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Title: Airopaidia
Containing the narrative of a balloon excursion from Chester, the eighth of September, 1785, taken from minutes made during the voyage; hints on the improvement of balloons ... To which is subjoined, mensuration of heights by the barometer, made plain; with extensive tables. The whole serving as an introduction to aërial navigation.
Author: Thomas Baldwin
Release date: December 15, 2024 [eBook #74910]
Language: English
Original publication: United Kingdom: J. Fletcher, 1786
Credits: Tim Lindell, Robert Tonsing, and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK AIROPAIDIA ***
AIROPAIDIA:
OR
AËRIAL RECREATION.
+Descriptions+ _of_ the aërial Scenes _are illustrated with
_ENGRAVINGS_, by the best Masters: two of which are_ +coloured+.
_The_ one, _a circular View from the Balloon at its greatest
Elevation; the_ City of Chester _appearing in the_ Center.
The other, _a Specimen of Balloon Geography: being a Prospect
from_ above _the Clouds, of the Country between_ Chester, _and_
Warrington _in Lancashire, with the Track of the Balloon in the
Air_.
_A_ third _represents the Balloon over Helsbye-Hill in Cheshire,
with a beautiful View of the adjacent Country_.
AIROPAIDIA:
+containing
the NARRATIVE of a
BALLOON EXCURSION+
from +chester+, the eighth of September, 1785,
taken from +minutes+ made +during+ the Voyage:
H I N T S
+on the IMPROVEMENT of BALLOONS,
and MODE of INFLATION by _STEAM_:
MEANS to prevent their DESCENT over WATER:
occasional ENQUIRIES
into the STATE of the ATMOSPHERE,
favouring their DIRECTION:
with various philosophical
OBSERVATIONS and CONJECTURES.+
+to which is subjoined,
MENSURATION of HEIGHTS by the BAROMETER,
_MADE PLAIN:_
with extensive TABLES.+
The +whole+ serving as an +introduction+ to
AËRIAL NAVIGATION:
+with a copious+ INDEX.
+By THOMAS BALDWIN, Esq. A. M.+
- - - - - Addita +navigiis+ sunt
Multa. _Lucretius De Rerum Nat._ L. 5, V. 335.
Nihil +perfectum+ simul ac +inceptum+.
+Usus uni rei+ deditus, et +naturam+ et +artem+ sæpe
vincit.
_Cicero._
CHESTER:
Printed for the Author, by J. Fletcher; and sold by W.
Lowndes, No. 77, Fleet-street, London; J. Poole, Chester;
and other Booksellers.
1786.
Price, in Boards, 7s. 6d.
TO THE
PRINCIPAL INHABITANTS
OF
_CHESTER:_
For their +polite attention+ on the Day of Ascent, and Preservation
of +order+ during the +inflation+: on which, the Success of aërial
Experiments so much depends, and throu’ the Want of which, so many
have already failed; for the kind Anxiety manifested during his
Absence; and for their friendly +congratulations+, on his safe
Return; the following Account of the Balloon-Excursion, written at
their Request, is, by their Permission, with all Gratitude, Esteem
and Respect,
+dedicated+,
by their most obliged,
and most obedient Servant
+the+ AIRONAUT.
AN ACCOUNT OF THE PLATES; WITH DIRECTIONS
FOR PLACING THEM.
1st. _An Account of the Plates._
1. (_a_) _A Circular View from the Balloon at its greatest
Elevation_, (Page 58.) The Spectator is supposed to be in the Car
of the Balloon, suspended above the _Center_ of the View: looking
_down_ on the Amphitheatre or _white_ Floor of Clouds, and seeing
the _City of Chester_, as it appeared throu’ the _Opening_: which
discovers the Landscape _below_, limited, by surrounding Vapour, to
something less than _two_ Miles in Diameter.
The Breadth of the _blue_ Margin _defines_ the _apparent_ Height
of the Spectator in the Balloon (viz. 4 Miles) _above_ the
_white_ Floor of Clouds, as he hangs in the Center, and looks
_horizontally_ round, into the _azure_ Sky.
2. (_b_) _The Balloon over Helsbye-Hill in Cheshire_, at half past
II. on Thursday the 8th of September, 1785. (Page 78.)
It is seen in the _South-west-Quarter_.
The View was taken in a _high_ Field, at the End of Sutton-Causeway.
Helsbye-Hill, tho’ upwards of 600 _Feet high_, appeared from the
Car of the Balloon, to be on the _same Level_ with the _Grounds
below_.
3. (_c_) _A Balloon-Prospect from above the Clouds_, (Page 154,)
or _Chromatic_ View of the Country between Chester, Warrington and
Rixton-Moss in Lancashire: shewing the whole Extent of the aërial
Voyage; with the _meandering_ Track of the Balloon throu’ the Air.
4. _The Explanatory Print_ (_d_), (Page 155:) which elucidates the
former by giving the Names of the principal Places mentioned in the
Excursion.
N. B. _The Circular View_ is seen to the best Advantage, when
placed _flat_ on a Table or Chair, and _rather_ in the Shade: the
Eye looking _directly_ down upon the Picture.
Whoever will be at the Trouble of viewing _distinct_ Parts of the
_Balloon-Prospect_, throu’ a very small Opening, made by rolling
a Sheet of Paper into the Form of a hollow Tube, and applying it
close to either Eye, at the same Time shutting the other; or by
looking throu’ the Hand, held a little open, and close to the Eye;
may form a very accurate Idea of the Manner, in which the _Prospect
below_ was represented _gradually in Succession_, to the Aironaut;
whose Sight was bounded by a Circularity of Vapour, as in Section
79, 221.
2d. _Directions for placing them._
Place the _Top_ of the +circular view+, _even_ with the _Top_ of
the Page.
The Plate will then lye over at the Bottom, and at the _right_ Side
of the Page.
Fold the Bottom up into the Book, even with the Margin: and the
_right_ Side in like Manner.
Observe to place the _Bottom_ of each of the other Plates, even
with the _Bottom_ of the Page.
The Plate will then lye _over_ at the Top, and at the _right_ Side
of the Page.
Fold the Top _down_, into the Book, _even_ with the Margin: and the
right Side, in like Manner.
The circular View, to _face_ Page 58.
The Balloon over Helsbye-Hill, to _face_ Page 78.
The Balloon Prospect, to _face_ Page 154.
The explanatory Print, to be placed _on_ Page 155: and, when
unfolded, to be seen _along with_ the Balloon-Prospect.
Literal and other Errors proper to be examined, and
corrected with the Pen, before the Book is read.
Page.
6. Note [1]—ειαδεν _write_ ευαδεν.
18. Note [6]—_Cube_ of the Velocity, &c. _write_ (as in some
Copies) Square of the Velocity, &c. the Resistence will be as
3 × 3 = 9.—See Chambers’s Dictionary, under +resistence+.
23. Section 21. _Blot out_ [Signs] of Currents.
26. _Before_ All Things being thus prepared, _insert_ [_Section_]
_viz._ 25.
35. Line 13.—I o’Clock, _write_ I. o’Clock.
54. Section 52.—an Extent above them of 77 Miles, _write_ an
Extent of 102 Miles. See the Occasion of this Mistake in Note
(_a_) Calculation SECOND, which makes the Answer 102 Miles, 1
Quarter, 320 Yards; and the Ans. to the
PROBLEM being 102 1 307
—————————————————————————
gives the Prospect 13 Yards
less than _that_ over the Clouds.
84. Line 4.—great Turnpike-Road, _write_ great public Road.
84. Note [26] _After_ See Moore’s Practical Navigator, _insert_
See Page 98 [34].
98. _After_ Note [34] _add_ See Section 84, Note [26].
118. Line 5.—from a vertical Situation only, to be seen, _write_
to be seen from a vertical Situation only:.
174. Line 1.—excessine Diminution _write_ excessive Diminution.
177. Line 9.—contain _write_ contains.
202. The Sections 259, 260, 261, are repeated.
234. Line 6.—a Yard, _write_ two Yards.
236. Line 3. _After the Words_ in Danger of breaking; _add_ the
Bottom of the Balloon must be opened, or the upper Valve
drawn. _And erase the Remainder of the Sentence._
237. Line 4.—which is a Sign that the Balloon descends, _write_
(which is a Sign that the Balloon descends).
242. Line 21.—supercede, _write_ supersede.
263. Line 5.—commonly: ascend, _write_ commonly ascend:.
266. Line 21.—their Passage _write_ its Passage.
271. Line 14.—each 4 Feet _write_ each 4 Inches.
278. Lines 15 and 18.—third Tables _and_ third Table, _write_
fourth Tables _and_ fourth Table.
283. Note [119].—more than the three first Decimals _write_ more
than the four first Decimals.
288. Line 5. _After_ .0000076, _insert_ which, being divided by
.1, gives a Cypher less.
288. Line 11.—with 4° on .25, _write_ with 4° on 25.
290. Note [120]—at low Water.) _write_ at low Water.
292. Line 23.—there will remain the greater Height, _write_ there
will remain, +secondly+; (see Section 367) the greater Height.
303. Line 6.—(viz. the 8,) _write_ (viz. the .8,).
309. Line 10. Marginal Note.—_7th Step in Section_ 366. write _7th
Step in Section_ 368.
310. _After_ Line 23, _insert_ _Air_-Thermom. 56°.
311. Line 1.—By the Practice of the first Example, _write_
Practice of the second Example.
312. Line 29. _After_ The Answer, &c. _insert_, made by rejecting
a Cypher,.
317. Before the last Line but two, _insert_ +end of the first
stage+.
318. Line 23.—the 2d Tenth, _write_ the 1st Tenth.
319. Line 13.—, gives 7. _write_, gives 97.
322. last Line but two.—and the remaining Feet _write_ the
remaining Feet.
AIROPAIDIA:
CHAPTER I.
[Sidenote: Introduction.]
Section 1. The Public have, for a considerable Time, been entertained
with Accounts of aërial Voyages.
Such Accounts are, in many Respects, vague and unsatisfactory: by no
Means adequate to the Expectations and Wishes, which have been formed
by those, who have not yet penetrated the profound Heights of the
Atmosphere.
[Sidenote: Mistakes to be noticed, as Examples of Avoidance.]
2. The Voyagers have, now and then, been pretty accurate in Regard
to Time Place Distance and Velocity: Circumstances highly worthy of
Remark, in order to estimate the Improvement already made in this
wonderful Discovery, and point out its Use: but neither ought the
_several Occasions of Failure_ in the Experiments to be omitted; as
they will be found to arise more from a Want of Prudence and Foresight
in the Managers, than from any Defect in the Machine, or the Principle
on which it acts. Such Failure ought therefore to throw an additional
Light and Credit on the Art: and give a Spur to Ingenuity, which, it is
not to be doubted, will continue to drive forwards with the same rapid
Success; nor rest, till the Art itself is brought to the highest Degree
of Perfection; till airostatic Ships make the Circuit of the Globe: a
+Navigation+ which, from its Novelty and Importance, deserves to be
considered in a separate Treatise.
[Sidenote: Aërial Voyagers defective in their Descriptions.]
3. Balloon-Voyagers have likewise been particularly defective in
their Descriptions of aërial Scenes and Prospects: those Scenes of
majestic Grandeur which the unnumbered Volumes of encircling Clouds,
in most fantastic Forms and various Hues, beyond Conception glowing
and transparent, portray to a Spectator placed as in a Center of
the Blue Serene above them: contemplating at the same Instant, and
_apparently_ at some Miles Distance immediately below, a most exquisite
and ever-varying Miniature of the _little Works of Man_, heightened by
the supreme Pencil of Nature, inimitably elegant, and in her highest
Colouring.
Such are the Scenes which, Ballooners all allow, constitute the true
Sublime and Beautiful: inspire Ideas of rational Humiliation to a
thinking Mind, and raise the most careless Mortal to an unknown Degree
of enthusiastic Rapture and Pleasure.
Every Beholder is a Judge of the Scenery around him: and no one, it is
presumed, ever ascended into the Atmosphere on a _mild Day_, with a
sound and well ballasted Balloon, that did not wish to taste the Luxury
of a second Voyage.
[Sidenote: Disappointment shoud excite the Ardor of the Scientific.]
4. Yet notwithstanding, as Ignorance is known to be the Parent of
Fear, the Bulk of Mankind, which are by far the greater Number, will
long continue to entertain absurd Apprehensions concerning it; to
oppose and ridicule the Invention; as they will oppose every other
Discovery, which they have neither Talents _Inclination_ or Leisure to
understand.
This Reflexion shoud, on the contrary, rather excite than check the
Ardor of the Skilful and Scientific, to cherish and promote the Art.
In the History of Airostation, each Event is yet new and _uncompared_.
_Every_ Circumstance ought therefore to be carefully recorded: since
it woud be unfair to fix Bounds to Science; or argue, that such
Inferences, as shall demonstrate the great Utility of the Invention,
may not be drawn from Circumstances which Inattention might pronounce
to be most trifling and minute.
[Sidenote: The Reader cautioned.]
5. The Reader is requested to observe that, this Account being
addressed to the Generality, and not to the Curious and Philosophic
only; many Circumstances are added, which woud otherwise have been
considered as superfluous: and some it was thought proper to repeat, in
order to connect the Thread of the Narration, without the Necessity of
frequent Reference to the Sections.
[Sidenote: Squalls of Wind the Day preceding the Ascent.]
6. An Agreement having been made with Mr. Lunardi, that he shoud
resign his Balloon to Mr. Baldwin on Wednesday the 7th of September;
an Advertisement to that Purpose appeared in the Chester Paper: and
on Wednesday Morning, a great Number of Spectators assembled in the
Castle-yard of the City of Chester: where many waited till half past
IV in the Afternoon; Mr. Lunardi declaring that, on Account of the
Violence and Unsteadiness of the Wind which blew from the South and
South-West, it was dangerous to attempt the Inflation of his Balloon;
and Mr. Baldwin continuing to assert that, if it coud be filled, he
was willing to go up.
The Weather was _then_ moderate: but Mr. Baldwin, thinking the Hour
too late to begin the Inflation, which, judging from the two former
Inflations, coud not probably have been completed till after _Sunset_;
made a Proposal to Mr. Lunardi, that he shoud postpone the Exhibition
till the next[1] _Day_. The latter, after some Reluctance, arising from
a Fear lest the Public shoud disapprove his Conduct, politely complied
with his Request, on Mr. Baldwin’s saying that he woud take the Blame
on himself.
CHAPTER II.
+Preparations for the Voyage.+
[Sidenote: Cannon first fired at IX.]
Section 7. On Thursday the 8th of September 1785, at IX in the Morning,
one of the Cannons (a Six-pounder) was first fired in the Castle-yard,
to inform the City and Neighbourhood, that the necessary Preparations
were making to inflate the Balloon.
Till VIII that Morning, the Air had been hazy: but was then clear,
bright and calm _below_, with an upper Tier of light Clouds in the
Zenith moving from South-West by West, and dense ones rising in the
Horizon.
[Sidenote: At X, the Inflation began with a small Balloon.]
8. At X o’Clock, the Process began with the Inflation of an airostatic
Globe eighteen Feet in Circumference, of Silk Tiffany, made the latter
End of the Year 1783, and decorated with Painting, Mottoes and Devices:
in the Performance of which little Work, Mr. Baldwin was (in the
modern Phrase) the sole Projector, Architect Workman and Chymist.
[Sidenote: An airostatic Globe liberated as Pioneer to the great one.]
9. The Airostat was presently liberated by the Hands of Mr. Lunardi;
and continuing to turn gently the same Way round its own Axis, afforded
a beautiful Spectacle to the Beholders: remaining in Sight about half
an Hour. It was intended to serve as a Sort of Pioneer, to delineate
the Track of the great Balloon.
[Sidenote: Its Fate.]
10. It fell at some Miles Distance, ’tis said unfortunately on a Hedge,
and was presently torn to Pieces by the Eagerness and Avarice of the
Pursuers, who expected and undeservedly obtained the Reward promised in
the Letter appended to it.
[Sidenote: Second Cannon at XII.]
11. At XII the Cannon fired a second Time, to announce that the Process
was in a proper Degree of Forwardness.
At this Time Mr. Baldwin went, with some Friends, to take an early
Dinner: he also recapitulated the Articles, to be certain that Nothing
was omitted.
[Sidenote: Inventory for the Voyage.]
12. The following Inventory, with which he ascended, may be of Use to
future Aironauts; to whom _only_ it is addressed.
The Cable and Grapple are considered as Part of the Balloon. (See
Section 13.)
12. Article 1. A portable Barometer,[2] with a common Syphon or
Bulb, (purchased at Lausanne.)
12. 2. Martin’s Thermometer,[3] with Farenheit’s Scale[4] for the
Degrees of Temperature.
12. 3. Mariner’s Compass in a double Box, to be used when the
Sun is intercepted from the View by Clouds, in order to discover
whether the Balloon turns round.
12. 4. Down, or small Feathers, to be loose in the Pocket, and
thrown out, when enshrined in Clouds; or at any other Time, to shew
the Rise or Fall of the Balloon.
12. 5. An Asses’ Skin Patent Pocket-book; as Wet spoils Paper.
12. 6. Two _red_ Lead Pencils: each Pencil ready pointed at both
Ends, to save Time and Trouble: preferable to Ink, which may be
spilt or frozen.
The Strokes with _red_ Lead are not so easily obliterated, as when
made with a _black_ Lead Pencil.
12. 7. A small sharp Knife pointed, and ready open, or which will
open easily. A Pair of Scissars.
12. 8. A _wicker_ Bottle of Brandy and Water, only three Parts
full, half and half: such Bottles are more secure: and such Mixture
will not soon freeze. The cochuc or elastic Bottle is still better.
A Cork-screw.
12. 9. _Compact_ Provisions, which do not soil the Fingers or
Pocket-book, as Confectionaries, Fruit, Biscuit, Bread.
12. 10. A _boarded_ Map of the Country over which the Aironaut may
be supposed to pass: the Back serving as a Table.
12. 11. Two Needles with large Eyes: the _raw_ Silk put through,
and tyed on a Knot at the Ends to prevent the Needles from being
lost: to be ready at the Instant wanted, to sew up any Holes within
Reach, in the Balloon; the Holes being first tyed up with Twine.
The Needles to be stuck into Parchment, containing a small Hank of
_raw_ Silk: the Needle Silk run round the Parchment, to keep the
Hank dry.
The whole Hank to be tyed by one End to the Side of the Car; when
above all Clouds, to shew, by the Divergency of the Threads, the
Electricity of the Air.
12. 12. A few Yards of Dutch Twine, loose in the Pocket, to tye the
Neck of the Balloon in descending.
12. 13. For easy Experiments; 1st, Dutch Twine, half a Mile long,
on a Reel, or Pulley, or two Lengths on different Reels: also
to each Reel a Flag, made of white Linen, a Yard square; and
stretched by a slender Lath; one Side of the Flag being bound and
stitched round it: also a Piece of Twine, two Yards long, is to be
fastened by its Ends to the Ends of the Lath: a Loop is to be made
in the Middle of the Twine: and to the Loop is to be applied round
the Middle of the Lath another Piece of Twine, which will prevent
the Lath from being bent; and will keep the Flag always stretched.
By this Apparatus, Observers from below may be enabled to estimate
the Height of the Balloon, as will be shewn in its proper Place.
12. 14. 2dly, To try the Density of the Air, at different Heights,
_above_ the freezing Point with Water; _below_ it, with Brandy.
In a Basket take two Pint-bottles, one full of Water, the other
of Brandy; and six or eight empty ones: also a small Metal
Tunning-dish.
Let one End of a String be tyed round the Neck of each Bottle: and
the other End sealed to the Top of a large Cork much tapered, to
enter the Mouth easily. Round each Neck, tye a Parchment Label,
large enough to contain in abbreviated Characters the Number of
the Bottle; Time of Observation, Heights of the Barometer and
Thermometer, while on the Ground.
When an Experiment is made in the Air; pour off a full Bottle into
an empty one: put the Cork into the emptied Bottle, and mark again
the Time, Barometer and Thermometer: which are to be compared
with an Eudiometer below, to discover the Rarity and Purity of the
Atmosphere.
12. 15. A third white Linen Flag, made as above, and tyed to the
upper Hoop of the Balloon, so as to hang in Sight, will give Notice
of a Change in the Wind.
12. 16. A Yard of thin Ribbon, two Inches broad, tyed to the lower
Hoop, will mark the Rise and Fall Of the Balloon.
(12. 17. A Magnet and Iron Filings in a thin Pewter Dish with a
Cover; Also
The Prism and large Telescope were left, as too heavy.) And the
Sextant or Quadrant coud not be procured in Time. They woud, have
been of little Use, as no Horizon of the round Earth was seen
during the Excursion: and it is presumed, that the circular Horizon
is seldom visible, when the Balloon is at any considerable Height;
the Accumulation of Vapour between the Eye and Horizon preventing
it: tho’ such Vapour remains invisible to Spectators from below.
12. 18. Eight Bladders, each above half blown, and differently
coloured for Ornament, tyed round the _upper_ Part of the Car,
Breast high when the Aironaut stands upright: in Case the Balloon
fall into Water.
12. 19. Speaking Trumpet: also a live Pigeon, in a small Basket of
Matting.
12. 20. Pepper, Salt, Ginger; to try the Effects of Tastes, which
have been said to become insipid on the Peak of Teneriffe.
CHAPTER III.
ADDRESSED TO AIRONAUTS.
[Sidenote: New Kind of Cable and Reel recommended.]
Section 13. The following Anchor and Cable, for greater Safety and some
particular Uses, are recommended as an Improvement.
A _strong_ Iron double Grapple, moving on a Swivel, fastened to a
_Rope_,[5] half a Mile, or better _a Mile_ long: and, if not all; a
Part of which at least, at the Distance and for the Length of ten Yards
from the Grapple, shoud be of Silk, as a non Conductor: also other ten
Yards, at its upper End, counting from the Reel or Pulley to which the
Silk shoud be tyed.
The Reel or Pulley being at least eighteen Inches in Diameter, and
fixed vertically in the Center of the upper Hoop, seven Feet above the
Bottom of the Car; by Means of three or four Iron Rods fastened in
the Bottom of the Car, and meeting together above the Reel: the Rods
so strong as to prevent the Shock which otherwise the Aironaut woud
receive in alighting on the Ground.
The Reel shoud have one, or two Iron Winches or Handles, one at each
End of the Reel; with moveable Handles of Wood round them. The Reel
may be furnished with sudden Checks; or gradual Clamps, as in a Mil, to
retard the Velocity.
SIGNS TO BE OBSERVED, WHEN IN THE AIR.
[Sidenote: Cautions against two Extremes.]
14. The two Extremes to be avoided are, too lofty an Ascent: and too
precipitate a Fall.
[Sidenote: 1st. Too lofty an Ascent.]
The former is to be apprehended when Balloon has swelled considerably,
and strains as if ready to burst; from the Shape of an inverted Cone,
or Children’s Top, changed to that of an oblate Spheroid, or Turnep.
It is therefore necessary to look up at the Balloon from Time to Time:
and either open the Mouth, or as it is sometimes called the Neck, _for
an Instant_; or draw the Valve; which is done by pulling a Cord fixed
at the Top of the Machine and running thro’ it to the Hand, till the
Balloon only appears full without straining.
These Operations are to be occasionally repeated during the _Ascent_.
If it is required to rise still higher; gradually throw out Ballast,
and repeat the Operations.
The proposed Quantity of Ballast being thrown out, the Balloon will
have acquired its utmost Height, and become stationary, i.e. neither
rise nor fall.
The self Descent of the Balloon is only in Proportion, as the
inflammable Air or Gass escapes thro’ imperceptible Holes in the Silk
or Seams.
2dly. +To prevent too precipitate a Fall+.
[Sidenote: 2ndly. Caution against too precipitate a Fall.]
15. 1st. Tye, or compress the Mouth of the Balloon, for a Moment; which
must always be opened, on observing that the Balloon is again risen to
so great a Height as to _strain_, or be distended as above mentioned.
2d. In descending, throw out Ballast, when the Balloon is within a
Quarter of a Mile of the Ground, but not before, i.e. at 26 Inches
by the Barometer: and, if the Fall is precipitate, not less than 25
Pounds Averdupoise, Pound by Pound, or at once, if there should be
Occasion.
3d. In Case of Accident, as the Escape of Gass; or if the Balloon be
not furnished with +an Equatorial Hoop+; prepare to throw out all the
Ballast at the above Height, but not before; as the more forcible the
Fall,[6] the greater the _Resistance_ from the Air: cut away Ends of
Cords; tear off Ornaments: part with Shoes, Cloaths. All which must be
made _loose_ and _ready_ to throw out, at the Moment the Balloon begins
to descend. Before the Landing, particular Care must be taken, that the
Weight of the Aironaut be sustained, by grasping the Hands round the
+opposite+ Sides of the upper Hoop; so that the Feet may not touch the
Bottom of the Car. The Knees shoud likewise be bent. Repeating the
above, at each Rebound of the Balloon, if any; the Aironaut will alight
in the gentlest Manner: and probably the Balloon may act as a Parashute
or Umbrella, which _alone_ will, at all Times, ensure an easy Descent.
SIGNS WHEREBY TO JUDGE WHETHER THE BALLOON IS RISING OR FALLING.
SIGNS OF RISING.
[Sidenote: Signs of Ascent or Descent.]
16. 1. When the Aironaut perceives a Pressure upwards against the Soles
of his Feet.
2. When some Objects, on the Surface of the Earth immediately below,
diminish, and others disappear.
3. When an upper Cloud approaches or involves the Balloon.
4. When a lower Cloud leaves the Balloon.
5. When Rain Snow or Hail beat +violently+ against the Top of the
Balloon.
6. When Feathers, Balloon-Flag, or Ribbon seem to be drawn forcibly
downwards.
7. When Objects on Earth, or among Clouds below the Balloon, rise and
present themselves _beyond those_, which, the moment before, were
thought most distant.
8. When the Balloon appears broader and shorter; also fuller at the
Bottom; being more distended than at the first Ascent.
SIGNS OF DESCENT.
[Sidenote: Signs of Descent.]
17. 1. When the Aironaut perceives the Bottom of the Car withdrawing
itself from the Pressure against the Soles of his Feet.
2. When Objects on Earth, and surrounding Prospects encrease in
Magnitude and Number.
3. When a lower Cloud approaches or involves the Balloon.
4. When an upper Cloud leaves the Balloon.
5. When Weather beats against the Bottom of the Car or Balloon.
6. When Feathers, Balloon-Flag, or Ribbon appear to be drawn upwards.
7. When the most distant Objects _set_, and disappear.
8. When the Balloon seems taller; and its lower Hemisphere less
distended, tho’ continuing _tight_.
SIGNS OF PROGRESSIVE HORIZONTAL MOTION.
[Sidenote: Signs of progressive Motion deceitful.]
18. These are equivocal and deceitful.
When the Aironaut has lost Sight of the Earth by intervening Clouds;
the Balloon seems at Rest, and only the lower Clouds appear to move:
whereas the contrary may be true, the Clouds may rest, and only the
Balloon move.
In this Case, Attention must be paid to the half Mile white Flag, whose
Situation and Motion must be observed, with respect to the Balloon,
and to the Earth before the Cloud intervened. If the Flag retains
its Situation with Respect to the Balloon, it may be inferred that no
Change in the Direction has happened: if its Situation alters, the
Sun or Compass is to be observed: and an Estimate made of the new
Current of Air by which the Balloon is affected: its Velocity, Sound,
Temperature, &c.
[Sidenote: To descend when lost.]
19. But to acquire a Certainty of course, it will be proper to descend
below the Cloud: or move by Compass, Map, and a Knowledge of the
Country: or try the long Cable (Section 13.)
[Sidenote: Signs of Wind horizontal.]
20. It is likewise necessary to know the _Signs of Wind_, or Currents
of Air.
SIGNS OF NEW AND SUDDEN HORIZONTAL CURRENTS.
When the Feathers, Balloon-Flag, or Ribbon, compared with Sun or
Compass, take a new and sudden horizontal Direction.
21. +of currents from above+: properly named _Waves Torrents and
Tide of Air_.
[Sidenote: Signs of depressing Torrents and Tide of Air.]
They are very frequent, and require to be guarded against: are
sometimes or long Continuance, at other Times momentary: against the
first throw out Ballast at the Height of a Quarter of a Mile, but not
before, or _as hereafter directed_: when momentary, and above that
Height, Nothing is to be apprehended: the Balloon will appear broader
and recover its Form.
CHAPTER IV.
PREPARATIONS FOR ASCENT.
[Sidenote: Preparations for Ascent.]
Section 22. Before half past I, Mr. Lunardi had inflated his Balloon
in the finest Manner; and having, with the most obliging and spirited
Attention, made such Preparations, and taken such Precautions, as he
thought were necessary to ensure the Success of the Expedition; sent to
inform Mr. Baldwin (who continued purposely absent, that he might not
disturb or precipitate the Process; but that every Circumstance shoud
be conducted with Deliberation and without Hurry) that all Things were
ready for his Departure.
[Sidenote: The Public reminded of the Necessity of preserving order
during the Inflation of Balloons.]
23. And Mr. Baldwin takes this Opportunity of returning his best
Thanks to his Friends and the Public, on the Day of Ascent, for
keeping +the small Circle clear+, by strictly adhering to the Words
of the Advertisement, which declared, “that in order to prevent an
interruption of the Process in the Inflation of the Balloon, no Persons
_were_ to be admitted +within the circle+, except those Gentlemen who
politely undertook +in turn+ to hold the Lines which detained the
Balloon.”
[Sidenote: Lead Weights placed at first in the Car, to prevent any
Fatigue in holding the Lines, and the Necessity of weighing, unless at
the Time of Ascent, to determine the Power of Levity.]
24. It may be proper to mention that Mr. Baldwin being resolved to
prevent the disagreeable Circumstances of being _weighed_ in the
Presence of Thousand spectators, at a Time when it is uncertain whether
the Balloon has _acquired_ a sufficient Degree of Levity to raise his
own Weight, together with the Instruments, Provisions, Ballast, and
other Articles, all which are known or easily calculated; finding
some Days before, his own Weight, and having calculated the rest as
under[7]; he ordered his Servant, on the Day of the Excursion, to bring
Lead Weights equal to the _Sum total_, with an overplus Weight of 10lb.
for Levity of Ascent, and place them _gradually_ in the Car, attached
for that Purpose to the Balloon, soon after the Inflation began. By
which Means the Gentlemen who held the Cords were quite at Ease: nor
was there Occasion to tye the Lines during the Inflation, to Posts
fixed in the Circumference of the Circle; nor consequently to _cut
them_ afterwards.
But it will be seen that Mr. Lunardi inflated the Balloon in a superior
Manner.
25. All Things being thus prepared, Mr. Baldwin stepped into the Car:
and finding, that, besides his own Weight, the Provisions, Articles,
Ballast, &c. the Balloon woud support an additional Weight, and _still_
rise with superior Levity; Mr. Lunardi put in 12lb. of additional
Ballast, and _guessed_ the encreased Levity at 10lb. more.
Additional { Ballast 12
{ Levity 10
———
22
Added to the 234
———
Make the Sum 256lb.
All which added to the Weight of the Balloon, _by Information only_,
as follows:
Balloon varnished 113
Netting and Cords 18
Car and Hoops 24
Mended and added Parts 5
Grapple and Cable 4
———
164
With the 256
Make the total Levity of
the Gass to produce an
Equilibrium, equal to 420lb.
The Weight of a Quantity of Air equal in Bulk to the Balloon, being
secluded; and the Gass substituted in its Room.
[Sidenote: Weight of Articles.]
26. The Calculation of the Weight of Articles was, as follows:
Pounds
Articles. Averd. Ounces.
1. Eight coloured Bladders[8]
(Section 13, Art. 18) 1 – 0
2. Preparations against extreme
Cold.
+A Winter Dress.+
Flannel or woollen Socks }
Cap }
Gloves }
Drawers } 0 – 14
Under Stockings }
———— Waistcoat }
3. Brandy, Water, Flask, and
Refreshments 1 – 8
4. Barometer (portable) 0 – 12½
5. Thermometer 0 – 3
6. Dial-Compass (a Mariner’s
Compass in a double Box,
will traverse better) 0 – 3½
7. Two white Flags, 0 – 4
with Dutch Twine on two
Reels furnished with Swivels 2 – 8
8. Asses Skin Pocket Book,
Blank Cards, Pencils,
Knife and Scissars 0 – 4½
9. Map of Cheshire boarded,
the superfluous Parts cut
away 0 – 3
10. Speaking Trumpet 0 – 8½
11. Mr. Lunardi’s Flag 3 – 8
12. Basket and eight Pint Bottles
labelled, one full of
Brandy, another of Water 8 – 3
———————
20 – 0
[Sidenote: Weight of Ballast.]
27. The Ballast consisted of three Bags of dry Sand, and two red grit
Stones, taken while in the Car, _additional_.
1st Bag tyed up weighed 12lb.
2d Ditto 12
3d untyed Ditto 20
1st red Grit 7
2d red Grit 5
——
In all 56lb.
CHAPTER V.
ASCENT WITH 20lb. OF LEVITY.
[Sidenote: Ascent at 40M. past I, with 20lb. of levity.]
Section 28. At 40 Minutes past I, the Balloon having a Levity which not
less than 20 Pounds Weight woud counterpoise, Mr. Baldwin was liberated
by the Hands of Mr. Lunardi, who suffered no one to approach the Car:
and he ascended, amidst Acclamations mixed with Tears of Delight and
Apprehension, the Misgivings of Humanity, and other usual Sensations
of Surprize, which, in a brilliant and numerous Assembly, will long
continue to accompany a Spectacle so novel interesting and awful, as
that of seeing a Fellow Mortal separated in a Moment from the Earth,
and rushing to the Skies.
[Sidenote: Employments of the Aironaut.]
29. The Balloon well inflated, tower’d aloft in an upright and
perpendicular Direction, with a quick Motion, and an accelerated
Velocity.
The Aironaut having stood up, for a Minute or two, waving his Hat in
the left, and saluting the Spectators with Mr. Lunardi’s coloured Flag
in the right Hand; put on his Hat, and having fastened the Flag-Staff
horizontally among the Lines of the Balloon, immediately betook himself
to different Employments, before he woud indulge in looking over the
Brink of the Car; lest the Novelty of the Prospect shoud call off his
Attention from _Things of Moment_.
[Sidenote: Sensation of rising described.]
30. The Force of Ascent was, from the first, plainly _palpable_: the
Sensation being that of a strong Pressure from the Bottom of the Car,
upwards against the Soles of the Feet.
[Sidenote: Caution against the vitriolic Acid Liquor.]
31. His first Point being to guard against a Deluge of acidulous
Liquor, which, he was told, had fallen, to the Quantity of three
Quarts, on the Head and Shoulders of a former Aironaut, from the
Trunk or Bottom of the Balloon, which ended in a wide circular Opening
of eighteen Inches Diameter; he found that when the Weight either of
himself, or of the Ballast, was not exactly in the Center of the Car;
the Opening of the Balloon woud, without any Trouble, hang so as to
lie on the Outside of the Car: but he did not perceive more than a few
Drops issue from the Mouth: which happened a few Minutes after he arose.
[Sidenote: Attitude, and farther Employments.]
32. This Difficulty vanishing; he changed his erect into an inclined
Posture between sitting and kneeling; sometimes with the right
Knee near the Bottom and Center of the Car: and having both Hands
quite free, the Balloon being subject to no _sensible Motion_; he
reconnoitred all the Lines and Cords: coiled the Rope or Cable to which
the Anchor or grappling Iron was fixed: tyed fast its proper End to
the upper Hoop: observed and felt the superior Thickness of the Cord
leading to the Valve: coiled it, in order that it might be free to act:
placed the untyed Bag of Ballast near the Outside of the Car: also the
tyed Bags at proper Distances to preserve the Equilibrium: unwrapped
one of the white Flags, tyed it to the String on one of the Reels, and
just threw it an Inch or two over the Side of the Car: then placed his
Watch, _open_ Knife, Scissars, Thermometer and Compass on his right
Hand: the Barometer being swung above in Sight towards the left.
[Sidenote: Change of Attitude, and Observation of the reddish Vapour.]
33. He then stood on his Feet, with a Design to look down: but his
Attention was drawn to the Opening of the Balloon, which began to
breathe out by Intervals a visible _reddish Vapour_; in Form like that
which is seen at the Top of a Brewery, only that the under Surface was
not jagged but smooth, altho’ wavy and uneven. The Particles which
composed it were so large as to be distinctly visible: and appeared,
as if endued with a very strong repelling Power, from the great and
seemingly equal Distances, of about half a Quarter of an Inch, from
each other.
It was observed by a scientific Spectator from below, that the Parts
of the Balloon, which reflected the Sun’s Rays, appeared of a bright
Copper-Colour: but the _reddish_ Vapour issuing from its Mouth put on
the Form of a lambent Flame. A similar Appearance had been observed by
him, in a former Ascent of the same Balloon, the Neck or Mouth being
then likewise open; and also by others, who declared they saw the
Balloon on Fire.
The Change of the +red+ into Flame-Colour, when seen at a great
Distance, may it not be owing to this, that the direct Rays, being
mingled with those which are intercepted between the Eye and the
Object, became in Part absorbed, and in Part refracted; and therefore
coud not reach the Sight?
[Sidenote: The Gass not offensive.]
34. This gentle Evaporation of inflammable Air, or Gass, continued:
disappearing at the Distance of four and five Inches below the Opening:
nor did it offend the Smell; not descending within its Influence.
[Sidenote: Attention to the Balloon, and Dimensions of the Car and
Hoops.]
35. He then looked upwards at the Balloon, and perceived that it was
considerably swelled in its Dimensions: and that the Distention had
raised the Bottom-Opening of the Balloon half way between the two
Hoops: i.e. from his Hip to his Shoulder, as he stood upright. The
Height from the Bottom of the Car (which was a thin circular Board four
Feet and a half, Diameter, placed on a strong Netting, and covered with
green Bays) to its Top or the lower Hoop, was three Feet; with the
Netting continued round between the lower and upper Hoop.
[Sidenote: Stationary, and Notes made.]
36. He was aware that the Swelling of the Balloon, and copious Vapour
then issuing from it, denoted the Moment when it began to lose its
ascensional or elevating Power; and that its accelerated Motion was
diminishing.
He therefore looked at his Barometer and Watch, which was 53 Minutes
past I.[9]; took up his Pencil, and on a Card (marked before he left
the Earth, as follows:
Chester-Castle-Yard. Thursday, the 8th of Sept. 1785, I. o’Clock,
Barometer 29⁸⁄₁₀, Therm: 65 in the Shade towards the North;) he wrote
“Rose at 40 Minutes past I.” He then looked again at the Barometer,
which continued falling for some Minutes, and fluctuating up and down
within the Space of an Inch or more. It first began to rest at 23¼, and
a little after at 23½. Having looked again at his Watch, he put down
“57 Minutes past I. became stationary: Barometer 23¼: Therm: still 65,
sometimes lying in the Shade, and sometimes exposed to the Sun: the
Balloon turning round frequently thro’ East to South.”
[Sidenote: Fluctuation of Barometer.]
37. The Fluctuation of the Barometer, he imagined to arise from
continued Exertions of the Gass within the Balloon, opposed by the
atmospheric Air, which varying in Density and Temperature woud give an
unequal Resistance to the Balloon: and both Gass and Air being elastic,
the Power of Ascent would act by Intervals, and communicate its
Pulsations to the Quicksilver in the Tube. His own irregular Motions in
the Car would increase the Fluctuation.
[Sidenote: The Compass traversed, but was useless.]
38. The Compass likewise traversed backwards and forwards, pointing due
North, and unaffected by the Turns of the Balloon: but was useless, as
the Sun shone bright the whole Time of the Excursion.[10]
[Sidenote: Aironaut first looked down at Leisure.]
39. Thing’s taking a favourable Turn, he flood up, but with Knees a
little bent, more easily to conform to accidental Motions, as Sailors
when they walk the Deck: and took a full Gaze before, and below him.
[Sidenote: Scenes below described.]
But what Scenes of Grandeur and Beauty!
A Tear of pure Delight flashed in his Eye! of pure and exquisite
Delight and Rapture; to look down on the unexpected Change already
wrought in the Works of Art and Nature, contrasted to a Span by the
+new perspective+, diminished almost beyond the Bounds of Credibility.
Yet so far were the Objects from losing their Beauty, that +each+
was +brought up+ in a new Manner to the Eye, and distinguished by a
Strength of Colouring, a Neatness and Elegance of Boundary, above
Description charming!
The endless Variety of Objects, minute, distinct and separate, tho’
apparently on the same Plain or Level, at once linking the Eye without
a Change of its Position, astonished and enchanted. Their Beauty was
unparalelled. The Imagination itself was more than gratified; _it was
overwhelmed_.
The gay Scene was Fairy-Land, and Chester Lilliput.
He tried his Voice, and shouted for Joy. His Voice was unknown to
himself, shrill and feeble.
There was no Echo.
[Sidenote: Let down the white Flag, 2 Furlongs, equal to half the
Length of the Twine on one Reel.]
[Sidenote: Its Uses.]
40. He then returned to an Employment which, tho’ irksome, he imagined
would contribute to the Amusement and Information of Spectators below,
if it coud be completed while he continued in Sight; as it woud furnish
them with Ideas of Height and Distance, altogether new and interesting,
_as will be seen in their proper Place_: and unwound half the Reel; the
white Flag hanging out to the Length of 440 Yards or a Quarter of a
Mile.
[Sidenote: The Reel defective.]
41. The circular Motion of the Balloon was communicated to the Loop
in the Middle of one Side of the Lath or Reel, round which from End
to End the Twine was wrapped, and by which it hung on his Finger, and
pressed it to a Degree of Pain.[11]
[Sidenote: The Employment again suspended.]
The Work was again suspended.
He coud not long withstand the Temptation of indulging his Eye with a
View of the glorious and enchanting Prospect.
[Sidenote: The Beautiful preferred to the Sublime, in Prospects.]
42. But the Beautiful among the Objects below was still more attractive
than the Sublime among those around.
[Sidenote: Inverted Firmament what.]
On looking down South by West, the Balloon often turning gently to the
right and left, and giving the Aironaut an Opportunity of enjoying the
circular View without a Change of Attitude; innumerable Rays of Light
darted on the Eye as it glanced along the Ground: which, tho’ of a gay
green Colour, appeared like an inverted Firmament glittering with Stars
of the first Magnitude.
43. This splendid Appearance was owing to the Rays of the Sun reflected
from certain Pits or Ponds of Water, of which there is one at least in
most Fields or Inclosures throughout the County: but particularly in
the low Grounds of Leach-Eye and Dodleston.
[Sidenote: Broad Turnpike Road a narrow Foot Path.]
The Object that next drew his Attention, _while ascending_, was the
Overley Turnpike-Road, which is remarkably wide, (resembling the
Emilian Way across the Atrian Fens, between Bononia and Ferràra in
Italy) raised over Saltney Marsh, leading to North-Wales and Holyhead:
composed of Sea-Sand cast up above high Water Mark. This appeared like
a narrow Foot-Path well trodden, of a _white_ Colour, and strait as if
drawn by a Line.
[Sidenote: River Dee red.]
44. Nothing however raised his Curiosity more than the Change in
Colour of the River _Dee_, Avon ddû, (i.e. _Thee_) which in the
British Language signifies the _black River_, from the Appearance of
its Waters, when seen from an Eminence running in their deep Channel
between the Mountains of Wales; but which glides by Chester with a
Silver Stream. This River,—Thanks to the cool Climate; not like the
_green_ Mincius of Virgil!—had now acquired the unvaried Colour of
_red Lead_. Nor coud he discover even the Appearance of Water; but
merely that of a _broad red_ Line, twining in Meanders infinitely more
serpentine than are expressed in Maps.
[Sidenote: Cause of the Change conjectured.]
Whether the Change arose from the Transparency of its Waters, when
seen at the Height which was _apparently_ 7 Miles, _as will be noticed
hereafter_, though the Barometer made it scarcely a Mile and Half, is
uncertain. He was at first inclined to think, that the Rays, having
suffered a double Refraction, were reflected to the Eye, from the
reddish Sand which forms their Bottom, tho’, at the Depth of 7 Yards
at an Average, above the Cause-Way, or _artificial_ Cascade near
Chester Bridge: or possibly the Water of Rivers when seen at a certain
Distance, may act as Water composing Clouds when view’d from below, at
a certain Height and Angle; reflecting only the _red_ Rays: the rest
being refracted, or absorbed.
The Colours of Objects shone more brilliant and lively at that amazing
Height, than if seen on a Level with themselves.
Nor did the Eye seem to want the Aid of Glasses: as every Thing, that
coud be seen at all, was seen distinct.
[Sidenote: The City of Chester _blue_.]
45.The _Redness_ of the River Dee was curiously contrasted by a Change
equally novel but more pleasing, in the Colour of the City of Chester,
when seen directly from above, on a Scale not larger than the Plan of
it, in Burdett’s Map.
The Town was entirely _blue_.
The highest Buildings had no apparent Height: their Summits were
reduced to the common Level of the Ground. Nor was the Cathedral
distinguished; nor any Tower or Spire discerned.
The Whole had a beautiful and rich Look; not like a Model, but a
coloured Map.
The Roofs of all the Houses appeared, as if covered with _Lead_, in the
most elegant Taste.
Strangers may wish to be informed, that in most of the Northern
Counties, the Buildings are covered with _blue Stones_ called
+Slates+[12] found in the Mountains; instead of artificial _red_ Tiles,
as in London, and the South of England.
CHAPTER VI.
BALLOON VERGING TO THE SEA.
[Sidenote: Sympathy of the Spectators, on seeing the Aironaut verging
towards the Sea.]
Section 46. Before a farther Description of aërial Scenes is attempted,
it woud be improper not to mention a Circumstance which happened on the
first Ascent of the Balloon: and too strongly called forth the tender
sympathetic Feelings, by raising, in the Minds of the Spectators,
_alarming Apprehensions_ for the Safety of the Aironaut, on seeing the
Balloon move gently towards the Sea.
They were however, in a great Measure, soon relieved from their
Anxiety: for, by rising into another Current, he escaped the Danger:
skirting the Coasts of the River Mersey; which coud not be seen from
the Balloon at the Distance of little more than a League, tho’ the Sun
was supposed to shine the whole Time on the Water.
The upper Current was, in Fact, rendered visible to the aërial
Traveller, for more than two Hours before, and at the Time of his
Ascent; by lofty Clouds of the second Stratum, flying in a safe
Direction.
