enters the University of Edinburgh, 282;
      enters Peterhouse, 282;
      migrates to Trinity, 282;
      degree in Cambridge, 283;
      elected Fellow of Trinity, 284;
      appointed Professor at Marischal College, 284;
      marriage, 287;
      essay on Saturn's rings, 285;
      dynamical top, 285;
      appointed professor at King's College, 287;
      lecture on colour at the Royal Institution, 287;
      work on the Electrical Standards Committee, 287;
      appointed Professor of Experimental Physics at Cambridge, 288;
      plans the Cavendish Laboratory, 288;
      lectures at Cambridge, 290;
      work on the Cavendish Manuscripts, 134, 293;
      delivers the Rede Lecture, 293;
      method of protecting buildings from lightning, 294;
      death, 294;
      colour-top, 295;
      experiments on colour-blindness, 296;
      colour-box, 297;
      awarded the Rumford Medal, 297;
      wheel of life, 297;
      real-image spectroscope, 298;
      discovery of stresses in Canada balsam, 298;
      of the insensibility of the _fovea centralis_ to blue light, 298;
      statistical method, 299;
      explanation of the viscosity of gases, 299;
      investigations of Faraday's lines of force, 300;
      statement of the laws of electro-magnetic induction, 301;
      mechanical illustration of the ether, 302;
      explanation of induced currents, 304;
      of the mechanical action between currents and currents, and
        between magnets and currents, 304;
      of self-induction, 306;
      electro-magnetic theory of light, 306;
      contrivance for overcoming the principle of the dissipation of
        energy, 328.

    Maxwell's experiment for showing electro-magnetic rotation, 258.

    Mayer's determination of the mechanical equivalent of heat, 323.

    Mechanical equivalent of heat, definition of, 193;
      Rumford's determination of, 192.

    Mercury, melting point of, 145.

    Mirabeau's declamation on Franklin, 123.

    Mixed plates, colours of, 223.

    Moral perfection, Franklin's endeavour to attain, 56.

    Mother-of-pearl, Young's explanation of the colours of, 224.


    N.

    Nautical Almanack, Young appointed superintendent of the, 232.

    Newton's analysis and synthesis of white light, 213;
      rings, Young's explanation of, 222;
      theory of light, 219.

    Nicol prisms given to Clerk Maxwell, 282.


    O.

    [OE]rsted's discovery, 255.

    Ohm's law, discovered by Cavendish, 143;
      meaning of, 143.

    Optical glass, Faraday's work on, 259.

    Otto von Guericke, contributions of, to electricity, 3;
      experiments of, with the Magdeburg hemispheres, 17.


    P.

    Paris, Dr., Faraday's letter to, 243.

    Pascal takes a barometer up the Puy de Dome, 17.

    Pennsylvania fireplace invented by Franklin, 63;
      _Gazette_ published by Franklin, 53.

    Perpetual motion, Rumford's contrivances for, 150;
      impossibility of, 322.

    Philadelphia, Franklin's first arrival in, 46;
      Library, foundation of the, 55.

    Photometer, Rumford's, 187.

    Pigments, effects of mixing, 217.

    Points _versus_ knobs, 95, 131.

    Polarization, explained by transverse vibrations, 226;
      of light discovered by Malus, 226.

    "Poor Richard's Almanack," 60.

    Pressure of the air the cause of suction, 29.


    R.

    Radiation, Rumford's experiments on, 184;
      of cold, Rumford's experiments on, 186.

    Rede Lecture, delivered by Clerk Maxwell, 293.

    Refraction of light, laws of, 1;
      mentioned by Pliny, 1.

    Relative economy of different sources of light, 188.

    Resistance of conductors, Cavendish's experiments on, 142.

    Roemer, measurement of the velocity of light by, 2.

    Rosetta Stone, discovery of the, 234;
      inscription on, 234.

    Royal Institution, foundation of the, 169;
      Young's lectures at the, 212;
      Faraday's appointment at the, 245;
      Maxwell's lecture on colour at the, 287.

    Royal Society, origin of the, 13-15.
    =Rumford=, Count, birth and parentage, 148;
      life as a medical student, 153;
      becomes a schoolmaster at Concord, 154;
      marriage, 154;
      summoned before the Committee of Safety, 156;
      imprisoned at Woburn, 156;
      first journey to London, 158;
      receives an appointment in the Colonial Office, 158;
      experiments on the explosion of gunpowder, 158, 179;
      elected F.R.S., 158;
      made lieutenant-colonel in the British army, 159;
      promoted to colonel, 160;
      visits Elector of Bavaria, 160;
      cured of martial ambition, 160;
      enters the service of the Elector of Bavaria, 161;
      knighted by George III., 161;
      reforms in the Bavarian army, 162;
      attack on the beggars, 163;
      made Count of the Holy Roman Empire, 165;
      robbed of his manuscripts, 166;
      visited by his daughter, 166;
      his roaster, 166;
      experiments on fire-places, 166;
      founds the Rumford Medal, 167;
      appointed Minister Plenipotentiary to the Court of Great Britain,
        169;
      founds the Royal institution, 169;
      plans for the Institution, 169;
      residence in Paris, 175;
      marriage with Madame Lavoisier, 175;
      death; 176;
      Cuvier's _éloge_ on, 176;
      statue at Munich, 178;
      experiments on the conduction of heat in fluids, 181;
      on the convection of heat in viscous liquids, 184;
      on the weight of heat, 185;
      on radiation, 185;
      on the conduction of heat, 186;
      on the apparent radiation of cold, 187;
      shadow-photometer, 188;
      experiments on the relative economy of candles and tapers, 188;
      on the traction of carriages, 189;
      on friction as a source of heat, 189;
      determination of the mechanical equivalent of heat, 192.