CHAPTER VII.
[Sidenote: Aërial Scenes continued.]
Section 47. A Few Seconds of Time before the Balloon had attained its
greatest Height; the Velocity of Ascent being every Instant retarded
by the Escape of Gass thro’ the Opening;—the _remarkable Stillness_
which prevailed in so elevated a State of the Atmosphere, _apparently_
many Miles above all visible Vapour, far beyond the Sight of every
living Creature, and where the human Voice was no longer heard from
below; the larger Objects, with which the Surface of the distant Earth
was covered, as Rivers Woods Inclosures, diminishing to the View, yet
encreasing in their Beauty;—coud not but make a lively Impression on
the Mind of the Aironaut.
The striking Contrast and Novelty of his Situation filled him with
unusual and pleasing Sensations.
He had just left, for the first Time, his native Earth, where he had
continued for a while the central Object to some _thousand_ Spectators;
whose Eyes, he knew, were still turned towards him; that he was still
the Subject of their Conversation: yet no human Figure met his Sight;
no human Sound vibrated on his Ear.
An universal Silence reigned! an empyrèan Calm! unknown to Mortals
_upon Earth_.
The Sky was painted with a purer, and more transparent Azure. The Sun
shone hot, and with a brighter Lustre. His Beams were _white_ and
sparkling: not surrounded with Haze or Vapour: but too fierce for the
human Eye to look upon a second Time with Pleasure.[13]
[Sidenote: Objects which filled the Mind of the Aironaut with Wonder
and Delight.]
48. A Chearful Serenity filled the Breast of the Aironaut.
In an erect Posture, and with the utmost Composure he gazed around:
reflecting with Wonder and Delight on a Situation, where the
+Beautiful+ and +Sublime+ were seen united, in a Manner perfectly novel
and engaging.
[Sidenote: Novel situation illustrated by a familiar Comparison.]
If it be allowed, for the Sake of Illustration, to compare _great_
Things with _small_; he found himself suspended in the central Concave
of an unmeasurable Crater Bowl or Bason; and considerably above the
Rim or Margin, so as to peep fairly over it: for by looking _straight
before him_, while the Balloon continued gently turning on its vertical
Axis, he coud see quite round into the +Blue+.
The Earth was the _Miniature-Picture_[14] painted on the Bottom of the
Bowl, on the Inside. The Sides of the Bowl next the Bottom were rather
obscure: as the Objects, on the Surface of the Earth not immediately
under the Eye, being foreshortened, were indistinct, either on Account
of their immense Distance, or by mere Accumulation of Vapours, and
mixed with Haze and Cloudiness.
[Sidenote: The Comparison carried on.]
From thence to the Top of the Bowl, was fantastically grouped, spotted,
and dash’d with Clouds dense and luminous, in the strangest and most
grotesque Forms; still smaller and more numerous, as the Eye was more
extended: The Rim or Margin ending, not in a fringed Border; but in
a plain smooth Line; to represent the amazing Distance, at which,
the upper Surfaces of _Clouds in Perspective_ lost all their rugged
mountainous and fringed Shapes; and terminated even and smooth: making
a perfect horizontal Ring in the Heavens, somewhat below the Eye of the
Observer. The whole formed a glorious _Concave_: and the Imagination
was lost in the surrounding distant Azure.[15]
[Sidenote: _Apparent_ Altitude of the Balloon when stationary.]
[Sidenote: The _apparent_ Heights proportioned to the _barometric_
Height.]
49. Considering more attentively the Dimensions of this vast
Amphitheatre; as he long continued _apparently_ in the _same_ Spot,
and seemed to himself a mere Atom floating _invariably_ in the Center
of the empty Space; yet as a sole thinking Being there, whose Mind
was bent on estimating the Extent of his View, so accurately defined
by the circular Horizon of dense accumulated Vapour; and judging, as
of other Distances, by _the natural Eye_ alone; pointing downwards on
Objects which were only distinguishable when immediately below it,
frequently no more than the Circuit of a Mile on the Earth’s Surface,
the _vertical Boundary_ of the profound Abyss; all else being obscured
by Haze, or removed from Sight by Volumes of intervening Cloud; he coud
not divest himself of the Idea, but that the _apparent_ Depth below him
was at least _seven_ Miles: _three_ from the Earth to the upper Surface
of the superior Clouds,[16] and _four_ above them.[17]
OBJECTION REMOVED.
[Sidenote: _Improbability_ of a concave Appearance of the Clouds and
Earth, _lessened_, by a familiar Illustration.]
50. Some may find a Difficulty in conceiving, how the whole Prospect of
Clouds and Earth together coud put on a _concave_ Appearance: both of
which were in Reality _convex_, with Respect to the Situation of the
Observer in the Car.
A familiar Illustration may help to remove the Objection.
Imagine a Person placed in the Center of a Plain, or Carpet; extended
every Way beyond the Reach of the Eye. If in that Situation he was
gradually elevated; the _distant_ Parts of the Carpet woud _seem_
to rise with him: and those Figures of the Pattern woud alone be
distinguished, that lay immediately below the Eye: the more remote
becoming dim and faint. The whole would put on the Form of a concave
Bowl; as soon as he had risen to so great a Height, as plainly
to perceive the Figures of the surrounding Pattern more and more
foreshortened, in Proportion to their Distance from the Center of the
Carpet.
CHAPTER VIII.
Section 51. The Perspective of the Clouds was entirely new; and
remarkable both for Beauty and Grandeur.
The lowest Bed of Vapour that _first_ put on the Appearance of Cloud
was of _a pure white_; in detached Fleeces; encreasing as they rose.
They presently coalesced, and were aggrandized into +a Sea+ _of
Cotton_, but more _white_; and _dazling_: tufted here and there by
the light Play of Air, and gentle Breezes in every Direction: but
where undisturbed, the Whole became an extended Firmament or _white_
Floor of thin Cloud, thro’ whose Intervals the Sun must shine with
fiercer Gleam. The upper Surface was quite even: not blended with the
Air above, but defined and separated with the utmost Exactness; being
condensed by the Coolness, and checked in their Ascent, by the Levity
of the superior Regions.
Thro’ this _white_ Floor uprose in splendid Majesty and awful Grandeur,
at great and unequal Distances, a vast Assemblage of _Thunder-Clouds_:
each Congeries consisting of whole Acres in the densest Form.
[Sidenote: Circular Boundary of the _celestial_ Prospect from the
Balloon _above_ the clouds.]
52. Their conglomerate and fringed Tops rising, at different Distances,
in circular Order, one above the other, to the Number of _thirty_:
till they became imperceptible from their remote Situation: the Eye
commanding an Extent of 102 Miles.[18]
Their Form was, as if Pieces of Ordnance were discharged
perpendicularly upwards into the Air: and that the Smoke had
consolidated, at the Instant of Explosion, into Masses of Snow or Hail:
had penetrated thro’ the upper Surface or _white_ Floor of common
Clouds, and there remained visible, and at Rest.
Some indeed had not wholly lost their Motion: continuing still to
be lifted up. Others ponderous and sleepy, nodded, by mere Weight,
their monstrous Heads. It seemed as if they had persisted in mounting
upwards, till they coud rise no higher: their lower Parts pressing
perpendicularly against the upper, which gradually swelled them out
on _all Sides_. By partial and temporary Movements of the Air, some
broad _unwieldy_ Caps lost the _vertical_ Direction of their Columns.
The Columns likewise underwent a similar and gradual Change: rolling
from their Pedestals or spiral Bases; and, at Times, assuming +every
organized Shape+ that Fancy coud suggest.
[Sidenote: Opinion of Philosophers.]
53. The imperceptibly slow yet perpetual Changes they underwent,
strongly called to Remembrance, the Opinion of the great Berkeley,[19]
as well as of the ancient Philosophers, that AIR GIVES FORM TO THINGS:
scarcely a Breath of which seemed, however, to disturb their general
Order.
The Constitution of these enormous Masses was such as to reflect _some_
of the Sun’s Rays, and to transmit _others_ in a Variety of Colouring.
[Sidenote: The Colours of the Thunder Clouds.]
54. The Parts next the Sun were of a _snowy_ Whiteness. Then of a
_bright luminous Yellow_ melting into a _dusky Sulphur_: afterwards
of a _Purple_. The Rays being now shorn; a Degree of Opacity and
Transmission took Place throu’ half the Substance of the Cloud, which
seemed of a _transparent Blue_ like the _Onyx_.
[Sidenote: Delightful Tints visible only from the Balloon.]
55. These _delightful Tints_ must be ever eclipsed to a Spectator on
the Surface of the Earth, looking upwards throu’ the gross Atmosphere
that surrounds it; but highly _interesting_ to one who is suspended
in a ratified and unencumbered Medium of the etherial Regions, where
the Eye darts without Resistance above Clouds, and all visible Vapour.
[Illustration: _A VIEW from the_ BALLOON _at its GREATEST elevation see
Page IIII.a._
Publish’d May 1ˢᵗ. 1786, by T. Baldwin Chester.]
Note: the Print, representing a circular View from the Balloon at
its greatest Elevation, is taken from a Scene described in the above
Chapter.
CHAPTER IX.
OTHER AËRIAL SCENES DESCRIBED.
[Sidenote: Balloon Shadow traced on the Clouds.]
Section 56. During the Time that the Balloon from being stationary at
23¼ (corresponding to the Height of about a Mile and a half) began to
_decline_, which it must have done with a brisk Motion, imperceptible
to the Aironaut at the Time, tho’ since recognized, on Account of the
great Opening at the Bottom; he traced its _Shadow_ over the Tops
of Volumes of Clouds below. It was at first small: in Size and Shape
like an Egg: but soon encreased to the Magnitude of the Sun’s Disk;
and woud have made a solar Eclipse to a Spectator looking from the
Cloud: still growing larger, as the Balloon descended, or Clouds arose.
But his Attention was presently called to another equally novel, but
more captivating Appearance; that of an _Iris_ encircling the whole
_Shadow_, at some Distance round it. The Colours were remarkably
brilliant.
This _celestial Phantom_ attended the Aironaut for a few Minutes:
conforming, as a Vessel at Sea, to the Change of _Surface_; now plainly
visible, now indistinct and disappearing; as it passed _throu’_ the
_luminous_ or _shadowy Wave_ of Clouds _apparently_ at Rest.
[Sidenote: The Iris, a Frame to the pictured Land, vanishes.]
57. The Clouds, in which this Phenomenon continued, were of the
superior or second Stratum in Height, as in fair Weather; rare;
of a transparent _Blue_ and purest _White_, alternate. At the End
of four Minutes they dispersed, so as to admit an unexpected Sight
of the pictured Land thro’ +them+, and thro’ the Place of _the
Balloon-Shadow_; whose Form first vanishing, _the Iris_ remained, for a
few Seconds, complete, and in resplendent Beauty.
58. _Írides_, of the same Kind, tho’ of less vivid Colours, are seen
round the Moon, in a mild Evening; as thin light Clouds move slowly
under it.[20]
[Sidenote: Sun hottest when the Balloon was stationary.]
59. The Sun shone brighter and fiercer, when the Balloon was at its
greatest Height: the _Heat_ piercing throu’ his Cloths, (which were of
a _dark_ Colour;) while the Aironaut _stood_ with his Face from the
Light.
[Sidenote: Lunardi’s Flag thrown out, at the Height of a Mile.]
The Mouth remaining open, it continued to descend, as appeared by
the Barometer which had risen nearly to 24 Inches: at which Instant
Mr. Lunardi’s _coloured_ Flag was thrown out, for the Information of
a Friend; and that Spectators below might judge what was nearly the
perpendicular Height of a Mile in the Air, according to Halley’s Table.
[Sidenote: The Flag was seen to descend for 3 Minutes.]
60. The Flag was seen by the Aironaut descend for three Minutes: at
which Time it became invisible. It fell, _not_ perpendicularly; but in
large Spirals, and by Jerks; darting first on one Side, then on the
other. The Resistance of the Air made it act as a Parashute. The Flag
was instantly pursued, and taken up in a Field one Mile distant from
Chester. The Descent of the Balloon must have been retarded, being four
Pounds and a half lighter.
[Sidenote: The Dove turned out.]
61. The Pigeon was then taken out of the Basket of Matting: Thermometer
54; Barometer 25³⁄₁₀. It trembled much. Being turned loose, it looked
frequently up at the Car; but flew downwards in cylindrical Gyrations
eight or ten Yards in Diameter, according to the Turn of its Head to
the right, which seemed to rest in an oblique Attitude: the Wings and
Tail continuing extended as much as possible, but without Motion,
during its Descent. The Bird was out of Sight in a few Minutes: but
continued, as _the Owner_ observed, full half an Hour, in the Air.
CHAPTER X.
[Sidenote: 4th Cannon heard.]
Section 62. At 10 Minutes and a half past II. o’Clock, the fourth or
last Cannon, a Six-pounder (to announce, by preconcerted Agreement,
that the Balloon began to be invisible to Spectators in Castle-Yard,
Chester) was distinctly heard by the Aironaut; but had no Effect on
the Balloon: did not agitate it in the least: the contrary of which was
expected.
For the same Cannon, discharged the third Time at the Distance of 30
Yards from the Balloon, when it had risen a few Feet from the Ground;
affected it so strongly, that the Aironaut was +then only+ obliged to
keep himself upright, by holding the Cords with his Hands.
[Sidenote: Balloon first invisible to the Inhabitants of Chester.]
63. At 17 Minutes past II. was heard the Sound of a Number of Voices,
which it was then imagined came from Chester, as the farewel Salute
after the last Cannon: but it was afterwards known that the Balloon did
not become wholly invisible, till that Shout.
[Sidenote: Distance of the Balloon calculated.]
64. From an Observation made by a Spectator in the Castle-Yard, just
half an Hour intervened between the Discharge of the third, and of
the last Cannon; as therefore the Report was half a Minute, or 30
Seconds[21] longer in reaching the Balloon; the Distance of the Balloon
at the Time of the Report was _nearly_ six Miles and a half.
[Sidenote: Chester seen as a _small_ Model.]
64. The single thin white Cloud of the first or lowest Order in Height
that rendered Chester invisible to the Aironaut, was observed several
Minutes before, _apparently_ to pass under the Balloon, retire from
it, to approach, and expected to invelope, the _blue_ City of Chester:
which for a long Time had been kept in View, and seen _obliquely_,
under the _common_ Perspective, with a small Degree of Elevation
above the Level of the Ground: suggesting to his Mind the curious and
complete Model of Paris, exhibited some Years ago _on a small Table_,
in many Towns of Europe.
[Sidenote: The Sight _doubly_ deceived in the Distance.]
The Cloud appeared, four Miles Distance at least from the Aironaut;
below; and as if touching the City. The contrary Supposition, it seems,
took Place, among the Inhabitants there: who thought, a Cloud, a Mile
above them, had surrounded and inveloped the Balloon.
[Sidenote: Condiments tasted as usual.]
65. The Pepper Salt and Ginger were tasted, and found to retain their
usual Pungency: contrary to what Travellers have reported to happen on
the Peak of Teneriffe.
[Sidenote: Silk electric.]
The small Hank of yellow raw Silk tyed to the upper Hoop, and hanging
down from it, appeared _rough_, as if electric: and, tho’ drawn thro’
the Hand, continued _furred_ as before.
[Sidenote: _White_ Flag wholly hung out from the Car.]
66. It was now thought a proper Time to finish the original Work of
unwinding the remaining Part of the half Mile of Twine: which proved
equally tedious, as at the first; and took up a considerable Time.
When completed, the _white_ Flag was extended exactly half a Mile from
the Car.
[Sidenote: Cattle discovered from the Balloon.]
[Sidenote: Ballast thrown out,]
67. Perceiving that the Balloon was descending very _briskly_, by the
Appearance of Cattle in the Corner of a Field; first, _one_ of the two
solid Weights was cast down: then the _other_.
[Sidenote: Time in falling estimated.]
A Return of Sound to the Balloon, from the lighter which weighed five
Pounds, was heard in 130 Countings of a Watch, which made 120 of the
same full Beats in a Minute.
Before the Weight became invisible; it _appeared_ to move a good Deal
out of the Perpendicular: owing either to an under Current; or to a
Deception of Sight, respecting the horizontal Motion of the Balloon in
a different Direction, during the Descent of the Stone.
The other must have fallen in soft Grass, or otherwise: as it was not
heard.
CHAPTER XI.
Section 68. At 28 Minutes past II. the solid Weights before mentioned
were thrown out.
At 29 Minutes the Barometer had fallen to 25 Inches.
[Sidenote: Balloon reascending.]
A Handful of Feathers were sent adrift, which fell quick: demonstrating
_likewise_ the Ascent of the Balloon, a second Time: but, tho’ 12
Pounds lighter, it did not seem to regain its original Height: judging
+merely+ from this Circumstance, that no more Gass escaped _visibly_
from the Mouth.
[Sidenote: Apparent Size and Situation of the _white_ Flag.]
69. It is somewhat remarkable, that, on repeated Enquiries from
unprejudiced Persons, the _white_ Flag, when suspended from the Car
above 440 Yards, appeared 4 Yards long: and when at the end of the
_half Mile_ Twine, seemed about 8 Yards long, to Spectators from
below, in different Places: that sometimes it appeared before, and
sometimes behind the Balloon: while to the Observer in the Car, it
seemed regularly to follow the Balloon: unless when a _new_ Motion was
impressed upon the latter: at which Time the _white_ Flag was situated
almost under the Car: or when the Balloon changed its Direction; the
Flag being _then_ not always _discoverable_.
When seen _edgewise_ or _foreshortened_; it woud _appear_ to be
_nearer_ the Car than it really was.
[Sidenote: Effect of the _white_ Flag on the Balloon.]
70. As there was a Peculiarity attending the Situation of the _half
Mile_ Flag, which may prove of singular Use in Airostation; it ought
not to be passed over in Silence.
The half Mile Flag hanging loosely from the Car; not perpendicularly
under, but following it, frequently at an Angle of about 45 Degrees;
shews that the Flag met a Resistance from the Air, unfelt by the
Balloon: which out strip’d it, in Proportion to the _greater_ Surface
which the Balloon exposed to the Wind.
Taking also into the Account, that the Balloon remained in Equilibrio;
while the Flag was subject to the Force of Gravity: which Force was
restrained from Exertion, otherwise than as a _Vis Inertiæ_, to keep it
always in a perpendicular Situation.
The Resistance of the Air, acting in an horizontal Direction against
the _Vis Inertiæ_ of the Flag, must have a Tendency to drive it back:
which being ineffectual; the Flag must consequently _rise_; and in
rising _will retard the Balloon_.
A Power may therefore be communicated to a Balloon, in the Direction of
the Wind, which shall _retard_ its Progress throu’ the Air: a Subject
which seems capable of farther Prosecution.
CHAPTER XII.
[Sidenote: Beautiful Effects of the _white_ Vapour on the Prospects
below.]
Section 71. From 28 Minutes after II, till the Balloon had passed over
the _Forest_ of +Delamere+, and the steep Crag of +Helsbye-Hill+; thin
light semi-transparent Vapours, which seemed to be collecting at a
_vast Depth below_; moving slowly in all Directions; rising to great
Heights, falling, melting away, and again condensing;—(the Land, one
while covered with a +white+ _Veil_; then _caught_ thro’ Openings for
a few Seconds; the Objects appearing more distinct and _coloured_,
from being seen in detached Groupes and single _Pictures framed_ and
_enshrined_ in fleecy +Vapour+; _now again_ discovered by a Glance of
the Eye, and _then_ repeatedly escaping from the Sight;)—+wonderfully+
heightened the Grandeur, Gaiety and _inimitable_ Beauty of the _ever
varying_ Prospects.
An Illustration taken from Scenes _abroad_.
72. Appearances of a similar Kind are frequent in the _noble and
venerable_ Structures appropriated for divine Worship _abroad_: whose
Walls are decorated with the _finest Paintings_; the Subjects solemn
and _engaging_; suited to inspire a _chearful Devotion_.
While the inferior Clerics perfume the Garments of the _Priests_
officiating and offering Incense before the _high Altar_; which is
ornamented with _full-Length Portraits_ in the richest Drapery, of
Persons whether male or female, reputed of sound Morals and exemplary
Piety; accompanied by Guardian Saints and happy Angels;—Columns
of _white_ Smoke, wafted from _Silver_ Censers, rise to a certain
Height in slow _majestic_ Movement, before the Eyes of the _kneeling_
Suppliants, who are _instantly shut out_ from the _enchanting_ View;
till the Clouds dispersing, shew by _Intervals_, a Glympse of the
_celestial_ Prospect, and of the _higher_ Orders of Beings, who _look
down_ with _Complacency_ upon them; and seem _actually_ +descending+
throu’ Openings of the Clouds which _appear_ at Rest.
CHAPTER XIII.
[Sidenote: 2d Balloon-Iris.]
Section 73. At 33 Minutes after II, the Balloon-Shadow was _again_ the
Center of a brilliant _Iris_, painted at some Distance round it on
Clouds below.
[Sidenote: Bottle filled with _light_ Air.]
74. One of the Pint-Bottles for light Air was prepared (as in Article
14, of Section 12;) and dropped from the Car.
The _Water_ it contained was poured down, to observe the Effects of
_Air_ and _Light_ on the Drops.
The Air did _not_ at that Height oppose a Resistance sufficient to
break the Stream into _small_ Drops. Nor did they seem to coalesce:
remaining, while they continued in Sight, of the same Size; some very
large, others less so; and at the same _relative_ Distance, as when
they first left the Bottle.
The Colours seemed _stronger_ than usual.
It may be _here_ observed that none of the Bottles were returned; tho’
found, and a Reward promised.
The Country People, as soon as they saw a Bottle; imagining it must
contain some Liquor, immediately contrived to open it: by which
Procedure, the Intention of the Experiment was frustrated.
The Bottles, which are _dangerous_ Companions even without Liquor,
shoud, notwithstanding, be left in the Car: at least till the Time of
_landing_ the Balloon.
[Sidenote: Burton and Flint seen at the _first_ rising.]
75. While the Balloon was _first_ rising; a gentle Motion of the lower
Current of Air carried it immediately towards the Sea. (Section 46.)
At which Time, the Aironaut by a _Glance_ discovered the Mouth of the
River Dee, four and five Miles wide, _yawning before him_: the Prospect
extending to the Sea, as far as the _Smoke_ from the Lead-Works near a
Place called Flint on the Welch Coast; and to Burton-Head on the Wirral
Side; distant ten Miles from Chester.
He has since been informed; that the Balloon seemed to +rest+, for a
few Minutes, in the Air: and then _return slowly_ over Chester.
[Sidenote: Balloon in a _quiescent_ Bed of Air.]
It is therefore more than probable, that as the Balloon continued
to ascend; it was _becalmed_ in a _quiescent Stratum_ or Bed of the
Atmosphere, which existed for a certain Depth or Thickness, between
the lower and upper Current: and that the Direction of the Balloon was
changed; the Instant it arrived within the Influence of the _upper_
Current.
[Sidenote: Of _rowing_ the Balloon to any Point of the Compass.]
Consequently, with a proper Apparatus to ascend and descend _at Will_,
without Loss of Gass or Ballast; the Balloon woud have remained
suspended _invariably_ at the same Height, and _vertically_ over the
same Spot of Earth: or, with propulsive Machinery; might, on the same
Level, have been _rowed_ to any Point of the Compass.
[Sidenote: The Balloon, influenced on its Approach towards _Water_.]
76. In passing _only_ +across+ Trafford Meadows, three Miles from
Chester; the Balloon lost its usual progressive Motion over the
Country: for more than a Quarter of an Hour, following the Course of
the River Goway to the West North-West, and towards the Sea, as at
Chester: turning gently backwards and forwards round its own Axis,
near the Villages of Great and Little Barrow: and making Curves over
the Meadows, whose Breadth at those Places was about a Mile.
[Sidenote: Its Progress marked.]
The Balloon then returned into its former Direction: inclining,
_again_, towards a Brook and Meadow near Alvanley: passed Eastward a
little to the left of Manley (_white_) Mill: crossed the Forest of
Delamere, and Crag of Helsbye, (about twice the Height of Shooter’s
Hill, near London;) whose lofty Summit was _apparently_ reduced to a
common Level with the Valley made by the River Wever, and with the
adjacent Sea Marsh. Nor coud it have been distinguished by a Stranger,
as an _Eminence_.
[Sidenote: Hills and Vallies on a Level.]
Indeed, the Wood near Kingsley, which grows on a sloping Ground,
skirting the Hill, and _from_ the Sun, put on a _dusky_ Hue; and the
Tops of the Trees a _darker Green_: this Difference of _Colour_,
conveyed the _faint Resemblance_ of a rising +Slope+. A _real_
Knowledge of the Country probably contributed to aid the Imagination in
this Distinction.
Note: the Print representing a View of the Balloon over _Helsbye Crag_,
refers to a Scene in the above Chapter.
CHAPTER XIV.
[Sidenote: 39 Minutes past II, Frodsham Town and Bridge seen.]
Section 77. At 39 Minutes after II, Thermometer 60, Barometer 23¾,
corresponding to the Height of a little more than a Mile,[22] _the
Vapours dispersing_, discovered the Town of Frodsham, and Bridge over
the Wever distant from the Town one Mile: the Balloon still continuing
at a vast Height; having risen imperceptibly from the Time that the
Ballast was thrown down.
From a Conversation held the next Morning at Frodsham, with some
intelligent Persons who had descried it gliding gently throu’ the
Air; the Balloon appeared so extremely _minùte_, that it was thought
impossible to be the +one+ expected the same Day to rise at Chester
with an Aironaut.
[Illustration:
R. Newton } Arm. design et pinx. Stothard delin.
T. Baldwin} Sharp sculps.
_The_ BALLOON _over HELSBYE HILL in_ CHESHIRE _see page IIII b._
Published May 1ˢᵗ. 1786, by T. Baldwin Chester.]
[Sidenote: Half Mile _white_ Flag like a Feather.]
To use their own Expression, “_it coud not have been larger than a
Bladder, if they had seen it on the Ground_.” The same Persons observed
the _white_ Flag, like a _Feather_ about 8 Yards Distance from the
Balloon.
A second Air Bottle was thrown down.
[Sidenote: Course of the Balloon traced to shew the Manner in which it
was affected by the _Water_.]
78. The Town of Kingsley being to the East; Frodsham-Bridge half a Mile
to the West; the Conflux of the Rivers Wever, and the _wide_ Mersey
falling into the Sea one Mile farther Westward; the Balloon proceeding
in its usual Course over the Country in the _upper_ Current; began to
be _impeded_, on its vertical Approach +across+ the Meadows to the
Wever; was actually stopped; and being _entangled_ by the _River_,
evidently changed its former Direction: imitating, if possible,
_its_ Meanders; or at least making Gyrations in Circles of different
Diameters, at the same Time turning different Ways round its Axis:
describing Curves, something similar to that of the Moon round the
Earth in her Orbit; or of Saturn, Jupiter, and Mars, as those _Curves_
are delineated in the _Prints_ of Long’s Astronomy:[23] the Course of
the River being its _changeable_ Center.
79. It is to be observed, that if the Balloon had continued to pursue
its _former_ Course; no Danger was to be apprehended of its falling on
the Sea, or on the broad Branch of the River Mersey towards Warrington.
On the contrary, it must have gone into the Heart of the adjoining
County, and passed near Manchester.
It is likewise worthy of remark; that unless a Fragment of light
Vapour intervened for a few Seconds; the Country immediately below the
Observer was _continually_ illuminated by the Sun’s Rays: tho’ none but
the larger Objects were distinguishable at the Bottom of the profound
Abyss, _more_ than two Miles in Diameter at one View: that being the
utmost Boundary of the circular Prospect below.
[Sidenote: Circularity of Prospect below, bounded by _Vapour_.]
80. The _Sea_ tho’ known to be _near_ by the Dashing of its Waves upon
the Shore, which were plainly heard, was totally eclipsed: as if by
Haze or Vapour, which began to be accumulated only at a certain Height
_below_ the Balloon; yet in such a Manner as _not_ to prevent the solar
Rays from penetrating throu’, and shining bright upon the Water.
81. There was now sufficient Leisure to trace the incredible Variety
of most beautiful _Curves_, into which the Stream had worked the Bed
of the River Wever in a Course of _Time_, and in the Compass of a few
Miles: an Appearance which _demonstrates_ the Incorrectness of +Maps+.
Some _actual_ Clouds presented themselves in detached Groupes over the
Land: and the _Land_ itself _shone_ plainer throu’ the Intervals, than
in Places near which _no_ Clouds appeared.
[Sidenote: Sight of Warrington.]
82. On reconnoitring the scattered Town of Frodsham, which like Chester
was of a _light_ +Blue+; the Balloon moving _by Intervals_ round its
Axis, the Prospect seemed to _open_ on a _sudden_; and the Aironaut
coud discover the Town of Warrington: the Plan of which was small,
neat, but of a _darker Blue_, inclining to _Grey_: the Slates[24] there
used being almost peculiar to the County of Lancaster.
83. From this _Enlargement_ of the Prospect over Land, he imagined that
the Balloon was either _gently_ descending; or that it appeared throu’
the _clear_ Intervals of _actual_ Clouds _below_ him.
[Sidenote: Pleasurable Circumstance peculiar to the Balloon.]
84. He had Time however to make the following Remarks. Cattle, if
grazing in the Meadows, were not distinguishable; or at least were
not distinguished. It was in vain to look for Sheaves of Corn,
or Hattocks on the Ground: possibly from a Sameness of _Colour_
like the growing _Stalks_, and _Field_: or _protruding_ but a
small Degree of +Elevation+; tho’ the _Shadow_ even at _twelve
o’Clock_[25] was something _longer_ than the _perpendicular_
Height of +each+ Object.[26] Noises of Carriages along the great
public Road; especially Waggons and Carts +heavily+ laden; (the
Gratings of whose _Wheels_ against the _Stones_ seemed uncommonly
_harsh_;) were discriminately heard, tho’ not _discoverable_ by the
Eye. Numbers of human Voices were almost +continually+ huzzaeing:
except while +stationary+ at the first Rise; when +all around+ was
wrapt in the Sublimity of +Silence+; which afforded a pleasurable
Contrast;—diffusing a +delicious Calm+.
A third Bottle of Air was thrown out.
CHAPTER XV.
[Sidenote: Balloon over Aston-House, at 4 Minutes past III, and near a
Mile high.]
Section 85. At 4 Minutes past III, the Balloon remained _vertically_
over the River, and over the elegant Mansion called Aston.
[Sidenote: Wind _below_.]
86. A Wind was heard +below+ for a few Seconds: and the Air felt
a _little cool_. Thermometer 55, or Temperate: Barometer 25½,
corresponding to the Height of near a Mile.[27]
[Sidenote: The Balloon going to Sea, determined the Aironaut to
_descend_, in Hopes of finding a Sea-Breeze in _Time_.]
87. The Balloon continuing its eccentric Movements from _Side to
Side_ across the Meadows; yet still gliding _down_ the River, in a
North-West by North Direction, almost at right Angles to that which
it _before_ had held; consequently _towards_ the Sea, and in a Line
which continued must pass throu’ the Center of the Channel: some Step
it was necessary to take, and +soon+. By throwing out Ballast, the
Balloon woud instantly rise: but it woud probably, as _before_, rise
into +a Calm+, and therefore _descend_ nearly in the same Line: which
woud merely _protract_ the Time till the Balloon had reached the Center
of the Channel: where, having no Resource, the Ballast being then
expended; there might be some Risque in waiting for a Vessel, tho’ the
Balloon woud not for +several Hours+, have lost its _levitating_ Power,
so as to have sunk with the Aironaut. To him however it immediately
occurred, that there might be an +under+ Current of Air, as usual in
the Middle of the Day, blowing from Sea to Land: and, that if the
Balloon was made to descend +quickly+ into the Sea-Breeze; it might, in
a few Minutes, be carried so _far_ within the Country, as to be _soon
beyond_ the Influence of the _Sea_ and _River_: and +then+, by throwing
out some Pounds of Ballast, woud return into the _upper_ Current, and
pursue a _safe_ Course towards Manchester; or even towards Prescot and
Liverpool, if an easterly Wind prevailed _above_.
88. In Consequence of these Expectations; he looked downwards _towards_
the Sea, _then_ wholly _invisible_; tho’ the Murmuring of its Waves was
_more_ plainly heard.
[Sidenote: Smoke blown to Land by a Sea-Breeze.]
+Thick Smokes+ were distinguished issuing from _different_ Places along
the Marsh near the Coast: and _apparently_ skirting the Ground, as if
impelled by a _brisk_ Wind from the Sea.
89. No Time was to be lost.
The Balloon having reached the Cascade; and continuing to move more
regularly along the Course of the River, past the _Bridge_, and
proceeded to _Rock-Savage_.
[Sidenote: The Balloon still going to Sea, the Mouth was opened.]
90. The Neck or _Mouth_ which remained shut, by its own Pressure
against the Outside of the upper Hoop, as _it_ lay over it; was
instantly brought within the Hoop, and set +wide open+ in a
perpendicular Situation.
Not more than a Couple of Minutes had elapsed before Sounds were more
audible and louder.
Cattle and Corn in the Fields became visible.
[Sidenote: Ballast in Hand ready to throw out.]
91. The Observer very deliberately stooping to put down his Card and
Pencil; with his _left_ Hand grasping the Hoop of the Car, and with his
Right holding a Sand-Bag, to throw over as he approached the Earth;
found that the Balloon was _influenced_ by an +under+ Current blowing
from the Sea: and marked his Progress by the half Mile +white+ Flag;
whose Stretcher having acquired a Position parallel to the Plane of
the Horizon, placed the Flag in an excellent Point of View: the Balloon
_towing_ it _apparently_ with a _slow_ Motion, over the distant Tops of
the _dark-green_ Trees.
CHAPTER XVI.
BALLOON DESCENDING.
[Sidenote: Air chilly. Therm. 55; Barom. 26½.]
Section 92. No sooner had the Balloon _descended_ within the Influence
of the _Sea Breeze_, than it became +instantly+ _condensed_ by a
certain +chilliness+ which +then+ began to prevail.
[Sidenote: Balloon in the _under_ Current.]
93. This Height has _since_ been considered as the +Level+ of +fleecy
Vapour+, +Scud+, or lowest Stratum of Clouds, in +bright+ and +warm+
Weather.[28]
No _visible_ Clouds were presented _near_ the Spectator. On the
contrary, they seemed to _shrink back_ to the Distance of a Mile
round the Eye; and then _immediately_ appear above it, the Balloon
continuing to descend. Nor did any _circular_ Horizon of the Earth shew
itself; till the Balloon had reached below this Level: viz. Barom. 26½,
Thermom. 55. i.e. Temperate.
Prospects were most +extensive+ and beautiful at this Altitude: which
the Barometer estimates at full half a Mile.[29]
Looking again at the Barometer, scarce a Minute afterwards; it had
risen to 27.
[Sidenote: Sudden Effect of cool moist Air on the Balloon.]
94. The Condensation by Chill and Moisture, and quick Contraction of
_its_ Dimensions acted like a _Charm_ on the _Balloon_.
In a Moment; as if dropped from the Clouds, the +Sea+ suddenly
presented itself.[30] It seemed +near+, and of a +red+ Colour.
_Circular_ Landscapes of the _distant_ Countries filled the Eye.
Almost the whole Extent of the Channel was a perfect Calm: and rather
_dazled_ the Sight. But from the Peninsula of Hale to that of Runcorn,
and upwards, a _partial_ +Breeze+ from the North-West _ruffled_ the
Surface (which was there of a _dark_ and menacing Complexion;) and
seemed in its Course to have reached and _influenced_ the Balloon:
whose Descent proving _more_ rapid than was expected; the Sand-Bag tyed
up, weighing 12 Pounds, was opened, and the Sand _dispersed_.
[Sidenote: Ballast thrown down, 12lb. and 12lb.]
95. The Aironaut continuing as before to _stand_ upright in the Car,
and having resumed his Card and Pencil; Thermometer _again_ at 55°,
on finding the Descent not _sufficiently_ retarded, wrote swiftly,
“+no more remarks, mind the ship+:” meaning the Balloon: and briskly
stooping for the second Bag of Sand, weighing likewise 12 Pounds,
_dispersed_ it by _Handfulls_ in the same Manner.
[Sidenote: Descent at first rapid.]
96. The circular Mouth of the Balloon continuing wide open, at about
18 Inches Diameter; so much _cool_ and _moist_ Air rushed in during
the Descent; that, tho’ its Momentum or acquired Motion was retarded
by _Dispersion_ of the Ballast, it had not yet recovered an +actual
levity+: being too near the Ground before the second Bag was discharged.
_Presuming_ however that 24 Pounds Weight of Ballast thrown out,
was sufficient to break the Fall, tho’ in a cool moist _condensing_
Atmosphere of _pure defloguisticated_ Air; the Event of _landing_ was
_waited for_.
[Sidenote: A _depressing_ Torrent of Air on the Balloon.]
It has been _since_ imagined that a _heavy_ +depressing+ torrent of
_cool_ Air took Place from the North-West at a certain Height over the
Water, and _assisted_ the Descent of the Balloon.
[Sidenote: The Balloon descended with a _rushing_ Noise.]
97. In order to judge with what Rapidity the Balloon descended, when so
+low+ as to be within the Influence of the _under_ Current, while the
_cool moist_ Air rushed in at the Bottom, and most probably pressed out
the Gass; the following Intelligence has been communicated by a Person
of Veracity.
[Sidenote: Anecdote shewing the Rapidity of Descent, at first.]
As two credible Farmers were working, with their Servants, in the
+harvest+; on hearing a hollow, rushing Sound in the Air, which they
took to be a _Whirl-wind_, or _distant Thunder_, and which seemed
every Moment to encrease and approach them; they all retreated under a
large Oak. While there, they first perceived the swift Descent of the
Balloon. Two, who were afraid of Thunder, then began to take Courage,
boldly exclaiming they shoud never fear Thunder again, since the
_Falling_ of a Balloon coud be attended with so _terrible_ a Noise.
CHAPTER XVII.
BALLOON STILL DESCENDING.
Section 98. The Car, gliding _over_ Trees in the _farther_ Hedge-Row of
a Grass Field, glanced on the Ground.
[Sidenote: Caution on Landing.]
The Aironaut, being _prepared_ for the Event, supported a _Part_ of the
Weight of his Body by his Hands, grasping the _upper_ Hoop.
The Balloon _stooping_, and declining from the North-West Breeze, drew
the _upper_ Hoop out of the Perpendicular: by which Means, the Bottom
of that Division of the Barometer-Frame which contained the _Tube_,
pressed against the Bottom of the Car on the Ground, was _separated_
from the remaining Half of the Frame, and fell on the _Grass_.
[Sidenote: More Ballast parted with, viz. seven Pounds.]
The Balloon, then rising with an elastic _Bound_, elevated the Car a
few Yards, and descended to the Ground, but _more_ gently than before:
rose again; and the Aironaut perceiving that the progressive Motion
of the Breeze was bringing the Balloon near a _third_ Hedge; took up
his Knife, (which lay by him _ready open_ for Use) and _cut away_ the
remaining Half of the _Barometer-Frame_; threw out the _Basket with
the Bottles_, and _Tunning Dish_; the _Speaking Trumpet_; the _Woollen
Gloves_, the remaining half Mile of _Twine on the Reel_.[31]
The Car _cleared_ the Hedge, and _slightly_ for an _Instant_ touched
Ground, the _third_ Time.
[Sidenote: Farmers offering their Assistance.]
99. During these Operations; the Aironaut had observed different
Persons in Motion towards him, who proved to be several _Farmers_ and
_Labourers_ who had run themselves out of Breath to _overtake_ the
Balloon.
One asked the Aironaut, whether he intended to alight; and was
answered, “_Not for any Time_.”
[Sidenote: Proof of the _gentle_ Descent.]
100. The Car alighted each Time so _smoothly_, that neither the _Watch_
nor _Thermometer_ that lay near each other on the _green_ Bays at
the Bottom, were displaced. Nor was the _Glass Tube_ containing the
Quicksilver, separated from the Division of the Frame in which it was
originally fixed: but the whole was brought back, a few Days after,
in a perfect State: except a small Hole, made in Consequence of the
inverted Situation of the _Mercury_ in Vacuo, _which_ fell against the
Top of the exhausted Tube.
[Sidenote: Balloon landed near Frodsham.]
The Car _first_ landed at 28 Minutes past III, in a Field belonging to
a Farm called Bellair, in the Township of Kingsley, near two Miles East
by South from the Town of Frodsham, and twelve from Chester.
END OF THE FIRST PART.
AIROPAIDIA.
THE
SECOND PART
OF AN
AËRIAL EXCURSION
FROM CHESTER THE EIGHTH OF SEPT. 1785.
CHAPTER XVIII.
RE-ASCENT OF THE BALLOON.
Section 101. Bellair-Meadow: half past III o’Clock:[32] Thermom. at 55:
_bright_ Sun: _few_ Clouds in Sight.
[Sidenote: Balloon rapidly re-ascending.]
The Balloon being now 31 Pound lighter; taking a Direction +from+
the Sea-Breeze into the Country, and _again_ towards Aston-Hall[33];
mounted up like a Sky-Rocket, with accelerating Velocity: its upper
Parts _nodding_ from Side to Side, as if to _shake off_ the _resisting_
Column of Air immediately above it.
[Sidenote: The Neck tyed.]
[Sidenote: Drawing the Valve, while Mouth of the Balloon is _open_,
shewn to be _dangerous_.]
102. There being no proper Opportunity of closing the Mouth of the
Balloon on its _near_ Approach to the Sea, or during the _Swiftness_ of
its Descent; tho’ there had been _frequent Inclination_ to attempt it;
this _little_ but +essential+ Work was instantly resolved upon. And the
more so, as the Mouth had continued open _from_ the first: and as Mr.
Lunardi did not _happen_ to mention this Circumstance: the Utility of
which, tho’ _too late_ to be put in Practice, had, but a few Minutes
before, very plainly suggested itself. His Directions were, to _open_
the Valve in order to descend: which woud _possibly_ have _encreased_
the Rapidity of Descent: and, by _introducing_ a thorou’ Air _upwards_,
while the Motion of the Balloon was in a _contrary_ Direcion, might
have occasioned a _dangerous Rupture_ of the lower Parts of the
Balloon, _which_ actually took Place in a preceding Excursion.
[Sidenote: The Balloon drawn _sideways_.]
103. The Balloon, tho’ rising _quick_, seemed _not_ to be wholly
disengaged from the Ground, but to have received a Check; and to _lean_
a little out of the Perpendicular: particularly the Car, which was
evidently drawn a _different_ Way _from_ the Balloon.
[Sidenote: The half Mile _white_ Flag impeding the Balloon.]
On perceiving that the half Mile _white_ Flag, fastened to the _upper_
Hoop of the Car, sensibly impeded the Elevation of the Machine,
by _trailing_ along the Ground, (the Balloon being yet within the
Influence of the Sea-Breeze, or _lower_ Current of Air;) the Question
was, whether it woud not be imprudent to suffer the Balloon to rise
near half a Mile, before the _white_ Flag; was _disentangled_ and free
to follow it.
For as neither the _Twine_, nor the _lower Cords_ of the Balloon were
of Silk; the Twine having lain on the Trees or +moist+ Ground, might
become a +conductor+ from the Earth to any Stratum of Air that had
+less+ or +more+ than what is called its natural Quantity[35] of the
+electric+ Fluid.
[Sidenote: Twine _cut_, lest it shoud prove a _Conductor_ of
_Electricity_.]
Adding to the above, a Wish to rise higher the _second_ Time than the
first; stooping for the Scissars, the String was _cut_: reserving a
Remainder to tye the Neck of the Balloon; which was immediately done by
gathering the Parts of the Balloon into the Hand, wrapping a Couple of
Yards loosely round, and tying them on a +slip+ or +bow+ Knot: one End
of which was +purposely+ left hanging three Feet downwards, to _untye_
instantly on Occasion.
[Sidenote: Additional Levity of one Pound.]
This additional Levity of _nearly_ one Pound, gave the whole Quantity
of Ballast thrown over in a _few_ Minutes, _nearly_ 32 Pounds.
[Sidenote: Remarks on the Balloon.]
104. The intelligent Farmer who stood near the Balloon, when it
alighted at Bellair, had observed it for some Time _before_ near the
Sea, and marked its Return, as coming _apparently_ from _Overton_.
At first, which was _more_ than five Minutes before it came to the
Ground, it seemed to him as if it coud not have been _larger_ than a
Bladder.
He saw it reascend, first _sideways_, then upright; moving from the Sea.
Afterward it rose _rapidly_, and rather _towards_ the Sea and
Warrington, distant twelve Miles.
[Sidenote: _Apparent_ Size of the Balloon, when seen from _below_.]
He watched it for a Quarter of an Hour: and caught it by Intervals,
near and above a Cloud in the _blue_ Sky, at so great a Height that it
looked like a _Lark_: and at last: so _small_ that the People who stood
near him coud none of them regain a _Sight_, when they had once lost it.
105. The remaining _white_ Flag was unfolded, and tyed to one of the
Balloon-Cords attached to the _upper_ Hoop, at a proper Distance to
_play_ freely in the Wind: and, notwithstanding all that has been
said to the contrary, shewed _instantaneously_ and _plainly_ the
corresponding Changes made by the Wind in different Directions.
And, as the Breeze was accompanied with a Sensation of _Coolness_
against the Face of the Aironaut, looking towards that Quarter from
whence the Wind came, as indicated by the Flag; (which Quarter was
not in a Line with the Path of the Balloon;) the Flag must have shewn
that the Change was made by the _Air_ in _its peculiar_ progressive
Direction, and not by _its_ Resistance or Progress in the Track of the
Balloon.
[Sidenote: _Balloon_ moving in a Direction _different_ from that of the
_Air_.]
106. It is probable that the _Momentum_ of the Balloon, acquired by its
centrifugal or accelerating Force upwards, might have kept it in _one_
Direction, while it continued to rise throu’ _different_ Currents.
CHAPTER XIX.
BALLOON STILL RE-ASCENDING.
[Sidenote: Balloon vertical over Aston, for 8 Minutes.]
Section 107. The Balloon being now _wholly_ unconfined, continued to
_rise_ with _great_ Rapidity: crossed the Meadow in the Sea-Breeze, and
remained as _before_, for 6 or 8 Minutes,—by Intervals _gently_ turning
on its Axis—almost wholly _vertical_ over Aston-Hall, but rather more
to the _Eastward_ of it.
The Country still exhibited _bright gay_ and +extensive+ Prospects.
108. _Three_ Sail of _Vessels_ appeared in the +Channel+: and _four
more_ were sailing down the River Wever, _apparently_ just under the
Balloon, diminishing to _mere Cockle-Shells_, or like _Boats_ which
have _no_ Rigging.
Shouts continued.
Corn and Cattle were visible in the Fields and Meadows.
Aston, tho’ a _large_ and _elegant Mansion_, appeared like a _House_
which Children _build_ with _Cards_.
[Sidenote: Chilliness felt at the same Height in re-ascending.]
109. A Chilliness in the Air was again perceived in rising, as he
imagined, to the _same_ Height at which he felt it in _descending_,
indicated by the Thermometer at 55°. (Sect. 92.)
He then found himself inclined to taste the _Brandy and Water_, ready
mixed by his Order, and to eat a Biscuit: but on putting the Liquor to
his Lips; thought it _too_ strong, so drank none, nor eat any Thing.
110. The _three_ Sail, and the +Channel disappeared+.
[Sidenote: River _red_.]
The River put on a deep _red_ Colour, like the Dee. Its Meanders seemed
to _encrease_; as its Width _diminished_ to a _broad_ Line. Its Water
was _lost_ to the Sight.
Corn and Cattle were no longer distinguishable.
The House at Aston was yet a beautiful tho’ minute Object: the Balloon
moving several Times round it; as if loth to quit _that_ and the River.
The Cascade was become a _white_ Line: and the _fine_ Bridge below, a
_yellow Straw_ crossing the broad _red_ Streak.
Of the _four_ Vessels in the Wever, _not_ an _Atom_ visible.
The Shouting entirely ceased.
[Sidenote: Rocks Woods and Meads reduced to a _coloured Plain_ of the
_mellowest_ Tints.]
111. The _blue_ scattered Houses, wide public Road called
Sutton-Causeway over Frodsham Marsh, the Meadows Fields and Woods, the
_lofty_ Hills, Helsbye Crag and Halton-Tower, were _reduced_ to _one
common_ Level; and diminished to the Size and Semblance of a _coloured_
Map, but it was the _superb_ and _finished Colouring_ of +Nature+.
[Sidenote: Balloon higher than at the _first_ Ascent.]
112. Ceasing to look _down_ on the smooth +Lawns+ _below_, which were
_now_ of the richest and _fullest_ Patterns, seen as throu’ the _small_
or inverted End of a common Perspective-Glass, and _spun_, as it were,
to a _fine Thread_; Pleasure and Delight, tho’ of another Kind, fill’d
the Imagination of the Beholder: who, raising his Eyes on a Level with
himself, so as to look _straight before_ him; found that the Balloon
had _already_, and almost beyond his own Belief, soared to so amazing
a Height in the Atmosphere, as to raise him _far_ above the +Rim+ of
the immense Bowl or Crater; and that it was still _stealing_ with
_Rapidity_ upwards.
[Sidenote: Contemplation of the Prospect.]
113. During the Contemplation of this magnificent Prospect, a _perfect_
Calm took Place, and _soothing Silence_ reigned.
And thus; for _a while_ detached, _far_ detached from Earth, and _all_
terrestrial Thoughts; wrapt in the _mild Azure_ of the _etherial_
Regions; suspended in the Center of a vast and almost endless Concave;
come, as a _mere_ +Visitor+, from _another_ Planet; surrounded with
the stupendous Works of _Nature_, yet _above_ them;—the +glorious Sun+
except, which enlivened +all+, and shone with pure celestial Lustre;—a
peaceful +Serenity+ of _Mind_ succeeded; an +enviable+ EUROIA.[36]
An Idea of which it is not in the Power of Language to convey, or to
describe.
CHAPTER XX.
[Sidenote: Breathed freely. Thermometer 60.]
Section 114. Respiration at so great an Altitude was perfectly free
and _easy_: _forced_ Trials being made for Information on that Point:
a Sensation of Levity seemed _rather_ to be communicated by the Air
to the Lungs: but this might be the Effect of the Imagination. It was
however a _curious_ Circumstance to find the Breath _not_ visible; the
Thermometer rising +again+ to 60. Nor did the Pulse seem to be quicker
than _usual_, in this elevated tho’ _inactive_ Situation.
[Sidenote: Thunder-Clouds as before.]
[Sidenote: Fairy Landscapes striking.]
115. The Perspective of a vast Series of Thunder-Clouds of a
_sulphúreous_ and _metallic_ Tinge, placing themselves in Ranks, each
beyond the other, in _bright_ and tremendous Order, and a Sort of
_Battle-Array_, beyond Conception _grand_ yet _beautiful_; coud not
pass _under_ him without Notice. The immense circular and visible
Distance of the +nebulous+ Horizon, extended +now+ 102 Miles _at the
least_ round the Eye, as already mentioned (Sect. 52); was a grand
Source of the Sublime. Nor did the contracted View of the Landscape
below fail, in Turn, to _regain_ an Attention to its _indiscriminate_
yet _pleasing_ Scenery.
116. +On a sudden+ he was called back to himself.
[Sidenote: Bladders _crackling_.]
Several of the +Bladders+, which were tyed round the Car, in Case the
Balloon shoud _alight on_ the Sea, and were +dry+ on the Outside, began
at the same Instant to +crackle+; being greatly distended by the Air
within. When pressed with the Hands and Fingers, they felt extremely
hard, and _ready_ to _burst_.
[Sidenote: Balloon _bloated_.]
On looking upwards at the Balloon, it appeared +greatly+ inflated: the
external Pressure of the surrounding Air being _much lessened_, in so
elevated and _rarified_ a State of the Atmosphere.
[Sidenote: Balloon _quilted_ by internal Pressure.]
117. The Balloon _pressed_ in an unusual Manner _throu’_ the Meshes of
the Net, quite round.
[Sidenote: Balloon shorter and broader.]
118. The Shape was much altered by this Distention of the Sides: and
its _perpendicular_ Diameter _shorter_ than before.
[Sidenote: Neck 8 Feet above the Car.]
119. The Neck or _Mouth_, which was _tyed_, had actually risen
_upwards_, and was +then+ near _eight_ Feet _above_ the Bottom of the
_Car_.
[Sidenote: Neck cut off in a former Excursion.]
120. It was not known till afterwards, that Mr. Lunardi on his second
aërial Voyage from Liverpool, had been obliged to cut off the _lower_
Part of the _Neck_, weighing upwards of _two_ Pounds and a _half_, in
order to lighten his Descent near Tarporley in Cheshire; and that he
had not _Silk_ sufficient to repair the Loss.
CHAPTER XXI.
[Sidenote: An Attempt to reach the Twine by _climbing_ on the Car.]
Section 121. In vain did the Aironaut strive to reach the _Neck_ of the
Balloon, from the _Car_. Attempting to put his Feet on the _opposite_
Sides of the _lower_ Hoop, by grasping the _upper_ with his Hands; he
coud not in _that_ Situation raise himself so high _as before_; nor let
go his Hold with _either_ Hand.
He then stepped _down_ into the Car. The Agitation of _which_, brought
within the Reach of his Hand, the loose _End_ of the Twine (_purposely
tyed on a Bow or Slip Knot_) that had stuck to one of the Side-Cords,
and held the _Center_ of the _Neck_ rather _out_ of the Perpendicular.
CHAPTER XXII.
BALLOON AT ITS GREATEST HEIGHT.
[Sidenote: Mouth of the Balloon opened.]
Section 122. Being cautious how he suffered the +lightest+ Gass
to escape throu’ the Top of the Balloon, which must have happened
in drawing down the String of the Valve; yet apprehending the
+Possibility+ of an immediate Rupture at its +present greatest+
Elevation;—glancing his Eyes _around_ to take a +farewel+ View;—he
_pulled_ the Twine, that tyed the +Neck+.
[Sidenote: Balloon _shrunk_ to its usual _Shape_.]
123. _Instant_ Relief was given to the Balloon: which shrunk into the
Shape which it had assumed in the former Ascent, when the Gass began to
issue in visible Vapour, the _Neck_ likewise _lowering_ itself to the
Height of his Shoulders, as in Section 35.
[Sidenote: Mouth _opened_ at 41 Minutes past III.]
124. On stooping he found the Time 41 Minutes after III, and the
Thermometer 57.
[Sidenote: No _visible_ Vapour escaped.]
Nor was he surprised that no _visible_ Vapour escaped; as he had
imagined that much _common_ Air had been pressed into the _Mouth_ of
the Balloon: and which, being _heavier_ than Gass, woud _go out first_.
[Sidenote: Why the _Valve_ at the Top is not to be _opened_.]
On that Ground he was confirmed in his Resolution _not_ to open the
Valve at the top, which always emits the _lightest_ Gass.
[Sidenote: The _Neck_ being made _Air-tight_, the Balloon rose _again_.]
125. As soon however as the Neck of the Balloon reached his Shoulder,
he _gathered_ the Silk in his Hand, and held it _Air-tight_ tho’
untyed, to prevent Evaporation of much _real_ Gass: presuming that
if any Levity remained; the Balloon woud presently _rise_ again, and
_swell_.
And he was pleased to find the Event answer his Expectations.
CHAPTER XXIII.
AIR WARMER ABOVE THAN BELOW.
Section 126. It was a Matter both of Surprize and Pleasure to observe
that the Thermometer had risen +again+ to 60, when the Balloon had
soared _above_ the Sea-Breeze; as the Aironaut had expected to feel the
extreme Rigour of Winter; and had made Preparations against _intense_
Cold.
Nor did he find any Difficulty in Respiration _during_ the Excursion;
which may possibly be accounted for from the _Warmth_ of the Air.
[Sidenote: The Breath not visible during the Excursion.]
That the Breath[37] was _not_ visible at _any_ one Time, and
particularly while the Balloon was elevated above the _under_ Current,
might it not be owing to the uncommon +dryness+ of the Air, which woud
_dissipate_ the Vapour at the Instant of _Exposure_?
[Sidenote: Encreased Shadows seem to raise the Objects.]
127. It was remarked, some little Time _before_, and _during_ the
_last_ Glance of the Prospect taken at the _highest_ Elevation, that
the House at Aston was still visible, and the _dark coloured_ +Line+
forming its +diminutive+ Shadow seemed _thicker_ in Proportion to the
_Plan_, than when the Mansion was _first_ seen before the Re-ascent.
And it had a _sensible_ Effect in _apparently raising_ it above the
_common_ Level.
[Sidenote: Prospects _below_ noted.]
128. The Circuit of the _Land-Abyss below_ was also greatly
_contracted_: and a Haziness inclining to a _dark Green_ seemed to
cover the _outward_ Verge _round_ the _Lawn_.
The _red_ River Wever only appeared.
The Channel and _broad_ Branch of the River Mersey towards Warrington,
had long since vanished.
[Sidenote: _Down_ View like the Pattern of a Turkey-Carpet.]
The Lawn itself, which composed the Ground-View, was full of
_innumerable_ Enclosures _almost_ +close+ to each other; with _much_
Wood:—dwindling to the Pattern of an elegant Turkey-Carpet: which,
according to Principles of Mahommedan Faith, tho’ wrought in _gay_ and
_vivid_ Colours, is _made_ to exhibit +no exact+[38] _Resemblance_ to
the Works either of Art or Nature.
[Sidenote: The Earth _glowing_ with _primary_ Colours only.]
129. The Colours, of which the Ground Work was _principally_ formed
(except +white+; also the _roughened_ Sea, which _alone_ was +black+;
and Shadows, which _constantly_ gave a _transparent_ +violet+) were
four simple and _primary_ ones, viz. +red+, +yellow+, +green+, and
+blue+: all which seemed to +glow+, tho’ in a _less_ Degree, like the
Colours of the Prism.
This unmixed _Coloration_ of Objects, to be seen from a vertical
Situation _only_, to be seen without _Refraction_, is a new singular
and _pleasing_ Phenomenon.
[Sidenote: _Cromátic_ view of the Earth, an Appearance peculiar to the
Balloon.]
130. A View, taken _above_ the Level of the Clouds, may, from this
Circumstance, without Impropriety, be called a +chromatic view+ or the
Earth: of which, the _Print_ is an Example: delineating the Extent
of the aërial Excursion; and placed at the End of the _second_ Part,
including the Re-ascent.
CHAPTER XXIV.
BALLOON ABOVE THE INFLUENCE OF WATER.
[Sidenote: Balloon above the Influence of the Waters and Sea-Breeze.]
Section 131. The Balloon pursued its former _gentle_ Course in the
_upper_ Current of Air moving from the South West, and Aston House:
and had risen _above_ the Influence of the _Waters_ and _Sea-Breeze_.
[Sidenote: Balloon repeatedly swelling.]
132. In Consequence of having _held tight_ the Neck of the Balloon, the
Gass _within_ began _again_ to expand, and the Machine became _more
bloated_ than when _stationary_ at the first Ascent: the Bottom of the
Balloon being drawn up to the Height of his Hand, when the Arm was
stretched, and himself on Tip-toe.
[Sidenote: The Valve first tried.]
133. Tho’ the late Descent, at the last +Opening+ of the Balloon, had
been rapid; which was known _chiefly_ by the Want of Reaction from
the Bottom of the Car against the Soles of the Feet; yet being still
_far above all_ Clouds; fearless of the _Currents_, _Rocks_, and
_Shoals_, to which +all maritime+ _Navigation_ is subject; he took the
Opportunity of trying the upper Valve; _purposely_ to know the Effect.
So retaining the Bottom of the Balloon in his _right_ Hand, he drew
the Valve Cord with his _left_.
Immediately he heard it _click_: which proved that it was quite open,
and in good Order.
[Sidenote: The Valve answered.]
134. He tried the Valve three Times _smartly_, and deliberately.
The Escape of the inflammable Air or Gass was like the _growling_ Sound
made in a Mill by the Grinding of the Mill-stones, but by no Means so
loud.
CHAPTER XXV.
THIRD BALLOON-IRIS
[Sidenote: Balloon-shadow.]
Section 135. The _successive_ Operations of untying the Neck, and
_repeated_ Trials of the Valve, brought the Observer so low, that he
coud trace the _Image_ of the Balloon on the _upper_ Surface of _light
silvery_ Clouds beneath him.
[Sidenote: Third Balloon-Iris.]
[Sidenote: Iris remained.]
[Sidenote: The Earth disappeared.]
136. _Iris_, a bright _celestial_ Nymph, his _former_ Attendant, deck’d
in gay Attire as usual for the Bow, made her _third_ Appearance:
instantly _encircling_ the Balloon. Nor was her Stay so short as
before; as if to _recompense_ the Aironaut for the lost Sight of Earth
and all _terrestrial_ Objects, which then began to _disappear_.
137. In less than _a Minute_ after the _Deflation_; the Neck of the
Balloon continuing to be held tight in the Hand; the Balloon _quickly_
encreased in Bulk, and soared _aloft_, as before.
[Sidenote: Balloon alternately rising and falling.]
138. It continued _rising_ as long as the Hand coud _reach_ to hold the
Neck _tight_: and, on loosing it _an Instant_, made a rapid Descent: on
Account of the _Gass_ which escaped, and of the atmospheric _Air_ which
rushed in by the _same_ Opening at the Bottom.
[Sidenote: The Play of _fast_ and _loose_ repeated.]
139. The alternate Play of +fast and loose+, was frequently and
_successfully_ repeated: the Balloon always rising till it swelled out
of the Reach of the Hand: at which Time it was let go: and the Neck
(as well as the Balloon) descending; was _presently_ caught in the
Hand, and made _Air-tight_ as before.
[Sidenote: Manouvres seen at the Distance of 15 Miles.]
140. These Manouvres were performed, at a Height _far_ above the Level
of _all_ Clouds, and in Sight of Numbers of People: some of whom were
at least 15 Miles distance: yet coud plainly, from an Eminence called
_Hoole-Mill_ Field, a Couple of Miles from Chester, discover the
Balloon at an amazing Height, darting up and down several Times; or as
they expressed themselves, “_quivering and warping in the Air_.”
CHAPTER XXVI.
SENSATIONS ACCOMPANYING THE BALLOON.
[Sidenote: Situation safe and pleasant.]
Section 141. The alternate Elevation and Descent of the Balloon gave
sufficient Leisure to reflect on the +security+ and +pleasure+ of his
Situation, thus _wafted_ on the _Pinions_, and _merging_ in the _Ocean_
of Air.
Indeed the whole Excursion was a Continued Scene of Pleasure.
The Eye and the Imagination were beyond Measure delighted.
142. If there had been any Thing to wish for, it was the _living_
Pencil of +Angelica+,[39] or some other celebrated Painter: in order to
gratify the World with the _bright Miniatures_ and _Colouring_ of so
much _variegated_ Beauty.
143. As it woud be difficult, if not impossible, by _mere_ Description,
to convey an adequate Idea of the different +Sensations+ experienced
while in the Car; (for Pleasure is itself unspeakable;) yet the Fancy
may possibly, without Censure, be a Moment _indulged_, in its Allusions
to such familiar Subjects as approach nearest to +them+: so as not to
leave the _public_ Mind _wholly_ in the Dark, with Respect to the above
Points of natural and general Curiosity.
[Sidenote: The _Swing_ a favourite Amusement.]
144. Most young People, whenever they have Opportunity, amuse
themselves on the +slack rope+, or Swing: the Pleasure _encreases_ in
Proportion to the _Loftiness of Ascent_ they are _able_ to acquire.
[Sidenote: The Mogul enjoys the Air without Fatigue, by Means of the
_Swing_.]
145. In the East, where the Heat of the Climate forbids robust
Exercises; the _Swing_ is considered as a princely Diversion: and of
which the +Mogul+ himself _condescends_ to partake. He is swung by
Slaves: and thus enjoys the _pure_ Air _without_ Fatigue.
[Sidenote: The Balloon and Swing compared.]
146. The Ascent of the Balloon is not unlike what is felt, in the
_ascending_ half of the Swing: and the Descent is attended with that
agreeable Sensation known to those who _sink_ throu’ the _descending_
half.
[Sidenote: A favourite Diversion among the Russians.]
[Sidenote: Artificial Declivity of _waved_ Ice.]
147. A Diversion similar to the above is peculiar to the _North of
Europe_, practised by the Russians, particularly the Inhabitants of
Zarsko Zelo; and accompanied with a Sensation _so delightful_, that
they seek it in the _open_ Air, amidst the _utmost Severity_ of the
_Frost_. It is a Sort of Boat or _Car_, in which they _glide_, for a
considerable Distance, _down_ an _artificial_ Declivity of _waved_ and
_polished_ Ice: being drawn up by Servants; they launch precipitately
forwards, and _down_ again as before.
[Sidenote: Amusements of Gestation in common with the Balloon.]
148. _Sledges_ drawn _swiftly_ over the undulated Surface of a _snowy_
Country, a favourite Diversion in many Parts of Germany, in Lapland,
and Siberia: Skaiting on _level_ Ice; the Motion of a Vessel on
_smooth_ Water; of a _fleet_ Horse; also of Wheel-Carriages rolling
over +even+ Gravel, or a _grassy_ Plain, are each a _Luxury_ of the
same Kind; and _grateful_ to the Nerves.
[Sidenote: Vertical Flying-Coach.]
149. There is yet another Amusement, which is said to be of _German_
Extraction, still frequent in the North of England, called the
_vertical_ +Flying-Coach+.[40]
Two Persons are required to turn the Machine (when full): which moves
like the four Sails of a Windmill: a Seat being placed at the End of
each Sail.
150. The _Pleasure_ communicated to the _Nerves during_ the Descent,
is to some Constitutions so _exquisite_, as to be full as much as the
human Frame can support: others are affected by it in a _gentler_
Manner.
These different Diversions, flowing from the same Principle in common
with the Balloon, viz. that of _being carried with a gentle Motion_,
are _one or other_ suited to all Ranks and Ages.
151. The Pleasure of the double Slack Ropes, when seated in the Car
appended between them, is perhaps in itself _superior_ to that of most
others.
152. The _vertical Flying-Coach_[41] compleats the _Circle_, of which
the Slack Rope describes but the lower _Half_.
[Sidenote: Balloon and Vertical Flying-Coach compared.]
153. The Sensations communicated by the Motion of the Balloon, come
nearest those of the vertical flying Coach, tho’ _more_ gentle, and if
possible, _more_ pleasing.
[Sidenote: No Sickness or Giddiness in the Balloon.]
At Sea, the most experienced Mariner is sometimes _sick_ or _giddy_.
154. Nothing of the Kind happens in the Balloon: where an infinite
Variety charms the Imagination.
[Sidenote: The Spirits raised.]
155. The Spirits are raised by the _Purity_ of the Air[43], and _rest_
in a _chearful_ Composure.
[Sidenote: The Greatest Height conveys no Fear of falling.]
156. Even when _stationary_ above the Clouds, the _Height_ conveys
with it no _Danger_ of _falling_: any more than _when_ in a Vessel at
Sea, (as off the West-India Islands, for Example) the _Fish_ are seen
gliding over the clear _white rocky_ Bottom, at the Depth of twenty
Fathom: as the Aironaut seems perfectly unconnected with the Earth, and
unconcerned about it.
[Sidenote: The Depth below the Clouds gives no Idea of Distance.]
157. Nor does the Depth _below the Clouds_ give an Idea of _Distance_.
On the contrary, the _smooth chequered Lawns_ which form the Surface
of the Earth, are presented to the Eye, as on a _Level_ with the
_Clouds_ themselves: _at least_ +come up+ to their +undersides+, and
appear so much a Part of _them_; that the _Clouds_ occupy the Place of
_Earth_: and the Aironaut seems able to descend from the _Car_ upon the
_Clouds_, and to walk from Side to Side over the _empty_ Space, as over
a Sheet of _transparent_ Ice, across a _River_, whose Depth is equal to
the _small_ but indefinite Thickness of the Clouds.
158. It is from _frequent_ +experience+ only that the _Diminution of
Objects_ presuppose their _Distance_.
CHAPTER XXVII
USEFUL CONCLUSIONS.
[Sidenote: Change in the _Form_ of the Balloon while descending: with
Conclusions drawn from the Change.]
Section 159. It was remarkable that, the lower Parts of the Balloon
regularly adopted a _similar_ Form at each Descent: not unlike a
_Ship’s Bottom_; looking up, at the Head or Prow, while on the Stocks:
the _Neck_ of the Balloon forming a beautiful _central_ Pillar; in
Shape like that of a _Speaking Trumpet_ inverted.
[Sidenote: Time of Descent discovered by the Form of the Balloon.]
And hence may be derived a Piece of _useful_ Information: as the
_precise_ Time of descending is discovered by bare _Inspection_ of the
Machine.
[Sidenote: Balloon adopting the Form of an elliptic Solid.]
160. Another Conclusion seems likewise deducible from the above, that
if the Balloon is so burdened, as to _descend_ while it retains the
Form of an +elliptic solid+;[44] it will descend more rapidly, than
if it contained less Gass: the Force of Descent in both Cases being
supposed the same.
For if the Diminution of Gass be so great as _not_ to fill the upper
Hemisphere of the _Balloon_; the Resistance of the atmospheric Air
_below_ woud probably give _it_ the Appearance of a _Concave_ or
Umbrella, which woud greatly _check_ the Descent: viz. in Proportion to
the Square of the Number of Feet of which the Surface was composed.
[Sidenote: An equatorial Hoop prefered to a Parashute.]
161. Hence also the evident Utility of an +equatorial hoop+ for
Balloons: in Preference to a Parashute, which woud be only an
Incumbrance.
CHAPTER XXVIII.
[Sidenote: An uncommon Sound in the Air.]
Section 162. At 40 Minutes past III, when the Balloon was _apparently_
some Miles above the Level and Summit of the Clouds; a +sudden+ and
uncommon _Sound_ was heard for three or four Seconds only.
A Sort of _hollow_ Wind seemed issuing from a Plain of Clouds in the
North-East Quarter, greatly below the Balloon: which as +suddenly+
ceased.
[Sidenote: An unusual Motion communicated to the Balloon.]
The Instant the Sound was heard; a gentle Motion was _impressed_ on the
_Balloon_, as if by a Hand touching _it_ near the _Top_.
163. Clouds to the North-East appeared, for the first Time, in _rapid_
Motion towards the Balloon.
They _sailed_ directly _under_ it: filled up the Chasm, and drew a
_white_ Veil over _all terrestrial_ Objects.
[Sidenote: Conjecture in the Cause of the Motion.]
164. It has been _since_ imagined, that a fresh Wind _descended_ from
the South-West Quarter in the upper Current, and was heard in the
North-East, being ecchoed from the upper Tier of Clouds _below_: and
that the Balloon, finding less Resistance than the +range+ of Clouds,
soon overtook and passed them: particularly as the lower Part of the
_white_ Flag vibrated only in the usual Direction.
165. The _encreased_ progressive Motion of the Balloon was _not_
perceived (Section 18): being considered as at _Rest_, and the
_apparent_ Motion _referred_ to the _Clouds_.
CHAPTER XXIX.
[Sidenote: A narrow Ditch the Duke of Bridgewater’s Canal.]
Section 166. In a few Minutes, a Side-Break throu’ the Clouds
discovered a long ill-formed narrow Line or Ditch, something less
than a Foot in Breadth, extending several Ways: and which from its
Proximity to Places that were known, and coming into View; viz. the
Country about Norton and Halton-Castle; proved to be the Duke of
Bridgewater’s Canal.
[Sidenote: A Glympse of Runcorn Gap.]
+Suddenly+ came in Sight the _spacious_ +open+ of the Mersey above
Runcorn Gap: which appeared of a +ruddy+ Colour, and _very_ near: as if
the Balloon had again _felt_ the Influence of the _River_.
[Sidenote: _Balloon-Geography_ first suggested for _Maps_.]
167. A new System, that of _Balloon-Geography_ here suggested itself:
in which the Essentials of _Proportion_ and _Bearings_ woud be far more
accurate, than by the present Method, both for _Maps_ and _Charts_,
viz. To make Drawings by +sight+, from the Car of a Balloon with a
_Camera Obscura_, aided by a Micrometer applied to the under Side of
_the transparent_ Glass.
[Sidenote: Air presumed to be warm with South-West Wind long continued.]
The Season proper for such an aironautic Expedition, would be _any_
_calm bright_ Day: the Wind having blown from the South West Quarter,
for some Days before, which is _frequently_ the Case: the Air, at
_such_ Conjuncture probably remaining +warm+, to the Height of a Mile
or more, unless in the very Midst of Winter.
[Sidenote: Balloon Geography for _Charts_.]
168. And particularly for Charts, which in a _maritime_ Country are
_most_ useful: as Balloons have an extraordinary Predilection to become
_stationary_ over Channels and Rivers; altho’ a very _strong_ Gale of
Wind, shoud continue the _whole_ Time to blow in an horizontal Course
directly +under+ the Balloon.
[Sidenote: Balloon in a Calm with a _strong_ Wind _below_.]
Of which Event the Writer of this Account was an _Eye-Witness_, in
the Case of Mr. Lunardi: who was _detained_ above 20 Minutes over the
_broad Bend_ of the River Mersey, near Ince, in Cheshire, the Day he
_landed_ between Tarporley and Beeston-Castle, ascending from the New
Fort at Liverpool. He quitted his Station by the Escape of Gass, and
descended into the _Stream_ of Wind, which continued as _violent_ as
before.
CHAPTER XXX.
Section 169. The Summer Scenes of Fairy-Land below, being soon eclipsed
by the _quick_ Intervention of a _Range_ of Clouds; the +sudden+
Contrast of which was highly pleasing to the Imagination; a Prospect of
+mid winter+ instantaneously succeeded.
[Sidenote: The Center filled up in an Instant.]
170. The Earth’s _Surface_ throu’ an immeasurable Crater of Vapour
accumulated round the Aironaut, who was suspended, and seemed fixed
in the Center above it, _no longer existed_. And, if it will not be
allowed, that a _new_ Earth, and a _new_ +sky+ appeared; at least, let
the Imagery and Resemblance of what was really seen, be taken from that
+earth+, which in Fact did _not_ appear.
A +world+ of _Clouds_, +greater+ than the +one+ below, became, for the
first Time the _sole_ Object that engrossed the Sight. (See Section
144.)
[Sidenote: View of the Clouds taken from _above them_.]
171. The Balloon was _apparently_ raised some Miles above the _Surface_
of a _concave shallow_ Plate, or Shell, or rather an immense Plain,
_which_ was in general smooth and well defined: but the _dense_
tonìtruous Masses, rising here and there _above_ the Rest, greatly
resembled steep and +rugged mountains+ seen in Perspective, at
different Distances from 5 and 10 to at least a hundred Miles.[45]
An unvaried deep cerùlean and pellucid Azure, without a Cloud above,
enclosed the +novel earth+: whose Surface, whether Valley, Plain, or
+mountain+ _in Appearance_; seemed as if covered to a prodigious Depth,
by successive Falls of Snow, driven and polished by the Winds and
Frost, and dazzling to the Sight: the Sun still shining above all, with
+white+, unremitting and invigorating Rays.[47]
CHAPTER XXXI.
[Sidenote: Brilliant Colouring of _dense_ Clouds.]
[Sidenote: Aironaut lost in the _blue Fields_ of Air, by the
Intervention of Clouds below him: which prevented all _farther_
Knowledge of his Situation, and also a Sight of the Earth itself.]
Section 172. A Thunder Cloud in most grotesque Form;—of superior
Magnitude, Density, and +brightness+—a _celestial Colouring_;
and whose _Shade_ was itself a _Colour_ of semi-transparent and
transcendent _Blue_ and _Violet-Purple_;—remaining for several
Minutes, _exactly under_ the Balloon, _tempted_ the Aironaut to descend
into it; and, if possible, investigate its Structure and Composition.
Blanchard, he knew, had passed throu’ +many+ without Danger: any Fears
that might otherwise have been entertained on that Head were therefore
groundless: particularly as Gass, i.e. _inflammable Air_ and the
_electric Fluid_ (supposing an electric Atmosphere had surrounded the
Thunder Cloud) mutually _repel_ each other. He however declined the
Trial: among other Reasons which then offered; that the temporary and
apparent Rest of both Balloon and Clouds portended _his_ Situation
to be over the Center of _some Water_: so that if _Gass_ had been let
out in order to _descend_; _enough_ might _not_ have remained to make
Choice of a proper Place to _land_.
173. Some Minutes after; on the _Retreat_ of the Clouds, or
_progressive_ Motion of the Balloon; he found himself suspended over
the most _enchanting_ Meanders of a Rivulet.
Where he coud not tell.
CHAPTER XXXII.
[Sidenote: The Aironaut was lost, tho’ in Sight of a Country well known
_when below_.]
Section 174. He _thought_ himself again over the Wever.
[Sidenote: At 47 Minutes past III, over a _red_ Rivulet.]
At 47 Minutes after III, the Prospect _beneath_ opened, just wide
enough to shew, that he was suspended in the open Space over the Center
of some Rivulet.
The Map of the Country which had been so carefully studied, was _now_
consulted for the first Time, but coud not bring to his Recollection
any Traces of the extraordinary Curves which then met his Eye.
They bore not the least Resemblance to any Part of the River Mersey.
No River like that below him had ever presented itself.
Its _Doublings_ were so various and _fantastic_ as to exceed the Limits
of Credibility.
[Sidenote: The Neck of the Balloon tyed some Time _before_ to prevent
the Descent.]
175. He was still stationary, at an immense Height, without the _least_
Inclination to descend: having _some Time before_ taken the Precaution
to tye _again_ the Neck of the Balloon, as soon as he had perceived it
did _not_ inflate, as at first, to any _dangerous_ Degree.
No Towns, no Houses appeared. No _public Roads_ were discoverable. No
Voices were heard.[48]
The Country beyond the Rivulet began to disclose itself: but was quite
_new_ to him at that _Altitude_, and seemed as if almost covered with
Wood.
176. His _Watch_ shewed the Time of the Day, and the Sun alone
_sufficiently_ indicated the Point of the Compass.
The _white_ Flag manifested _no_ Change in the Wind.
But whether he was near Liverpool, Wigan, or Manchester, he coud not
discover.
[Sidenote: The Country _below_ unknown to the Aironaut, _when_ in the
Balloon.]
177. He was entirely +lost+ in the _blue Fields_ of Air; far above the
Summits of the Clouds; tho’ the Balloon was in Sight of the Earth, and
of Numbers who were gazing at it.
178. The _Colour_ of the new Rivulet was full as +red+, as any he had
seen before.
He thought it might be an insignificant Brook, which tho’ curiously
curved, was too small to be inserted in the Map.
Still he continued over it: turning and returning _gently_ in small
Curves.
179. He presently passed _Northward_ of the Rivulet _over_ a woody
Country, in which he coud discover _no_ Variety of _Colouring_ either
in the Ground Work or Enclosures; the whole having a _dark green_ Cast.
[Sidenote: Unusual Objects below.]
An Appearance of a very distant and remote _Plain_ then presented
itself; the Size of a moderate Carpet: of a _ruddy_ Colour; and
surrounded by a _green_ Border. Being an unusual Object it continued to
engage his Attention.
180. Not far from the first, another of the same Kind, of a more dusky
Cast, but _less_ and somewhat nearer, that is _more under_ him, then
attracted his Notice.
He wished to _decipher them_, but in vain.
[Sidenote: The Prospects opened, which demonstrated his Descent, owing
to the Loss of Gass.]
181. The Sun shone +bright+ on both: and in a very few Minutes, the
_circular_ Prospects _encreased_: which was now become a _regular_ and
undeniable Signal that the Balloon had begun to _descend_. (Section 17.)
The _latter_ Plain appeared, at the first, about the Size of a common
_Handkerchief_.
The Balloon continued to descend.
[Sidenote: The same Spot perpetually varying to the Eye of the
Aironaut.]
182. In a Couple of Minutes, the Plain appeared intersected +closely+
every Way, like the _Coat_ of a _ripening Melon_. Descending a little
_lower_; it seemed covered with a _Net_, the _Meshes_ of which were
distinct. And _lower_ still; it extended itself _greatly_ on _all_
Sides: (at which Time a certain Degree of _Chilliness_ prevailed:) and
was then _again mistaken_, and looked upon as a +dry+ _Heath_, deeply
overrun with Shrubs of the same Name.
[Sidenote: Ballast thrown out gradually.]
183. The Descent of the Balloon being _rather_ quicker than was
expected, or desired; it was deemed expedient to have Recourse to the
_last_ Bag of Sand, which lay open, and weighed 20 Pounds.
It was accordingly thrown out, a Handful at a Time.
[Sidenote: The remaining Ballast thrown out _at once_, in all 20lb.
weight.]
But that Method not seeming _sufficient_ to _check_ the Descent, when
at the Height of 150 or 200 Yards; _all_ the Sand was poured out, and
the Bag thrown down.
[Sidenote: Gentle Landing of the Balloon.]
This had the desired Effect: and the Balloon continuing to descend with
a Motion _uniformly retarded_, alighted, as the +down+ _of a Thistle_,
in the gentlest Manner, without +any+ _Rebound_.
[Sidenote: Anchor and Cable not made use of.]
184. There being scarcely a _Breath_ of Air abroad, the Aironaut made
no Use of his Anchor and Cable: but continued as from the first,
+standing+ _upright_ in the Car; which, having moved a Yard or two
_only_ along the Ground, rested in a perpendicular Situation.
The Balloon, suspended over him like a _vast_ Umbrella, +levitated+
_vertically_ in the grandest Manner.
185. He was _alone_ when he alighted: but, in a _few_ Minutes, found
himself surrounded by the Country-People, who had waded _above
Ancle-deep_, and came running from all Parts, to see the +wonder+, and
contribute their _Assistance_.
[Sidenote: Landed at 53 Minutes past III. Thermometer 59.]
186. He _landed_ exactly, at 7 Minutes before IV: Thermometer 59: but
+where+ he coud _not_ tell.
The first Question was “Pray where am I?” And the Answer;—in
_Lancashire_.
On asking the nearest Distance to a Turnpike-Road; the People said he
was within _two Fields_ of one, and offered to conduct him thither.
He accepted their Offer, and shared _his Liquor_ among them.
CHAPTER XXXIII.
Section 187. The Balloon alighted _near_ the _Middle_ of a +moss+;
called +rixton-moss+, a Place he had never before heard of.
[Sidenote: Rixton-Moss, its Magnitude.]
It was a large Tract of unenclosed +wet+ Land, above four Miles
long and above two broad, intersected by Ditches or Water Courses,
which divide the Moss into Fields of a _moderate_ Size. The whole is
surrounded by _tall_ Forest Trees.
This was the _lesser_ of the two dusky Plains, which appeared about the
Size of a Handkerchief, and which he wished to decipher, but in vain.
188. Rixton-Moss is situated five Miles North North East of Warrington,
and a little to the left of the Turnpike Road leading from thence to
Manchester, and 25 from Chester.
[Sidenote: Chat-Moss in Lancashire.]
189. He has since been informed that the other Plain, about the Size
of a moderate _Carpet_, was no _less_ a Place than +chat moss+, a vast
_Tract_ of barren _wet_ Land, _many_ Miles in Extent.
[Sidenote: The _Rivulet_ seen when _above_, was the River Mersey near
Warrington.]
190. Curiosity tempted him to make particular Enquiry concerning the
Rivulet over which he hung, _admiring_ the Beauty of its serpentine
Meanders; and, from a Description given of his Manouvres over _Lymm_,
situated to the East of Warrington, and from a peculiar Curve,
appearing in the Form of a _true Lover’s Knot_, when over the Gunpowder
Water-Mills, he was convinced the _Rivulet_ coud have been no _other_
than the broad Branch of the River +Mersey+.
[Sidenote: The Excursion performed in two Hours and a Quarter.]
191. The +aërial excursion+ was performed in two Hours, and a Quarter,
within two Minutes.
The Distance of the Balloon-Course, if traced along the Ground, 30
Miles. Section 130.
[Sidenote: Balloon, unknown to the Aironaut, going at the Rate of 30
Miles an Hour.]
192. In comparing the Dates at Bellair and Rixton-Moss; it is certain
that the Balloon, excluding the Force of _Ascent_, must have moved
_forwards_, during some Part of the Re-ascent, at least at the Rate of
30 Miles an Hour: tho’ the Aironaut, for the most Part, imagined he was
gliding throu’ a serene Atmosphere.
Probably the progressive Motion was encreased, from the Time the
unusual Sound was heard, in Section 162.
Note: The Print, representing a +chromatic+ View above the _Level_ of
the Clouds, of the Country from _Chester_ to _Rixton-Moss_, is to front
the _left_ Page, at the End of this Chapter.
END OF THE RE-ASCENT.
CHAPTER XXXIV.
THE SEQUEL.
[Sidenote: Flights with the Balloon for +three+ Hours longer.]
Section 193. The Sequel contains an Account of _several Flights_ made,
in Presence of the Aironaut, by different Persons, during _three_
Hours, in the Car of the Balloon, viz. from the Time he alighted, till
_after_ +sunset+.
[Illustration: _A_ +Balloon Prospect+ _from ABOVE the_ CLOUDS _see
page IIII c._
Publish’d May 1ˢᵗ. 1766, by T.Baldwin Chester.]
[Illustration: The +Explanatory+ Print. _see Page IIII. d._]
Rixton-Moss, +Lancashire+, IV. o’Clock P.M.
The Afternoon being _fine_, the Sun _bright_, and the Air _calm_;
finding the Country People remarkably civilized and kind; and having
dispatched a Messenger on Foot to return in a Post Chaise from
Warrington; the Aironaut was resolved to gratify the Curiosity of his
numerous Followers, and give the young People a Taste for Balloons, by
treating them successively with an Airing.
194. Indeed it was no inconvenient Method of removing and conducting
the Machine: and _possibly_ different Positions of the Balloon might
furnish a _useful_ Hint.
[Sidenote: The Aironaut indulged the People of the Country with
_Flights_ in the Balloon.]
Having asked aloud _who chose to ride_, several answered in the
Affirmative. So having pitched upon a young Fellow of less Weight than
himself; bid him get up, between the Cords, over the Hoop, into the
Car; stand near the Middle, and hold an opposite Cord in each Hand.
He obeyed with the greatest Alacrity: and seemed to be _a noisy bold_
Adventurer.
[Sidenote: The Aironaut _first_ quitted the Car; but continued to
_conduct_ the Balloon.]
195. The _Aironaut_ then got out; and having suffered the Balloon to
rise; fastened the End of the Cable to _central_ Meshes of the Net, at
the Bottom of the Car: ordering the strongest and tallest Man to hold
the Cable, and let it go by Degrees till the Anchor or grappling Iron
_alone_ remained in his Hand.
[Sidenote: Behaviour of different Adventurers.]
The Balloon now rising _above_ the Height of the Trees, and giving
the Adventurer a new and extensive Prospect of the Country; he became
_silent_; _pale_; his _Countenance_ the _Picture_ of _Distress_;
looking _down_ as if for _Help_.
The Conductor repeatedly bid him take Courage. But, in vain.
By lowering the Car _within_ the Height of the Trees, he seemed to
_recover_ from his _Dismay_.
CHAPTER XXXV.
Section 196. The Route of the Balloon being now throu’ a _flat woody_
Country, with _tall_ Trees growing in the Hedge Rows; a Difficulty
occurred, how to conduct the Cable, when the Balloon was _above_ or
_between_ the Trees, without entangling: which gave the Conductor
much Trouble, as he was frequently obliged to walk round a Field, the
Balloon being held in the Center, before he coud espy a proper Opening.
[Sidenote: March of the Balloon.]
The Procession marched slowly forward: and the young Man was carried
among _his Peers_ in Triumph through the Air, across the Turnpike-Road,
into the Middle of an open Grass Field, where he descended; took a
Companion _less heavy_, and left the Car.
This Stripling was a good Deal surprised the Instant he rose above the
Trees; but ventured to look around: and appeared on the _whole_ much
delighted.
197. A great Concourse of People were now collected.
Accidental Carriages halted: joined the Cavalcade, and partook of the
Diversion: the _greater_ Part following the Balloon throu’ the _open_
Fields adjoining the Road.
[Sidenote: Caution to prevent the Escape of the Balloon.]
The Conductor _generally_ preferring the beaten Track; yet _suspecting_
the Balloon with its Adventurer in the Car, might _designedly_ be
suffered to _escape_, took the Precaution to have the Grapple held by
_nearest_ Relations to the Person in the Car.
198. The Gass evaporating; a smart young Fellow, who seemed ready
for the Jaunt, stepped in: on which the former resigned his Place.
But he was no sooner raised a few Yards above his Companions, than
the _florid_ Colour forsook his Cheeks; he _trembled_; bent himself
_double_ with Fright; and the Balloon was obliged to be hauled down.
[Sidenote: A Venus in the Car of the Balloon.]
199. A fond Mother then requested that her Child, a fine blooming Girl,
might ascend: boasting of her Courage, and comparing it with that of
the Person who had none.
The _Venus_ smiled, and mounted her Car with great Spirit.
[Sidenote: Politeness of the neighbouring Gentlemen.]
200. Some Ladies and Gentlemen of the Neighbourhood who had watched
the Balloon, while it hung at an immense Height over Lymm, and the
Gunpowder Works on the River Mersey, came, in their Evening Walk, to
meet it: joined the Procession; gave the Aironaut _polite_ Invitations
to their Houses, and shewed him every possible Civility.
[Sidenote: Effect of Air in _Motion_ on the Surface of the Balloon.]
201. The Resistance made by the _Surface_ of the Balloon, against the
_least Breath_ of Air moving _horizontally_, was _frequently_ tried
by occasionally holding the Grapple: and it was a decided Point, that
the _least Motion of the Air_ was sufficient, together with the Action
of _Levitation_, to prevent the Person, who held the Grapple when the
Cable was extended, from transporting the Balloon against the Current:
nay it was with Difficulty he coud remain in the _same_ Place: the
Balloon sometimes pulling him forwards, and almost off his Feet.
[Sidenote: Effect of _calm_ Air on the Surface of the Balloon.]
202. When the Air was perfectly _calm_, which frequently happened while
the Balloon migrated with different Passengers, as the Evening was the
finest in the World, and the Country flat and woody in the Hedge-Rows;
it was with _Difficulty_ that the Conductor coud draw the Balloon
after him, faster than the Rate of a moderate _Walk_: viz. three Miles
an Hour.
CHAPTER XXXVI.
[Sidenote: Sun set at 34 Minutes past VI.]
Section 203. The Sun set at 34 Minutes past VI. and, tho’ it was _then_
near that Time, the Post-Chaise was _not_ arrived.
204. On Enquiry for a dry smooth Meadow, he was recommended to proceed
a little farther, to a Place on the Road within three Miles of
Warrington.
205. Having by this Time gratified the Curiosity of the Country in
admitting Boys and Girls to the Age of six or seven Years, into the
Car; and being arrived after Sun-set at the Place appointed, viz.
_Milton’s Croft-Green_; he ordered the Balloon to be laid on its Side
along the Ground: having removed the Car, and opened the Mouth; the
inflammable Air or Gass, was soon pressed out by Means of a _long Pole_
rolled _across_ it by two Men, standing one at each End of the Pole:
beginning at the Top or upper Valve, which was held down close to the
Ground; and ending at the Mouth or Neck.
It was then rolled up, put into the Car; and the whole Apparatus placed
on the Top of the Chaise which arrived the Moment wanted.
[Sidenote: Balloon put up at 53 Minutes past VI.]
206. The Operation was completed at 53 Minutes past VI: the Conductor
having accompanied the Balloon on Foot exactly +three+ Hours.
[Sidenote: Balloon in the Air five Hours and a Quarter.]
207. The Balloon had therefore continued _floating_ in the Air, with
different Persons, in the whole, for the Space of five Hours and a
Quarter.
The Conductor, promising to accept the very polite Invitation offered
him by Mr. _Stanton_, a Gentleman who is principally concerned in the
Gunpowder-Works upon the Mersey; called at his House, and partook of
some Refreshments.
He then drove to Warrington, where he was met by a Person whom
Curiosity had inspired to follow the Balloon _on Foot_ from Chester, as
long as he coud keep it _in View_.
208. Mr. Lunardi likewise with great Civility dispatched his Servant to
assist the Aironaut in _the Care_ of the Balloon; but he did not arrive
in Time; not reaching Warrington till VIII. at Night: having lost Sight
of the Balloon about _Daresbury_, four Miles from Warrington.
209. Nor was it visible to any, at least very few, of the Inhabitants
of that Town, which was equally hidden from the Aironaut: who, _then_
ignorant of his Situation, must have remained a considerable Time
suspended above the Clouds; which concealed both the Town and River.