    Rumford Medal, foundation of the, 167;
      recipients of the, 167;
      awarded to Fresnel, 233;
      awarded to Clerk Maxwell, 297.

    Rumford roaster, 166.


    S.

    "Sandford and Merton," influence of, on the negro traffic, 197.

    Saturn's rings, Maxwell's essay on, 285.

    Sea-water, resistance of, 142.

    Séguin's attempt to measure loss of heat in the steam-engine, 323.

    Self-induction, effect of, on sudden discharge, 142;
      of electro-magnet, 268;
      effect of, in induction coil, 321.

    Sensation of heat, cause of, 33.

    Seraphic love, Boyle's essay on, 15.

    Shaw's, Dr., comments on Boyle, 37.

    Snellius's laws of refraction, 1.

    Socratic method adopted by Franklin, 44.

    Specific inductive capacity, discovered by Cavendish, 139;
      rediscovered by Faraday, 272.

    Spectral colours, mixed by Boyle, 31;
      mixed by Maxwell, 297.

    S.P.G., foundation of the, 30.

    Spheroidal waves in Iceland-spar explained by Young, 226.

    Stamp Act, 112.

    Standards Commission, report of, 232.

    Statistical method, Maxwell's, 299.

    Steeple struck by lightning at Newbury, 92.

    Stereoscope, Maxwell's real-image, 298.

    Stokes's, Professor G. G., exhibition of the bright centre in the
        shadow of a disc, 222.

    Suction caused by atmospheric pressure, 29.

    Surface-tension, 228;
      suggested by Segner, 229;
      Young's investigations on, 229.


    T.

    Table of results of experiments on Boyle's law, 27.

    Tatum's lectures on natural philosophy, 240.

    Telephone, Graham Bell's, 319.

    Temperature, its nature, 33.

    Thermometers first hermetically sealed, 2.

    Thomson's, Professor James, application of the principle of
        dissipation of energy to the freezing of water under pressure,
          327.

    Thomson's, Sir William, statement of the principle of dissipation of
        energy, 327;
      vortex theory of matter, 312;
      mirror galvanometer, 313;
      replenisher, 316.

    Thunder-storms, Franklin's theory of, 81.

    Torpedo, Cavendish's experiments on the, 140;
      Davy's experiments on the, 251.

    Traction of carriages, Rumford's experiments on, 189.

    Trial plate used by Cavendish, 139.

    Tyres, relative advantages of broad and narrow, 189.


    U.

    Undulatory theory founded by Hooke and Huyghens, 218.

    Union of the American States, Franklin's plan for, 68.

    University of Philadelphia, foundation of the, 64.


    V.

    Vacuum, Boyle's argument on the cause of a, 23.

    Velocity of electricity, 93;
      of light measured by Roemer, 2;
      of light deduced from electro-magnetic theory, 306.

    Viscosity of gases explained by Maxwell, 299.

    Voltaic pile constructed by Faraday, 241.

    Vortex theory of matter, 312.

    Voss machine, 316.


    W.

    Wallis, Dr., account of the Royal Society by, 14.

    Wealth, ways to acquire, 100.

    Wheel of life, Clerk Maxwell's, 297.

    Wilson, Dr., account of Cavendish by, 132, 147.


    Y.

    =Young=, Thomas, Principal Forbes's opinion of, 194;
      birth and parentage, 194;
      early education, 195;
      becomes a London medical student, 199;
      paper on the power of adjustment of the eye, 199;
      elected F.R.S., 200;
      visit to Cornwall, 201;
      first visit to the Duke of Richmond, 201;
      enters the Medical School at Edinburgh, 202;
      declines secretaryship to the Duke of Richmond, 202;
      visits Gordon Castle, 204;
      visits Inverary Castle, 205;
      enters the University of Göttingen, 206;
      examination in medicine at Göttingen, 207;
      enters Emmanuel College, 207;
      discovers the principle of interference, 208;
      appointed Professor of Natural Philosophy at the Royal
        Institution, 174, 210;
      lectures at the Royal Institution, 212;
      theory of colour-vision, 214;
      his colour-top, 215;
      colour-diagram, 215;
      his Bakerian lectures, 218;
      explanation of the rectilinear propagation of light, 221;
      of Newton's rings, 222;
      eriometer, 223;
      explanation of coloured halos, 224;
      of the colours exhibited by mother-of-pearl, 224;
      interference spectra, 225;
      explanation of spheroidal waves in Iceland-spar, 226;
      of the colours of thin plates, 227;
      hypothesis  of an electric ether, 227;
      investigations on surface-tension, 229;
      modulus of elasticity, 230;
      his marriage, 231;
      appointed physician in St. George's Hospital, 231;
      superintendent of the Nautical Almanack, 232;
      death, 233.

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