He saw Warrington but twice when +above+: for a short Time, at a great
Distance, and a _mediate_ Altitude.
210. The following Day he returned to Chester: was met by the
Militia-Music, and ushered with loud Huzzaes into his native City.
On his safe Arrival; besides the private and sincere Congratulations
of his Relations and Friends; the Bells rang: his Flags were carried
in Procession, and every public Demonstration of Joy was shewn on the
Occasion.
TO THE INHABITANTS OF CHESTER
THANKS.
END OF THE EXCURSION
THROU’ THE AIR.
AIROPAIDIA.
CHAPTER XXXVII.
+OBSERVATIONS,
HINTS, and CONJECTURES,
on the
SUBJECT
of the
BALLOON and EXCURSION
FROM CHESTER THE EIGHTH OF SEPT. 1785.+
OF THE WEATHER, IN THE VICINITY OF CHESTER, ABOUT THE TIME OF THE
EXCURSION.
Section 211. For more than ten Days _before_ the Balloon-Voyage, the
Wind had blown (_interruptedly_ on Account of the Sea-Breeze) from
South and South by West.
Monday the 5th of September:
A Conjunction of the Planet Mercury and the Moon, at +one+ in the
Afternoon.
Tuesday the 6th:
A violent Hurricane in the South of England, at London, Portsmouth, &c.
The same Day at Chester North-North-West, and distant from London 182
Miles; South-Breeze; Rain most of the Day. Thermometer at Noon in the
Shade, 62: and 14 Divisions colder each Night, than the _following_
Day, at an Average of five Years. Barometer, below _Much Rain_, viz. at
28 Inches ⁹⁄₁₀ths.
Wednesday the 7th:
Violent Squalls from South and South-West, with hazy Air, till half
past IV in the Afternoon. Thermom. 58; Barom. Changeable, viz. 29½.
Thursday the 8th, which was the Day of the Excursion:
Much bright Sun. (On Enquiry) calm _below_ till half past III in the
Afternoon, then West Sea-Breeze: South-West Breeze _above_ till half
past IV. Calm bright Evening.
Also the upper Stratum of Clouds thin and _white_, in _quick_
Motion, when seen from _below_ till Noon: at which Time the Sky was
almost cloudless: and, from _above_ the upper Stratum, were seen,
interspersed, Multitudes of detached Thunder-Clouds in large Masses,
rising at Intervals, in the _Middle_ of the upper Surfaces of white
Clouds, and stretching _above_ them.
Friday and Saturday moderate: South and South-West Breeze.
Sunday the 11th. The Planet Mercury stationary.
Cloudy Morn. South-West Breeze. Thermom. at 60 at Noon. Barom. _above_,
Changeable, viz. at 29½. +Much thunder+ and Rain in the Afternoon.
212. Quere, Had the _Thunder_-Clouds on Thursday, tho’ not remarked
by any from +below+, yet visible to a great Extent from the Balloon
_above_ them,—any Connexion with the _Thunder_ that happened +three+
Days after?
[Sidenote: Weather, to be prognosticated, by _Sight_, from the Balloon]
Answer: It appears to the Observer, that the _Thunder_ was _gradually_
collecting in the Air from _Thursday_ till Sunday: and if so; will not
Balloons, when more _frequent_, prognosticate the Weather, _by Sight_,
better than any other known Methods?
CHAPTER XXXVIII.
ON CERTAIN APPEARANCES AT DIFFERENT ALTITUDES OF THE BALLOON.
[Sidenote: Of the highest visible Clouds which are always _white_.]
Section 213. The highest visible _white_ Clouds, often seen in detached
Streaks, during the finest and also in the worst Weather, (if not
intercepted by lower Clouds) and which, when melting away, are known in
some Counties by the common Appellation of Horse-Tails; and, suspended
over Great-Britain, are frequently _marbled_ or dappled by the Wind;
putting on the Appearance of white Waves, like Sea-Sands ruffled
and left by a rapid Tide;—had been disturbed, separated, and almost
_melted_ down by the _Storm_ the Day preceding the Excursion.
Two of them _only_ were still visible in Streaks, near the Sun’s Place,
at the first Ascent. They seemed without Motion, and became afterwards
_invisible_.
Saussure, the celebrated Professor of Philosophy at Geneva, is very
exact in his Definition, Description, and Height of these Appearances:
and thinks it _probable_, their Situation may be “_at least fifteen
English Miles above the Surface of the Earth_.”
“Car quand je considere ces fines Pommelures, &c.” “For when I consider
these delicate Dapplings, which, in a Series of fair Weather, begin to
cover the azure Vault of Heaven with a white and transparent Gauze, and
which portend Rain a long Time before it happens; I am led to believe
they occupy a very elevated Situation in the Atmosphere” (Essais sur
l’Hygrometrie, P. 271.)
It seems however that _Crosbie_, in his Excursion from Dublin on the
25th of January 1785, pierced throu’ and soared above these _fine
Webs_, at the Height of 16 Inches by the Barometer in a _frosty_ Air.
[Sidenote: Of the _Chilliness_ perceived at a certain Height.]
214. It has been already noted, that at a certain Height, a Kind of
+chilliness+ was perceived, not ascertainable by the Thermometer.
The Sensation was _suddenly_ impressed four Times, in ascending and
descending to and from the same Height, viz. about 26 and 27 Inches,
equivalent to between 500 and 1000 Yards above the Surface of the Earth
at the first Ascent.
From the Uniformity of Effect at the same Height; the Sensation may be
ascribed to the same Cause, viz. the Level of the first or lower Tier
of Clouds: altho’ the Aironaut did not pass throu’ any visible Cloud
or Vapour, during the Excursion. See Section 93.
[Sidenote: Remarkable Appearances of Earth and Clouds.]
215. At the same Height likewise, tho’ the Observations have not been
set down at large; the Appearances of the Earth and Clouds were very
remarkable.
During the Ascent of the Balloon, between the Altitudes of 26 and 27
Inches; the _circular_ Prospects of the subjàcent Earth _instantly_
contracted, and, during the Descent, about the same Height, _instantly_
enlarged themselves to the Eye of the Aironaut.
216. At the same Height mentioned before, the _circular_ Prospects of
the Clouds appeared on the same horizontal Plane with the Eye: tho’ at
the Distance of a Mile. See Section 49.
In _this_ Situation, the Observer endeavoured to discover the Thickness
of the _Stratum_ of Clouds: but was always baffled by a Deception of
Sight worth recording.
The _Strata_ were plainly composed of three or more Heights of Clouds,
_sailing_ at great Intervals, one above the other: all which regularly
_vanished_, as he approached their respective Levels: as if _instantly_
thrown into the Circumference of a Circle, whose Radius was a Mile.
During the Ascent, in passing their supposed Level, the Clouds
_instantly_ appeared _far below_ him: and during the Descent, as far
_above_.
217. Quere: Is it not from the same Cause, that all Vapour is
_generally_ invisible to a certain Height and Distance from the Eye?
It being incontrovertible that more Vapours rise about +noon+, than
at any other Hour, particularly at Sea, while the Sun continues to
_shine_; which, notwithstanding, are wholly _invisible_, till arrived
at a _certain_ Height?
[Sidenote: Visibility of Vapours by mere Distance.]
And hence the Visibility of Vapours by _mere_ Distance, which contains
a sufficient Number of Particles to intercept and refract the Light,
without Cold, Condensation, or _actual_ Accumulation: viz. by
Refrangibility of those primary Rays of Light, which Air and Vapour
united are most _apt_ to reflect or transmit.
Mons. Saussure has proved by his Horse-Hair comparàble Hygrometer, that
“the Air shews Signs of _greatest_ Humidity an Hour after Sunrise, and
of _least_ Humidity, between three and four in the _Afternoon_.” But
the Air being _then_ also the hottest, will _dissolve_ or evaporate the
greatest Quantity of Vapours, and raise them _above_ the Hygrometer
(which by its _Heat_ will not retain, but on the contrary repel and
_dissipate_ them) to great Heights in the Atmosphere.
See “Essais sur l’Hygrometrie, C. 6, P. 315.”
218. In general then:
Is not the _Cause_ of the above Deceptions, _not_ an _Absence_, but a
_Transparency of Vapour_ to a certain Distance: (just as the Zenith
_appears_ +cloudless+, when the Air is _overcast_ around;) beyond which
Distance, the _Number_ and relative Proximity of Particles with Respect
to the Eye, is such, as to intercept the Rays of Light: _when only_,
they put on the _Colour_ of Air, and Form of Vapour and Cloud?
And hence the probable Reason, why +no+ _circular_ Horizon of the
Earth’s Surface was presented during the Excursion, Section 79: and
why it seldom has or can present itself to Aironauts or _Mountaineers_,
at any _considerable_ Height above the Region or Level of Clouds, even
tho’ Clouds do _not_ appear in the Air, either to themselves, or to
Spectators _below_.
This Point seems capable of Illustration by Analogy, from the
Impossibility of encreasing the _Magnitude_, and at the same Time,
_Distinctness_ of distant Objects, seen throu’ a _common_ Telescope;
on Account of the Quantity of Vapours between them and the Eye
_Which_ +vapours+ may be magnified till the Object appears confused
and obscure; and even at last become substituted in the Place of the
Object, under the Form of Opacity and _Cloudiness_.
219. The _greater_ the Height of the Balloon, the more _contracted_ was
the Circle of Vapour below it; and the more limited the Prospect of the
Earth’s Surface below the Vapour.
220. It seemed probable that the Sun shone as _bright_ on the Countries
around the Observer, as on Objects immediately below him: which Objects
coud not have been illuminated by the Sun’s Rays, darting throu’ the
+apparent+ and _contracted_ +opening+ under him; as the Rays which
shone on the Balloon, fell beyond the _Opening_, _obliquely_ on Clouds
which caught the Shadow of the Balloon.
221. The extreme _Rarity_ or _Tenuity_ of the Vapours was _evident_
from the _progressive_ Course of the Balloon, which was _always_ in the
Center of a _circular_ Opening, limiting the lower Prospects; except
when the Spectator lost all Sight of the Earth, by dense, watry,
intervening Clouds.
[Sidenote: Novel Situation peculiar to the Balloon, again described.]
This _august_ central Situation, +always changing yet still the
same+, had the most striking Effect on the Senses and Imagination.
Yet, however pleasing the Recollection of this +glorious appearance+;
however _strongly_ impressed, accurately described, or richly painted;
it must fall infinitely short of the original +sensation+. Unity and
Sameness were there contrasted with _perpetual Variety_: Beauty of
Colouring; Minuteness, and consummate Arrangement;—with _Magnificence_
and _Splendor_: _actual_ Immensity;—with _apparent_ Limitation:—all
which were _distinctly_ conveyed to the Mind, at the _same_ Instant,
throu’ the Intervention of the Organs of Sight: and, to complete the
Scene, was added the Charm of +novelty+.
CHAPTER XXXIX.
CONJECTURES ON THE CAUSES OF THE CIRCULAR TRANSPARENCY TO A CERTAIN
DISTANCE BELOW THE BALLOON, AND OF THE RED LIGHT FROM THE SEA AND
RIVERS, WHEN SEEN ABOVE THE LEVEL OF THE SUPERIOR CLOUDS.
[Sidenote: On the circular Transparency.]
Section 222. Quere: As Red is the heaviest and Blue the lightest
Colour; and as _red_ Rays blended at a certain Angle with _blue_
Rays, produce Opacity: further; as +red+ is the _predominant_
Colour reflected from Water, while in the Form of _dense_ Cloud, for
Instance at the Rising and Setting of the Sun; and +blue+ the Colour
always reflected from the light Medium of Air or Sky; Does not this
Mixture of least and most refrangible Rays, which, when aided with the
intermediate primary ones, causes a _Transparency_ near and round the
Eye of a Spectator placed either on Earth or among the Clouds; produce,
at a greater Distance and different Angle, such a Degree of Opacity, as
actually to give the Idea of Clouds surrounding him at a Distance?
The latter Part at least is true, that Vapour and Air, which are
_naturally_ qualified to _transmit_ +red+ and +blue+, rather than
any other Light, will, at a certain Angle, when _blended_, produce
an +opacity+. (See the Letter sent by +Newton+ from Cambridge to Dr.
Derham, in order to be presented to the Royal Society,—in “Miscellanea
Curiosa, Vol. 1, Page 109.”)
[Sidenote: On the red Light from the Sea and Rivers.]
Quere: May not the Rivers below act as a Prism; as Clouds, about
Sun-set or Sun-rise, do to a Spectator on Earth, and reflect only the
primary Colour +red+, the _heaviest_ and least refrangible Ray?
It being also considered that Refraction cannot change the primary
Colour: nor are Rays, in the Direction from below to the Zenith,
refracted; tho’ seen from a rarer into a denser Medium.
Possibly, a Pencil of Rays, in coming up from the River below may be
stripped or drained by the double Absorption of the Atmosphere and
River, and the Colour +red+ only, suffered to reach the Eye: “being
the last to quit its Basis the Water.” (See Morgan’s Observations on
the Light of Bodies, &c. &c. Phil. Trans. for the Year 1785, Part 1,
Vol. 75, Chap. 91.)
CHAPTER XXXX.
ON THE EXCESSIVE DIMINUTION OF OBJECTS ON THE SURFACE OF THE
EARTH, TO A SPECTATOR SITUATED ABOVE THE REGION OF CLOUD, AT THE
BAROMETRIC HEIGHT OF NEAR A MILE AND HALF, PERPENDICULAR.
[Sidenote: Recapitulation of the Scenery below.]
Section 223. The Earth’s Surface was presented to the Eye throu’ a
_circular_ Opening as already described.
This Opening discovered a _Plain_, smooth and level as a Die: a Sort
of _shining_ Carpet, enriched with an endless Variety of Figures
depicted _without_ Shadow, as on a Map: what was really Shadow forming
a separate Colour, and not considered at the Time, as _Shadow_. The
Objects were distinctly marked, and perfectly known to be Miniatures of
the Face of Nature.
All was _Colouring_: no Outline: yet each Appearance curiously defined
by a striking Contrast of simple Colours, which served to distinguish
the respective Boundaries with most exact Precision, and inconceivable
Elegance.
+Red+ Rivers, +yellow+ Roads, Enclosures +yellow+ and _light_ +green+,
Woods and Hedges _dark_ +green+, were the only Objects clearly
distinguishable, and their Colouring extremely vivid. The Sun’s Rays
reflected from the Surface of the Sea, and other Waters, dazzled the
Sight.
+All+ living Creatures were invisible.
224. The Area of each Inclosure, computed to contain a certain Number
of Acres, was seen from above under the Form of a Miniature Picture of
a certain Magnitude or visible Extension, perpetually diminishing, as
the Eye recedes to a greater Distance.
And the Case is similar, whether the Miniature be seen from _above_, or
_along_ the Ground.
The Miniature also lessens as the Distance encreases, according to a
certain Proportion so exactly;[49] That,
1. If the _Distance_ and _Magnitude_ of a tangible Object be known
by Mensuration; a Judgment is formed, and Laws laid down, for its
corresponding _Miniature_ on the Eye.
2. If the _Miniature_ be seen, and _Distance_ known by Mensuration; the
Mind forms a Judgment of its tangible _Magnitude_.
3. And lastly, if the _Miniature_ be seen, and _Magnitude_ of a
tangible Object is known by Mensuration; the Mind makes an Effort, to
the Estimation of its Distance from the Eye.
These are some, among many Modes of Comparison, by which the Mind
acquires a tolerable Degree of Proficiency, in estimating _Distances_
of familiar Objects, _known_ from the Appearance of their respective
Miniatures on the Fund or Bottom of the Eye.
And so far most Theories agree.
But such _ocular_ Test is only true, while the Comparison is made in
_nearly_ the same Medium.
For an Object, if seen at the same Distance _along_ the Ground, will
appear less as it rises above it; and least in the Zenith; as the Sun
and Moon, at Setting or Rising, appear _large and oval_; but at their
greatest Elevation, are _small_ and _round_: because being seen, when
passed out of a Medium impregnated with Vapours, which in some Measure
intercept the Rays of Light: for the +fainter+[50] a distant Object
appears, the _greater_ it is apprehended to be.[51]
Possibly indeed an Object at the same Distance, if brighter at one
Time than another, will _contract the Pupil_ in Proportion to its
Brightness: which may have the same Effect, as if the Object had made
a _smaller_ Miniature on the Retina; and will regularly strike the
Mind with an Idea of _Magnitude_, _only_ equal to its corresponding
_Contraction_; i.e. less, when the Object is bright, and greater when
faint.
225. If a like Reasoning be applied to the Ascent of Balloons; and it
be said that they do not rise so high as is imagined, because their
Magnitude is diminished, merely from being elevated into a Portion of
the Atmosphere _least_ impregnated with Vapours; it will follow, that
to a Spectator in the Balloon; known Objects on the Surface of the
Earth below,—being seen from a rarer into a denser Medium, also into
one which contains a great Quantity of Vapours;—shoud appear _larger_,
than when seen along the Ground, at a Distance equal to its Height in
the Balloon: all which is contrary to Matter of Fact: particularly if
the Barometer gives a proper Estimate of the Height, of which there
is little Doubt: a proper Allowance being made, _in certain Cases_,
on Account of the Refraction: for, as before mentioned, (Section 44)
Objects seen from the Balloon at a Mile and Half _barometric_ Height,
continued, with invariable Uniformity, to suggest the Idea of at least
seven Miles.
226. By a general Comparison of Enclosures, and of separate Buildings
when they coud be distinguished from the Balloon above the Region of
Cloud, with the most distant Extremities, (on the horizontal Level) of
Fields or Houses situated along the Sides of Hills or Mountains, at a
known Distance by Miles, making Allowance for their being seen in a
straight Line;—the latter seemed at least five Times _larger_ than the
_former_: supposing them at equal Distances.
To give an Instance. Supposing the most distant Extremities of a known
Building or Enclosure, situated on the Side of a Hill or Mountain,
presented a Miniature of a _familiar_ Magnitude to the Eye of the
Spectator on the Ground, at the known Distance of a Mile and Half; the
same Object when seen from the Balloon at the same _barometric_ Height,
appeared full five Times less.
This Comparison was made by Memory, the Morning after the Excursion,
tho’ suggested while in the Balloon, from the wonderful Minuteness of
all Objects then presented to the Eye.
The Author being likewise familiarized to judge of Heights; having
been on several of the chief Mountains in Europe: also, of comparative
Distances, from his Situation near a large City, in a populous,
enclosed Country; on a high Plain, within View of the Sea, Mountains,
Hills, Enclosures, Buildings, and Objects whose Magnitude and Distances
were known.
227. The Balloon itself, a Globe twenty-five Feet in Diameter, was seen
in the Air on the Day of Ascent, at the Distance of 19 Miles.
[Sidenote: The Magnitude of Objects seen from the Balloon compared with
those of the Sun or Moon near the Meridian, when seen from below.]
228. The Reason already given, for the Solution of the famous Question
concerning the apparent Magnitude of the horizontal Moon, seems no
less applicable to Objects on the Earth’s Surface, when seen from the
Balloon: which _Diminution_ of Objects _below_ confirms the Defect of
Dr. Smith’s Hypothesis.
For, as they appeared _extremely bright_; being shone on by the Sun,
and seen throu’ the Air in a perpendicular Line, containing the least
possible Quantity of Vapour; the Brightness must have exceeded that
of the same Objects, when seen along the Ground: and consequently the
Miniatures of the former must have been less than the latter, and also
their respective Distances _seem greater_.
CHAPTER XXXXI.
CONJECTURES ON THE CAUSES WHICH INFLUENCE THE DESCENT OF BALLOONS
IN THEIR PASSAGE OVER WATER.
[Sidenote: Recapitulation of Facts.]
1. Conjectures concerning the regular Tendency of the Balloon to
_descend_ on its _Approach_ towards +water+.
2. Its _greatest_ Descent, when in the Zenith, over the Middle of
Rivers.
3. Recovery and _Re-ascent_ to the former Level, as it _recedes_ from
them.
Section 229. Article 1. On the first Ascent in the Castle-Yard,
Chester, the Balloon gently moved towards the River Dee, and the Sea.
And woud probably have gone out to Sea, if the ascensive Power had not
presently raised it above the Influence of the Water; into an upper
Current of Air, which was visible at that Time, and for two Hours
before the Ascent, by the Motion of superior Clouds in a safe Direction
towards the Land.
229. 2. The Balloon was _affected_ in passing across the River Goway,
and Trafford Meadows, which are a Mile wide: first moving Westward,
and again towards the Sea; making several Curves: then resting and
_lingering_ between Great and Little Barrow: as the Aironaut was _well_
informed by Persons of _Veracity_, who observed it: his Attention being
engaged at that Time by other Objects.
229. 3. A proportionable Effect was observed in _crossing_ a small
Brook near Alvanley.
229. 4. The River Wever and its broad Meadows above Frodsham-Bridge
actually stopped the farther Progress of the Balloon: tho’ its Course
was _merely_ +across+ the River.
The Deviation was gently tho’ _invariably_ towards the +sea+: and, if
not _timely_ prevented, the Balloon must have fallen in the Middle of
the Channel.
229. 5. The same Case woud have happened on the Re-ascent at Bellair;
if the _levitating_ Force had _not_ as at first, overcome the Influence
of the +waters+, and lifted the Balloon into the _same_ upper Current,
which continued to move in its former safe Direction.
229. 6. Different Branches of the Duke of Bridgewater’s Canal near
Preston-Brook might _possibly_ affect it in a small Degree: and, tho’
Clouds a little afterwards, secluded the Aironaut from a Sight of the
Earth; yet the Balloon was known to hang, for some Time, over the
Mersey near Warrington.
229. 7. The Balloon descended and alighted on the Middle of a large
Tract of wet Moss Ground.
The Writer saw Sadler’s Balloon rise at Manchester, the 11th May, 1785,
and descend near Blencow-Bridge, at the Conflux of _two_ Rivers.
The above Facts give sufficient Indications of the constant Tendency
which Balloons have, to descend on Water.
CHAPTER XXXXII.
Section 230. Three Causes seem generally to concur in producing the
Effect of Descent, over Water.
1. The Water itself.
2. The Air above it.
3. Change of Temperature,
Section 231. Article 1. So long as Gass escapes from the Balloon; it
will be instantly and _reciprocally_ attracted, throu’ the _Crevices_,
by the Moisture contained in the _Air_, particularly over _Rivers_:
its specific _Gravity_ within the Balloon, woud be encreased,[52] and
consequently the Balloon itself rendered less buoyant:
The Gass woud, on the contrary, be repelled by _electric_ Air: which
woud lessen its Tendency to escape, throu’ the Pores of the Silk.
But it is _presumed_ that Air-tight Balloons will be little affected by
_external_ Moisture.
231. 2. Moist Air over Water being generally cooler than over the
adjacent Land, will, so long as the Gass continues at its former
Temperature, assist and raise the Balloon _thus_ moving into a _denser_
Stratum: but no sooner is the Balloon contracted by the external Cold,
than it descends into a Medium of Air, whose specific Gravity is
proportionable to the contracted Bulk of the Balloon, and rests when
equal to it.
231. 3. Water is also a Conductor of Electricity, tho’ a feeble one:
and there is moreover a strong chemical Affinity between +water+,
inflammable Air, Gasses, Floguiston, and Electricity.[53]
231. 4. Water will therefore +conduct+ the Gass to itself: i.e. will
draw the Balloon _downwards_, and with accelerating Velocity; as the
Attraction is stronger, the nearer the Water.
231. 5. But if the Air over the Water be warmer than that over Land;
then the Balloon, moving into a warmer Medium, as over the Sea in
frosty Weather, most undoubtedly descends: till the included Gass
has received the additional Encrease of Temperature from that of the
Air, at which Time it will have a Tendency to reascend, and will rest
suspended in Equilibrio, as in the former Case.
The above Causes however may be considered, as _trivial_.
The first may be avoided by making the Balloon _Air-tight_: and the
second easily guarded against by throwing out a little _Ballast_.
The _only_ formidable one, if any, is
+the depression of the atmosphere+.
This it will be necessary to consider with some Degree of Attention.
CHAPTER XXXXIII.
Section 232. Whoever consults Antiquity,[54] or is acquainted with
modern Mèteorism, will ascent to the Truth of the Facts there recited,
viz. That the Storms of +dispersion+ called _Prester-John_, and
_Ox-Eye_ over Table Bay at the Cape of Good-Hope (not to mention
those of +collection+, as _Whirlwinds_[55] and _Waterspouts_;)
_descend_ on Sea and Land from the _middle_ Regions of the Air, often
_perpendicularly_ +downwards+: and then blow violently from a Center,
to all Parts of the Compass at once: a necessary Consequence of their
beating _forcibly_ upon the Land or Water.
The Ancients maintained that the Origin, of Wind was a mere
_Depression_ and _Percussion_ from the Cold of the middle _Region_:
and it shoud be remarked that their Observations were made on the
_Continent_, and in _warm_ Climates.
Now what is seen to Excess in the _hottest_ and _coldest_
Climates;[56] most probably takes Place, in a less Degree, in temperate
ones.
Therefore, on a Change of Weather, the upper Atmosphere _descends_:
whether its Effects are _Cold_, as in Winter; _Warmth_, as in Spring;
_Wind_ or _Wet_; at the proper Seasons of the Year.
233. The Balloon, with which Dicker Junior ascended at Bristol, April
19, 1784, on a +windy+ Day, proved the Truth of the Conjecture: for
tho’ the Aironaut threw out most of his Ballast; yet after each Ascent
and Recovery, he was repeatedly darted _downwards_ +even+ with the
Ground.[57]
234. A similar Event happened to Crosbie, in his Passage over the Sea
from Dublin to England; for, tho’ he too discharged his Ballast, the
Wind kept him _down_ and +even+ with the Water.
The Weather at that Time seems to have been an Εκνέφιας, Procella,
Percussion, Squall, or Tornado, i.e. a Storm of +depression+, and
+dispersion+.
235. The Eknèfiai Winds come from cool Points on each Side the North.
Bacon also observes that all +boisterous+ Winds, as Procella, Typho,
and Turbo, have the evident Direction of a Precipice, or Projection
_downwards_, more than other Winds: they seem to rush down like a
Torrent or Cascade: and are then reverberated or beat back from the
Earth, in all Directions.
Stubble, Corn, or Hay in the Meadows are raised, and spread around in
the Form of an +extended canopy+, (_inverted Cone_, _elliptic Solid_,
and _hyperbolic Curve_.) See “Bacon’s Historia Ventorum”, Pag. 43, ad
Articulum 10.[58]
236. If then it be allowed to reason from that Analogy which took Place
in most of the Cases already mentioned; the _gentler_ Depression.
of Balloons over Water in _milder_ Weather, may be owing to a Cause
somewhat similar, tho’ not so evidently an immediate Object of the
Senses, viz. _an actual tho’ invisible Descent of Air upon the Water_.
237. Blanchard in his Passage over the Sea from Dover to Bologne in
France, when near the Middle of the Channel, suffered an unexpected
Depression, and at the same Time was nearly +becalmed+.
A +calm+ also took Place on the Irish Sea: which must have prevented
Crosbie from landing,—without _Wings_, or some _propulsive_ Machinery,
connected with the Balloon.
238. Lunardi rose from Liverpool when the Wind blew _boisterously_:
yet was _becalmed_ twenty Minutes over the _broad_ Turn of the Mersey
near Ince, when above the Level of the Wind: and, descending into
the same Stream of Wind, was hurried along towards Beeston-Castle in
Cheshire.
CHAPTER XXXXIV.
[Sidenote: Depressing Columns of Air known to the Egyptians.]
Section 239. The Existence of depressing Columns of Air was well known
to a People more ancient than either Romans or Greeks.
240. The sultry Climate of Egypt, whose Situation is that of an
extensive Meadow watered by a _broad_ River, and enclosed by Mountains
to the East and West; consequently not subject to general horizontal
Currents of Air, except along the Line of its Meridian,—is _the
Country_, wherein Columns of +cool+ Air descending on the Water, woud
be soon observed.
And they, in Fact, were almost the only People who applied the
Observation to common Life: having, according to Herodotus, as well as
later Writers, built lofty Structures +open at the top+. By which Means
the cool Air +rushing+ downwards greatly refreshed the Inhabitants.
The ancient Pantheon, at present called All Saints Church, now standing
at Rome; built in the lowest Situation of a Street named the Piazza di
Navona is on this Construction: and the Hint probably taken from an
Egyptian Model.
241. In all inland Countries, whose Lakes are frequently surrounded
by Mountains, as Bala-Pool in North-Wales; those of Westmoreland
and Cumberland; the Lake of Geneva in Swisserland;—the Air rushes
+forcibly+ on the Surface of the Water in descending Torrents: this the
Writer has frequently observed.[59]
(In other Languages, the Words applicable to Wind on a Lake, or
the Ocean, signify Descent: as, Καταβαινω, and Επικειμαι· also the
Northerly or _descending_ Wind corresponded to the Εκνὲφιας while the
Southerly or _ascending_ Wind answered to the Απογη.)
All this, which may be allowed to take Place in _bad_ Weather, may
perhaps be excepted to, in _fine_, and still more so, in the _finest_
Weather.
As the slightest Change is first observable on the Surface of Water,
whether on Lakes or the Ocean, the _Descent of Air_ in the finest
Weather is familiar to Mariners by the Appellation of +light airs+,
playing in Eddies: and particularly in the _variable_ Latitudes; i.e.
between 32 and 42: to these the Writer can also witness: as well as on
small and large inland Lakes, by partial _Dimplings_ and _Rufflings_ of
the Surface.
OBJECTION TO THE THEORY REMOVED.
242. It may be objected to the above Theory, that the Wind plainly
blows in an horizontal Direction, as may be seen from the Motion of
Clouds and Trees.
To which it may be answered, that if Clouds are not beside the
Question; as it is not asserted that a single Column of Air presses
from so great a Height to the Earth; (tho’ it be the Case in Squalls;)
yet it is extremely difficult to determine whether Clouds move in a
Direction exactly parallel to the Plane of the Horizon: and it is
much more probable that they are in a perpetual Change, _encreasing_
or _melting_; rising or falling, according to the _Pressure_ and
specific Gravity of the _Medium_ in which they float; its Tendency to
Moisture or Driness, Cold or Heat; also the different Combinations and
Decompositions, with Respect to which, the Atmosphere is in perpetual
Variation.
The Motion of Trees, if carefully attended to, seldom shew Effects of a
regular horizontal Current.
And since the more _powerful_ the Wind; the more evident and accurate
may be the Observation; it will be found, that the _first_ general
Effect is an oblique Depression, succeeded by a Recovery or instant
Exaltation: then a momentary Pause, or actual Retreat of the Wind; and
in a few Seconds, a Return of the depressing Torrent.
But the strongest, and, at the same Time, an irrefragable Proof, is by
_Appeal_ to Men of _Science_ in the Navy, or to skilful Pilots, who
are conversant with Winds and Waves; who have weathered Storms off
Cape Hatteras in Latitude 36; (where probably the Wind is perpetual;)
or have made an East-India Voyage:—whether, if a Gale blew in an
horizontal Direction +only+; the Ocean coud produce such an Inequality
of Surface: or whether when the Sea runs +mountains+ _high_; the
tremendous Surges must not arise from the _violent_ Action of Winds
repeated at Intervals, sometimes _descending_ perpendicularly; but
oftener in forcible elastic Torrents of oblique +depression+, and
instant _Resilition_?
CHAPTER XXXXV.
[Sidenote: A _gentle_ Depression of Air over _moist_ Places in _fair_
Weather.]
Section 243. Intimations of depressing Columns in moderate Weather,
are the _sluggish_ Clouds, which often make their _first_ Appearance,
and remain longest, nay almost continually, _over_ and _along_ great
Rivers, and Chains of Mountains, both during a Calm, or from whatever
Point the Wind blows.
And hence the greater Quantity, Violence, and Continuance of Wind and
Rain, which then _descend_:[60] also of the _greater_ Purity of the Air
_during_ such Descent.
244. As, therefore, it is plain that atmospheric Air +descends+
_frequently_, both in bad and fine Weather; if a Cause can be assigned
so general, as to make it probable, that such +depression+ does almost
continually take Place:—tho’ at present the Effect is only evident to
the Senses, by actual Experiment in the Passage of Balloons throu’
such Columns;—it will be sufficient to put Balloonists on their Guard
against the Effects of such _Depression_.
245. In order to investigate the Theory of Depression; it may not be
unacceptable, particularly to those who have not had Leisure to peruse
the Experiments on Air, by Dr. Priestley, or the Collection on the same
Subject by Cavallo;—just to extract a few short Quotations, on the
chemical Affinities of Air and Water.
246. Article 1. “Water, as Rain, imbibes only the pure Air of the upper
Regions, leaving the lighter and floguisticated Air to ascend.”[61]
246. 2. Felìcè Fontana says, “Common Air receives an Encrease of Bulk
and _Elasticity_ from being shaken in Water.”[62]
246. 3. Air absorbs Water, and Water absorbs Air:[63] and the
Absorption of Air by Water is promoted by Agitation: it also absorbs
twice as much _defloguisticated_ Air, as common Air:[64] the whole
Bulk of the Air absorbed being equal to one-twelfth of the Bulk of the
Water: yet the Bulk of the Water seems but _little_ encreased: the Air
being contained within the Interstices of the Water.
247. The following is a pretty and an easy Experiment, to shew how
the +absorption of water by air+ takes Place, under the immediate
Inspection of the Observer.
Admitting the Sun’s Light into a Room, throu’ one Window only; pour a
Pint of _boiling_ Water into a large Bason: hold the Bason, which will
not be half full, next the Light, in such a Manner, that the Sun may
shine on the Water and Bason; yet the Eyes be shaded by the Top of the
Window Frame.
Incline the Side of the Bason towards the Light, so that the Water may
rise even with the Top.
The Eye being placed just above the upper Side of the Bason, farthest
from the Light; look on the Water.
You may then observe the Surface of the Water next the Light, refract
the Sun’s Rays, and produce the primary Colours, particularly the
+red+ and +green+: which tho’ _transient_, _continue_ to be _seen_
in Succession; as Vapours rise above the Surface of the Water. Their
_first_ Ascent is plainly discoverable: remaining above its Surface,
in the Form of _small Dust_, gently agitated, not _separately_ but as
a _whole_. Nor do they seem to rise into Steam, till assisted by the
Action, and Contact of _dry Air_, which like _dry_ Spunges, _licks off_
and absorbs the small Dust already accumulated by the Force of the Heat
from below, and then becomes visible under the Appearance of Steam,
flying off in distinct hollow Vesicles.
The more _still_ the Air of the Room, the more slowly will the Spunges
of Air come in Contact with the Body of small Dust.—Besides the small
Dust already mentioned; the Heat will detach solid Globules of Water;
which will remain floating on the Surface of the Body of Water: till
the dry Air descends and transports them with it; the Air at the same
Instant dissolving the solid Globules into hollow Vesicles.
But the most extraordinary Phenomenon, and which cannot be mistaken,
is, that as soon as a Spunge of Air has dipped into the Surface of
Water, and received its Lading; the Vesicles continue to accumulate,
till another fresh Spunge descends in a similar Form, which may be
traced upon the Surface of the Water, and seen in its Shadow, or rather
in Beams of Light at the Bottom of the Bason, at the Instant it has
flown off with its Burden: for that Part of the Surface of the Water
transmits new Rays of Light, on Removal of the Vapour carried away by
the Dip and Play of Air.
248. The Removal of the Vapour, likewise exhibits a curious Appearance
on the Surface of the Water: which seems as if divided into irregular
Parcels detached from each other; like the reticular Daplings visible
on the under Side of Clouds elevated to the highest Stratum of the
Atmosphere, and there evaporating or dissolving.
249. So powerful is the Attraction between Air and Water; that, while
the Steam is rising above and round the Sides of the Bason; _Waves
of fresh Air_, by Intervals, press the exterior Parts of the Steam
_inwards_, in order to get at the Surface by descending into the Bason.
This Operation is best discovered, when the Bason is held _even_.
And the whole Process may be observed more distinctly, if the Bason
is raised and fixed on a Frame, near the Height of the Eye of the
Observer, standing upright: who will then be able to trace minutely the
exact Form of the Steam, and Insinuation of the Waves of Air into the
Center of each Curl, or rising Curvature: an Appearance, similar to
which, may be seen in _Water_ flowing from a small Orifice in a close
Vessel; the fresh Air forcibly entering in an opposite Direction;
forming a visible Cavity and Curvature in the Center of the Stream. See
Halley’s Experiments on Evaporation in the open Air, and in a close
Room, in Lowthorp’s Abridgement of the Phil. Trans. Vol. 2, P. 108.
Having once remarked the foregoing Process at Leisure; the same may be
seen over any open Vessel of Water just warm enough to emit visible
Steam: but the Air shoud be as _still_ and _calm_ as possible: the
Steam never rising from all Parts of the Surface at once; but a
depressing Spunge of Air always descends to the Surface, the Instant a
Lamina of Vapour has been detached.
Such is the regular and invariable Process of Evaporation.
The same Process may be distinctly traced over the Surface of a Piece
of Water or River, the Air being perfectly calm, in a gentle Frost,
at Sunrise, particularly in Autumn, while the Water retains a Warmth
superior to that of the Air.
250. Hence it follows that _as much light_[65] and _warm_ Air as is
raised with the Steam by Evaporation from the Surface of any Water;
_so much heavy_ and _cool_ Air is +instantaneously+, constantly, and
forcibly +depressed+ upon its Surface, in order to supply the Vacancy,
restore the Equilibrium, and continue the Evaporation.[66]
251. Now, besides the mutual Affinity that Water has to almost all
Kinds of Air, and to Floguiston; added to its Power of Absorption;
and as the +sea+, particularly in Summer, also +rivers+ and _damp_
+meadows+ are generally _cooler_ than the Lands and Countries bordering
on them; Currents of _damp cool_ Air press forwards to supply the
Defect or Vacancy caused by Heat, Rarefaction and Elevation of _dry
warm_ Air, which is necessarily, and almost constantly rising into
the Atmosphere, from heated Lands, Plains, and gentle Eminences _long
shone_ on by the Sun.
252. Consequently the pure, cool, defloguisticated Atmosphere, is
almost continually descending from above; sometimes imperceptibly,
often forcibly, on the Surface of the Sea, the Channels of Rivers,
Meadows, and all wet Land. Which Depression acts, in Proportion to
its Strength, on the Balloon; and always with a sensible Effect: for,
being in Equilibrio with the Air at all stationary Heights; the _least_
Depression of the Atmosphere makes the Balloon descend, considerably.
253. This Reasoning is, in many Cases, applicable to the Air, and
consequently the Weather and Cold of Mountains.
Nor can it otherways be accounted for, why the Snow is perpetual,
and the Cold so intense, on Mountains under the Equinoctial, and
between the Tropics: but which admits an easy Solution on the above
Hypothesis.[67]
CHAPTER XXXXVI.
Section 254. The Subject of +depressing torrents+ requires an accurate
Investigation: as it will serve to point out the proper Time of Day or
Night, when an Aironaut ought so to calculate his Voyage, as to arrive
over the Middle of the Channel, or Arm of the Sea, at some particular
Hour: in order to wait for a Sea Breeze which may waft him to the other
Side.
A Point not difficult to be ascertained.
Also, this Idea of +depression+, if properly considered and digested;
may prove a sufficient Foundation on which to establish a new Theory
of the _Weather_, so ill determined at present, from its _aggregate
Weight_ or _Elasticity_ only, as indicated by the Barometer.
255. If a Conjecture may be formed on a Subject, material in itself,
yet of which so little is actually known; woud not _the proper Time_ of
undertaking a Voyage over the Channel be such, that the Aironaut shoud
find himself three Parts of the Way across, by +nine+ _o’Clock_ in the
Morning?
256. In _warmer_ Climates, where the Seasons are more regular; the
_Land-Breeze_ blows to Sea from Midnight till X. in the Morning: at
which Time, the _Sea-Breeze_ blows to Land; continues till V. or VI. in
the Evening; and is succeeded by a +calm+, which lasts till Midnight.
Whence it follows, that during the Time of the Sea-Breeze, there is
a constant Tendency towards a +gulph of air+, _along the Middle_ of
the Channel: the Equilibrium of which is as constantly supplied by a
_Depression_ of the upper and in general cooler Strata of Air; and
therefore a _dangerous_ Time for the Passage of Balloons.
On the contrary, during the Night, and till ten in the Morning, there
is an _Accumulation_ of Air, _along the Middle of the Channel_: which
consequently is a proper Time to ensure a _safe_ Passage; by the
Assistance of +wings+, or some +propulsive+ Machinery.
[Sidenote: Of the horizontally calm mediocèanal depressing Current.]
257. The Deficiency or Vacuity being supplied from the etherial
Regions; it might be taken for granted, that such Ether must be
_considerably_ lighter than the adjacent common Air on an equal Level,
and therefore _proportionably_ dangerous for the Passage of Balloons.
But if it be considered that such Air, acting as a +wedge+, or more
probably in the Form of an hyperbòlic Solid,[68] to fill up the
Vacuity, descends with Rapidity from a _colder_ Atmosphere impregnated
with aqueous Vapours _invisible from below_; and that both the Air
and Vapour have reciprocal Affinities and Attractions, electric and
mechanical, with the Body of Water beneath them; and are often rendered
still cooler by its constant Agitation and _Evaporation_; also, that
the Supply being immediate and cotemporary, with the +double tide
of air+ flowing from the _middle_ over the _opposite_ Shores;—there
possibly may be little or no Difference between the aggregate or
_barometric_ Gravity of _such_ Columns, and those which are formed
by the Sea-Breeze on either Side of them: therefore the Descent of
Balloons is owing, among other Causes, to an almost perpendicular
actual Depression of the superincumbent Atmosphere.[69]
Following up the Idea of a Sea-Breeze, blowing, at a Medium, for 20
Miles over Land; altho’ the Stratum of the +lower current+ of Air, or
Sea Breeze, may not exceed +half a mile in depth+, measuring from the
Ground upwards; nearly equal to 26 Inches of the Barometer _above_,
the Thermometer also _above_ being at 55, i.e. _Temperate_:—yet this
Observation may prove of essential Service, while the +upper current+
of Air, i.e. the general Wind blows +towards+ the Sea, (which will be
found to take Place more _frequently_ than is, at present, imagined;)
or while the Balloon is influenced that Way; as was the Case with
Sadler and his Companion when over the Nore: who, on his accidental and
sudden Descent, fortunately found Safety in the +sea-breeze+.
Which Breeze was sought for, and made Use of by the Author, when in the
Balloon, near Frodsham, in Cheshire.
For, as the Sea-Breeze is pretty general, Aironauts shoud not be too
apprehensive: as they have it in their Power, by proper Management, to
drop into the Breeze—for +either shore+: if they are provided with a
Machinery to waft themselves across the intermediate _depressing_ or
_accumulating_ +mediocèanal column of air+: which Space, between the
two Shores, is, as before hinted, frequently +becalmed+.
258. Further: as the above Theory of a _mediocèanal_ Depression seems
to receive additional Confirmation from _each_ Balloon Experiment;
Lunardi _descending_ on the 5th of October last, when near the
Middle of the Bay of Edinburgh or Firth of Forth;—it may be found
_prudent_, to keep the Balloon continually rising, till the Aironaut is
_one-third_ of the Passage _over_.
258. 2. For if the general Wind in the upper Current be not strong; the
Aironaut may expect to be _becalmed_, with Respect to the horizontal
Direction of the Current, the Instant he finds, by the Rise of the
Barometer, that the Balloon _descends_; i.e. when it is acted upon
by the depressing Column: in which Case, the _higher_ he has soared,
the _safer_: as he will have more Room and greater _Latitude_ for
Exertion by Means of the Machinery: which Machinery will be greatly
_aided_ by the Force of the descending Column or Gravity; and will
act on a similar Principle with the Ferry-Boats over the River Po in
Italy; which are a Sort of horizontal Pendulum. For the Aironauts will
continue to _descend_, at the same Time that their _Wings_ furnish the
Means of a progressive Motion.
Therefore, before the Time that the Balloon has reached the Surface
of the Water; they will have crossed the depressing Column; and find
themselves wafted _gently_ by the _new_ Sea-Breeze setting in towards
the opposite Shore.
259. If the Aironaut _rises up_ to Sea with a Wind blowing from the
Land on each of the opposite Sides of the Channel, and arrives above
the Middle of the Channel, while the same Wind remains; it is probable
that the Balloon will continue to rise higher as he proceeds towards
the Middle, _where_ the +mediocèanal accumulation+ has for some Hours
taken Place; and therefore he need not be under any Apprehension of
falling: but, as before, it being probable he will also be _becalmed_;
the Necessity of propulsive Machinery is equally urgent, in order to
pass the Center of the _Accumulation_: after which, the Balloon will
ride Home to the opposite Shore in the new Sea-Breeze, by _that_ Time,
just beginning to set in.
260. With the Assistance of propulsive Machinery, it is imagined the
Aironaut may be enabled in a few Minutes to force throu’ the calm
mediocèanal Accumulation, or Depression: after which, he will have
little Occasion to make Use of it.
261. +Sunrise+ is, probably, the +safest+ Time of all, to ascend
towards the Sea, with an _Air-tight_ Balloon: arriving with the
Assistance of the Wings, throu’ the _calm_ mediocèanal Accumulation:
and there waiting till the new _Sea-Breeze_ sets in to the _opposite_
Shore.
CHAPTER XXXXVII.
[Sidenote: Difficulties, proposed by Mons. Sauffure stated; and their
Solution attempted.]
Section 259. It may be observed here, that the two Difficulties
proposed by Sauffure, are, in a great Measure, removed; in admitting
the Doctrine of mediocèanal _Depression_, and consequent alternate
_Accumulation_,
In a distinct Chapter, treating of the Variation of the Barometer,
which he allows has Need of farther Explanation; he asks (Page 308)
what Reasons can be assigned, why the _East_ Winds, which are _cold and
dry_, make the Barometer _descend_, in England and Holland: yet, the
_West_ Winds, which are _moist and temperate_, make it _rise_?
The East Winds _here_ blow chiefly in Spring.
Now it is universally agreed, that the Sea, is sooner heated by the Sun
than the Land: and on Account of the marine Acid exhaled,[70] is also
less cold,[71] during that Season, in the same Latitude.
In Spring, therefore, the great Atlantic or Western Ocean, being
_less_ cold than England, Holland, and Eastwards; the Air pendent over
the most extensive Tract of _dry and cool Land_ in the World, rushes
Westwards to supply the Equilibrium of _warm light_ Air rising upwards,
and causing a temporary mediocèanal Accumulation: which (altho’ the
specific Gravity of the cold Air is greater) must produce an actual
Deficiency in the aggregate Weight of the Atmosphere over England and
Holland: consequently the Barometer falls.
Again: the West Winds which blow at other Seasons; if, in Winter;
are not frequent, except about Noon after frosty Nights which have
equalized the Air for the Transmission of vigorous Sunshine: and shoud
be looked upon as (what they are really observed to be) _low_ partial
Sea-Breezes, or +eddy+ _Currents_, insinuating themselves near the
Surface, and setting Eastwards frequently against the upper and more
general Winds; and therefore produce a temporary Accumulation.
If, in Summer; the Supply of cool Air to the heated Land, being
made not only from the _Northern Ocean_, and lofty _Mediterrànean
Mountains_; but also from the _Atlantic Breezes_; the latter, tho’
_moist and temperate_, must also tend towards an Accumulation of the
Atmosphere over England and Holland: and therefore the Barometer rises.
CHAPTER XXXXVIII.
[Sidenote: Facts and Observations tending to confirm the Doctrine of
Accumulation and depression.]
Section 260. Before the Subject of mediocèanal Accumulation and
Depression of Air, is wholly quitted; it may be well mention and
compare a few Facts and Observations, which will elucidate the
Doctrine; and in their Turn, receive Light from it.
261. If, in the Middle of a _hot sunny_ Day, Vapours lighter than the
Air, were to rise from the Ocean, (which they will continue to do, in
hollow Vesicles or Bladders, till the Expansion breaks the Bubble, at
which Time the Water woud fall to the Earth, if not drank up by the
Attraction of _dry_ Spunges of Air;) there woud be a constant Wind
blowing from _Land to Sea_, to fill up the Chasm: but at such Time, the
Land is more heated than the Sea: therefore hot Air and Vapour arise
from both; and the Breeze, on the contrary, blows from _Sea to Land_;
consequently if the Vacuities were not _continually_ supplied from the
etherial Regions, and from the Ocean, all Animals woud actually die,
for Want of Air, as in a _hot close_ Room.
Such Supply is therefore constantly made, by Depression of the
Atmosphere, and Absorption of the Water.
262. What happens on a great Scale, above the Ocean, as _before_
hinted; probably, happens on a smaller, over Channels or Arms of
the Sea: and on a still smaller; over and along Rivers, Brooks, wet
Meadows, and damp Grounds.
263. In the variable Latitudes on the Atlantic Ocean; _cool fresh_ Air
is supplied from above, by descending Vortices of Wind and Showers:
i.e. _Storms_ of +collection+.[72]
264. It may be remarked, in Confirmation of the above Doctrine,
that triangular or Latteen Sails are used, and more useful, in a
Mediterranean Sea, surrounded by high Lands, from which the Wind
suddenly descends in Squalls; than in the open Atlantic, where the Wind
is more equal.
264. 2. Perhaps there cannot be a better Account of the depressing
Torrent of Air, than that which Bacon has given, in describing the
Motion of Wind on the Sails of Ships, in a _Squall_.
“All Wind acting on the Sails of a Vessel, tends to depress or sink it.
Wherefore _in strong Gales_, they first haul down the Yards, and take
in the Topsails: afterwards all the Sails: cut away the Masts: throw
the Lading overboard, the Guns, &c. to lighten the Vessel, and keep her
above Water.”[73]
CHAPTER XXXXIX.
[Sidenote: Torrents of Air on _Etna_, and _Teneriffe_.]
Section 265. With Respect to Mountains: on reading what Travellers have
written, particularly Ullòa;[74] they seem to answer the Intention
of supplying cool Air to the surrounding Plains, or Continents; by
Depression and Condensation: and also, if on Islands; to the Sea
itself.
266. Brydone, in his Tour throu’ Sicily and Malta, in 1773;[75] giving
an Account of his Ascent to the Top of Etna, says, that at the Foot of
the Crater, the Snow was frozen hard and solid:[76] and that the Crater
was so hot; it was impossible to descend into it.
Further: “that the Smoke rolled down from the Sides, like a Torrent:
till of equal Gravity with the Air, when it shot off horizontally;
forming a long Track, according to the Direction of the _Wind_: which
there rose to a +violent+ Degree: so that it was with Difficulty he
coud settle the Barometer for an Observation.”
He also adds “that _Clouds_ began to _gather_ round the _Mountain_; but
were _dispelled_ by the Wind.”
Now from the foregoing Theory is it not probable to suppose, that a
_Torrent of Air rushed_ continually down from the etherial Regions,
not only to supply the Fire of the Crater; but also the Vacuity caused
by the perpetual Elevation of Vapours and heated Air from below:
the Torrent likewise _depressing_ into the Track with itself, the
Volumes of Smoke which were seen to roll directly down the Sides of
the Mountain: that this descending Torrent of Air, in its Progress,
dispelled the Clouds forming round the Sides of the Mountain, by the
Ascent of warm Vapours condensing, as they rose, on their Approach to
the cold Mountain: the Smoke shooting _horizontally_, from that Height
_only_, at which an _horizontal Current of Air_ began to take Place?
For it can hardly be imagined that the Air at the Top of Etna, found
to be “_electrical_,” and which must have been replete with a Mixture
of Floguiston, inflammable Air, Gasses, and other aërial Fluids highly
rarefied, heated, +dry+, (and consequently lighter,) _at the Instant_
of rising out of the glowing Cauldron, became so condensed as to fall
like Water, without partaking of the Motion of a _violent_ Wind,
supposed to blow in an horizontal Direction.
267. Glas, in his Account of Teneriffe,[77] reports, that the Clouds
are generally half as high as the Peak, above the Sea,[78] i.e.
according to him, near the Height of a Mile and Half: “_below_ which
Clouds, the _North Easterly Winds_ +generally+ prevail: and, at the
same Time, _above them_, we find a _fresh Westerly_ +Gale+: which I
believe to be the Case _in every Part of the World when the_ +trade
wind+ blows.”
In Page 253, he says, that in ascending above the Level of the Clouds,
he found the Air sharp, cold and piercing: and the Wind blew strong
from South West, and West South West: so that the Wind blew towards the
Mountain from three different Points at least, viz. the Trade Wind,
from North East below the Clouds; just above them, from South West:
and still higher, a fresh Gale, from West.
“The Air on the Top of the Pike was thin, cold, piercing; and of a dry
parching Nature, like the South Easterly Winds which I have felt in the
great Desert of Africa, or the Levanters in the Mediterranean: or even
not unlike those dry easterly Winds which are frequent in the Northern
Parts of Europe, in clear Weather, in the Months of March or April,”
Page 257.
This dry Wind answers to the Eknèfiai (before mentioned) i.e. _Wind
descending_ +from the clouds+.
Glas further observes (Page 250) that the Clouds, in fine Weather,
descend gradually towards Evening, and rest on the Woods till Morning:
when they re-ascend, and remain suspended above them, till the
succeeding Evening.
Here then a nocturnal Depression of the Atmosphere is obvious. But this
Appearance will not prove that the Air does not descend below the Level
of the Clouds: for, tho’ the Clouds descend with the Air; Vapour-Air,
of which they are composed, becomes _transparent_ both by Dissolution,
in a warmer Stratum, and Proximity to the Earth, as before mentioned.
[Sidenote: Conclusion drawn from the above, applicable to Balloons.]
268. From the Variety of Winds experienced at different Heights, not
only on _Teneriffe_, but in different Places; it is plain, that if
Balloons can be made durable and Air-tight; they may be wasted between
the Tropics by an East or West Current at Pleasure: and also throu’out
the Globe; the Occasion being made, in some Respect, subservient to the
Time.[79]
CHAPTER L.
CORROBORATING PROOFS OF A DEPRESSION.
Sect. 268. Art. 1. The Author is well informed, that, during
an Engagement at Sea;—in _ten_ Minutes after the Action has
commenced;—tho’ it blew a _Gale_ before; (that is, tho’ it blew
_violently_;) the Agitation of the Air, arising from the Explosion of
the _great Guns_, and small Arms, woud counteract the Wind, and produce
a dead Calm.
268. 2. Quere: does not the _new elastic_ Air, produced from the
Nitre,[80] give an instantaneous Compression and Dilatation to the
_incumbent_ atmospheric Air, round the Place of Action, while the
_lighter floguisticated Air_ passes throu’ it, raising, and affecting
to its highest Limit, the _whole_ Atmosphere. And does not the Effect
of a sudden Calm, suppose the Wind to _descend from above_ with a Kind
of _saltatory_ Motion, instantly counteracted by the _new elastic_
Air?—For if the Wind be supposed to blow sideways or horizontally, _to
any considerable Height above_ the Water, woud not the fresh _lateral_
Air glide away, and prevent the Continuance of the Calm?
269. When a Squall happens, or only Rain falls; Air will _rush_ from
all Sides, and from _above_, to supply the Vacancy of the fallen Cloud
and Vapour.
The Air immediately _above_ must fall: the lateral Air gravitating
towards other Places. Hence _Cold_, and a bright Sky after Rain.
270. The Theory of Accumulation may account for the frequent _warm_
Rains in Winter, and during the Night.
For the preceding diurnal Accumulation over the Sea, may _circulate_
during the Night, at a great Altitude, to restore the Equilibrium and
Loss of _cold_ Land Air sent by a low or Ground-Wind to Sea, during
the Day-Time: particularly, as the _Accumulation_ over the Sea, during
Winter, is almost _continual_.
271. The _Wind_ would more frequently be perceived to _descend_ and
_rebound upwards_, (Trials of which might be made by holding an
Umbrella, extended at right Angles with its Axis, upright in the Hand;)
if the same Opportunity offered, of opposing as great a Surface to it
in a perpendicular, as is every Day done, in an horizontal Direction:
for in walking, the whole Height of the Body, and half its Surface, is
opposed horizontally to the Wind: but the Head only, which is covered,
is opposed to the perpendicular Pressure.
272. As every Circumstance in the Order of Nature is so admirably
contrived that each apparent Inconvenience rectifies itself; in
_heavy_ Winds continuing to blow from a +cold+ Point; the Construction
of the Atmosphere is such, that the _warm light_ Air from the opposite
Points will necessarily rise up and flow over the cold Stratum, and
by their Tendency to an Equilibrium, will produce an Air _less cold_,
before the _same_ Wind is exhausted.
273. On the one Hand; it is probable, that, as cold Winds are heavy;
the Eknèfiai Winds are covered with frequent Waves of the Apogay, or
light warm Air rolling over them, frequently from the opposite Points.
274. On the other Hand, as the _Apogay_ Winds are naturally light and
warm, it is _improbable_ that they shoud be _frequently_ covered with
Waves of _cold heavy Air_, rolling over them from Eknèfiai Points.
It may therefore be reasonably concluded, that the Eknèfiai Winds, when
approaching or opposed to the Apogay, shoud be considered as _Ground
Winds_, (i.e. Winds blowing next the Surface of the Earth, tho’ they be
supposed at the same Time to descend) which receive the Apogay above
them: and that the Apogay being warm light and +moist+, (which last
will have the same Effect, as if they were more elastic;)[81] being
also more turbulent, and endued with greater Velocity, press back the
Eknèfiai from the Surface of the Earth, and upwards; and at the same
Time flow above them.
By which means the Eknèfiai partake of their Qualities;—become less
_cold_, less _heavy_, and less _dry_.[82]
CHAPTER LI.
Section 275. If then this Reasoning be allowed; aërial Travellers will
not be subject, when, at a considerable Height, even in Winter, to
great Degrees of Cold, supposing that the Air does not actually freeze
the Waters below; and the Apogay or Southerly Winds have continued for
a few Days.
On the Contrary; Aironauts may expect Cold, encreasing with their
Ascent, even in Summer, tho’ _warm_ below; supposing the Eknèfiai or
Northerly Winds to have continued but for a Day before the Ascent: they
may possibly, indeed by soaring higher, rise into the regular Stratum
of the warm Apogay floating above them.
276. From what has been said, there seems a Degree of Probability, that
the Air for a Number of Miles, _above warm cultivated Plains_ shoud
differ materially in its Temperature, from Air above Mountains, or
_even on a Level_ with their Summits.
That the former Air, in moderate Weather, shoud continue _warm and
rarefied_: while the latter is _cool and condensed_.
For the same Reason the Air over the Sea, on the Hours of Accumulation;
i.e. during the Night, in Summer, and frequently in Winter, shoud be
found _warm_ and _rarefied_: especially during a Continuance of the
Apogay Winds.
277. It is likewise probable that the Atmosphere will be found
+respirable+ at much greater Heights, than is at present imagined:
during the Continuance of the Eknèfiai Winds; and also, on Account of
the _defloguisticated_ Air,[83] which is _drier_ and _less elastic_ in
Proportion to its Rarity.[84]
278. The Height of 10 Miles seems not too great to limit human
Respiration, shoud any Attempt be made, to soar with a Balloon in a
mild Atmosphere; and particularly between the Tropics.[85]
But an Objection woud be found in the Size of a Balloon sufficiently
capacious to contain nearly 6 Times the Bulk to which the Gass woud
necessarily expand itself, at the Height of 10 Miles.
[Sidenote: First Cause of Limitation, in the Ascent of Balloons.]
[Sidenote: Second Cause of Limitation in the Ascent of Balloons.]
279. It seems most likely that the primary Cause that will affect the
Ascent of Balloons is the Difficulty of encreasing the Dimension of the
Balloon: the Second, is from the excessive Cold; if the Wind blows from
any Points of the North.
Supposing the Construction of the Atmosphere to be as represented by
different Authors, (which, by the Way, is scarcely credible) ten Miles
will perhaps be the utmost attainable Height.
280. There is a Circumstance relative to the Motion of the Air, which
has not been sufficiently attended to: and bears some Analogy with that
of a _Thorough Air_.
This Circumstance may not improperly be called the _Reception_ and
_Dispersion of Air_.
In cold Climates, it is an Object of Dread: in warm ones, a most
desirable Piece of Luxury.
A gentle Undulation of the Air is perceived in Peru, and other hot
Climates, by Persons sitting in _Arbours_ sheltered from the Sun.
The surrounding Air is instantly _contracted_ by _Condensation_, during
the Absence of the Sun’s Rays, and therefore occupies a _less Space_:
_fresh Air_ is _received_, and as instantly _dispersed_ by Expansion
towards those Parts, which are the warmest, i.e. where there is least
Resistance: so that a gentle Breeze is constantly kept up, _probably_
by a Depression from _above_.[86]
281. Analagous to this, are those Winds which generally _rise early_
and die away at _Sunset_: the nocturnal Condensation of the Air being
sufficient for the +reception+: as Air suffers some Compression without
Tumult.
To demonstrate the Changes owing also to remote and invisible Causes
least suspected; Boyle somewhere speaks of an Instrument he made, which
was so nicely contrived, that he coud tell, while sitting in his own
Apartment, whenever any detached Cloud passed beneath the Sun’s Disk.
The Principle on which it acted seems to have been that of a Reception
and Dispersion of Air that took Place within _the_ +shadow+ proceeding
from the Cloud.
282. An oblique Argument supporting the Doctrine of Depression,
asserted to take Place, in fair Weather, is that _Wind_ drys up the
Moisture from the Ground more than the _Sun_: and that March which is
the _windiest_, is also the _most drying_, tho’ _not_ the _hottest_
Month.
Bacon, in his Enquiry into Motions and Undulations of the Air, uses a
Metaphor, which tho’ somewhat facetious, is strictly philosophical.[87]
“_For when_ +winds+ _lead_ +the dance+, _it woud be agreeable to know
the_ +figure+.”[88]
And it is probable, that they really press the Earth with a saltatory
progressive undulating Motion, _descending_ in elastic Steps of sudden
Compression; and _rising_ with quick alternate ones, of Dilatation and
Expansion.
Dicker’s Balloon gave Proof of this.
283. Lastly: the +chill+ _of Air_ which always takes Place over
+water+, and _moist_ Grounds, even in the +finest weather+, strongly
favours the _Reception_ and _Dispersion_ of _it_, to the surrounding
and more heated Lands: (which can only be supplied, as before
mentioned, by Torrents of fresh Air _gradually descending_ from the
etherial or middle Region of the Atmosphere;) and seems to produce the
same Effect, viz. a constant Breeze, with that of the Arbor, Shade, or
Shelter from the _Sun_: also with that of the _Shadow_ from the Cloud
passing under his Disk, which affected a complete Thermometer and
Hygrometer.
284. On a Change of Weather from Frost to Thaw, the Colour of the
_upper Air_ +first+ alters from a _clear and deep_, to a _dull and
faint_ Blue, or to a muddy Haze, not distinguishable into Clouds, but
visible above them; a vivid Brightness still remaining, for many Hours,
to about 500 Yards above the Surface of the Earth.
Or, soft _warm_ Showers fall gently, without Wind, or any apparent
Change in its Direction.
All which seem to favour the Accumulation and Descent of _warm Air_, by
Waves of the Apogay rolling over the Eknèfiai Winds.
CHAPTER LII.
[Sidenote: _Proper_ Days in the Month for the Ascent of Balloons.]
Section 285. As the _safest Hour_ of the Day has been already pointed
out, for the Ascent of those Aironauts, who propose to cross a Channel,
or Arm of the Sea, in a Balloon _Air-tight_ or nearly so: it may not be
useless to throw out a few Hints on the properest Days in _each Month_,
for the Ascent of Balloons.
286. It will perhaps be found true, that the more frequent Winds
are generated near the Surface of the Earth: but that _Storms_ are
generated from above. Cold, Heat, Drought, and Moisture produce the
more frequent and diurnal Winds: but the Conjunctions and Operations of
the Moon and Planets contribute to the Production of Storms and other
Inequalities of the Atmosphere: more especially the _Moon_: at the New
and Full. These Attractions first affect the _superior Parts_ of the
Atmosphere.[89]
287. “We are sure in the calmest Weather, to have some Breeze at Noon,
and at full Tide.” Therefore, both are improper Times for Balloons to
be at Sea: the Time of low Water and Midnight woud be best in those, if
equal in other Respects.
Changes of Weather as to Wind or Calm happen about the New and Full
Moon.[90]
288. Varieties of Tide produced by the united or divided Forces of the
Sun and Moon, occasion similar Changes in the Atmosphere nearly at the
same Time.
For Instance, at the Time of the New Moon or Conjunction, i.e. when the
Earth, Moon, and Sun, are _nearly_ in a Line; the Moon being between
them: also at the Time of the Full Moon; i.e. when the Moon, Earth, and
Sun are _nearly_ in a Line; and the Earth between them, which is called
the Opposition.[91]
In the first Case, the Moon and Sun attract the Atmosphere of the Earth
conjointly, or with united Force: in the second Case; the Earth being
between them, they act in Opposition to each other, still nearly in the
same Line.
At these Times, the +spring+ _Tides_ are at the _highest_ i.e. once
every Fortnight; and in the two interval Weeks are the +neap+ or
_lowest_ Tides: for a like Reason.
Because, in the latter Case, a Line supposed to be drawn from the Moon
to the Earth, and another from the Earth to the Sun, woud form nearly a
right Angle: or in other Words; because the Moon and Sun woud attract
the Earth at right Angles to each other, or in a lateral Direction:—the
Moon woud draw one Way and the Sun another:—their Forces woud be
divided.
Now it is a Fact, that the Ocean is raised considerably twice every
twenty-five Hours, by the Attraction of the Moon, when she comes to
the Meridian. So that the Surface of the Sea, instead of putting on
the Form of a Sphere, or Globe, will be changed into an _oval_ Figure,
whose longest Diameter being produced, woud pass throu’ the Moon.
In like Manner a similar Elevation must take Place, as often as the Sun
is in the Meridian; either above or below the Horizon.
Moreover, this Elevation is _greatest_ on the New and Full Moon,
because the Moon and Sun do then conspire in their Attractions: and
_least_ in the Quarters: as they will then draw different Ways; the
_Difference_ of their Actions only producing an Effect.
Lastly, the Intumescence will be of a _middle_ Degree, at the Times
between the Quarters, and New and Full Moon.
289. As in the Ocean, so in the Air above it; a Tide of Air must roll
along the Atmosphere, throu’ the whole Extent of it; and rise upwards
twice in about 24 Hours.
And since the Height of the Atmosphere is computed by Halley at 45
Miles, and the Depth of the Ocean at an Average, but half a Mile; the
Air will more easily and quickly obey the Attraction of the Moon and
Sun, than the Tide of the Ocean: and, as it revolves in a Sphere which
is about 100 Times larger than that of the Ocean, the Agitation and the
Velocity of its Tide, will be something greater, in Proportion to its
Elasticity, and inferior Density to the Water of the Ocean.[92]
290. The _Weight_ of the Air must now be considered.
The Weight of the Atmosphere in England does not exceed 31½ Inches
of Mercury in the Barometer: nor does the least Weight fall short of
28½: the greatest Difference in the Weights may be taken at 2 Inches:
dividing 30 (nearly equal to the whole Weight) by 2, the Answer is 15.
So that the under Parts of the Atmosphere being pressed upon by about a
fifteenth Part less Weight at one Time, than at another; the _specific
Gravity_ of the Air will sometimes be a fifteenth Part lighter.
But the Height of the Atmosphere being estimated at 45 Miles, which is
equipoised by about 30 Inches; when equipoised by a fifteenth Part less
Weight; (that is, dividing 45 Miles by 15; which amounts to the same as
if a fifteenth Part of the whole Height was taken away; the Answer is
3 Miles;) shews that the Atmosphere is 3 Miles higher at one Time than
at another, over certain Places; indicated by the Barometer at those
Places.
Such an Accumulation of Air, arising only from Pressure or specific
Gravity in one Part of the Atmosphere, and not in another; by its
Tendency to an Equilibrium; and when to this Tendency is added its
_elastic_ Force;—must be productive of +winds+, _descending Torrents_,
Inundations of Air, or Storms, near the Surface of the Earth: and
nearly such a Difference in the Barometer has been known to happen in
a few Hours.
Such Accumulation, however, is not properly _the Tide of Air_.
291. At the New and Full Moon, the united Attractions of the Moon and
Sun raise the Spring Tides in the Ocean to the average Height of 10
Feet and a half.[93]
And in the Moon’s Quarters, the Moon drawing one Way, while the Sun
draws another, viz. at a right Angle, made by Lines from the Sun and
Moon to the Earth’s Center; the average Height of the Neap Tides in the
Ocean will be 6 Feet 7 Inches.
The same Attraction which raises Water 10 Feet and a half, will raise
Air, whose Density is 800 Times less, to almost one third of that to
which the whole Pressure of the Atmosphere can raise Fluids:[94] Now it
has been before seen, that the Pressure of the Atmosphere raised the
Air 45 Miles: so that the Air is raised by the united Actions of the
Moon and Sun, at the New and Full Moon, to one-third Part of 45; i.e.
to 15 Miles. And for the same Reason, the Air is raised at the Moon’s
Quarters to 10 Miles:[95] the Difference between which is 5 Miles.
There is consequently a real _Tide of Air_ five Miles higher at
each New and Full Moon, than at her Quarters: which Tide rolls
with incredible Velocity along the Verge or highest Limit of the
Atmosphere; and is generally productive of Wind below.
292. The Elasticity of the Air must likewise be brought into the
Account, as contributing greatly to its Motion: the Spring of Air
always increasing as the Pressure encreases.
Considerable Changes must therefore ensue in the inferior Parts of the
Atmosphere.
For as the Effect of the Moon’s Attraction is to diminish the Weight of
the Atmosphere (tho’ its Quantity be increased) by elevating the Column
of Air in the Line of her Meridian; the Rarefaction of the Air is
therefore encreased, first _at the Top_ of the Atmosphere; afterwards
it gradually descends to the Bottom, or Surface of the Earth: so that
the incumbent Weight being diminished, the Air beneath will be greatly
_expanded_.
At whatever Height therefore any _Quantity of Vapour_ or superior
Cloud _rested_, while the Moon was in her Quarter; it woud _gradually
descend_ at the Approach of the next New or Full: at which Times it
woud remain suspended at a Height, where an Expansion took Place
equivalent to the former Expansion, at the Moon’s Quarter: and, if
the Height during the Moon’s Quarter was only equal to that of common
Clouds; such Vapour woud, at the New and Full Moon, _descend_ in Mist,
Rain, Snow, or Wind.
293. Little Reliance is to be placed, in these _Northern_ Climates, on
the aggregate Weight (_or elastic Power_) of the Air, indicated by the
Height of the Barometer, near the Times of the New and Full Moons:
tho’, in general, it will _descend_ about those Times.
[Sidenote: Proper Days for Ascent.]
These Things being so; it woud be improvident to undertake an aërial
Excursion, either three Days before, or three Days after the Day,
either of the New, or Full Moon: the Ascent shoud be forborne every
other Week; at least till the Art is a little more advanced.
The two remaining alternate Weeks in each Month, viz. when the Moon is
in the Quarters, and the Tide of Air flowing throu’ the Atmosphere, is
checked, counterbalanced, and equalized, by the lateral Attractions
of the Moon and Sun, acting at right Angles, i.e. on different Parts
of the Air, pendent on the Earth’s Surface;—more settled and regular
Weather may be naturally expected; and particularly freer from the
Extremes of _Wind_ and _Cold_.
Moreover, as the Almanack, and Ephèmeris[96] may be always consulted;
the Day fixed on shoud not be _marked_ with Conjunctions of the
Planets.[97] The Inequality of their united Attractions greatly
deranges the Equilibrium of the upper Parts of the Atmosphere;
producing sudden Squalls and Gusts of Wind: which, tho’ of short
Continuance, perhaps a few Hours, are inauspicious to the successful
Inflation and Ascent of a Balloon, during the Infancy of the Science.
(See Section 211.)
CHAPTER LIII.
ON THE MEANS OF SUSTAINING A BALLOON ABOVE THE SURFACE OF THE
WATER, BY A TEMPORARY LOSS OF BALLAST: AND OF RECOVERING THE
BALLAST.
Sect. 294. Art. 1. The two Inconveniencies arising from a _Discharge_
of Ballast, while the Balloon is under the _Pressure_ of a mediocèanal
Column of Air, are,
1. First, lest the Balloon shoud rise too _high_; for by opening the
Valve in order to descend; Gass escapes: which is an _actual Loss_: and
the Balloon is rendered incapable of supporting its Burden at the same
Height, as before.
2. The present Impossibility of resuming the Ballast, in order to
_descend_, or _check the Elevation_, on approaching either Shore, or at
any other Time.
294. 2. These Inconveniencies are to be remedied by the following
Methods.
If _Sand_ be the Ballast fixed on; put as much of it into a Bladder
by Means of a Tin Funnel, as, when _less_ than _half_ blown, it will
contain, without sinking below the Surface of +fresh+ _Water_.
_Prepare_ the intended Weight of Ballast, in Bladders, after the same
Manner.
Also to +each+ Bladder _with Ballast_, tye another Bladder _without
Ballast_, half blown.
Tye fast each Set of Bladders, so prepared, with a _leathern_ Thong;
the Ends of which may be left a few Inches to _spare_.
The Grapple may remain in the Car.
294. 3. When the Balloon _begins_ to descend over Water; lower out the
Cable, by Degrees.
Tye a Pair of Bladders, one of which contains Ballast, very tight,
round the End of the Cable.
Then a second Pair, at such a Distance that the intermediate Part of
the Cable, will _float_.
Repeat this Process, till the proper Effect is obtained; or the whole
Ballast is discharged.
294. 4. The Car and Balloon may be _hauled_ or wound _down_ to
the Surface of the Water: and the Ballast resumed, as the Balloon
approaches the Shore.
294. 5. If it be found necessary, the Ballast may be _discharged_ by
cutting the +thongs+, _gradually_: or the +cable+, _at once_.
294. 6. If the Wind be _contrary_, and the Weather _moderate_; the
Tide, or Stream may, by _Calculation_ and _Foresight_, be made to serve
the Purpose of the Aironaut, in towing the Ballast which floats on its
Surface: and thus checking, or gently drawing the Balloon after it.
294. 7. In such Cases, the Aironaut woud do well in applying his
_propulsive_ Machinery.
A GENERAL OBSERVATION.
294. 8. To prevent the car of the _Balloon_ from being drawn out of
the Perpendicular, a Circumstance not infrequent; it is necessary to
have some Contrivance, by which the Cable shall run throu’ a moveable
Pulley, on a Swivel, in the Center above the Car; and that the
Aironaut shall be able _instantly_, by a Screw, or otherways, to fasten
the Pulley and Cable so tight, that the Stress shall remain on the
Center above the Car, however _forcibly_ the Cable may be stretched.
CHAPTER LIIII.
ANOTHER METHOD OF SUSTAINING A BALLOON OVER WATER, WITHOUT LOSS OF
GASS, OR OF BALLAST.
Section 295. Let the Ballast consist of that Kind of Rope (wound on
a Reel) that is either by Nature or Art, _specifically_ lighter than
fresh Water: as a _hollow cylindrical_ Rope of Silk, in which Corks
are thrust: the Silk to be dipped into elastic Varnish, to prevent the
Absorption of Water into the Pores: or a common Rope well varnished; or
covered over with a cylindric Case of varnished Silk, might answer the
same Intention, if Corks or Bladders were tyed at proper Distances: in
which Case, the Rope might, at the first Ascent of the Balloon, hang
from the Center above the Car, at its full Extent, suppose a Mile or a
Mile and half in Length, without the Encumbrance of a Reel.
If Bladders are used; those that hang near the Car shoud not be more
than _half blown_.
By the above Expedient; as soon as the Balloon began to decline,
from Evaporation of Gass, or Depression of the Atmosphere, and the
lowest Part of the Rope touched the Water; the Balloon woud continue
to levitate, in Proportion to the Quantity of Rope sustained on the
Surface of the Water.
The Aironaut woud move less _swift_ indeed, but more conveniently;
as he woud not be obliged to rise _above_ the Wind: but be able to
_lower_, and _raise_ himself at Pleasure: _first_, by pulling up a Part
of the Rope into the Car; and having there _made it fast_;
_Secondly_, by cutting away, as he saw Occasion, the loose End, and
Folds of the Rope so drawn into the Car with him.
CHAPTER LV.
ON THE NECESSITY OF ASCERTAINING THE PROPER MODES OF DIRECTION, BY
DIFFERENT AND FREQUENT EXPERIMENTS.
[Sidenote: On the Necessity of frequent Experiments, in different Modes
of Direction.]
Section 296. The Necessity of making frequent Experiments, in order
to prove how far the Balloon is capable of Direction, by different
Combinations of the mechanical Powers, is so apparent; that no Balloon
shoud rise a second Time, without the Application of Machinery to that
End.
Each Candidate for Fame, as Proprietor of a Balloon for _public
Exhibition_, ought to vie in his Pretensions to a Superiority of
Manouvres.
Their respective Performances woud appear in the public Papers; and
Decisions be made to the Advantage of the Art.
For it is probable, that by such _Comparison_ chiefly;—the +comparison+
of _experimental Blunders_ and _Mistakes_, and not by an Union of
Theory and Practice, cemented by liberal Patronage, the Balloon can
arrive to any Degree of Perfection, in a Country, which is the Scene
of _perpetual Contention_: where the Sum of Life seems devoted but
to +party+; and where the _precious_ Time of the +great+ is sunk in
Luxury, and their _exalted_ Talents lost in the _Labyrinth_ of Politics.
[Sidenote: Precautions to secure a Landing.]
297. _To strive against the Stream_ is proverbially impossible: and it
woud be literally so, to attempt by any Kind of Machinery to force the
large Surface of a Balloon, with any Degree of Velocity, against _a
Stream of_ +air+. (Section 201.)
Ships, which have the Aid of an Element 800 Times _denser_ than the
+air+, are obliged to wait _in Port_, till the Wind is favourable.
But neither is this considered as an Argument against _maritime
Navigation_: nor does the _Perfection_ of the Balloon require its
Ascent in a Storm: tho’ the Preference due to the Balloon, on such
Occasion, woud be decisive in its Favour: as the latter woud presently
surmount the Wind, and _lie to_, in the _calm Air above_ it.
Sect. 298. Art. 1. By Wings, or some propulsive Machinery, acting
forcibly in a Direction required, and with Ease to the _Operator_;
+two+ _useful Manouvres_ may be attempted, and will frequently be
_found successful_.
[Sidenote: _First Manouvre_: to secure the Landing in windy Weather.]
298. Art. 2. First, To +retard+ the Course of the Balloon during its
Descent; in such a Manner, as to prevent the Wind from _damaging_ the
_Machine_, or _snapping the Cable_: and thus to land with Safety, and
at the _smallest Distance_ +beyond+ the Place assigned.
[Sidenote: Preparatory Apparatus: and _Signal-Rope_.]
298. 3. A _silken_, or other _light_ Rope is to be provided: and to run
throu’ a _snatch Block_ fastened to a +rudder+, or to the +car+, as in
Crosbie’s Balloon.[98]
Which Rope _alone_ woud lessen immediate and unforeseen Danger, by
using the Balloon as a Sail, if it actually alighted on the Water.
298. Art. 4. The same Rope being _a Mile_, or _a Mile and Half_ in
Length; the _Whole_, or a Part of it, might be suffered to run off the
Wheel, and, falling on the Surface _below_, in _misty_ Weather, woud
serve as a Signal to determine whether the Aironaut was over Land, or
Water.
Also by winding up his Wheel, he might, if the Weather was moderate,
bring himself _down_ to the Grapple, which might be so contrived as to
_run down_ the Rope, and remain at the Bottom, by Means of a Knot, or
other Check.
He might also _loose_ his Grapple, and _rise_ again: or when down; pull
the Valve-Cord, and land.
298. 5. With a +second+ short Cable, snatch Block and Grapple, he woud
be able to _moor_ the Balloon, from which, he might, by procuring the
Country People to load the Car with fresh Ballast equal in Weight to
himself;—get out, and even leave the Balloon in their Care.
The Precaution of knowing whether he was over a fresh Water-Lake,
(for he might hear the Sea) might be useful in misty and low cloudy
Weather by Day, or during the Night; without expending Gass in the
_exploratory_ Descent.
298. 6. To facilitate the landing, the _Signal-Rope_ may be used to the
greatest Advantage, particularly in windy Weather; by _lowering out_
a Part, or the Whole, whether a Mile, or Mile and half, so that the
Grapple may take Effect on the Ground, at the Distance of its Length
_by Estimation_, _short_ of the Place where the Balloon is intended to
land.
As soon as the Grapple _holds_; it is in the Option of the Aironaut, to
tye Parcels of his Ballast _loosely_ round the Cable, to run downwards
along with it.
(For _which Purpose_, Iron-Rings with _Spring-Swivels_, which _open_
by _Pressure_ of the Fingers, and _shut_ of themselves, might answer
better than the _leathern Thongs_, as the former might be put, in _an
Instant_, round the Cable, and woud run down _quicker_.)
These Parcels of Ballast are to be sent down, in Succession, till
the Balloon has acquired such Degrees of +false levity+, as will be
sufficient to counteract that Tendency which the Wind will have to
_depress_ the Car of the Balloon forcibly on the Surface, so long as it
is connected with the Grapple _on the Ground_.
298. 7. When this Point is effected, the Balloon will remain suspended
in the Air; and being acted upon by the Wind, will be pressed into a
Direction approaching to an horizontal Line, in Proportion to the
encreasing Power of the Wind.
And here the Necessity of having the Cable fastened to a Center above
the Car, in order to retain its Perpendicularity, is most evident.
The Aironaut, in this Situation, may venture to wind up the Cable
_gradually_, and descend, to the Grapple.
298. 8. Secondly: When the different Currents of Air, have been tried
by Descent and Ascent of the Pioneer-Balloon,[99] and found to be _all_
unfavourable; the Aironaut is to _rise_ still higher, into a Calm,
pursue his Course horizontally in the +blue serene+, by propulsive
Machinery: estimating the Velocity, by the _evident Resistance_ of the
half Mile white Flag described in Section 12, 13. and 12, 15. hanging
at a proper Distance _below_, and of that which hangs loosely at the
Side of the Car, to shew a Change in the Direction of the Wind, (then
made by a Resistance of the Air): or he may judge o£ the Velocity and
Direction, by the _Flight_ of a _Feather_, repeatedly let loose at
certain Intervals of Time.
CHAPTER LVI.
NEW MODE OF ASCENT, TO DETERMINE THE INSTANT THE BALLOON IS ARRIVED
AT ANY GIVEN HEIGHT: TO MEASURE THE HEIGHTS: AND TO ESTIMATE THE
DENSITIES OF THE AIR AT THE GIVEN HEIGHTS.
ALSO, A METHOD OF ASCENDING TO A FIXED BAROMETRIC HEIGHT: THERE TO
REMAIN SUSPENDED IN EQUILIBRIO.
Section 299. Previous to the Ascent, provide a Cord, which shall have
sufficient Strength to support twice its own Weight, when so great a
Quantity of it is _coiled_ together, as, if extended, woud measure half
a Mile or a Mile.
Weigh the whole _Coil_, or any Number of Yards, so as to obtain the
whole Weight.
Mark the whole Length of the Cord, with different _coloured_ Worsted,
or otherways, at the Distance of every eight Yards: as a _sounding_
Line.
Note the Marks in a Pocket-Book.
These Things being done; give the Balloon, by +inflation+, a Power of
Levity _at least_ equal to the known Weight of the Cord: which may
be easily obtained by throwing into the Car, already _ballasted_ and
prepared, a Weight equal to the Aironaut, together with that of the
_Cord_.
The Cord must also, previous to the Ascent, be rolled upon a Reel,
(made fast in the Ground) whose Diameter shoud be +two+ Feet: each Turn
of the Wheel may be called two Yards.
A Barometer with an attached Thermometer fixed in the same Frame, also
a second or detached Thermometer placed at the Distance of a Yard from
the Frame, shoud remain upon the Ground during the Inflation.
The same Apparatus of Barometer with attached and detached Thermometer,
shoud be suspended in the Car.
The Instant the Balloon ascends, an Observer below is to note in a Book
the _Point_ at which the Quicksilver stands in each of the +three+
Tubes of the lower Apparatus, also the Time of Ascent: the Aironaut the
same.
The Rope is, previous to the Ascent, to be tyed to a Center above the
Car: and as soon as the Balloon has elevated the Car 100 Yards; the
Observations, as before, are to be set down below, and by the Aironaut:
and repeated at the Height of each 100 Yards: a Drum to beat; during
the Time each Observation _below_ is _noting_ down; and the Balloon not
suffered to rise, till the Drum has ceased. By such repeated _Notice_,
and _Silence_; the Aironaut will know the _exact Height_, at which the
Balloon is checked in its Elevation: and the _exact Time_ during which
its Elevation is impeded.
This Process is to continue, till the Rope is raised to its full Length.
At which Instant a double-barrel Gun is to be fired: the exact Time
noted _below_: and the Time of hearing the Sound noted above.
These Notes are to be compared at the Aironaut’s arrival on Earth.
300. For such _nice_ Experiments the Aironaut shoud ascend half an Hour
before +sunrise+, or _Sunset_: and the Day chosen by the foregoing
Rules.
The Air must be +quite calm+: but it is not necessary that it shoud be
free from Clouds or Mist.
When the Rope is at its full Extent, the Operator _below_ is to shorten
it, by winding down the Balloon, 100 Yards: the Signals _below_, being
repeated, till the Balloon is arrived within 100 Yards of the Ground.
[Sidenote: To estimate the Densities at different Heights.]
301. While one Observer _below_ is writing down the Observation to
be made the Instant the Balloon has risen exactly 100 Yards; another
Operator is to weigh, by Hand, with Spring Steel-Yards, the Force of
Levity already acquired, which is to be noted down by a third Bystander.
This Process is to be repeated at every 100 Yards.
The Levity, it is true, will encrease as the Balloon rises, (probably
in a geometric Progression;)[100] yet the Cord, by rising with the
Balloon, will greatly check it: if, however, it prove insufficient for
that Purpose, and, lest the Cord shoud be in Danger of breaking; the
Bottom of the Balloon must be opened, or the upper Valve drawn.
If the _Cord_, _Rope_, or _Balancer_, be sufficiently strong;
there will be no Necessity for the Aironaut to throw out Ballast
occasionally; nor for the Observations in the former Part of this
Section: the _Densities_ will likewise be more easily determined, by
the _Weights_; which shew the _Encrease_ of Levity and Expansion of the
Balloon, at each of the _given_ Heights: Allowance being made for the
Weight of the _Balance Rope_, _raised_ by the Balloon.
[Sidenote: Method of ascending to a fixed _barometric_ Height: there to
remain suspended _in Equilibrio_.]
302. The Aironaut, may, at any Height, marked by looking at the
Barometer, when at 24 Inches for Example, or as soon as he finds his
Balloon sufficiently expanded, pull up the Rope over a Pulley; or, wind
it upon a Reel of two Feet Diameter, within the Car; and continue
to do so; till he finds that the Barometer begins to _rise_, (which
is a Sign that the Balloon _descends_), by the additional _Weight_
of the Balancer just brought into the Car: on which, by preconcerted
Agreement, he may throw out a +white+ Flag, prepared to hang a Yard
below the Car.
On Sight of the Flag, the Person at the Reel _below_ is to cut the
Rope: which Rope, or a Part of it, is to be drawn into the Car.
The Balloon will rise no higher; but remain in _Equilibrio_ in the Air,
at that Height.
CHAPTER LVII.
ON BALLOONS. THEIR DEFECTS AND FARTHER IMPROVEMENTS.
Section 303. These Defects are best known from the History: a Detail of
which is given to the World in an entertaining, elegant, and scientific
Manner, by a celebrated Writer on other Subjects, _Mons. Faujas de
Saint Fond_, in two Volumes, 12mo. for the two last Years, illustrated
with Engravings by the best Masters.
And he promises a Continuation, or annual Register of Experiments and
Improvements.
The Title of the Book is, “Description des Experiences de la Machine
aërostatique, &c. &c.”
304. Mr. Cavallo has favoured the British Nation with a cursory
tho’ clear Account of the same, in his “History of Airostation:” a
Continuation of which it were to be wished he woud likewise publish
annually.
305. It might contribute greatly to the Improvement of the Art; if
Mr. Faujas woud give Engravings on a large Scale, of the different
Machinery, already used or invented to direct the Balloon, with their
Proportions: particularly the +moulinet+ of _Blanchard_: as well as
that lately tried by Messrs. Auban and Vallet; whose Machinery is still
_more distinguished_ and +effectual+.
306. The Titles and Sizes of all useful Books written on the Subject,
also the Places where they are to be had, might likewise be inserted,
at the End of each _annual_ Volume.
307. The principal Defects of the British Balloons are, in
1. The Construction.
2. Production of Gass.
3. Mode of Direction, and
4. Security of landing.
First, Defects of the Construction are both in the Form, and
Composition.
The Form ought to be that of a +right+[101] _Cylinder_,[102] by which
the _Capacity_ is doubled without encreasing the Resistance: ending
above and below, each in a Hemisphere. A cylindrical Trunk, 2 Feet in
Diameter, being added to convey the Gass _into_ the Balloon; and suffer
it to escape, when too much expanded in the etherial Regions.
It shoud also be furnished with a Valve, at the Bottom, of equal
Diameter with the Trunk: keeping itself Air-tight; and opening outwards
by a _given_ Resistance, (as that of ten Pounds Troy,) from the inside
Gass.
There must be an upper Valve as usual: occasionally to promote a
_swift_ Descent.
308. The Form will likewise continue to be defective, till an interior
Balloon for common Air is adopted, according to the Plan laid down by
the ingenious Mons. Meunier, lately appointed by the French Academy
of Sciences at Paris, one of the Commissioners for the Improvement of
Airostation.
The Use of which interior Balloon by Compression of the surrounding
Gass in the external Balloon, prevents, it is said, the Loss of Ballast
and of Gass: two very considerable Advantages.
For the actual Sum total of Gass not being diminished; the Balloon will
continue longer in the Air, before an Escape of Gass, throu’ the Pores
of the Silk, makes it descend.
There will, on the same Account, be less Occasion to take in _meer_
Ballast, for the Purpose of throwing it _overboard_, to prevent the
Descent.
Therefore an equal Weight of Articles necessary to remain in the Car,
may be substituted in Place of the Ballast.
309. Art. 1. And, since it is next _to impossible_, the Atmosphere
shoud continue for 24 Hours together, of the _same Density, Weight, and
Temperature_; or, in short, without Motion;—the Aironaut will have
a Power of seeking, at _different_ Heights, for that Current of Air,
or _Wind_, which suits him best: or, in a very few Minutes, to rise
above all Currents; become stationary, and _lie to_ in the +serene+,
waiting for a _Wind_: which, as before mentioned, he may readily find,
by lowering out a Mile of Twine, and his _white_ Flag: attending to it,
with a small perspective Glass, or Magnifier.
309. 2. Another most _material_ Advantage is to be able, in a _high
Wind_, to chuse the Spot on which he proposes to alight: or wait for a
favourable Opportunity to descend.
[Sidenote: To ascertain the Height of the Balloon by a Quadrant.]
310. To compute the Height and Distance of the Balloon, by Means of a
_white_ Flag, or other _visible_ Object, suspended from the Car, at a
certain Distance below it.
Let the Observer take the Altitude of the Car with a Quadrant: and also
the Altitude of the Object or Flag.
Then by a Case in plain Trigonometry; if the Altitude of the Car be by
the Quadrant 59° = HAC, the Altitude of the Object 55° = HAO, and the
Length of the Line veered out be 200 Yards, or otherwise = CO.
[Illustration]
Then the Complement of HAO = AOH = 35°; and the Complement of the Angle
HAC = ACH = 31°; and the Supplement of OAC + ACO = AOC = 145°.
Then, CAO 4° : CO 200 :: AOC 145° : AC; and Radius : AC :: CAH 59° : CH
1409 Yards, the Height of the Balloon taken at the Time.
Next, Radius : AC :: ACH 31° : AH 846 Yards, which is the horizontal
Distance of the Place on the Earth from the Observer, over which the
Balloon was then suspended.
This Method finds the Height truer than the Barometer, and with fewer
Circumstances of Confusion.
And if the Balloon Art coud be perfected, so as to make them stationary
at any Height; this Circumstance woud afford excellent Opportunities of
proving the Heights by the Barometer: besides which, the Distance also
has been obtained: a Point not before attempted.[103]
CHAPTER LVIII.
OF THE AIR-BOTTLE BALLOON.
Section 311. Till the Particulars of Meunier’s Invention are made
public,[104] an additional _Air-tight_ Balloon, or Air Bottle, at least
15 Feet in Diameter, of a _globular_ Form, appended below the Car, and
furnished with a _Condenser_, to be worked by _pulling upwards_, or,
as the Bellows of an Organ, by the alternate Motion of the Feet of
the Aironaut, standing upright in the Car, may be used instead of the
interior Balloon; to keep the _great Balloon_ at a _given_ Height: and
consequently prevent the Aironaut _from rising too high_: to atchieve
which Purpose, during the _first Ascent_; a Rope or Balancer may be
used, a Mile and half long, fastened to the Car, and rising with the
Balloon, (to _check_ its Power of _Ascent_,) till an Equilibrium is
produced: at which Instant, on Sight of the _white_ Flag from the Car,
the Balance-Rope is to be cut, by the Operator _below_. (Section 302.)
If the Aironaut perceives by the Rise of the _Barometer_, that the
Balloon descends; he may throw out a _little_ Ballast, (perhaps a Pound
or two), and then wind up his Balancer, or suffer it to remain at any
Length, at his Option.
312. By keeping the Balloon at a given Height _only_; no Gass is
expended in preventing the necessary Tendency of Balloons to a
perpetual Elevation: also, during the self Descent of the Balloon; by
opening the Air-Bottle, the Aironaut will supersede the Necessity of
throwing out Ballast, for a Re-ascent.
313. The Air-Bottle-Balloon shoud be covered by a strong _light_ Net,
of a Dimension rather less than the Bottle, which will hinder it from
bursting: the Resistence of the _condensed_ Air within, being then
chiefly on the Net, and but little on the Bottle.
The Net may be made of Silk and Cotton Thread; lest the Meshes, by the
Pressure of the Knots, shoud eat into the Bottle.
CHAPTER LIX.
SUPERIORITY OF THE AIR-BOTTLE TO AN INTERIOR BALLOON.
Section 314. The Air-Bottle can be attended with no Sort of Danger.
For, if it burst; the only Effect is to raise the Balloon: which is
made to descend, at Pleasure, by opening either the _lower_ or upper
Valve.
Whereas an interior Balloon condensed with common Air, presses against
the surrounding exterior Gass: and the Gass, against the +inside+ of
the _great Balloon_, when the latter is in an elevated and rarefied
Atmosphere; which Atmosphere, in Proportion to its Height, makes _less_
Resistance to the _Outside_ of the great Balloon: and thereby encreases
its Tendency to a Rupture.
By the Application of the Air-Bottle, which will be to a Balloon, what
an Air-Bladder, or _Swim_ is to a Fish; a concomitant Advantage is
derivable.
For the common Balloon and Air-Bottle, which may be called +a double
balloon+, will, in their _present imperfect_ State, be able to remain
a Day, or perhaps a Couple of Days in the Air: there being no Loss of
Gass: unless by Evaporation, throu’ the Pores of the Silk.
And this Advantage of _a double Balloon_ may be effected with little
+expence+ (except that of a complete Net) to the different Proprietors,
who may make alternate Voyages, with the Balloons _thus_ united: one
being inflated with Gass; the other occasionally with three or more
Atmospheres of common Air _condensed_.
CHAPTER LX.
HINTS FOR THE DIRECTION OF THE BALLOON.
Sect. 315. Art. 1. In the London Chronicle, from the 20th to the 22d
of August, 1785, is a Letter from Bury, containing an Account of Mr.
Poole’s Balloon, with the following Circumstance, viz. “It was found
necessary, before the Balloon was liberated, to cut away the Wings,
intended to act as Sails, which had been constructed by an ingenious
Piedmontese, patronized by +lord orford+, and which it was supposed,
woud have contributed _to facilitate the Direction of the_ Balloon, but
were found _greatly to retard the Celerity_ of its Motion.”
Now if any Credit can be given to Newspaper Accounts, (that of the
Beccles Balloon being an entire Fable,) it is to be lamented that the
Wings were cut away for the Reason assigned: as it seems the only one
that could properly be offered for applying them.
315. 2. Balloons already rise like a Rocket, and press forward almost
with the Celerity of the Wind: it is therefore evident, that these
Celerities must be _greatly retarded_, in order _to facilitate the
Direction_: and consequently that the Wings bid fair to have answered
the Intention of their ingenious Projector. And why precipitately cut
them away, before the Balloon was left to the Pleasure of the Winds?
since no regular or safe Manouvres ought to have been attempted, till
that Time.
There appears to have been much the same Reason for rejecting the
Piedmontese Wings, that there was for condemning the use of a
Parashute, to which a Dog being appended was killed in the Descent:
because the Parashute was not let loose at a sufficient Height, nor was
it properly distended.
315. 3. It seems, that as the Wings had _greatly_ +impeded+ the
Balloon; a certain _Addition_ to them might have _nearly_ +stopped+ it
in the Air.
For the Balloon having once acquired an uniform Motion, by encreasing
the Surface of the resisting Body, or Wings, the Balloon maybe retarded
to a certain Point. But the Resistence encreasing woud raise the
resisting[105] Body above its Power of Action, and therefore, in Fact,
lessen it; by which Means the Balloon woud continue to be propelled in
the Direction of the Wind, with a Force equal to that Diminution.
Suppose, for Instance, that, instead of the half Mile Flag, which
evidently checked the progressive Motion of the Balloon (Section 70) a
larger square Surface, of varnished Silk, or a triangular Latteen Sail
(like the Αρτεμων of Le Roi[106]) was substituted, and kept stretched,
by a hollow Cane, or Yard.[107]
315. 4. Also, that by Means of a Fan or small Oar, acting as a Rudder,
to be folded and taken back into the Car at Pleasure, the Balloon was
compelled to move with a given Side foremost; that the Sail was let
down below the Car, by strong silken Cords fastened to each Angle;
and lastly, that leaden Weights, (each weighing an Ounce Averdupoise
when widely perforated, and put throu’ the Ends of each Cord before
it is fastened to the Car), be let down to each Angle; occasionally
encreasing the Weights (or Sail) in Proportion to the Wind; which
relative Weights (or Sail) will best be determined by repeated
Experiments; will not such an Apparatus or Anemometer-Sail, acting as a
Vis Inertiæ nearly at right Angles against the Force of the Wind, check
the Balloon; till the encreasing Resistence raising the Sail upwards
towards the Horizon diminishes its Power of Action? With this Sail
therefore, which requires little Attention; and with the Assistance of
Wings moved by Levers, pressed alternately downwards as the Bellows
of an Organ, by the Feet of the Aironaut and mere Weight of his Body,
standing upright near the Center of the Car; the Balloon may probably
be, in some Respect, subject to Direction, and move obliquely against
the Wind, or with Force in a Calm.
The Balloon and Anemòmeter-Sail, like the Earth and Moon will turn on
their common Center of Gravity.
315. 5. It is possible to erect a light hollow Mast throu’ the Car, and
throu’ the Balloon, by Means of a cylindrical Tube of varnished Silk,
extending from Top to Bottom, in order to sustain the Balloon in an
upright Situation, and make it keep Pace with the Car, when the latter
is propelled by the Wings. The Mast shoud be covered with soft Cotton,
to lessen the Roughness of the Friction. It may also contain within it,
another slenderer hollow Mast, after the Manner of a Cane Fish-Rod;
either to be lowered out, and placed horizontally across or below the
Car, to serve as a Guard for the Bottom of the Anemòmeter-Sail; or to
be let down to any Depth occasionally: and other Sails connected, by
the usual wooden Rings, and kept tight by Cords running throu’ Blocks
fastened to any Part of _the equatorial Hoop_, as used at first, by
the _gallant Admiral of the Air_ +blanchard+, and afterwards too
precipitately rejected; since, in Case of a Rupture of Gass throu’
the upper Hemisphere of the Balloon; the equatorial Hoop preserves
the Parashute complete: and for Want of which Hoop, young Arnold had
certainly lost his Life, if the Water of the Thames had not broke his
Fall.
During the Descent of the Balloon, the Sails are to be taken in, and
the lower Mast projected into its Socket.
315. 6. Different Trials may be repeatedly made: the Effects of which,
whether evidently useful or _apparently otherwise_, being carefully
recorded and regularly published _in Detail_, may afford Data for
the Prosecution of further Discoveries, and lay the Foundation for a
rational Superstructure of _airostatic Navigation_.
[Sidenote: On the Manner in which the Wind, Anemòmeter, and propulsive
Machinery will probably operate on the Balloon.]
Sect. 316. Art. 1. By adding Weights, and encreasing the Surface of
Anemòmeter-Sails; the Vis Inertiæ will become so powerful in the
Direction of the resisting Medium of the Air; that the Wind in the
opposite Direction will force the Balloon out of its Vertical, and
incline it to the Horizon. The Car will be a Fulcrum Axis or Center of
Motion: on an imaginary Point of which, as on a Pivot, the Balloon and
Sails will turn opposite Ways, balancing each other in every Situation.
316. 2. The Balloon must therefore be brought back into the Vertical by
a counter Exertion of the Wings: to which the Vis Inertiæ must always
be made to bear a just Proportion.
The Declination of the Balloon is the only Inconvenience foreseen to
result from an Anemòmeter too large, or too heavily laden: and it is
instantly remedied by slacking the Sail.
One Thing still remains to be mentioned.
317. Balloons _durably_ Air-tight, and terminating in a _Hemisphere_
above, (Section 307); ought to have their Dimensions such, that there
shoud be no Occasion for more than their upper Hemisphere to be
inflated. Under which Form, they may with Ease and Safety be pitched
as Tents on the Ground; by Cords fastened at equal Distances to the
equatorial Hoop; and on Occasion by the Aironaut himself, while in the
Car: who may be provided with Iron Ring Stakes barbed, and fastened or
ready to be fastened to each Balloon-Cord: and, as soon as the Balloon
is moored by the Anchor, Grapple, and snatch Block, (Section 298, 3)
with a light Axe drive down the Stakes round the Car, and regulate them
when he alights from it, on the Ground.
CHAPTER LXI.
HINT FOR A VANE-SAIL TO PREVENT THE BALLOON FROM TURNING ROUND,
WHILE THE WIND CONTINUES STEADY.
[Sidenote: Hint for a _Vane-Sail_.]
Section 318. To the Block-Pulley in the equatorial Hoop, hoist a Sail,
whose Shape is as follows.
From the equatorial Hoop, let fall a Perpendicular: and from the lowest
circular Point in the Circumference of the Balloon, draw a Tangent, or
horizontal Line, till it meet the former: these Lines, together with
that Part of the Circumference intercepted between them, in the Points
where they touch the Circle, forms a Space, which is the Shape sought.
The Sail may be kept steady by a hollow Cane or Bowsprit thrust out
from the Car, and made fast with the usual Tackling.
319. Hint for an Umbrella-Pendulum or Valve-Swing, to project the
Balloon in a Calm in the ethereal Regions, above the Station of
Clouds; where the Resistence from the Air is much less than at the
Surface of the Earth.
[Sidenote: Hint for a _Valve-Swing_ to project the Balloon in a calm
and elevated Atmosphere.]
Let the Car of the Balloon be perforated so as to admit a light Gordon
Mast, or Pole 18 or 20 Feet long, perpendicularly throu’ it. (315, 3.)
At the Distance of five Feet from the upper End of the Pole, a light
hollow cylindric Tube of Iron, one Foot long, as a Bolt, shoud be put
throu’ it, at right Angles: so as to play smoothly in two Iron Bends,
fixed in the Car; one Bend so far moveable, as to rise with a Hinge to
admit the End of the Bolt; the other Part of the Bend to be perforated:
throu’ which a hollow Staple is to be fastened, with a spring Cotterel
chained: this Apparatus will prevent the Pole from turning round.
Two light Frames of Wood, of a parallelogrammic Form, each twelve Feet
by six, and covered with varnished Silk, are to be hooked, one on each
of the opposite Sides of the Pole, from its lower End upwards; the
Frames to be moveable in such a Manner, that on pressing the Pole one
Way on the Axis or Bolt, the Frames shall lie close; but on recovering
the Pressure, the Frames shall expand and open, so as to form an obtuse
Angle with each other, or to lie almost in the same Plane, when the
Recovery is made briskly, and with a Degree of Strength.
A Handle of Wood, the same Size with the Bolt, may be fastened throu’
the Substance of the Pole near its upper End.
The Operator is to stand in the Car, and work the Pole backwards and
forwards, which will give a progressive Motion to the Balloon in a
Calm.
This Method may possibly prove more effectual than the Umbrella-Wheels,
on an horizontal Axis, of Mons. Carra;[108] as the Umbrella-Pendulum
is easily unrigged, removed, and brought into the Car, in Case of a
Whirlwind; by Means of a _circular_ Rope fastened to the Axis or Bolt,
one End being in the Car, and the other put throu’ the Aperture at the
Bottom, and brought up from the Outside again into the Car.
The Umbrella-Pendulum may be made to turn round horizontally on the
Bolt; the Ends of the Bolt being fastened under a circular hinged
Socket, or Groove, of Iron.
CHAPTER LXII.
DEFECTS, IN THE COMPOSITION FOR BALLOONS, REMEDIED.
ALSO ON THE COCHUC-VARNISH.
Section 320. Balloons are defective in the Composition for _the
Varnish_; which, till lately, was incapable of rendering the Balloon
completely and _durably_ Air-tight.
321. It was sometime ago reported at Paris, that Mr. Dutourny de
Villiere had undertaken to construct a Balloon so truly _impèrmeable_,
that he woud warrant the Duration of it, for _several Weeks_ in the Air.
And it is _since_ known that this _Desideratum_ of the Art has been
effected, in the Composition for the celebrated Balloon of Messrs.
Auban and Vallet, +first+ made subject to Direction.
322. Mr. Berniard, a French Chymist, has made curious tho’ unsuccessful
Experiments, in order to melt the cochuc or elastic Bottle; as may be
seen in the 17th Volume of the “Journal de Physique.”
Mr. Faujas and others made similar Trials.
323. The Writer, unacquainted with what had _then_ been done in this
Matter, coud not help remarking the striking Properties of the _Cochuc_
in its present Form, to answer every Intention of the best Varnish,
if its Price was lower;—viz. _compact_, _pliant_, _unadhesive_, and
_unalterable by Weather_;—if it coud be dissolved, and afterwards made
to recover its present +unadhesive+ Form: an Art in which the East and
West-Indians are still _our Masters_.
He has, however, after expensive Trials and Combinations, been able to
reduce it into a _limpid Liquor_.
As it may prove a useful Ingredient for _Air-tight_ Varnish; the Secret
he now discovers to the World: and it is merely this.
324. “Take any Quantity of the Cochuc, as two Ounces Averdupois: cut it
into small Bits, with a Pair of Scissars.
Put a strong Iron-Ladle (such as Plumbers or Glaziers melt their _Lead_
in) over a common Pit-Coal or other Fire.
The Fire must be gentle, glowing, and _without_ Smoke.
When the Ladle is hot, much below a +red+ _Heat_; put a single Bit into
the Ladle.
If _black_ Smoke issues, it will presently _flame_, and disappear: or
it will evaporate without Flame: the Ladle is _then_ too hot.
When the Ladle is less hot, put in a second Bit, which will produce a
+white+ _Smoke_.
This +white+ _Smoke_ will continue during the Operation, and evaporate
the Cochuc: therefore no Time is to be lost: but little Bits are to
be put in, a few at a Time, till the whole are melted. It shoud be
continually and gently stirred with an Iron or Brass Spoon.
The Instant the Smoke changes from _white_ to +black+, take off the
Ladle; or the whole will break out into a violent Flame, and be spoiled
or lost.
(Care must be taken that _no Water_ be added: a few Drops only of
which, woud—on Account of its superior _specific Gravity_, for the
Cochuc swims in Water—make it boil over furiously, with great Noise.)
At this Period of the Process; two Pounds, or one Quart of the +best
drying-oil+, (or even of _raw_ Linseed-Oil, which, together with a few
Drops of Neat’s-Foot-Oil, must have stood a Month, or not so long, on a
Lump of Quick-Lime, to make it more or less +drying+)—being poured off
the Lime-Lees; is to be put into the melted Cochuc, and stirred till
hot: and the whole poured into a glazed Vessel, throu’ a coarse Gauze,
or fine Sieve.
When settled and clear, which will be in a few Minutes; it is fit for
Use, either hot or cold.
The Silk shoud be stretched all Ways horizontally, by Pins or
Tenter-Hooks, on Frames; which Frames, the greater they are in Length,
the better: and the Varnish poured on +cold+, in _hot_ Weather; and
+hot+, in _cold_ Weather.
It is _perhaps_ best, always to lay it on, when _cold_.
The Art of laying it on properly, consists in making +no intestine+
Motion in the Varnish, which woud create minute Bubbles. Therefore
Brushes of every Kind are improper.
Each Bubble breaks in drying, and forms a small Hole, throu’ which the
_Air_ will _transpire_.
CHAPTER LXIII.
ON VARNISHES, CONTINUED.
Section 325. To those, who are unacquainted with the Principles of
Chemistry, or the Books which teach it; and yet are desirous to make
Experiments, which may throw fresh Light on this curious and useful
Art, when applied to Varnishes for Umbrellas or Balloons; the following
detached Notes are recommended: which were communicated to the Author
by _different_ Artists; each _eminent_ in his Profession.
326. To make copal Varnish.
Procure some bluish Flemish alcaline Ashes, (an Ounce suppose): pound
them _very fine_, and lay them before the Fire, till they become _hot_
and +dry+.
Put them, while hot and dry, into Oil of Turpentine, (a Pint or Pound
for Instance): or, into the same Quantity of Spirits of Wine.
For by Means of the Alcaly,[109] all the Water invisibly contained in
the Oil or Spirits will be absorbed, and leave the Oil or Spirits,
+alcohol+, that is, quite pure, and highly rectified: which Process is
called _alcalizing_ the Turpentine, or Spirits.
Put the Turpentine or Spirits so alcalized, into a Copper Vessel, with
half an Ounce of +yellow copal+ _finely_ pounded and sifted.
Stir it, and the Copal will soon melt.
N. B. If you alcalize the Spirit of Turpentine, when the Copal is
dissolving, add a little Spirit of Wine: and if you alcalize the
Spirit of Wine, when the Copal is dissolving, add a little Spirit of
Turpentine.
The +sediment+ of the Varnish will dry on the Silk, in a few Hours.
The thicker the Varnish, the sooner it dries.
[Sidenote: To make _thin_ Varnish.]
327. Article 1. To make an excellent +thin+ Varnish.
To one Quart of _cold raw_ Linseed-Oil poured off from the Lees made
by a Lump of _unslacked_ Lime on which the Oil has stood, ten or eight
Days, at the least, in order to communicate a drying Quality: (or on
_brown Umber_ burnt and pounded, which will have the like Effect:)—add
half an Ounce of Litharge.
Boil them for half an Hour.
Then add half an Ounce of _the Copal Varnish_.
327. 2. While the Ingredients are on the Fire, in a Copper Vessel; put
in one Ounce of Chio Turpentine, or common Rezin: and a few Drops of
+neat’s-foot-oil+: and stir the whole with a Knife, or any clean Thing.
When _cold_, it is ready for Use.
327. 3. The Neat’s-Foot-Oil prevents the Varnish from being sticky, or
adhèsive: and may be put into the Linseed-Oil, at the same Time with
the Lime, or burnt Umber.
327. 4. To make the above Varnish _transparent_, or _white_; use Mastic
and Copal: to make it _brown_, use Seed or Shell-Lac, and _browner
still_, use _pounded burnt_ Umber.
327. 5. _Rezin_, or _Chio Turpentine_ may be added, till the Varnish
has obtained the desired _Thickness_.
327. 6. It must likewise be observed, that _Litharge_ rots the Silk:
therefore Trials must be made without the Use of Litharge.
327. 7. The _longer_ the raw Linseed-Oil remains on the unslacked Lime,
or Umber, the _sooner_ will the Oil dry, after it is used.
If some Months; so much the better. Such Varnish will _set_, i.e. will
not run, but keep its Place on the Silk, in four Hours.
The Silk may then be turned, and varnished on the other Side.
328. +on gum mastic, sandarac, seed-lac, shell-lac, and copal.+
328. 1. Gum _Mastic_ dissolves, _without pounding_, by adding a few
Drops of Oil of Vitriol: so do Gum _Sandarac_, and Gum _Copal_, when
finely pounded and sifted.
328. 2. Gum _Sandarac_, and Gum _Mastic_ are great Driers of
themselves: and may be substituted for Litharge.
328. 3. The Mastic dissolved in the Oil of Vitriol, gives a _sweet_
Smell to the Varnish.
328. 4. Sandarac will soon grow _dusk_ in the Fire: it melts into a
transparent Liquor.
328. 5. Sandarac, Seed-Lac, and Shell-Lac, must be finely pounded and
sifted, before they are used.
329. The Author having examined different Kinds of varnished Silks, in
different Places, does, from their Excellence, recommend those made by
_Fawkner_, Umbrella-Maker, Alport-Street, Manchester; a Person wholly
unknown to him, but from the Merit of the Work: which consists not only
in the Varnish itself; but in the peculiar Method of _applying_ it,
which the Author _is not at Liberty to make public_.
_Fawkner_ can warrant his Silk _Air-tight_; _soft_ and _unadhesive_;
durable, and _unalterable_ by that Excess of Heat and Cold, to which
the Balloon is, at the same Time, subject; viz. _internally_, to
the hot depredating and caustic Fumes, rising with the Gass: and
_externally_, to the _Sun_, _Wet_, _Frost_, and _Drought_.
CHAPTER LXIV.
HINTS ON IMPROVEMENT OF THE MACHINERY.
Section 330. In order to make Improvements of the Balloon still more
rapid and general; the Society for the Encouragement of Arts, who have
given no particular Encouragement, in Imitation of that at Lyons, to
the much-wished-for Art of directing the Balloon;—might offer a Premium
for different Inventions of a _propulsive Machinery_, the Models of
which are to be made at the Expence of the Society, within a certain
limited Sum: and, without condemning what cannot be known unless by
repeated Trials,—give Encouragement for such Trials: the Models to
remain with the Society for public Exhibition.
331. Also, Figures and Explanations of such Machinery as have been
tried, viz. the Fly or Moulinet of Blanchard; and of those which have
not succeeded for Want of Trial; might be sent by the Inventors, in
order to perpetuate the Invention, either to the _Society of Arts_;
or to the Editors of creditable Magazines, who woud be glad of such
ingenious Acquisitions, as it woud be a Means of procuring Purchasers,
and circulate the Knowledge of this _gigantic_ Infant Science.
Improvement woud then go on apace, and in a Chain: each Labourer
forging and finishing his respective Link.
Whereas at present every one is obliged to find his own Materials, sink
the Foundation, raise and finish the Building. And hence so little Work
is done, worthy the Inspection of a skilful Architect.
CHAPTER LXV.
ON THE UTILITY OF BALLOONS:
AN INTRODUCTORY CHAPTER.
Sect. 332. Art. 1. It seems a favourite Question, among those who
take a Pleasure in objecting to every Thing they neither do nor will
understand, to ask, “Of what Use can these Balloons be made?” and
without waiting for an Answer, to say—“they pick the Pockets of the
Public, risque the Lives of the Incautious, encourage Mobbing and
Sharpers, and terrify all the World.” These trite Reasonings are all
very true, but little to the Purpose: the Effects above described being
merely those arising from Novelty. If, says one in an inferior Station;
“they coud convert Balloons into common Stage Waggons; Goods might be
carried with the greater Expedition:” or, “into Stage Coaches,” says
another: or, “into Mail Coaches” says Palmer; “it woud be certainly
very clever, as I have the Patent:”—“or into comfortable Carriages
to step in out of +the window+, at a Moment’s Notice; that woud be
something,” cries a Nobleman: “it woud _save_ one a Couple of Sets of
Horses, and woud eat Nothing: one might ride one’s own Balloon Matches,
from one’s Window to Newmarket, and from Newmarket to +town+; dress for
Court as we _do_, and make _Nothing_ of it.”
Such are the different Ideas annexed by different Ranks of Men, to the
Word +utility+ when applied to Balloons.
332. 2. For once let the feeble Voice of a French Philosopher be heard,
the Abbée Bertholon: who may perhaps assert that all this is not
impossible.
A Series of Experiments only can determine: and let the following
Remarks serve as an Introduction to his Opinions.
332. 3. It is certain that the Progress already made in the Improvement
of Balloons, since their Invention only three Years ago, is far
superior to the Acquirements in every other Art.
The Antients knew, that excited Amber attracted Straws, and certain
other light Substances: but medical Electricity, and a Preservative
from Lightening, were notwithstanding reserved for the Moderns.
They likewise attended to some striking Effects of the natural
Loadstone: but were totally unacquainted with the artificial Magnet,
and the amazing Powers conferrable by it in the Disorders of the
Imagination: nor did they know the Polarity of its Needle, or
Application of it in the Compass.
They had not combined Nitre and Sulphur with Charcoal: much less had
they changed the Mode of War into Science, by establishing Founderies
for Cannon, and the Study of Tactics. Yet some Nations with a
Knowledge of the Moderns, as the Chinese, have not improved, even in
the Construction of their Vessels, according to the European Manner;
continuing still in practical Ignorance.
Nor have other Indians improved in Proportion to the Opportunities of
Instruction in several Arts.
Those of America, for Example, who continue to hunt, fish, and scalp:
neglecting the Plough, and other Arts of Property and Peace.
332. 4. And thus it has been with the British Nation on the Subject of
Airostation.
Cavendish, Priestley, and others, had produced inflammable Air,
weighed, and found it lighter than common Air: and all that had seen a
bright Fire might conclude, if they reasoned at all, that hot Air was
lighter than cold.
Yet if Montgolfier had not made, +on a large scale+ the Application
of hot Air, in a Bag open at the Bottom, and properly poised; Charles
and Roberts woud probably not have thought of applying the Gass of
Cavendish: and Mankind woud not _yet_ have soared into the etherial
Regions.
332. 5. In this the French are still before the English, and will
continue so to be, without a laudable and unlooked-for Emulation in
the latter. That the former admire Liberty, Montesquieu’s “Spirit of
Laws” may determine; but they are not _addicted_ to Politics. Their
Nobility are endowed with a liberal and enterprizing Spirit. They join
and patronize Men of Genius and Talents in the Cultivation of the Arts,
and Improvement of every Kind of experimental Knowledge. Their Pleasure
consists in a national Ambition to excel.
They have Leisure, and are sober.
Half that Time which Men of Fortune in France dedicate to Taste,
Invention, and Refinement; Britons spend among the Beasts and Birds:
the other half, at the Bottle, and in political Cabals.
_Present Profit_ is almost the sole Motive for Excellence in
Great-Britain: and Experiments[110] not made with that View, are seldom
repeated; are overlooked and forgotten.
CHAPTER LXVI.
ON THE UTILITY OF BALLOONS.
Section 333. The Balloon opens a new and unlimited Field for
Philosophical Discoveries.
334. The many curious and interesting Conjectures which Mons. de Luc
(before the Invention of Balloons) throws out, in the Course of 4 large
Volumes, on the Subject and Qualities of the Atmosphere; may now be
determined by actual Trial.
335. The Abbée Bertholon wrote in 1784: and has particularly mentioned
the following Points, as capable of ample Investigation, and.
Discussion.
Sect. 336. Art. 1. _The Temperature of the Air at different Heights._
Which will determine whether the Atmosphere be _practically Navigable_,
at all Times and Places.
336. 2. _The dissolvent Power of the Air by Means of an Atmometer for
Evaporation._
Probably the Height may be determined, to which Clouds commonly ascend
in order to find the proper horizontal Level, in which Balloons can
move with the greatest Ease, Safety, and Expedition.
336. 3. _Variations of the Barometer._
This will ascertain the exact Height, without Mensuration.
336. 4. _The_ +densities+ _at different Heights_.
A principal Object in de Luc’s abstruse and scientific Researches: not
only useful but necessary to determine the Laws of Refraction; without
which, Astronomy, and consequently +navigation+, must remain defective.
336. 5. _The different Effects of Tastes and Odors, at different
Heights_: _Experiments on Plants and Animals: also of_ +sound+.[111]
These may produce new and salutary Effects on the human Body: and
determine how far a Change from hot, putrid, and impure, to cool pure
Air, impregnated with the invigorating aërial Acid, may contribute,
without the Aid of Drugs, to the Recovery of the Sick, and Invalid: or
promote Longevity.
336. 6. _The Direction and Velocity of the Wind._
The different Currents and their different Heights, the Limitation of
each Stratum of Wind, together with their different Temperatures at
the same Time, will point out the proper Paths for the Balloon to move
in, at all Times, and _possibly_ without the Necessity of accurate
Direction: the Mode of Ascent and Descent being _already_ known, and
proper Instructions given for a secure Landing.
336. 7. _Electricity of the Air_, +meteors+.
This may lead to the Birth Place of Lightening, and Methods how to
avoid its Effects in the Air. Tho’ it be already known, that little
Danger is to be apprehended, on Account of the mutual Repellency
between the electric Fluid, inflammable Gass, and oiled Silk.
The Irides, the Coronaes, Haloes, and other Phenomena of Colours: the
Generation and Solution of which may be investigated on the Spot.
336. 8. _Geography may become a new Science._
336. 9. _Use of the Balloon for Signals in the calm Air, above
Molestation; above Winds still blowing below: to discover the Positions
of an Army, or Navy._[112]
336. 10. _To throw principal Men into a Town: and convey others out of
it._
336. 11. With the Montgolfier Balloon, to try Experiments on Light, and
Fire: to transport great Weights: raise them out of the Water: draw up
Piles, raise Trees, Vessels, &c.
336. 12. The Parashute to secure a Man from too precipitate a Fall, is
to be 5 Yards in Diameter, when extended: the Man,—weighing 140 Pounds,
and the Parashute weighing 10 Pounds, with a Surface of 150 square
Feet,—woud, in that Case, feel no greater Shock than if he had fallen
from the Height of six Feet.
336. 13. _Compass and its Variations: also the different Branches in
Astronomy._
His Hints on the Direction of the Machine are ingenious.
337. 1. Wheels furnished with Wings.
337. 2. Imitations of the Form and Motions of Fish.[113]
337. 3. Vessels to condense Air, as the Bladders of Fish.
337. 4. Wind-Guns, Wind-Fountains.
337. 5. Elopile and Vapour Steam.
337. 6. Contrary Currents at different Heights: Proof of.
337. 7. New Hints for Balloons to be raised by Steam.
337. 8. Mons. Gouan’s Invention to go +three hundred miles a day in a
calm+.
338. The general Use to which Balloons seem capable of being applied,
with the Assistance of propulsive Machinery, in the Calm which exists
above the Level of a +contrary+ Wind; is that of a common Vehicle, not
subject to the Inconvenience of Roads and Inns, between distant Places
and Countries, for Passengers, properly accommodated in a Boat-shaped
covered Car, furnished with Provisions, and occasional Siberian
Cloathing: the Car to be surrounded with, and resting on Bladders, one
_fourth blown_, and having each a few Drops of Water within, to keep
them moist and elastic;—to prevent an _accidental_ Shock in alighting
on Land; and from sinking, if on Water.
Such a Conveyance (the Balloon being once made _Air-tight_, and
furnished with an _Air-Bottle_ to ascend and descend _without Loss_
of Gass) is ready at all Seasons and Times: both Night and Day: for,
as the Aironauts will enjoy continual Sunshine without a Cloud, from
his Rising to his Setting: so, during the Night, the Light of the
+stars+, always intercepted in its Passage to the Earth by Clouds or
thick Vapours, will be greatly augmented, when above both: besides
the probable Increase of Light _reflected_ from the upper Fields
of white Clouds shone on continually by the different Planets and
Constellations: all which will afford an Illumination equal, if not
greater, than that of a cloudless frosty Night, when the Ground is
covered with Snow.
And such Light will be sufficient to read or write by: also to examine
the _Barometer_,[114] in order to know the _Height_ and Level of
the Balloon above the Surface of the Earth; and the +compass+ for
Direction.
If Aironauts propose to ascend by Night, and in the Moon’s Quarters;
observing likewise the Precautions already given; it may be proper also
to consult and take with them the Ephèmeris, in order to know the Time
when the Moon rises, and also when she is at the highest, i.e. in the
South, or has remained about half her Time above the Horizon.
The plainest Points, on which not only the Success of an Excursion, but
the Lives of Aironauts may depend, are too frequently neglected, as
unimportant and trivial.
CHAPTER LXVII.
THE PROCESS OF INFLATION.
[Sidenote: Process of Inflation on the Day of Ascent, viz. on Thursday
the 8th Sept. 1785.]
Sect. 339. Art. 1. Three cylindric wooden Vessels were sunk more than
half their Depth into the Ground: two of them, each, 5 Feet Diameter,
and 5 Feet high: the third, 8 Feet in Diameter, and 8 Feet high.
An oblong Hole, 4 Inches by 3, was made in each Vessel: and each Hole
was furnished with a solid wooden Plug (made tapering) 6 Inches in
Length: throu’ these the Vitriol was poured.
Besides which, there was an oblong Opening in each Vessel, large enough
to admit a Workman, to distribute the Iron equally over the Bottom, and
to pour in Buckets of Water: which Openings were well stopped, as soon
as the Iron and Water were poured in.
As the vitriolic Acid is _corrosive_, burning the Skin or Cloaths; the
following Precautions were taken.
An occasional moveable Tub was provided, 3 Feet high, and 3 wide: in
the Center of whose Bottom was an oblong Aperture, equal to that in
each of the Vessels: a corresponding Tin Tube, 6 Inches long, and
narrowing to the Bottom, was nailed by its Border on the Inside of the
occasional Tub; so as to go easily into any of the oblong Holes.
A Bottle of Vitriol being brought in its Basket by two Men, and made
to rest on the Top of one of the fermenting Vessels; a third Assistant
held the occasional Tub in his Hands, with the Plug-Staff fastened in
the Aperture of the Tin Tube; and the Instant a fourth Person opened
the Hole in the fermenting Vessel; the Assistant placed the Tin Tube in
the Hole, keeping the Plug tight, to prevent the Escape of Gass.
The Bottle of Vitriol was then immediately poured into the occasional
Tub: and the Bottle being removed, the Plug-Staff was taken out, and
the Vitriol suffered to run into the fermenting Vessel: the Assistant
watching for the Instant when the Vitriol was run out, in order to
_force in_ the Plug-Staff again, and prevent the Escape of Gass: after
which, the Tub was rinced with a few Quarts of Water, let also into the
Vessel.
The same Tub was then removed: the oblong Hole in the fermenting
Vessel instantly covered; and, by driving down the solid wooden Plug,
continued _Air-tight_; by Means of moist Clay, and a little Water,
kept purposely on the Tops of each Vessel, to discover by the Bubbles,
whether Gass escaped.
[Sidenote: 20 Hundred Weight of Iron-Turnings.]
In these Vessels, early on the Morning of the Inflation, were
distributed 20 Hundred Weight, at 120lb. Averdupoise to the Hundred,
consisting of cast Iron-Filings, and of a Mixture of Cannon-Borings.
The Borings were bright and fresh when thrown into the Water: and any
Bits of Wood that swam, were skimmed off.
_Rusty_ Iron emits Gass, that is heavier than common Air, and therefore
is improper.
[Sidenote: 16 Bottles of Vitriol.]
At the same Time, 16 Bottles of concentrated vitriolic Acid, or as it
is improperly called Oil of Vitriol, were brought in their Packages
near the Place, to be ready for Use: each Bottle at an Average
containing 112 Pounds Averdupoise, of Vitriol: each full Bottle and
Package together weighing from 136 to 148 Pounds.
[Sidenote: 4 Pints of Water to a Pound Averdupoise of Acid.]
339. 2. To the Iron in each Vessel, was then poured a Quantity of
Water, which was measured in the Proportion of about 4 to 1: i.e. 4
_Pints_ of Water to one _Pound_, of the vitriolic Acid.
The Height of Water and Iron in each Vessel, being then gaged, was
about 14 Inches.
In a Line with the two smaller Vessels, and between them, was fixed
another wooden Vessel or Cistern, filled with Water.
[Sidenote: Improvements suggested.]
(N. B. Fresh Water ought to have flowed continually into it, and to
have run over the Top of the Cistern: for the same Quantity being
once saturated, can no longer absorb the alcaline and fixed Air to be
separated from the Gass before the latter enters the Balloon.)
In the Cistern was fixed a Stage, consisting of 4 long Feet, (reaching
to the Bottom of the Cistern,) nailed at their upper Ends to the Inside
of an inverted Tub or Funnel, so placed over the Center of the Cistern,
that 3 Inches of the lower Part of the Rim of the Funnel were under
the Surface of the Cistern-Water: the Funnel was _cylindric_, 3 Feet
across, and 2 Feet high.
An Open was cut, 1 Foot Diameter, in the Bottom of the inverted Funnel:
on the Circumference of which was nailed a Tin-Cylinder or common
Conductor, 2 Feet high: and at a _certain_ Angle, as most convenient,
was soldered a cylindric Arm, of equal Diameter, and 1 Foot long;
having a Lip, Ring or Rim, on its outward circular Edge.
Round this Rim was fastened a varnished Linen Tube, of equal Diameter
with the Cylinder.
At a small Distance, about a Yard from the Cistern, stood a slender
Stillage, 3 Feet high; on which was supported a detached Tin-Cylinder
or Connecter, 1 Foot long and 1 Foot Diameter, made with a Rim at
each End: in the Center of whose lower Side was soldered, at right
Angles, another Tin-Cylinder or Evacuatory, 6 Inches long and 6 wide:
its Use is to let out any Water, that the Heat of the Mixture might
cause to boil and rise up out of the fermenting Vessels: and thus be
_evacuated_, without entering the Balloon: or, if condensed in the
Balloon, might run out by the same Orifice.
The opposite End of the varnished Linen Tube was fastened round one End
of the detached Cylinder on the Stillage: and round the other, was tyed
the Neck or Bottom-Opening of the Balloon.
Each of the 2 smaller fermenting Vessels was furnished with a cylindric
Tin-Tube; each Tube 4 Inches and a half Diameter, nailed on the Outside
of a circular Opening in the Top or Head of each Vessel; communicating
by additional rectangular Bends under the Funnel and Water in the
Cistern: the great fermenting Vessel had 2 Tubes, each 4 Inches and a
half Diameter; communicating with the Funnel.
[Sidenote: Improvements suggested.]
340. The Process woud have been more complete, if the fermenting
Vessels had been sunk till their Tops were even with the Ground: and
plaistered round their Outsides with soft moist Clay, six Inches thick,
to keep them Air-tight.
Also, if the common Conductor had been only 1 Foot high: its horizontal
or rectangular Arm only 6 Inches long: the Linen Trunk but 3 Feet,
joining the Connecter on the Stillage 1 Foot high, to communicate with
the Neck of the Balloon; which Neck shoud be 3 Yards in Length, and its
circular Opening 1 Foot, at least in Diameter.
CHAPTER LXVIII.
[Sidenote: Inflation began about X. in the Morning.]
Section 341. The Process of inflating the Balloon began about X. in the
Morning, by pouring 4 Bottles of Vitriol, immediately one after the
other, into the occasional Tub, properly placed over one of the smaller
fermenting Vessels: the Tub being instantly rinced with a few Quarts of
Water, which was suffered to fall into the same Vessel.
The oblong Hole was left purposely open for a Minute, till the strong
Smell of the Gass was perceived above the Orifice: i.e. till the Gass
had pressed out all the common Air that remained floating over the
Surface of the Mixture in the fermenting Vessel: which Smell being
_plainly perceived_, the _solid_ Plug was immediately _driven_ down.
And presently the Gass was known to press forward with an elastic
Force throu’ the Tin Conductor, by the Motion it communicated to the
Surface of the Water in the Cistern: thence upwards throu’ the common
Conductor: at its Departure from both of which throu’ the Linen Trunk,
and Neck into the Balloon, the Gass makes a guggling obtuse Sound by
quick Intervals according to the Quantity of Gass protruded.
And as the Intervals encreased, a Judgment was formed, that the
Operation began to be less vigorous: and consequently that it became
necessary, either to renew it by an Addition of more Vitriol and Water
in the same Vessel, or to set the other small Vessel in Fermentation,
the latter of which Mr. Lunardi preferred: this happened about half an
Hour after the Vitriol was poured into the first Vessel.
342. After the second half Hour, eight Bottles were poured, by four at
a Time, into the great Vessel.
And at one o’Clock, the Balloon, without any farther Trouble was
beautifully inflated.
No Iron Rods were used to stir up the Borings or Filings at the Bottom
of the Vessels: the Vitriol being found so heavy as to penetrate them
as fast as the Iron, contiguous to the Vitriol, had parted with its
Gass.
At each of the two former Inflations, a similar Accident happened which
may be imputed to the same Cause.
343. During the first Inflation, the solid oblong wooden Plug fell into
one of the fermenting Vessels: the hot Vapour, forcibly issuing from
the Orifice, was condensed in the Form of a _white_ Smoke; which being
mistaken by the Company, a Cry was immediately heard of Fire, Fire:
on which the Workmen retreated. Mr. Lunardi incautiously thrust his
Arm into the Orifice to extract the Plug: at the same Time being much
burnt, and failing in the Attempt; the Gass continued to escape, till a
new Plug was prepared.
344. During the second Inflation, one of the Plugs being driven too
forcibly; it was with Difficulty extricated, by the Strokes of a Hammer
against the Sides of it, which tended at the same Time to displace the
Boards forming the Top or Head of the Vessel: and, a little afterwards,
occasioned it to burst, unexpectedly +inwards+,[115] rendering the
Vessel useless for the Purpose of Inflation.
_Observation._ Therefore instead of the solid oblong wooden Plug, a
circular Hole, 4 Inches Diameter shoud be drilled in each Vessel: and a
corresponding solid wooden Plug 8 Inches long, 5 Diameter at the upper
Part, and tapering to near 3 at the Bottom, shoud be prepared by the
Turner.
In the upper Part of the Solid shoud be turned an inside Screw, to
which an outside Screw of the circular Plug-Staff, made of Oak, Ash, or
other heavy Wood, 4 Feet long, and 4 Inches Diameter, shoud be adapted:
the Worm of the Screw to be 5 Inches long.
A wooden Peg of Ash, about a Quarter of an Inch Diameter, may be put
throu’ a Hole near the Top of the Staff, as a Handle.
A Lever of such a Length and Weight will probably answer every
Intention, as no sudden Blows will be required to _fasten or extract
it_.
The occasional Tub, Tube, Plug, and Staff, shoud be fashioned after
this Model.
345. _The Price of the Iron and Vitriol for Inflation._
2000lb. of Iron Filings or Borings[116] delivered
on the Spot, at 6s. a Hundred, £. 6 0 0
16 Bottles of Vitriol, at an Average
38s. a Bottle 30 8 0
Concomitant Expences, 3 12 0
———————
£. Total 40 0 0
_Observation 1._ A great Saving might be made by conducting the Process
in a different Manner.
The Author making two Journies to Manchester, purposely to observe the
Process by Mr. Sadler; found that his Balloon was inflated in two Hours
each Time; by Means only of the two smaller _identical_ fermenting
Vessels which Mr. Lunardi afterwards purchased; but the Levity procured
by the former, tho’ he also expended 16 Bottles, was by no Means so
great as that gained with the Assistance of the great Vessel.
It has likewise been remarked by the Author, who has made several
Experiments to this End, that the Vessels always continued in
Fermentation and Ebullition, with a _quick Pulsation_, for at least 24,
and commonly during 48 Hours, after the Inflation was completed.
And, that not more than the Depth of _half an Inch_ of Filings had been
_calcined_ during the Operation: the rest being perfectly _bright_, and
untouched by the Acid.
_Observation. 2._ If therefore one Inch in Depth of Filings, be spread
over the Bottom of each of the _smaller_ Vessels only; the proper
Quantity of Water poured in; and _not more_ than two Bottles of Acid
used at once, in each Vessel; also, as soon as the Fermentation begins
to decline; other two Bottles, and a proportionable Supply of Water be
added; if suffered to work double, triple, or quadruple the Time;—the
Inflation will be as great, if not greater, for Instance, in six Hours
with eight Bottles, and two small _Tubs_, as it woud in three Hours,
with 16 Bottles, in the _same Vessels_.
The small conducting Tin Tubes ought instead of four and a half, to be
nine Inches Diameter: by which Means there will be no violent Pressure
of Gass to endanger the Bursting of the Vessels: particularly if the
Gass is not suffered to descend; but, on the contrary, according to
Instructions already given, either to rise, or move, in an horizontal
Direction, past the Evàcuatory, into the Balloon.
346. The Workmen may begin the Operation at twelve at Night, or at six
in the Morning: and the Time previously fixed for the Exhibition, may
be eight or ten Hours after the Operation has commenced.
The Necessity of a Current of fresh Water, throu’ a Pipe of at least
half Inch Bore, the larger the better, to supply the overflowing
Cistern, cannot be too much _insisted_ on: as the Levity of the Gass
almost wholly depends upon so trivial a Circumstance, as that of having
a plentiful Supply of _cold fresh_ and _soft_ Water.
347. _Observation 3._ Supposing the Balloon +air-tight+, near half the
Expence is thus saved in the Inflation.
Besides the greater Probability of +calm+ Weather for the Inflation,
if completed before X. in the Morning, more Time is given to remedy
Accidents, and rectify Mistakes: the Warmth of the Air likewise
encreases.
But above all; if an upper Current carry the Balloon to Sea, the
Aironaut may, (as before mentioned) drop into the Sea-Breeze, which
will waft him safe back till IV. in the Afternoon, or even later.
CHAPTER LXIX.
MENSURATION OF HEIGHTS.
[Sidenote: Rules for calculating Heights by Means of the Barometer and
Thermometers.]
Section 348. Rules for calculating the Height of Mountains, when
applied to those elevated Stations in the Atmosphere _attainable_ only
by Means of the Balloon, will henceforward become more useful, and
be more frequently practised: as the Lives of Aironauts _may_ depend
on a Knowledge of their _Height_ above the Earth; which, not being
determinable by _Sight_, in _all Weathers_, or at all Times, must be
referred to the _Barometer_ and _Thermometers_, they carry up with them.
De Luc, Horseley, Maskelyne, Shuckburgh, and Roy, have each written
+ably+ on the Subject, in the _Transactions_: tho’ few have either
Leisure or Inclination to follow them.
Sir George Shuckburgh has made successful Attempts to smooth the Way,
by Examples and Tables, yet is still too concise for actual Learners,
and the Generality of those who will have Spirit enough to go before
the Calculators in exploring the Atmosphere; but cannot dedicate
sufficient Leisure to overtake them in their Studies.
Each may therefore assist the other.
349. Whoever is at the Trouble of comparing the Observations made by
Shuckburgh, with the Directions here given, will find that the latter
contains the _Essentials_ of the former, with this material Difference,
that the Investigation moves here by Steps, which are all pointed out
to the Learner; and not by Strides.
Each Step is self evident: and, by carrying Conviction to the Mind, is
just what the Mind itself woud make use of, in the Attainment of any
_distant_ Truth.
To do every Justice to Sir George, the Merit of whose Performance wants
no Eulogium; his three Precepts are copied; tho’ rather as a Memorandum
for those who understand the Methods; than as plain Directions for such
as are yet to learn them.
It will be found likewise, that the first, second, and fourth
Tables are greatly enlarged: being calculated for those _extreme_
Temperatures, and Heights, which the Balloon _only_ can attempt to
reach: and the fourth Table, for greater Dispatch in computing the
Expansion of the Air.
The Foundation and Construction of each Table, is also methodically
traced and elucidated.
CHAPTER LXX.
METHODS TO ASCERTAIN THE TRUE HEIGHT.
Section 350. Methods to be pursued on taking and comparing Heights, in
order to ascertain the true Height of any Station in the Atmosphere, by
the Barometer and Thermometers.
For this Purpose it is necessary, 1st, to provide a Barometer, (whose
Bulb or Cistern is _large_ enough to contain all the Quicksilver in the
Tube;)—into the Frame of which, a Thermometer, on _Farenheit’s_ Scale,
is to be fixed or _attached_.
The Use of the _attached Thermometer_ is to point out the Temperature
of the Barometer.
2d. A second or _detached Thermometer_ is also to be provided.[117]
This is to be hung in the Shade at the Distance of a Yard (or two) from
the other:—to shew the _general_ Temperature of the Air at the same
Time and Place: and may be called the _Air Thermometer_.
A proper Person, on the Ground, having a good Watch, with Pen Ink and
Paper at Hand, is to attend the Instruments _below_ every ten Minutes,
(or at any other _preconcerted_ Intervals of Time,) putting down,
1st. The Time of each Observation.
2d. The Point at which the Quicksilver stands in the Barometer.
3d. The Degree of Temperature of the _attached_ Thermometer.
4th, and lastly, the Degree of Temperature of the _detached_ or
_Air_-Thermometer.
This Employment is to be carefully attended to; during the Time, that
_similar_ Observations, by _preconcerted_ Agreement, are making, with
three other _similar_ Instruments, on the Top of the Mountain, or any
elevated Station in the Atmosphere, by Means of the _Balloon_; and to
be written with a _red Lead_ Pencil, in a Patent Asses Skin Pocket Book.
[Sidenote: The Instruments to be compared on Return from the Mountain,
or upper Station.]
Each single Observation, made with one Set of Instruments _below_, is
to be compared with each single corresponding Observation, made with
the other Set _above_.
And two Observations are said to _correspond_, when both are made
_nearly_ at the _same_ Time, the one _below_, and the other _above_.
351. Take Shuckburgh’s first Example, (Ph. Tr. for 1777, 2d Part, Page
577.) viz.
“Let the Point at which the Quicksilver stands in the Barometer, on
the Ground, be 29 Inches 4 tenths: the attached Thermometer 50 Degrees
of Temperature, and the Air Thermometer, or general Temperature of the
Air 45°: at the same Time, that at the Top of the Mountain, or other
elevated Station in the Atmosphere, the Barometer stands at 25 Inches
19 Tenths, the attached Thermometer at 46°, and the Air Thermometer at
39° and ½: required the upper Height in English Feet.”
[Sidenote: Rules for the Work: and Practice of the first Example.]
352. The Work is divided into three Stages.
The End proposed in this first Stage is to bring the colder Barometer,
to the same _Expansion_ or _Temperature_ with the _other_.
353. 1st. Step. First, write down the Observation made on the Ground,
or at the Bottom of the Mountain, thus:
+Below.+ Barometer, 29 Inches 4 Tenths. attached Thermometer, 50
Degrees. Air Thermometer, 45°.
354. 2d. Step. Secondly, write down the Observation made at the Top of
the Mountain, or upper Station in the Atmosphere, thus:
+Above.+ Barometer, 25 Inches, .19 Tenths. attached Thermometer, 46°.
Air Thermometer, 29½.
355. 3d Step. Subtract the _colder attached_ Thermometer, from the
other attached Thermometer, thus: 46 colder from 50 warmer, and there
remains 4° warmer, viz. the Number of Degrees of Temperature to which
the _colder_ Barometer must be _expanded_, before it becomes equal in
Temperature to the _warmer_ Barometer: each Barometer being always
supposed _equal_ in Temperature with its _attached_ Thermometer.
356. 4th Step. Give the _colder_ Barometer the same _Temperature_ with
the warmer: or, which amounts to the same, give the _colder_ Barometer
that _Expansion_ which is communicated by the Addition of 4 Degrees of
Temperature.
Both Barometers will then have the same _Temperature_, or _Expansion_,
viz. an Expansion equal to the warmer Barometer.
This is to be done by referring to the first Table, for the Application
of which there are separate Instructions: see the Explanation of the
first Table.[118]
CHAPTER LXXI.
USE AND PRACTICE OF THE FIRST TABLE, IN THE FIRST EXAMPLE.
_The_ +use+.
Section 357. To find the Expansion of Quicksilver, and of the
barometric Tube in which it is contained: or, in other Words, to find
the Point to which the Quicksilver will rise in the Tube, (in Parts of
an Inch) with a given additional Temperature, on Farenheit’s Scale.
The Question in the first Example is, (Ph. Tr. for 1777, Page 578;)
To find the Expansion that arises, _with_ the Addition of 4 Degrees of
Heat, _on_ the _colder_ Barometer resting at Inches 25 .19 Tenths, in
order to give it an Expansion equal to that of another Barometer, 4
Degrees warmer than the former: the Temperature of _each_ Barometer,
being indicated by its respective _attached_ Thermometer.
N. B. During the Application of the first Table, the Investigation
moves forward two Steps only, viz. the 4th and 5th.
_The 4th Step, applied in the first Example._
358. The _Order_ to be observed in finding the Expansion of the
Quicksilver, with 4 Degrees on Inches 25 .19 Tenths of the Barometer.
1st. Find the Expansion, With 4° on 25 Inches only.
Then in order to obtain with 4° on .19, begin
2d. With 4° on 1 Inch above 25 Inches, i.e. on the 26th Inch.
3d. With 4° on .1, i.e. one Tenth of an Inch above 25 Inches: and
lastly,
4th. With 4° on .19, Tenths above 25 Inches.
_The_ +practice+.
359. 1st. In the _first_ Table, _with_ 4 Degrees on the left Hand
vertical Column, and with 25 Inches, along the upper Range; at the
Point of Meeting, is the Answer .0101[119] viz. the Expansion, or Rise
of the Quicksilver standing at 25 Inches, and receiving an additional
Heat of 4°: the Answer .0101 being the Expression for the ten thousand
one hundredth Part of an Inch, (viz. in Height, by Expansion.)
360. Add this Number, .0101, Part of an Inch, or Rise by Expansion, to
the Barometer resting at Inches 25, .19 Tenths, Units under Units, &c.
thus: .0101.
361. 2d. Now, in order to obtain the Expansion _with_ 4 Degrees,
_on_ .19 Tenths i.e. the nine hundred and tenth Part of an Inch of
Quicksilver in the Tube (above 25 Inches,) it must be considered, where
it ought to be found in the first Table.
Tenths of 1 Inch, above 25 Inches, it must be observed, are at some
intermediate Point between 25 and 26 Inches; that is, above 25, yet not
so high as 26, or more than 25, yet less than 26.
Therefore, to find the Expansion _with_ 4 Degrees, _on_ 1 Inch above
25, i.e. on the 26th Inch; look in the Table, first, _with_ 4 Degrees
on 25 Inches: then _with_ 4 Degrees on 26 Inches. The respective
Numbers are .0101 and .0105.
And by taking the Expansion _with_ 4° on 25 Inches, from the Expansion,
_with_ 4° _on_ 26 Inches, thus;
Expansion { .0101 on 25 Inches,
{ .0105 on 26 Inches,
—————
The Remainder .0004 is the Expansion with 4°
on 1 Inch, above 25, i.e. on the 26th Inch.
362. 3d. To find the Expansion, with 4° on .1 above 25 Inches; add
a Cypher and decimal Point to the former Answer, which then becomes
.00004, viz. the Expansion, with 4° on one Tenth, above 25 Inches.
363. 4th. Lastly, to obtain the Expansion _with_ 4°, _on_ .19, above
25 Inches, say: If one Tenth of an Inch, above 25 Inches, gives this
Expansion viz. .00004, what Expansion will nineteen Tenths above 25,
give? answer .19 Tenths more; thus:
If .1 : .00004 :: .19?
.19
——————
00036
0004
——————
.00076; then, in order to have as many decimal Places in the
Product as are contained both in the Multiplicand and Multiplier, add a
Cypher and Point to the left, and the Product becomes .0000076 which,
being divided by .1, gives a Cypher less.
viz. the Expansion with 4° on .19 above 25 Inches.
THE FIRST TABLE:
+shewing the expansion with HEAT on inches of the BAROMETER.+
+-------------------------------------------------------------------+
|+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| 1 |.00091 |.00102 |.00112 |.00122 |.00132 |.00142 |.00152 |.00162 |
| 2 |.00182 |.00204 |.00224 |.00244 |.00264 |.00284 |.00304 |.00324 |
| 3 |.00273 |.00306 |.00336 |.00366 |.00396 |.00426 |.00456 |.00486 |
| 4 |.00364 |.00408 |.00448 |.00488 |.00528 |.00568 |.00608 |.00648 |
| 5 |.00455 |.00510 |.00560 |.00610 |.00660 |.00710 |.00760 |.00810 |
| 6 |.00546 |.00612 |.00672 |.00732 |.00792 |.00852 |.00912 |.00972 |
| 7 |.00637 |.00714 |.00784 |.00854 |.00924 |.00994 |.01064 |.01134 |
| 8 |.00728 |.00816 |.00896 |.00976 |.01056 |.01136 |.01216 |.01296 |
| 9 |.00819 |.00918 |.01008 |.01098 |.01188 |.01278 |.01368 |.01458 |
|10 |.00910 |.01020 |.01120 |.01220 |.01320 |.01420 |.01520 |.01620 |
|11 |.01001 |.01122 |.01232 |.01342 |.01452 |.01562 |.01672 |.01782 |
|12 |.01092 |.01224 |.01344 |.01464 |.01584 |.01704 |.01824 |.01944 |
|13 |.01183 |.01326 |.01456 |.01586 |.01716 |.01846 |.01976 |.02106 |
|14 |.01274 |.01428 |.01568 |.01708 |.01848 |.01988 |.02128 |.02268 |
|15 |.01365 |.01530 |.01680 |.01830 |.01980 |.02130 |.02280 |.02430 |
|16 |.01456 |.01632 |.01792 |.01952 |.02112 |.02272 |.02432 |.02592 |
|17 |.01547 |.01734 |.01904 |.02074 |.02244 |.02414 |.02584 |.02754 |
|18 |.01638 |.01836 |.02016 |.02196 |.02376 |.02556 |.02736 |.02916 |
|19 |.01729 |.01938 |.02128 |.02318 |.02508 |.02698 |.02888 |.03078 |
|20 |.01820 |.02040 |.02240 |.02440 |.02640 |.02840 |.03040 |.03240 |
|21 |.01911 |.02142 |.02352 |.02562 |.02772 |.02982 |.03192 |.03402 |
|22 |.02002 |.02244 |.02464 |.02684 |.02904 |.03124 |.03344 |.03564 |
|23 |.02093 |.02346 |.02576 |.02806 |.03036 |.03266 |.03496 |.03726 |
|24 |.02184 |.02448 |.02688 |.02928 |.03168 |.03408 |.03648 |.03888 |
|25 |.02275 |.02550 |.02800 |.03050 |.03300 |.03550 |.03800 |.04050 |
|26 |.02366 |.02652 |.02912 |.03172 |.03432 |.03692 |.03952 |.04212 |
|27 |.02457 |.02754 |.03024 |.03294 |.03564 |.03834 |.04104 |.04374 |
|28 |.02548 |.02856 |.03136 |.03416 |.03696 |.03976 |.04256 |.04536 |
|29 |.02639 |.02958 |.03248 |.03538 |.03828 |.04118 |.04408 |.04698 |
|30 |.02730 |.03060 |.03360 |.03660 |.03960 |.04260 |.04560 |.04860 |
|31 |.02821 |.03162 |.03472 |.03782 |.04092 |.04402 |.04712 |.05022 |
|32 |.02912 |.03264 |.03584 |.03904 |.04224 |.04544 |.04864 |.05184 |
|33 |.03003 |.03366 |.03696 |.04026 |.04356 |.04686 |.05016 |.05346 |
|34 |.03094 |.03468 |.03808 |.04148 |.04488 |.04828 |.05168 |.05508 |
|35 |.03185 |.03570 |.03920 |.04270 |.04620 |.04970 |.05320 |.05670 |
|36 |.03276 |.03672 |.04032 |.04392 |.04752 |.05112 |.05472 |.05832 |
|37 |.03367 |.03774 |.04144 |.04514 |.04884 |.05254 |.05624 |.05994 |
|38 |.03458 |.03876 |.04256 |.04636 |.05016 |.05396 |.05776 |.06156 |
|39 |.03549 |.03978 |.04368 |.04758 |.05148 |.05538 |.05928 |.06318 |
|40 |.03640 |.04080 |.04480 |.04880 |.05280 |.05680 |.06080 |.06480 |
+---+-------+-------+-------+-------+-------+-------+-------+-------+
THE FIRST TABLE CONTINUED:
+shewing the expansion with HEAT on inches of the BAROMETER.+
+-------------------------------------------------------------------+
|+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| 1 |.00172 |.00182 |.00192 |.00203 |.00213 |.00223 |.00233 |.00243 |
| 2 |.00344 |.00364 |.00384 |.00406 |.00426 |.00446 |.00466 |.00486 |
| 3 |.00516 |.00546 |.00576 |.00609 |.00639 |.00669 |.00699 |.00729 |
| 4 |.00688 |.00728 |.00768 |.00812 |.00852 |.00892 |.00932 |.00972 |
| 5 |.00860 |.00910 |.00960 |.01015 |.01065 |.01115 |.01165 |.01215 |
| 6 |.01032 |.01092 |.01152 |.01218 |.01278 |.01338 |.01398 |.01458 |
| 7 |.01204 |.01274 |.01344 |.01421 |.01491 |.01561 |.01631 |.01701 |
| 8 |.01376 |.01456 |.01536 |.01624 |.01704 |.01784 |.01864 |.01944 |
| 9 |.01548 |.01638 |.01728 |.01827 |.01917 |.02007 |.02097 |.02187 |
|10 |.01720 |.01820 |.01920 |.02030 |.02130 |.02230 |.02330 |.02430 |
|11 |.01892 |.02002 |.02112 |.02233 |.02343 |.02453 |.02563 |.02673 |
|12 |.02064 |.02184 |.02304 |.02436 |.02556 |.02676 |.02796 |.02916 |
|13 |.02236 |.02366 |.02496 |.02639 |.02769 |.02899 |.03029 |.03159 |
|14 |.02408 |.02548 |.02688 |.02842 |.02982 |.03122 |.03262 |.03402 |
|15 |.02580 |.02730 |.02880 |.03045 |.03195 |.03345 |.03495 |.03645 |
|16 |.02752 |.02912 |.03072 |.03248 |.03408 |.03568 |.03728 |.03888 |
|17 |.02924 |.03094 |.03264 |.03451 |.03621 |.03791 |.03961 |.04131 |
|18 |.03096 |.03276 |.03456 |.03654 |.03834 |.04014 |.04194 |.04374 |
|19 |.03268 |.03458 |.03648 |.03857 |.04047 |.04237 |.04427 |.04617 |
|20 |.03440 |.03640 |.03840 |.04060 |.04260 |.04460 |.04660 |.04860 |
|21 |.03612 |.03822 |.04032 |.04263 |.04473 |.04683 |.04893 |.05103 |
|22 |.03784 |.04004 |.04224 |.04466 |.04686 |.04906 |.05126 |.05346 |
|23 |.03956 |.04186 |.04416 |.04669 |.04899 |.05129 |.05359 |.05589 |
|24 |.04128 |.04368 |.04608 |.04872 |.05112 |.05352 |.05592 |.05832 |
|25 |.04300 |.04550 |.04800 |.05075 |.05325 |.05575 |.05825 |.06075 |
|26 |.04472 |.04732 |.04992 |.05278 |.05538 |.05798 |.06058 |.06318 |
|27 |.04644 |.04914 |.05184 |.05481 |.05751 |.06021 |.06291 |.06561 |
|28 |.04816 |.05096 |.05376 |.05684 |.05964 |.06244 |.06524 |.06804 |
|29 |.04988 |.05278 |.05568 |.05887 |.06177 |.06467 |.06757 |.07047 |
|30 |.05160 |.05460 |.05760 |.06090 |.06390 |.06690 |.06990 |.07290 |
|31 |.05332 |.05642 |.05952 |.06293 |.06603 |.06913 |.07223 |.07533 |
|32 |.05504 |.05824 |.06144 |.06496 |.06816 |.07139 |.07456 |.07776 |
|33 |.05676 |.06006 |.06336 |.06699 |.07029 |.07359 |.07689 |.08019 |
|34 |.05848 |.06188 |.06528 |.06902 |.07242 |.07582 |.07922 |.08262 |
|35 |.06020 |.06350 |.06720 |.07105 |.07455 |.07805 |.08155 |.08505 |
|36 |.06192 |.06534 |.06912 |.07308 |.07668 |.08028 |.08388 |.08748 |
|37 |.06364 |.06716 |.07104 |.07511 |.07881 |.08251 |.08621 |.08991 |
|38 |.06536 |.06892 |.07296 |.07714 |.08094 |.08474 |.08854 |.09234 |
|39 |.06708 |.07078 |.07488 |.07917 |.08307 |.08697 |.09087 |.09477 |
|40 |.06880 |.07260 |.07680 |.08120 |.08520 |.08920 |.09320 |.09720 |
+---+-------+-------+-------+-------+-------+-------+-------+-------+
THE FIRST TABLE CONCLUDED:
+shewing the expansion with HEAT on inches of the BAROMETER.+
+-------------------------------------------------------------------+
|+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 |
| +-------+-------+-------+-------+-------+-------+-------+-------+
| 1 |.00253 |.00263 |.00274 |.00284 |.00294 |.00304 |.00314 |.00324 |
| 2 |.00506 |.00526 |.00548 |.00568 |.00588 |.00608 |.00628 |.00648 |
| 3 |.00759 |.00789 |.00822 |.00852 |.00882 |.00912 |.00942 |.00972 |
| 4 |.01012 |.01052 |.01096 |.01136 |.01176 |.01216 |.01256 |.01296 |
| 5 |.01265 |.01315 |.01370 |.01420 |.01470 |.01520 |.01570 |.01620 |
| 6 |.01518 |.01578 |.01644 |.01704 |.01764 |.01824 |.01884 |.01944 |
| 7 |.01771 |.01841 |.01918 |.01988 |.02058 |.02128 |.02198 |.02268 |
| 8 |.02024 |.02104 |.02192 |.02272 |.02352 |.02432 |.02512 |.0259? |
| 9 |.02277 |.02367 |.02466 |.02556 |.02646 |.02736 |.02826 |.02916 |
|10 |.02530 |.02630 |.02740 |.02840 |.02940 |.03040 |.03140 |.03240 |
|11 |.02783 |.02893 |.03014 |.03124 |.03234 |.03344 |.03454 |.03564 |
|12 |.03036 |.03156 |.03288 |.03408 |.03528 |.03648 |.03768 |.03888 |
|13 |.03289 |.03419 |.03562 |.03692 |.03822 |.03952 |.04082 |.04212 |
|14 |.03542 |.03682 |.03836 |.03976 |.04116 |.04256 |.04396 |.04536 |
|15 |.03795 |.03945 |.04110 |.04260 |.04410 |.04560 |.04710 |.04860 |
|16 |.04048 |.04208 |.04384 |.04544 |.04704 |.04864 |.05024 |.05184 |
|17 |.04301 |.04471 |.04658 |.04828 |.04998 |.05168 |.05338 |.05508 |
|18 |.04554 |.04734 |.04932 |.05112 |.05292 |.05472 |.05652 |.05832 |
|19 |.04807 |.04997 |.05206 |.05396 |.05586 |.05776 |.05966 |.06156 |
|20 |.05060 |.05260 |.05480 |.05680 |.05880 |.06080 |.06280 |.06480 |
|21 |.05313 |.05523 |.05754 |.05964 |.06174 |.06384 |.06594 |.06804 |
|22 |.05566 |.05786 |.06028 |.06248 |.06468 |.06688 |.06908 |.07128 |
|23 |.05819 |.06049 |.06302 |.06532 |.06762 |.06992 |.07222 |.07452 |
|24 |.06072 |.06312 |.06576 |.06816 |.07056 |.07296 |.07536 |.07776 |
|25 |.06325 |.06575 |.06850 |.07100 |.07350 |.07600 |.07850 |.08100 |
|26 |.06578 |.06838 |.07124 |.07384 |.07644 |.07904 |.08164 |.08424 |
|27 |.06831 |.07101 |.07398 |.07668 |.07938 |.08208 |.08478 |.08748 |
|28 |.07084 |.07364 |.07672 |.07952 |.08232 |.08512 |.0879 |.09072 |
|29 |.07337 |.07627 |.07946 |.08236 |.08526 |.08816 |.09106 |.09396 |
|30 |.07590 |.07890 |.08220 |.08520 |.08820 |.09120 |.09420 |.09720 |
|31 |.07843 |.08153 |.08494 |.08804 |.09114 |.09424 |.09734 |.10044 |
|32 |.08096 |.08416 |.08768 |.09088 |.09408 |.09728 |.10048 |.10368 |
|33 |.08349 |.08679 |.09042 |.09372 |.09702 |.10032 |.10362 |.10692 |
|34 |.08602 |.08942 |.09316 |.09656 |.09996 |.10336 |.10676 |.11016 |
|35 |.08855 |.09205 |.09590 |.09940 |.10290 |.10640 |.10990 |.11340 |
|36 |.09108 |.09468 |.09864 |.10224 |.10584 |.10944 |.11314 |.11664 |
|37 |.09361 |.09731 |.10138 |.10508 |.10878 |.11248 |.11618 |.11988 |
|38 |.09614 |.09994 |.10412 |.10792 |.11172 |.11552 |.11932 |.12312 |
|39 |.09867 |.10257 |.10686 |.11076 |.11466 |.11866 |.12246 |.12636 |
|40 |.10120 |.10520 |.10960 |.11360 |.11760 |.12160 |.12560 |.12960 |
+---+-------+-------+-------+--------+-------+-------+------+-------+
_The 5th Step, applied in the first Example._
364. Add this, to the former Expansion, thus:
Inches 25.19 Tenths
with 4° on 25 .0101 Expansion
with 4° on .19 .0000076 Expansion
——————————————
The Answer is 25.2|001076, viz. the Point at which the Quicksilver woud
stand, in the coldest Barometer, when equally _expanded_, i.e. of the
same Temperature with the warmer. Reject all but the first Decimal as
too minute: this is seen by a Line drawn between the first and second
Decimal.
Practice will shew how far to proceed, without computing the decimal
Parts of an Inch, to more than 4 Places; but it is always more exact,
to follow minutely the above Rules.
CHAPTER LXXII.
Section 365. Having therefore understood the Foundation, Construction,
and Use of the first Table; in the present Case, having also added the
decimal Parts of an Inch just found, for the Expansion,—to the Inches
and Tenths, expressing the colder Barometer; which will then have the
_same Expansion_, or _Temperature_ with the warmer, thus;
Inches.
25.19 _colder_ Barometer:
.0101 Expansion _on_ the same, in Parts of an
Inch with 4° of Temperature, (rejecting
all but the first Decimal as too
———————— minute,)
25.2|001 added; this Sum will express the
Point at which the Quicksilver in the colder Barometer
woud stand, when equally expanded, i.e.
in the same Temperature, with the warmer.
366. 6th Step. Place both Barometers, now of _equal_ Temperature with
the warmer, together, first, the _upper_ Barometer; and under it the
_lower_, thus: Inches 25. 2 Tenths.
29. 4
END OF THE FIRST STAGE.
* * * * *
367. The Ends proposed in the _second Stage_ of the Work, (the colder
Barometer being _now_ brought to the same Expansion or Temperature
with the warmer,) are two: First, to find, (by the Application of the
second Table) the Heights, in Feet and Tenths, in the Atmosphere,
corresponding to the Points at which the Quicksilver stands in both
Barometers, which have now the same Temperature, viz. that of the
warmer equal to 50°: on a Supposition that they were both exposed to
the Temperature of 31°.24, on Farenheit’s Scale, which is about the
Standard or freezing Point, for which sole Purpose the 2d Table is
calculated.
N. B. The _Second Stage_ includes two Steps only, viz. the 7th and
8th.
368. 7th Step. The Barometers being placed in one View, as before
directed, thus:
Upper Barometer, Inches 25 .2 Tenths.
Lower Barometer, Inches 29 .4; find, with the Temperature of 31°.24,
the corresponding Heights in the Atmosphere.
This is to be done by referring to the 2d Table, for the Application
of which there are separate Instructions: See the Explanation of the
second Table.[120]
CHAPTER LXXIII.
USE AND PRACTICE OF THE SECOND TABLE IN THE FIRST EXAMPLE.
_The_ +use+.
Section 369. To find the Heights, in Feet and Tenths, in the
Atmosphere, corresponding to the Points at which the Quicksilver
stands in both Barometers, which have _now_ the _same Temperature_,
viz. that of the _warmer_ Barometer, on a Supposition that they were
both exposed to the Standard-Temperature of 31°.24, on Farenheit’s
Scale.
_The_ +practice+.
_The 7th Step applied in the first Example._
370. Look at the first Column, in the _second_ Table, for
25.2, and the Answer is 6225.0 in the second Column; and for
29.4, and the Answer is 2208.2. The Answers are the Heights, in Feet
and Tenths, in the Atmosphere, at which the Quicksilver stands in both
Barometers, with the Temperature of 31°.24: corresponding to their
respective Points, for which _sole_ Purpose this Table is calculated.
371. 8th Step. Having placed the Barometers and their corresponding
Heights in the Atmosphere, shewn by the second Table, at one View:
subtract the lesser from the whole Height, and there will remain,
+secondly+; (see Section 367) the greater Height, viz. the Height
corresponding to the Barometer in the elevated Station, above the
Height corresponding to the Barometer, on the Ground, (both being at
the Temperature of 31°.24) thus:
Feet.
Inches 25.2 correspond to 6225.0
Inches 29.4 correspond to 2208.2; subtract:
——————
and the Remainder is 4016.8
viz. a Number in Feet and Tenths corresponding to the Height of the
upper above the lower Barometer, both being in the Temperature of
31°.34.
(See Page 295.)
THE SECOND TABLE.
The 1st Column shews the Quicksilver in the barometric Tube
standing at each Inch from 1 to 10, and at each Tenth from 10 to
32 Inches.
The 2d Column shews the Height of the barometric Tube, above
the _imaginary Level at 32 Inches_,—_with_ the Temperature of
31.24;—in Feet and Tenths, answering to Inches and Tenths of the
Barometer in the first Column.
The 3d Column shews the Height in Feet and Tenths, answering to a
Tenth of an Inch on the Barometer, being the +difference+ between
each two adjoining Heights in the 2d Column.
+-----+---------+-----------+
|Inch.| Feet. |Difference.|
| | | |
| 1 | 90309.0 | |
| | | 18061.8 |
| 2 | 72247.2 | |
| | | 10565.4 |
| 3 | 61681.8 | |
| | | 7496.4 |
| 4 | 54185.4 | |
| | | 5814.6 |
| 5 | 48370.8 | |
| | | 4750.9 |
| 6 | 43619.9 | |
| | | 4016.8 |
| 7 | 39603.1 | |
| | | 3479.5 |
| 8 | 36123.6 | |
| | | 3069.2 |
| 9 | 33054.4 | |
| | | 2745.4 |
|10.0 | 30309.0 | |
| | | 259.6 |
| .1 | 30049.4 | |
| | | 256.4 |
| .2 | 29793.0 | |
| | | 254.3 |
| .3 | 29538.7 | |
| | | 251.8 |
| .4 | 29286.9 | |
| | | 249.3 |
| .5 | 29037.6 | |
| | | 247.0 |
| .6 | 28790.6 | |
| | | 244.7 |
| .7 | 28545.9 | |
| | | 242.4 |
| .8 | 28303.5 | |
| | | 240.2 |
| .9 | 28063.3 | |
| | | 237.9 |
|11.0 | 27825.4 | |
| | | 235.8 |
| .1 | 27589.6 | |
| | | 233.7 |
| .2 | 27355.9 | |
| | | 231.6 |
| .3 | 27124.3 | |
| | | 229.6 |
| .4 | 26894.7 | |
| | | 227.6 |
| .5 | 26667.1 | |
| | | 225.6 |
| .6 | 26441.5 | |
| | | 223.7 |
| .7 | 26217.8 | |
| | | 221.7 |
| .8 | 25996.1 | |
| | | 220.0 |
| .9 | 25776.1 | |
| | | 218.0 |
|12.0 | 25558.1 | |
| | | 216.3 |
|12.1 | 25341.8 | |
| | | 214.4 |
| .2 | 25127.4 | |
| | | 212.7 |
| .3 | 24914.7 | |
| | | 211.0 |
| .4 | 24703.7 | |
| | | 209.3 |
| .5 | 24494.4 | |
| | | 207.7 |
| .6 | 24286.7 | |
| | | 206.0 |
| .7 | 24080.7 | |
| | | 204.3 |
| .8 | 23876.4 | |
| | | 202.8 |
| .9 | 23673.6 | |
| | | 201.2 |
|13.0 | 23472.4 | |
| | | 199.7 |
| .1 | 23272.7 | |
| | | 198.2 |
| .2 | 23074.5 | |
| | | 196.6 |
| .3 | 22877.9 | |
| | | 195.2 |
| .4 | 22682.7 | |
| | | 193.7 |
| .5 | 22489.0 | |
| | | 192.4 |
| .6 | 22296.6 | |
| | | 191.0 |
| .7 | 22105.6 | |
| | | 189.4 |
| .8 | 21916.2 | |
| | | 188.1 |
| .9 | 21728.1 | |
| | | 186.8 |
|14.0 | 21541.3 | |
| | | 185.5 |
| .1 | 21355.8 | |
| | | 184.1 |
| .2 | 21171.7 | |
| | | 182.9 |
| .3 | 20988.8 | |
| | | 181.6 |
| .4 | 20807.2 | |
| | | 180.3 |
| .5 | 20626.9 | |
| | | 179.0 |
| .6 | 20447.9 | |
| | | 178.0 |
| .7 | 20269.9 | |
| | | 176.7 |
| .8 | 20093.2 | |
| | | 175.4 |
| .9 | 19917.8 | |
| | | 174.3 |
|15.0 | 19743.5 | |
| | | 173.1 |
|15.1 | 19570.4 | |
| | | 172.0 |
| .2 | 19398.4 | |
| | | 170.9 |
| .3 | 19227.5 | |
| | | 169.8 |
| .4 | 19057.7 | |
| | | 168.6 |
| .5 | 18889.1 | |
| | | 167.6 |
| .6 | 18721.5 | |
| | | 166.5 |
| .7 | 18555.0 | |
| | | 165.4 |
| .8 | 18389.6 | |
| | | 164.1 |
| .9 | 18225.5 | |
| | | 163.7 |
|16.0 | 18061.8 | |
| | | 162.4 |
| .1 | 17899.4 | |
| | | 161.3 |
| .2 | 17738.1 | |
| | | 160.4 |
| .3 | 17577.7 | |
| | | 159.3 |
| .4 | 17418.4 | |
| | | 158.4 |
| .5 | 17260.0 | |
| | | 157.5 |
| .6 | 17102.5 | |
| | | 156.5 |
| .7 | 16946.0 | |
| | | 155.6 |
| .8 | 16790.4 | |
| | | 154.6 |
| .9 | 16635.8 | |
| | | 153.7 |
|17.0 | 16482.1 | |
| | | 152.9 |
| .1 | 16329.2 | |
| | | 151.9 |
| .2 | 16177.3 | |
| | | 151.1 |
| .3 | 16026.2 | |
| | | 150.2 |
| .4 | 15876.0 | |
| | | 149.3 |
| .5 | 15726.7 | |
| | | 148.5 |
| .6 | 15578.2 | |
| | | 147.6 |
| .7 | 15430.6 | |
| | | 146.8 |
| .8 | 15283.8 | |
| | | 146.0 |
| .9 | 15137.8 | |
| | | 145.2 |
|18.0 | 14992.6 | |
| | | 144.3 |
|18.1 | 14848.3 | |
| | | 143.6 |
| .2 | 14704.7 | |
| | | 142.8 |
| .3 | 14561.9 | |
| | | 142.0 |
| .4 | 14419.9 | |
| | | 141.2 |
| .5 | 14278.7 | |
| | | 140.5 |
| .6 | 14138.2 | |
| | | 139.7 |
| .7 | 13998.5 | |
| | | 139.0 |
| .8 | 13859.5 | |
| | | 138.2 |
| .9 | 13721.3 | |
| | | 137.5 |
|19.0 | 13583.8 | |
| | | 136.8 |
| .1 | 13447.0 | |
| | | 136.1 |
| .2 | 13310.9 | |
| | | 135.3 |
| .3 | 13175.6 | |
| | | 134.5 |
| .4 | 13041.1 | |
| | | 134.2 |
| .5 | 12906.9 | |
| | | 133.3 |
| .6 | 12773.6 | |
| | | 132.6 |
| .7 | 12641.0 | |
| | | 131.9 |
| .8 | 12509.1 | |
| | | 131.3 |
| .9 | 12377.8 | |
| | | 130.6 |
|20.0 | 12247.2 | |
| | | 130.0 |
| .1 | 12117.2 | |
| | | 129.3 |
| .2 | 11987.9 | |
| | | 128.7 |
| .3 | 11859.2 | |
| | | 128.0 |
| .4 | 11731.2 | |
| | | 127.4 |
| .5 | 11603.8 | |
| | | 126.8 |
| .6 | 11477.0 | |
| | | 126.2 |
| .7 | 11350.8 | |
| | | 125.6 |
| .8 | 11225.2 | |
| | | 125.0 |
| .9 | 11100.2 | |
| | | 124.4 |
|21.0 | 10975.8 | |
| | | 123.7 |
| .1 | 10852.1 | |
| | | 123.3 |
| .2 | 10728.8 | |
| | | 122.6 |
| .3 | 10606.2 | |
| | | 122.0 |
| .4 | 10484.2 | |
| | | 121.5 |
| .5 | 10362.7 | |
| | | 120.9 |
| .6 | 10241.8 | |
| | | 120.4 |
| .7 | 10121.4 | |
| | | 119.8 |
| .8 | 10001.6 | |
| | | 119.2 |
| .9 | 9882.4 | |
| | | 118.8 |
|22.0 | 9763.6 | |
| | | 118.1 |
|22.1 | 9645.5 | |
| | | 117.7 |
| .2 | 9527.8 | |
| | | 117.1 |
| .3 | 9410.7 | |
| | | 116.6 |
| .4 | 9294.1 | |
| | | 116.0 |
| .5 | 9178.1 | |
| | | 115.6 |
| .6 | 9062.5 | |
| | | 115.1 |
| .7 | 8947.4 | |
| | | 114.5 |
| .8 | 8832.9 | |
| | | 114.0 |
| .9 | 8718.9 | |
| | | 113.6 |
|23.0 | 8605.3 | |
| | | 113.0 |
| .1 | 8492.3 | |
| | | 112.6 |
| .2 | 8379.7 | |
| | | 112.1 |
| .3 | 8267.6 | |
| | | 111.6 |
| .4 | 8156.0 | |
| | | 111.1 |
| .5 | 8044.9 | |
| | | 110.6 |
| .6 | 7934.3 | |
| | | 110.2 |
| .7 | 7824.1 | |
| | | 109.7 |
| .8 | 7714.4 | |
| | | 109.3 |
| .9 | 7605.1 | |
| | | 108.8 |
|24.0 | 7496.3 | |
| | | 108.3 |
| .1 | 7388.0 | |
| | | 107.9 |
| .2 | 7280.1 | |
| | | 107.5 |
| .3 | 7172.6 | |
| | | 107.0 |
| .4 | 7065.6 | |
| | | 106.6 |
| .5 | 6959.0 | |
| | | 106.1 |
| .6 | 6852.9 | |
| | | 105.7 |
| .7 | 6747.2 | |
| | | 105.3 |
| .8 | 6641.9 | |
| | | 104.9 |
| .9 | 6537.0 | |
| | | 104.4 |
|25.0 | 6432.6 | |
| | | 104.0 |
| .1 | 6328.6 | |
| | | 103.6 |
| .2 | 6225.0 | |
| | | 103.2 |
| .3 | 6121.8 | |
| | | 102.8 |
| .4 | 6019.0 | |
| | | 102.4 |
| .5 | 5916.6 | |
| | | 102.0 |
| .6 | 5814.6 | |
| | | 101.6 |
| .7 | 5713.0 | |
| | | 101.2 |
| .8 | 5611.8 | |
| | | 100.8 |
| .9 | 5511.0 | |
| | | 100.6 |
|26.0 | 5410.4 | |
| | | 99.8 |
| .1 | 5310.6 | |
| | | 99.7 |
| .2 | 5210.9 | |
| | | 99.3 |
| .3 | 5111.6 | |
| | | 98.8 |
| .4 | 5012.8 | |
| | | 98.6 |
| .5 | 4914.2 | |
| | | 98.1 |
| .6 | 4816.1 | |
| | | 97.8 |
| .7 | 4718.3 | |
| | | 97.4 |
| .8 | 4620.9 | |
| | | 97.0 |
| .9 | 4523.9 | |
| | | 96.7 |
|27.0 | 4427.2 | |
| | | 96.4 |
| .1 | 4330.8 | |
| | | 95.9 |
| .2 | 4234.9 | |
| | | 95.7 |
| .3 | 4139.2 | |
| | | 95.2 |
| .4 | 4044.0 | |
| | | 95.0 |
| .5 | 3949.0 | |
| | | 94.5 |
| .6 | 3854.5 | |
| | | 94.3 |
| .7 | 3760.2 | |
| | | 93.9 |
| .8 | 3666.3 | |
| | | 93.6 |
| .9 | 3572.7 | |
| | | 93.2 |
|28.0 | 3479.5 | |
| | | 92.9 |
| .1 | 3386.6 | |
| | | 92.6 |
| .2 | 3294.0 | |
| | | 92.2 |
| .3 | 3201.8 | |
| | | 91.9 |
| .4 | 3109.9 | |
| | | 91.6 |
| .5 | 3018.3 | |
| | | 91.3 |
| .6 | 2927.0 | |
| | | 90.9 |
| .7 | 2836.1 | |
| | | 90.7 |
| .8 | 2745.4 | |
| | | 90.3 |
| .9 | 2655.1 | |
| | | 90.0 |
|29.0 | 2565.1 | |
| | | 89.7 |
| .1 | 2475.4 | |
| | | 89.4 |
| .2 | 2386.0 | |
| | | 89.1 |
| .3 | 2296.9 | |
| | | 88.7 |
| .4 | 2208.2 | |
| | | 88.5 |
| .5 | 2119.7 | |
| | | 88.2 |
| .6 | 2031.5 | |
| | | 87.9 |
| .7 | 1943.6 | |
| | | 87.6 |
| .8 | 1856.0 | |
| | | 87.3 |
| .9 | 1768.7 | |
| | | 87.0 |
|30.0 | 1681.7 | |
| | | 86.7 |
| .1 | 1595.0 | |
| | | 86.4 |
| .2 | 1508.6 | |
| | | 86.2 |
| .3 | 1422.4 | |
| | | 85.8 |
| .4 | 1236.6 | |
| | | 85.6 |
| .5 | 1251.0 | |
| | | 85.3 |
| .6 | 1165.7 | |
| | | 85.0 |
| .7 | 1080.7 | |
| | | 84.7 |
| .8 | 996.0 | |
| | | 84.5 |
| .9 | 911.5 | |
| | | 84.2 |
|31.0 | 827.3 | |
| | | 83.9 |
| .1 | 743.4 | |
| | | 83.7 |
| .2 | 659.7 | |
| | | 83.4 |
| .3 | 576.3 | |
| | | 83.1 |
| .4 | 493.2 | |
| | | 82.8 |
|31.5 | 410.4 | |
| | | 82.6 |
| .6 | 327.8 | |
| | | 82.4 |
| .7 | 245.4 | |
| | | 82.0 |
| .8 | 163.4 | |
| | | 81.8 |
| .9 | 81.6 | |
| | | 81.6 |
|32.0 | 00.0 | |
+-----+---------+-----------+
372. _Now_ apply the third Table, or Table for Tenths, _if necessary_;
including two more Steps, viz. the 9th and 10th: which, being useless,
in the first Example, are, for the present, omitted.
373. An Explanation of the third Table, or Table for Tenths, is,
however, for the Sake of _Order_, _here_ subjoined.[122] (See Page
298.)
THE THIRD TABLE, OR TABLE FOR TENTHS:
Serving to compleat the 2d Table, on Expansion of the Barometer,
with the Temperature of 31°.24.
1. The upper horizontal Figures shew the Number of Parts into which
the Tenth of an Inch has been divided.
2. The Figures in the left vertical Column express the Height
in +feet+, (above the imaginary Level, at 32 Inches of the
Barometer,) or Expansion corresponding to a single Tenth of an
Inch of Quicksilver.
3. The +feet+ in the Place of Meeting are called +tenths+: thus, 90
Feet are 9 Tenths of 100 Feet.
+-------+-----------------------------------------------------+
|_Feet._| _Parts into which the Tenth of an Inch is divided._ |
| | ⅒ | ²⁄₁₀ | ³⁄₁₀| ⁴⁄₁₀ | ⁵⁄₁₀ | ⁶⁄₁₀ | ⁷⁄₁₀ | ⁸⁄₁₀ | ⁹⁄₁₀ |
+-------+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 81 | 8 | 16 | 24 | 32 | 40 | 49 | 57 | 65 | 73 |
| 82 | 8 | 16 | 25 | 33 | 41 | 49 | 57 | 66 | 74 |
| 83 | 8 | 17 | 25 | 33 | 41 | 50 | 58 | 66 | 75 |
| 84 | 8 | 17 | 25 | 34 | 42 | 50 | 59 | 67 | 76 |
| 85 | 8 | 17 | 25 | 34 | 42 | 51 | 59 | 68 | 76 |
| 86 | 9 | 17 | 26 | 34 | 43 | 52 | 60 | 69 | 77 |
| 87 | 9 | 17 | 26 | 35 | 43 | 52 | 61 | 70 | 78 |
| 88 | 9 | 18 | 26 | 35 | 44 | 53 | 62 | 70 | 79 |
| 89 | 9 | 18 | 27 | 36 | 44 | 53 | 62 | 71 | 80 |
| 90 | 9 | 18 | 27 | 36 | 45 | 54 | 63 | 72 | 81 |
| 91 | 9 | 18 | 27 | 36 | 45 | 55 | 64 | 73 | 82 |
| 92 | 9 | 18 | 28 | 37 | 46 | 55 | 64 | 74 | 83 |
| 93 | 9 | 19 | 28 | 37 | 46 | 56 | 65 | 74 | 84 |
| 94 | 9 | 19 | 28 | 38 | 47 | 56 | 66 | 75 | 85 |
| 95 | 9 | 19 | 28 | 38 | 47 | 57 | 66 | 76 | 85 |
| 96 | 10 | 19 | 29 | 38 | 48 | 58 | 67 | 77 | 86 |
| 97 | 10 | 19 | 29 | 39 | 48 | 58 | 68 | 78 | 87 |
| 98 | 10 | 20 | 29 | 39 | 49 | 59 | 69 | 78 | 88 |
| 99 | 10 | 20 | 30 | 40 | 49 | 59 | 69 | 79 | 89 |
| 100 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 |
| 101 | 10 | 20 | 30 | 40 | 50 | 61 | 71 | 81 | 91 |
| 102 | 10 | 20 | 31 | 41 | 51 | 61 | 71 | 82 | 92 |
| 103 | 10 | 21 | 31 | 41 | 51 | 62 | 72 | 82 | 93 |
| 104 | 10 | 21 | 31 | 42 | 52 | 62 | 73 | 83 | 94 |
| 105 | 10 | 21 | 31 | 42 | 52 | 63 | 73 | 84 | 94 |
| 106 | 11 | 21 | 32 | 42 | 53 | 64 | 74 | 85 | 95 |
| 107 | 11 | 21 | 32 | 43 | 53 | 64 | 75 | 86 | 96 |
| 108 | 11 | 22 | 32 | 43 | 54 | 65 | 76 | 86 | 97 |
| 109 | 11 | 22 | 33 | 44 | 54 | 65 | 76 | 87 | 98 |
| 110 | 11 | 22 | 33 | 44 | 55 | 66 | 77 | 88 | 99 |
| 111 | 11 | 22 | 33 | 44 | 55 | 67 | 78 | 89 | 100 |
| 112 | 11 | 22 | 34 | 45 | 56 | 67 | 78 | 90 | 101 |
| 113 | 11 | 23 | 34 | 45 | 56 | 68 | 79 | 90 | 102 |
| 114 | 11 | 23 | 34 | 46 | 57 | 68 | 80 | 91 | 103 |
| 115 | 11 | 23 | 34 | 46 | 57 | 69 | 80 | 92 | 103 |
| 116 | 12 | 23 | 35 | 46 | 58 | 70 | 81 | 93 | 104 |
| 117 | 12 | 23 | 35 | 47 | 58 | 70 | 82 | 94 | 105 |
| 118 | 12 | 24 | 35 | 47 | 59 | 71 | 83 | 94 | 106 |
| 119 | 12 | 24 | 36 | 48 | 59 | 71 | 83 | 95 | 107 |
| 120 | 12 | 24 | 36 | 48 | 60 | 72 | 84 | 96 | 108 |
| 121 | 12 | 24 | 36 | 48 | 60 | 73 | 85 | 97 | 109 |
| 122 | 12 | 24 | 37 | 49 | 61 | 73 | 85 | 98 | 110 |
| 123 | 12 | 25 | 37 | 49 | 61 | 74 | 86 | 98 | 111 |
| 124 | 12 | 25 | 37 | 50 | 62 | 74 | 87 | 99 | 112 |
| 125 | 12 | 25 | 37 | 50 | 62 | 75 | 87 | 100 | 112 |
| 126 | 13 | 25 | 38 | 50 | 63 | 76 | 88 | 101 | 113 |
| 127 | 13 | 25 | 38 | 51 | 63 | 76 | 89 | 102 | 114 |
| 128 | 13 | 26 | 38 | 51 | 64 | 77 | 90 | 102 | 113 |
| 129 | 13 | 26 | 39 | 52 | 64 | 77 | 90 | 103 | 116 |
| 130 | 13 | 26 | 39 | 52 | 65 | 78 | 91 | 104 | 117 |
+-------+-----+-----+-----+-----+-----+-----+-----+-----+-----+
END OF THE SECOND STAGE.
374. The Ends proposed in the third and last Stage of the Work, are,
first, to add the _general_ Temperatures of the Air, or detached
Air-Thermometers, at each Place of Observation _above_ and _below_,
into one Sum.
Secondly, to divide that Sum: each Moiety of which is called the _mean
Temperature_ of the Air.
Thirdly, to apply that Moiety to each Barometer, (both of which have
been already brought to the Standard-Temperature of 31°. 24;) in order
to prove whether the Moiety (or Quantity of Heat assigned to each
Barometer by the _general_ Temperature of the Air) _exceeded_, _fell
short of_, or equalled the Standard-Temperature of the Barometers, by
the 2d Table.
And fourthly, from the Moiety or mean Temperature of the Air, to find
the true Height of the upper Barometer: which Temperature resolves
itself into three Cases.
375. 1st. If the Moiety or mean Temperature of the Air is greater than
the Standard Temperature, viz. that to which the Barometers are now
brought; find the Expansion of Air corresponding to such _Excess_ of
Temperature by the fourth Table, which Height by Expansion, being added
to the Height already found in the 2d Table, shews the true Height,
viz. of the upper Barometer.
N. B. The 3d and last Stage includes two Steps only, viz, 11th and
12th.
376. 11th Step. The detached Air-Thermometer _above_ was — — 39½
Degrees.
The detached Air-Thermometer _below_ was — — 45
1st. Add them, for the whole
Heat. — — — 2)84½ Degrees.
2d. For _mean Temperature_ of the
Air-Thermometers, or a _Moiety_ of
the Heat, divide by 2. — 42¼
3d. Deduct the Standard-Temperature
of — — — 31¼
from either Moiety, and the Remainder ———
— — — 11
is the 11 Degrees of Heat, more than the Standard[123]
for each Barometer.
For 42°¼, and 42°¼, equal to 84°½, was the whole Height of the Air at
both Places of Observation in the upper and lower Stations; of which
whole Height the detached or Air-Thermometer _above_ received 39°½, and
the detached or Air-Thermometer _below_, received 45°.
377. 12th Step. Find the Height corresponding to the Expansion of Air,
with Excess of Heat or Temperature above the Standard-Temperature of
the Barometers: and add it (as in the first Example) to the Height of
the upper Barometer, corresponding to the Standard-Temperature already
found in the _second_ Table, and the Sum is the _true_ Height of the
upper Barometer.
This is to be done by referring to the 4th Table, shewing Expansion
of Air with Heat; for the Application of which there are separate
Instructions: see the Explanation of the 4th Table.[124]
378. The Expansion of Air, in the first Example, is found by the
4th Table to be Feet 107.3 Tenths _higher_ than the 4016.8, viz. the
Remainder from the 2d Table (Section 371); which Numbers added give
4124.1 Feet: viz. the true Height of the upper Station required.
CHAPTER LXXIIII.
USE AND PRACTICE OF THE FOURTH TABLE, IN THE FIRST EXAMPLE.
_The_ +use+.
Section 379. To shew in Feet, and Tenths, what is the Expansion of Air
on each thousand Feet, from 1000 to 9000 Feet, _with_ each Degree of
Temperature from 1 to 100 Degrees, on Farenheit’s Scale.
_The_ +practice+.
_The 12th Step applied in the first Example._
380. For the Expansion of Air with 11 Degrees of Heat on 4016.8 Feet,
look in the fourth Table, _with_ 11 in the left Hand vertical Column
of Temperature, and (first) _on_ 4000 Feet, along the upper Line: the
Place of Meeting gives the Expansion of the Air, _with_ 11 Degrees _on_
4000 Feet: viz. 106.92.[126]
Next; look _with_ 11 Degrees, and (as there is a Cypher only in the
Place of Hundreds) _on_ 10, (viz. of the 16 Feet) call the 10, a 1000;
the Place of Meeting, or Answer is 26.73:
Thirdly; _with_ 11, _on_ 6, (viz. of the 16,) calling it 6000; the
Answer is 160.38:
Fourthly; _with_ 11, _on_ 8, (viz. the .8,) and the Answer is 213.84.
381. Having added the respective Expansions together, thus;
_with_ 11°, _on_ 4016.8 Feet. Tenths.
} 4000 = 106.92 106.92
} 10 = 26.73 .2673
_with_ 11° } 6 = 160.38 .16038
_on_ } .8 = 213.84 .021384
} ——————————
} Expansion 107.369064;
(See Page 306.)
THE FOURTH TABLE,
+shewing the expansion with HEAT, from 1 to 100 degrees, on each
THOUSAND FEET in the atmosphere, from 1000 to 9000 feet.+
+-----------------------------------------------------------------------+
|+degrees of the THERMOMETER, from 1 to 50, on farenheit’s scale.+ |
| +------+------+------+------+-------+-------+-------+-------+-------+
| | 1000 | 2000 | 3000 | 4000 | 5000 | 6000 | 7000 | 8000 | 9000 |
| +------+------+------+------+-------+-------+-------+-------+-------+
| 1| 2.43| 4.86| 7.29| 9.72| 12.15| 14.58| 17.01| 19.44| 21.87|
| 2| 4.86| 9.72| 14.58| 19.44| 24.30| 29.16| 34.02| 38.88| 43.74|
| 3| 7.29| 14.58| 21.87| 29.16| 36.45| 43.74| 51.03| 58.32| 65.61|
| 4| 9.72| 19.44| 29.16| 38.88| 48.60| 58.32| 68.04| 77.76| 87.48|
| 5| 12.15| 24.30| 36.45| 48.60| 60.75| 72.90| 85.05| 97.20| 109.35|
| 6| 14.58| 29.16| 43.74| 58.32| 72.90| 87.49| 102.06| 116.64| 131.22|
| 7| 17.01| 34.02| 51.03| 68.04| 85.05| 102.06| 119.07| 136.08| 153.09|
| 8| 19.44| 38.88| 58.32| 77.76| 97.20| 116.64| 136.08| 155.52| 174.96|
| 9| 21.87| 43.74| 65.61| 87.48| 109.35| 131.22| 153.09| 174.96| 196.83|
| 10| 24.30| 48.60| 72.90| 97.20| 121.50| 145.80| 170.10| 194.40| 218.70|
| 11| 26.73| 53.46| 80.19|106.92| 133.65| 160.38| 187.11| 213.84| 240.57|
| 12| 29.16| 58.32| 87.48|116.64| 145.80| 174.96| 204.12| 233.28| 262.44|
| 13| 31.59| 63.18| 94.77|126.36| 157.95| 189.54| 221.13| 252.72| 284.31|
| 14| 34.02| 68.04|102.06|136.08| 170.10| 204.12| 238.14| 272.16| 306.18|
| 15| 36.45| 72.90|109.35|145.80| 182.25| 218.70| 255.15| 291.60| 328.05|
| 16| 38.88| 77.76|116.64|155.52| 194.40| 233.28| 272.16| 311.04| 349.92|
| 17| 41.31| 82.62|123.93|165.24| 206.55| 247.86| 289.17| 330.48| 371.79|
| 18| 43.74| 87.48|131.22|174.96| 218.70| 262.44| 306.18| 349.92| 393.66|
| 19| 46.17| 92.34|138.51|184.68| 230.85| 277.02| 323.19| 369.36| 415.53|
| 20| 48.60| 97.20|145.80|194.40| 243.00| 291.60| 340.20| 388.80| 437.40|
| 21| 51.03|102.06|153.09|204.12| 255.15| 306.18| 357.21| 408.24| 459.27|
| 22| 53.46|106.92|160.38|213.84| 267.30| 320.76| 374.22| 427.68| 481.14|
| 23| 55.89|111.78|167.67|223.56| 279.45| 335.34| 391.23| 447.12| 503.01|
| 24| 58.32|116.64|174.96|233.28| 291.60| 349.92| 408.24| 466.56| 524.88|
| 25| 60.75|121.50|182.25|243.00| 303.75| 364.50| 425.25| 486.00| 546.75|
| 26| 63.18|126.36|189.54|252.72| 315.90| 379.08| 442.26| 505.44| 568.62|
| 27| 65.61|131.22|196.83|262.44| 328.05| 393.66| 459.27| 524.88| 590.49|
| 28| 68.04|136.08|204.12|272.16| 340.20| 408.24| 476.28| 544.32| 612.36|
| 29| 70.47|140.94|211.41|281.88| 352.35| 422.82| 493.29| 563.76| 634.23|
| 30| 72.90|145.80|218.70|291.60| 364.50| 437.40| 510.30| 583.20| 656.10|
| 31| 75.33|150.66|225.99|301.32| 376.65| 451.98| 527.31| 602.64| 677.97|
| 32| 77.76|155.52|233.28|311.04| 388.80| 466.56| 544.32| 622.08| 699.84|
| 33| 80.19|160.38|240.57|320.76| 400.95| 481.14| 561.33| 641.52| 721.71|
| 34| 82.62|165.24|247.86|330.48| 413.10| 495.72| 578.34| 660.96| 743.58|
| 35| 85.05|170.10|255.15|340.20| 425.25| 510.30| 595.35| 680.40| 765.45|
| 36| 87.48|174.96|262.44|349.92| 437.40| 524.88| 612.36| 699.84| 787.32|
| 37| 89.91|179.82|269.73|359.64| 449.55| 539.46| 629.37| 719.28| 809.19|
| 38| 92.34|184.68|277.02|369.36| 461.70| 554.04| 646.38| 738.72| 831.06|
| 39| 94.77|189.54|284.31|379.08| 473.85| 568.62| 663.39| 758.16| 852.93|
| 40| 97.20|194.40|291.60|388.80| 486.00| 583.20| 680.40| 777.60| 874.80|
| 41| 99.63|199.26|298.89|398.52| 498.15| 597.78| 697.41| 797.04| 896.67|
| 42|102.06|204.12|306.18|408.24| 510.30| 612.36| 714.42| 816.48| 918.54|
| 43|104.49|208.98|313.47|417.96| 522.45| 626.94| 731.43| 835.92| 940.41|
| 44|106.92|213.84|320.76|427.68| 534.60| 641.52| 748.44| 855.36| 962.28|
| 45|109.35|218.70|328.05|437.40| 546.75| 656.10| 765.45| 874.80| 984.15|
| 46|111.78|223.56|335.34|447.12| 558.90| 670.68| 782.46| 894.24|1006.02|
| 47|114.21|228.42|342.63|456.84| 571.05| 685.26| 799.47| 913.68|1027.89|
| 48|116.64|233.28|349.92|466.56| 583.20| 699.84| 816.48| 933.12|1049.76|
| 49|119.07|238.14|357.21|476.28| 595.35| 714.42| 833.49| 952.56|1071.63|
| 50|121.50|243.00|364.50|486.00| 607.50| 729.00| 850.5 | 972.00|1093.5 |
| 51|123.93|247.86|371.79|495.72| 619.65| 743.58| 867.51| 991.44|1115.37|
| 52|126.36|252.72|379.08|505.44| 631.80| 758.16| 884.52|1010.88|1137.24|
| 53|128.79|257.58|386.37|515.16| 643.95| 772.74| 901.53|1030.32|1159.11|
| 54|131.22|262.44|393.66|524.88| 656.10| 787.32| 918.54|1049.76|1180.98|
| 55|133.65|267.30|400.95|534.60| 668.25| 801.90| 935.55|1069.20|1202.85|
| 56|136.08|272.16|408.24|544.32| 680.40| 816.48| 952.56|1088.64|1224.72|
| 57|138.51|277.02|415.53|554.04| 692.55| 831.06| 969.57|1108.08|1246.59|
| 58|140.94|281.88|422.82|563.76| 704.70| 845.64| 986.58|1127.52|1268.46|
| 59|143.37|286.74|430.11|573.48| 716.85| 860.22|1003.59|1146.96|1290.33|
| 60|145.80|291.60|437.40|583.20| 729.00| 874.80|1020.60|1166.40|1312.20|
| 61|148.23|296.46|444.69|592.92| 741.15| 889.38|1037.61|1185.84|1334.07|
| 62|150.66|301.32|451.98|602.64| 743.30| 903.96|1054.62|1205.28|1355.94|
| 63|153.09|306.18|459.27|612.36| 755.45| 918.54|1071.63|1224.72|1377.81|
| 64|155.52|311.04|466.56|622.08| 767.60| 933.12|1088.64|1244.16|1399.68|
| 65|157.95|315.90|473.85|631.80| 779.75| 947.70|1105.65|1263.60|1421.55|
| 66|160.38|320.76|481.14|641.52| 791.90| 962.28|1122.66|1283.04|1443.42|
| 67|162.81|325.62|488.43|651.24| 814.05| 976.86|1139.67|1302.48|1465.29|
| 68|165.24|330.48|495.72|660.96| 826.20| 991.44|1156.68|1321.92|1487.16|
| 69|167.67|335.34|503.01|670.68| 838.35|1006.02|1173.69|1341.36|1509.03|
| 70|170.10|340.20|510.30|680.40| 850.50|1020.60|1190.70|1360.80|1530.90|
| 71|172.53|345.06|517.59|690.12| 862.65|1035.18|1207.71|1380.24|1552.77|
| 72|174.96|349.92|524.88|699.84| 874.80|1049.76|1224.72|1399.68|1574.64|
| 73|177.39|354.78|532.17|709.56| 886.95|1064.34|1241.73|1419.12|1596.51|
| 74|179.82|359.64|539.46|719.28| 899.10|1078.92|1258.74|1438.56|1618.38|
| 75|182.25|364.50|546.75|729.00| 911.25|1093.50|1275.75|1458.00|1640.25|
| 76|184.68|369.36|554.04|738.72| 923.40|1108.08|1292.76|1477.44|1662.12|
| 77|187.11|374.22|561.33|748.44| 935.55|1122.66|1309.77|1496.88|1683.99|
| 78|189.54|379.08|568.62|758.16| 947.70|1137.24|1326.78|1516.32|1705.86|
| 79|191.97|383.94|575.91|767.88| 959.85|1151.82|1343.79|1535.76|1727.73|
| 80|194.40|388.80|583.20|777.60| 972.00|1166.40|1360.80|1555.20|1749.60|
| 81|196.83|393.66|590.49|787.32| 984.15|1180.98|1377.81|1574.64|1771.47|
| 82|199.26|398.52|597.78|797.04| 996.30|1195.56|1394.82|1594.08|1793.34|
| 83|201.69|403.38|605.07|806.76|1008.45|1210.14|1411.83|1613.52|1815.21|
| 84|204.12|408.24|612.36|816.48|1020.60|1224.72|1428.84|1632.96|1837.08|
| 85|206.55|413.10|619.65|826.20|1032.75|1239.30|1445.85|1652.40|1858.95|
| 86|208.98|417.96|626.94|835.92|1044.90|1253.88|1462.86|1671.84|1880.82|
| 87|211.41|422.82|634.23|845.64|1057.05|1268.46|1479.87|1691.28|1902.69|
| 88|213.84|427.68|641.52|855.36|1069.20|1283.04|1496.88|1710.72|1924.56|
| 89|216.27|432.54|648.81|865.08|1081.35|1297.62|1513.89|1730.16|1946.43|
| 90|218.70|437.40|656.10|874.80|1093.50|1312.20|1530.90|1749.60|1968.30|
| 91|221.13|442.26|663.39|884.52|1105.65|1326.78|1547.91|1769.04|1990.17|
| 92|223.56|447.12|670.68|894.24|1117.80|1341.36|1564.92|1788.48|2012.04|
| 93|225.99|451.98|677.97|903.96|1129.95|1355.94|1581.93|1807.92|2033.91|
| 94|228.42|456.84|685.26|913.68|1142.10|1370.52|1598.94|1827.36|2055.78|
| 95|230.85|461.70|692.55|923.40|1154.25|1385.10|1615.95|1846.80|2077.65|
| 96|233.28|466.56|699.84|933.12|1166.40|1399.68|1632.96|1866.24|2099.52|
| 97|235.71|471.42|707.13|942.84|1178.55|1414.26|1649.97|1885.68|2121.39|
| 98|238.14|476.28|714.42|952.56|1190.70|1428.84|1666.98|1905.12|2143.26|
| 99|240.57|481.14|721.71|962.28|1212.85|1443.42|1683.99|1924.56|2165.13|
|100|243.00|486.00|729.00|972.00|1215.00|1458.00|1701.00|1944.00|2187.00|
+---+------+------+------+------+-------+-------+-------+-------+-------+
382. The decimal Points in the Answer must be changed, thus:
1. For the Place of _Thousands_ in the Question, (viz. 4000,) the
Answer must remain, viz. 106.92, as in the Table, which is calculated
for the Place of _Thousands_.
2. For the Place of _Hundreds_, in the Question, (viz. which in the
present Case was a Cypher;) if there had been a Figure or Figures in
the Place of hundreds; then the decimal Point in the Answer must have
been removed over _one_ Figure or Place to the left.
3. For the Place of _Tens_, in the Question, (viz. 10 Feet,) the
decimal Point in the Answer, must be removed over _two_ Figures, or
Places, to the left.
4. For the Place of _Units_, in the Question, (viz. 6) the decimal
Point in the Answer, must be removed over _three_ Figures, or Places,
to the left.
5. For the Place of a _Decimal_, in the Question, (viz. .8) the decimal
Point, in the Answer, must be removed over _four_ Figures, or Places
to the left, by adding a Cypher: and for the Place of each further
Decimal in the Question;—_one_ Place more in the Answer, by the further
occasional Addition of a Cypher, thus: _on_
Feet 4000, the Ans. 106.92 is still 106.92
10 26.73 becomes .2673
6 160.38 .16038
.8 213.84 .021384
——————————
107.369064
383. Which Sum, by rejecting all but the first Decimal, in the Answer,
is Feet 107.3 Tenths equal to the Expansion of Air, _with_ 11° of
Heat, _on_ 4016.8 Feet, the Height of the upper Barometer, with the
Temperature of 31°.24, according to the 2d Table.
END OF THE LAST STAGE.
* * * * *
[Sidenote: +Rule+ copied.]
384. The +rule+ underneath, consisting of 3 Precepts _only_, is laid
down by Sir George Shuckburgh, in the Transactions for 1777, Page
574, in order to ascertain the Height of Mountains, &c. (See Section
349).[127]
[Sidenote: 1st. Step, in Section 353.]
385. Recapitulation for each Step of the Work, in the first Example;
referring to the Sections.
[Sidenote: 2d. Step, in Section 354.]
Below. Barometer, Inches 29, .4 Tenths.
Attached Thermometer, 50 Degrees, Air-Thermometer 45°.
[Sidenote: 3d. Step, in Section 355.]
Above. Barometer, Inches 25, .19 Tenths.
Attached Thermometer 46°, Air Thermometer, 29°½.
From 50° subtract
46
——
and there remains 4 Degrees of Temperature
to be added to the colder Barometer.
[Sidenote: _4th Step, in Section 356._]
By Means of the first Table, find the Expansion of the _colder_
Barometer, with Degrees of Heat, viz. 4° on Inches 25, .19,
_gradually_, thus:
[Sidenote: 5th Step, in Section 364.]
with 4° on 25. = .0101
with 4° on .19 = .0000076
————————————————
25.2|
[Sidenote: 6th Step, in Section 366.]
Upper Barometer, Inches 25, .2 Tenths.
Lower Barometer, 29, .4
_End of the first Stage._
[Sidenote: _7th Step, in Section 368._]
By Means of the 2d Table, find the corresponding Heights in the Air, at
31°. 24.
[Sidenote: 8th Step, in Section 371.]
25, .2 Answer 6225.0
29, .4 2208.0
——————
The Remainder is 4016.8 Height in Feet, &c.
[Sidenote: _9th and 10th Steps, in Section 373._]
The 3d Table, or Table for _Heights_ in the Atmosphere corresponding to
the _Tenth_ of an Inch _on_ the Barometer, including the 9th and 10th
Steps, is useless in this first Example.
_End of the Second Stage._
[Sidenote: 11th Step, in Section 376.]
Detached Air-Thermometer, _above_, 29½
Ditto _below_, 45°
———
Whole Heat 2)84½
Half Heat or mean Temperature 43¼
Deduct Standard 31¼
———
Moiety above Standard 11°
[Sidenote: _12th step, in Section 377._]
By Means of the 4th Table, find the Expansion
of Air, with 11° on 4106.8 Feet
viz. 107.3
which added to the same Height
gives 4124.1 for the
true Height, in English Feet, of the _Mountain_,
or _upper Station_, sought.
_End of the last Stage._
CHAPTER LXXV.
PRACTICE OF THE SECOND EXAMPLE:
_With a distinct View of the Work. (Ph. Tr. for 1777, Page 579.)_
Section 386. The Point at which the Quicksilver stood in the Tube of
the Barometer on the Mountain, or in the Car of the Balloon, being
Inches 24.178 Tenths; its _attached_ Thermometer, Degrees 57.2 Tenths,
and its Air-Thermometer 56°; while the Barometer on the Ground stood
at Inches 28, .1318 Tenths; its _attached_ Thermometer, Degrees 61,
.8 Tenths, and its Air-Thermometer 63°, .9; what is the Height of the
_upper_ Station?
[Sidenote: 1st. Step.]
387. 1st. Step. Set down the Observation on the Ground, thus:
+Below+, Barometer, Inches 28, .1318 Tenths,
_Attached_ Thermometer, Degrees 61, .8 Tenths.
_Air_-Thermometer, 63°, .9.
[Sidenote: 2d. Step.]
388. 2d. Step. Set down the Observation, on the Mountain, or _in the
Car_, thus:
+Above+, Barometer, Inches 24, .178 Tenths.
_Attached_ Thermometer, Degrees 57, .2 Tenths.
_Air_-Thermom. 56°.
[Sidenote: 3d. Step.]
389. 3d. Step. From the _warmer attached_ Thermometer, subtract the
colder, thus:
61°, .8
57, .2
———————
4, .6
390. 4th. Step. Give the _colder_ Barometer the same Expansion, viz.
4°, .6 with the warmer, by the _first_ Table.
CHAPTER LXXVI.
PRACTICE OF THE FIRST TABLE IN THE SECOND EXAMPLE.
_4th Step applied in the 2d Example._
[Sidenote: _4th Step applied._]
Section 391. The _Order_ to be observed in finding the Expansion _with_
4°.6, i.e. with 4 Degrees, .6 Tenths of Heat, on 24.178, i.e. 24
Inches, .178 Tenths of the coldest Barometer.
Find the Expansion required, thus:
_Case the 1st._
1st. Part. _With_ 4° _on_ 24 Inches.
2d. Part. _With_ 4° _on_ .178 Tenths of an Inch above 24 Inches.
_Case the 2d._
1st. Part. _With_ .6 Tenths of a Degree, _on_ 24 Inches.
2d. Part. _With_ .6 Tenths of a Degree, _on_ .178 Tenths above 24
Inches.
+specifically+, _thus_:
1st. Part of _Case the 1st._ To find the Expansion,
_With_ 4° _on_ 24 Inches.
2d. Part of _Case the 1st._
_With_ 4°, _on_ .178 Tenths of an Inch above 24 Inches; begin thus:
_With_ 4°, _on_ 24 Inches: then,
_With_ 4°, _on_ 25: then,
_With_ 4°, _on_ 1 Inch above 24, i.e. _on_ the 25th Inch: then,
_With_ 4°, _on_ .1 Tenth above 24: then,
_With_ 4°, _on_ .178 Tenths above 24.
1st Part of _Case the 2d._ To find the Expansion,
_With_ .6 above 4° _on_ 24; begin thus:
_With_ 4° _on_ 24 Inches: then,
_With_ 5° _on_ 24: then,
_With_ 1° above 4°, _on_ 24, i.e. the 5th°: then,
_With_ .1 Tenth above 4°, _on_ 24: then
_With_ .6 Tenths above 4°, _on_ 24.
2d Part of _Case the 2d._ To find the Expansion,
_With_ .6 Tenths above 4° of Heat _on_ .178 Tenths above 24 Inches: to
be done thus:
_The_ +expansion+ _with 4°, on .178 Tenths above 24 Inches, being once
found; divide_ +it+ _by 4: and the Quotient is the Expansion with 1°
above 4°, on .178 Tenths of an Inch above 24 Inches_.
_Then for the Expansion with .1 Tenth above 4°, on .178 Tenths above
24 Inches; add a Cypher and decimal Point to the left of the same
Quotient._
_Then for the Expansion with .6; multiply that Sum into .6, and add a
Cypher and decimal Point._
_The Answer is the_ +part+ _of an Inch, to which .6 Tenths of a Degree
above 4° of Heat, on .178 Tenths of an Inch above 24 Inches, raises the
Barometer_.
_It is true, the_ +part+ _is so minute as to be rejected: yet the Mode
of Proceeding, in order to investigate the Expansion with Precision, is
proper to be retained_.
392. +practice+ of the first Part of _Case the 1st._
For the Expansion _with_ 4°, _on_ 24 Inches; look, in the first Table,
(Sect. 363) and in the left vertical Column, _with_ 4 Degrees of the
Thermometer; and along the upper horizontal Line, _on_ 24 Inches of
Quicksilver in the Tube of the Barometer: the Point of Meeting gives
the Expansion .0097;[128] which, preparatory to Addition,
is to be placed under the 24, .178 thus,
.0097
+practice+ of the 2d Part of _Case the first_.
393. In order to obtain the Expansion, _with_ 4°, of Heat _on_
.178 Tenths of an Inch above 24 Inches of the Barometer; let it be
considered where it ought to be found in the Table: for, Tenths of 1
Inch above 24 Inches, are at some intermediate Point between 24 and 25;
that is, above 24, yet not so high as 25: or more than 24, yet less
than 25.
Look therefore in the Table, _with_ 4 Degrees of Heat, _on_ 24 Inches;
then _with_ 4° _on_ 25 Inches: and the respective Numbers are .0097 and
.0101.
And by taking the Expansion _with_ 4° _on_ 24 Inches, from 4° on 25;
the Remainder will be the Expansion with 4° on 1 Inch above 24 Inches,
viz. on the 25th Inch, thus:
} 25 = .0101 from;
_With_ 4° _on_ }
} 24 = .0097 subtract:
—————
.0004:
This therefore is the Expansion _with_ 4°, _on_ 1 Inch above 24 Inches.
Then _with_ 4°, _on_ .1 Tenth of an Inch above 24 Inches.
The Answer is the same as the former, viz. .0004, with the Addition
of a Cypher and decimal Point to the left, thus; .0004 becomes .00004,
viz. the Expansion _with_ 4°, _on_ .1 Tenth of an Inch above 24 Inches.
Then for the Expansion _with_ 4°, _on_ .178 Tenths, say,
If the Expansion _with_ 4°, _on_ .1 Tenth above 24 Inches gives .00004
Part of an Inch, what will the Expansion _with_ 4°, _on_ .178 give?
Thus; .1 : .00004 :: .178?
Multiply the two last Terms, thus:
.00004
.178
——————
00032
00028
00004
———————
0000712:
and, as in Multiplication of Decimals, the Product must have as many
decimal Places, as are in the Factors; a Cypher must be added to the
left Hand, thus: .00000712: but having divided that Product by the
first Term .1, viz. a Decimal, the Answer is a Cypher less; viz.
.0000712.
This Answer is the Expansion _with_ 4°, _on_ .178 Tenths of an Inch
above 24 Inches: prepare it for _Addition_, as the former,
24.178
.0097
.0000712
+practice+ of the first Part of _Case the 2d._
394. For the Expansion of .6 Tenths of a Degree of Heat, (more than
the 4 Degrees) on 24 Inches of the _coldest_ Barometer; it shoud be
considered where such Tenths can lie in the Table.
Now .6 Tenths of 1 Degree, (more than the 4°) are at some intermediate
Point of the Thermometer between 1 and 2 Degrees: above 1; yet not so
high as 2: or more than 1; yet less than 2.
Therefore .6 Tenths of 1 Degree above 4 Degrees, are somewhere between
the 4th and 5th Degree: above 4; yet not so high as 5: or more than 4;
yet less than 5.
Look in the Table (Section 363); first _with_ 4 Degrees of Heat, _on_
24 Inches, and then _with_ 5 Degrees of Heat _on_ 24 Inches; and the
respective Numbers are .0097 and .0121: and by taking the Expansion
_with_ 4 Degrees _on_ 24 Inches, from the Expansion _with_ 5 Degrees
_on_ the same 24 Inches; the Remainder will be the Expansion _with_ 1
Degree above 4° _on_ 24 Inches: viz.
_with_ {5° = .0121} _on_ 24 Inches, as in whole
{4° = .0097} Numbers.
—————
Remainder, .0024
This therefore is the Expansion _with_ 1 Degree of Heat, above 4, viz.
_with_ the 5th Degree, _on_ 24 Inches of the Barometer.
Then say, if 1 Degree of the Thermometer (above 4, viz. the 5th Degree)
gives by Expansion, a certain additional Height, or Part of an Inch,
viz. .0024, _on_ 24 Inches of the Barometer; what Height will 6 Degrees
give? Answer 6 Times _more_.
Multiply the 2d and 3d Terms, and divide by the first, thus;
1 : .0024 :: 6?
6
—————
.0144
is the Expansion, or Height, in Parts of an Inch, for 6 Degrees.
And farther, to proportion for the Decimal; say as .1 Tenth of a Degree
gives a certain Tenth of the former .0024, in additional Height, viz.
.00024; what Height will .6 Tenths give? Answer, .00144.
Prepare this _Height_ for Addition to the Numbers already found.
+practice+ of the 2d Part of _Case the 2d._
395. To find the Expansion of .6 above 4° on .178 above 24 Inches.
The Expansion _with_ 4° _on_ .178 is already found to be .0000712:
divide it by 4, and the Answer is .0000178, viz. the Expansion _with_
1° _on_ .178 above 24 Inches:
And, for the Expansion with .1 Tenth; the Answer, with the Addition of
a Cypher and decimal Point to the left, becomes .00000178.
Lastly, for the Expansion with .6, say,
If .1 : .00000178 :: .6?
Multiply the 2d and 3d Terms, and divide by first:
.00000178
.6
——————————
.000001068.
The Answer is a Decimal less, viz. .00001068; i.e. the Decimal of an
Inch, to which .6 Tenths of a Degree above 4 Degrees of Heat, on .178
Tenths of an Inch above 24 Inches, raises the Barometer: which, after
all, is so inconsiderable, that it may be fairly rejected.
Yet the Rules by which these Deductions are made, may be useful in
other Cases.
Prepare for Addition, as before.
The Decimals, in the Answers, may be omitted, when they exceed four
Places.
[Sidenote: 5th Step.]
396. 5th Step. To proceed with the second Example.
Place the different Expansions now found, above each other, Units,
Tens, &c. under Units, Tens, &c. preparatory to Addition, thus;
For the Expansion _with_ 4°, .6 _on_ 24, .178:
1st. _with_ 4°, _on_ 24, .0097
2d. _with_ .6 _on_ 24, .00144
3d. _with_ 4°, _on_ .178 .0000712
4th. _with_ .6 _on_ .178 .00001068
—————————
The Expansions with 4°,.6 added = .01122188
To the Sum add the Height of
the _colder_ Barometer 24.178
———————————
24.1892|
The Answer is Height of the _colder_ Barometer, now equal in
Temperature to the _warmer_: (rejecting all but the four first
Decimals.)
[Sidenote: 6th Step.]
397. 6th Step. Place the Barometers _now_ of the same Temperature, i.e.
_equal_ to the warmer, in one View, thus:
1st. the _upper_ Barometer, 24.1892
2d. the _lower_ Barometer, 28.1328
END OF THE FIRST STAGE.
_The 7th Step applied in the second Example._
[Sidenote: _7th Step._]
398. Find the Height, in Feet, in the 2d Column of the 2d Table,
corresponding to Inches and Tenths of the _upper_ barometric Tube, in
the 1st. Column of the same Table, thus: (Sect. 371.)
The Barometer standing at 24.1892; it must be considered where, in the
2d Column of the 2d Table, a Height corresponding to _such_ Inches
and Tenths can lie: and the Answer is, somewhere _above_ 24 Inches .1
Tenth, but not so high as 24 Inches .2 Tenths: 24 Inches .1892 Tenths,
being _more_ than 24 Inches .1 Tenth, but _less_ than 24 Inches .2
Tenths.
First then, look in the 1st Column for Inches 24, .1 Tenth; and the
corresponding Height in Feet is 7388.0: but the Height for 24, .2, in
the 2d Column, beneath the former Number, is _only_ 7280.1.
[Sidenote: 8th Step.]
399. 8th Step. Subtract the latter from the former and the Remainder
is 107.9, the same as in the 3d Column: viz. the Height, in Feet and
Tenths, corresponding to one Tenth only, namely, the ist Tenth above
Inches 24, .1 Tenth: with the Temperature of 31.24 of Farenheit, for
which sole Purpose the 2d Table is calculated.
A new Question _then_ arises, viz. what are the Heights in Feet and
Tenths, corresponding to the remaining Tenths or Decimals of an Inch
above Inches 24, .1 Tenth,
viz. .08
.009
.0002? which is to be resolved, by Application of the 3d Table,
or Table for _Tenths_, which see, (Section 373.)
[Sidenote: _9th Step._]
400. _9th Step applied in the 2d. Example._
First for the _upper_ Barometer.
Look in the Table for Tenths, in the left vertical Column with 107,
(rejecting the .9, as too minute;) and along the horizontal Line at the
top, with 8: and find the Answer _gradually_, thus:
1st. With 107, and 8, (as a whole Number,) answering to .08: which, in
the Place of Meeting, gives 86 Feet.
2d. With 107, and 9, (as a whole Number,) answering to .009: which, in
the Place of Meeting, gives 97.
3d. With 107, and 2, (as a whole Number,) answering to 0002: which, in
the Place of Meeting, gives 21.
Place them in View, and add, and bring them back again into Decimals,
thus:
With 107 and 8, answering to .08 giving 86. Feet
and 9, to .009 9.7
and 2, to .0002 .21
—————
95.9|1
(Next: with the 9, _if required_; which was before rejected:) but there
being no .9 Tenths in the left Vertical, call it 90, and allow for it
in each Answer by moving the decimal Point two Places to the left,
thus: with
90, and 8, answering to .08 giving 72 = .72
and 9, to .009 81 = .081
and 2, to .0002 18 = .0018
————
To .8|00|28
Add the former Sum 95.9|
—————
Total = 96.7)
Which 95.9 is the _Height_ in Feet and Tenths corresponding to .0892
Decimals of an Inch above Inches 24 .1 Tenth: and 24 .1 gave Feet
7388.0 in _Height_; therefore an additional _Height_, of so many Tenths
of an Inch of Quicksilver in the Tube of the Barometer, must give in
Feet, a _less_ Height of the Barometer elevated above the _imaginary_
Level indicated at 32 Inches.
[Sidenote: _10th. Step._]
401. 10th. Step. Subtract the _Height_ in Feet, corresponding to the
_Expansion_ on .0892 Tenths of an Inch, (_less_ than Inches 24.2
Tenths, of the _upper_ barometric Tube,) from the _Height_, in Feet,
corresponding to _the Expansion on_ Inches 24.1 Tenth of the same
barometric Tube, continuing at the Standard Heat,[129]
viz. 7388.0
95.9
——————
The Remainder 7292.1 gives the real, viz. the _less_ Height of the
_upper_ Barometer, at 24.1892 with the Standard Temperature.
Repeat the same Process, viz. the 9th. and 10th. Steps, for the _lower_
Barometer, thus:
For the lower Barometer in the 2d. Example.
First, Find the Height, in _Feet_, of the lower Barometer, standing
at Inches 28.1318 Tenths, in the 2d. Column of the 2d. Table,
corresponding to Inches and Tenths of the Quicksilver in the barometric
Tube, in the first Column of the same Table, thus:
The lower Barometer standing at 28.1318; it must be considered, where
in the 2d. Column of the 2d. Table, a Height corresponding to such
Inches and Tenths can lye: and the Answer is, somewhere above 28
Inches, .1 Tenth, but not so high as 28 Inches .2 Tenths: 28.1318
Tenths being more than 28 Inches .1 Tenth, yet less than 28 Inches .2
Tenths.
First, then, look, in the first Column for 28.1, and the corresponding
Height, in Feet, is 3386.6:
but the Height for 28.2, is only 3294.0:
——————
subtracting the less from the greater;
the Remainder is 92.6,
the same as in the 3d. Column, viz. the Height, in Feet and Tenths,
corresponding to _one Tenth only_ above 28.1.
Having therefore found that Feet 92.6 Tenths, are the Height,
corresponding to one Tenth only above Inches 28.1 Tenth, of the lower
Barometer, with the Temperature of freezing; for which _sole_ Purpose,
the 2d Table is calculated;—a new Question arises, viz. what are the
Heights, in Feet and Tenths, corresponding to the remaining Decimals
above 28.1, viz.
.03
.001
.0008; to be resolved by Application of the third Table, or Table for
Tenths, which see, (in Section 373.)
Look in the 3d. Table, with 92, (omitting the .6 as too minute) and with
3 answering to .03, which gives 28 = Feet 28.
1 to .001, 9 = .9
8 to .0008, 74 = .74
——————
29.6|4
Which 29.6 is the _Height_ in Feet and Tenths corresponding to .0318
Tenths above Inches 28.1 Tenth: and Inches 28.1 Tenth gave Feet 3386.6
Tenths in Height: therefore an additional Height of so many Tenths or
Decimals of an Inch of Quicksilver in the Tube of the Barometer, must
give in Feet, a _less_ Height of the _lower_ Barometer, elevated above
the _imaginary_ Level indicated by the Quicksilver resting in the Tube
at 32 Inches.[130]
402. Therefore subtract the _Height_, in Feet, corresponding to the
_Expansion on_ .0318 Tenths of an Inch (_less_ than Inches 28.2
Tenths of the _lower_ barometric Tube,) from the Height, in Feet,
corresponding to the _Expansion on_ 28.1 Tenth of the same Barometer,
viz.
3386.6
29.6
——————
and the Remainder - 3357.0, gives the _real_ Height in Feet of the
lower Barometer, at 28.1318 when above the _imaginary_ Level, and with
the Temperature of _freezing_ by the second Table.
403. Then, by taking the Number of Feet and Tenths _above_ the
imaginary Level, (indicated by the Quicksilver, in both Tubes, resting
at 32 Inches) answering to the _Expansion on_ Inches and Tenths of
the _lower_ Tube, from the Number of Feet, &c. by the former Process,
answering to that of the _upper_ Tube; viz.
_upper_ 7292.1
_lower_ 3357.0
——————
the remaining Feet 3935.1 Tenth is the _Height_, by which the
_Station_ of the _upper_ Barometer exceeds the _Station_ of the
_lower_; both being at the Temperature of 31°.24 on Farenheit’s Scale.
See Section 371.
END OF THE SECOND STAGE
* * * * *
[Sidenote: 11th Step.]
Section 404. 11th Step.
(See the Practice in the 1st Example, Sect. 376.)
_Air_-Thermom. +above+ was 56°.
_Air_-Thermom. +below+ was 63.9
—————
Whole Heat 119.9(0 adding a Cypher)
Half Heat 59.95
Standard-Heat 31.24
which deduct; and there ——————
remains each Moiety, 28.71
above the Standard-Heat.
[Sidenote: _12th Step._]
405. 12th Step. (See the Practice in the first Example, Section 377.)
By the fourth Table, find the Expansion of Air, _with_ 28.71, (more
than the Standard-Temperature) _on_ Feet 3935, .1 Tenth, gradually,
thus:
406.
_First_ _with_ 28° _on_ Feet 3000 = 204.1[131]
900 as 9000 = 612.3
30 3000 = 204.1
5 5000 = 340.1
.1 1000 = 68.0
Note: 1st. The decimal Point in the Answer corresponding to the Place
of _Thousands_, in the Question, is to remain, as taken from the Table
calculated for thousand Feet, thus: 204.1.
2d. For _Hundreds_ in the Question, remove the decimal Point _one
Place_ in the Answer, thus: 612.3 becomes 61.23:
3d. For _Tens_, _two_ Places, thus: 204.1 becomes 2.041:
4th. For _Units_, _three_ Places, thus: 340.1 becomes .3401:
5th. And for each _Decimal_, a Place more, by adding Cyphers to the
left, if wanted, thus: 68.0 becomes .00680.
407. Place the plain and decimated Answers, in one View, and add the
latter together, thus:
204.1 = the same 204.1
612.3 = becomes 61.23
204.1 = 2.041
340.1 = .3401
68.0 = .00680
—————————
viz. Expansion of Air _with_} 267.7|179
28° _on_ 3935.1 }
408. _Second_, _with_ .71° _on_ Feet 3000 = 517.5
900 as 9000 = 1552.7
30 3000 = 517.5
5 5000 = 862.6
.1 1000 = 172.5
In order to decimate these Answers, it must be observed that the
Expansion was not _with_ 71 Degrees, but with .71 _Tenths_ of a Degree
of Heat; therefore the decimal Point corresponding to 3000 Feet in the
Question, must in the Answer be removed _two_ Places to the left, thus:
517.5 becomes 5.175: for the 100, three Places: for
1.5527 the 10, _four_ Places: and so
.05175 on.
.008626
.0001725
——————————
6.7|882485
The Expansion with .71 being found, viz.
Feet 6.7 Tenths; add it to the Expansion on
28 Feet already found, viz.
267.7
—————
274.4 Answer.
Which _Height_ in Feet and Tenths, corresponding to the _Expansion_
of Air with 28°.71 Tenths of a Degree of Heat more than the Standard
31°.24, being added to the _Height_ in Feet and Tenths, corresponding
to the _Expansion on Inches_ of the Quicksilver in the _upper_
Barometer, with the Standard-Heat, already found,
viz. 3935.1
gives the _real Height_ of the _Mountain_, 274.4
——————
or _upper Station_, sought. 4209.5
END OF THE THIRD STAGE.
* * * * *
_The second Example_ briefly _stated: referring to the Sections._
[Sidenote: Section, 391.]
409. Below: Barometer 28.1318.
Attached Thermometer 61°.8; Air ditto 63.9.
Above: Barom. 24.178.
Attached Thermometer 57°.2; Air ditto 56°. Degrees of Heat, viz. 4°.6
to be added to the _colder_ Barometer at Inches 24.178 Tenths, by the
first Table, viz. .0112
Parts of an Inch of the Quicksilver
in the Barometer,
raised by 4°.6 of Heat. ———————
The Sum 24.1892
is the +point+, in Inches and Tenths of an Inch, at which the upper
Barometer _now_ rests, being of _equal_ Heat with the lower.
_End of the first Stage._
[Sidenote: Section, 399.]
By the 2d. Table, find the _Height_, in Feet and Tenths, corresponding
to the _said_ +point+ when at the Standard-Heat; gradually, thus: the
_Height_ corresponding to Feet 24.1 is 7388.0: then with the Difference
107.9, (rejecting the .9).
[Sidenote: Section, 400.]
Find the Height by the 3d. Table corresponding to
.08 86.0 }
.009 9.7 } = Feet 95.9 Tenths.
.0002 .2 }
Which Height subtract from 7388.0
95.9
——————
And there remains, in Feet, 7292.1
The Height corresponding to Inches 24.1892 Tenths of the _upper_
Barometer, with the Standard Temperature of 31.24; for which sole
Purpose the 2d. Table is calculated.
Repeat the last Process with the _lower_ Barometer, resting at 28.1318,
gradually, thus:
[Sidenote: Section, 401.]
By the 2d. Table, find the _Height_ corresponding to 28.1, which is
3386.61; then with the Difference 92.6 (rejecting the .6) find the
corresponding _Height_, by the 3d. Table for the remaining Tenths or
Decimals of an Inch, above 28.1, viz.
.03 28.0 }
.001 .9 } = Feet 29.6 Tenths.
.0008 .7 }
[Sidenote: Section 402.]
Which _Height_ subtract from 3386.6
29.6
——————
And there remains, 3357.0 viz. the _Height_ in Feet
corresponding to Inches 28.1318 Tenths of the lower Barometer, with the
Standard Temperature of 31.24, for which sole Purpose the 2d. Table is
calculated.
[Sidenote: Section 403.]
Subtract the _Height_ in Feet, corresponding to Inches of Quicksilver
in the upper Barometer,
viz. 7292.1 from ditto in _lower_ Barometer,
viz. 3357.0 and there remains the _Height_ in Feet
—————— of the upper Barometer at the Standard-Temperature
viz. 3935.1 of 31.24.
_End of the second Stage._
[Sidenote: Section, 404.]
On which Number of Feet, viz. 3935.1, by the 4th Table, find the
_Height_, with 28°.71 of Heat:
_With_ 28°. _on_ Feet 3935.1 = 267.7 and
_With_ .71 _on_ the same = 6.7
—————
Sum 274.4: which
Height, more than the Standard-Heat,
being _added_ to 3935.1
the Height, with the Standard, ——————
gives the true Height, viz. 4209.5.
_End of the third Stage._
CHAPTER LXXVII.
PRACTICE OF THE THIRD EXAMPLE,
REFERRING TO THE SECTIONS.[132]
Section 410. _Below_: Barom. Inches 30, .0168:
Attached Therm. 60°.6; Air-ditto, 60°.2:
_Above_: Barom. - - Inches 29, .5218:
Attached Therm. 56°.6; Air-ditto, 57°.
Subtract the _colder_ ————— from the _warmer_,
and there remains 4° of Heat to be added to the _colder_ Barometer; to
give it an _equal_ Temperature: which is to be done by _the 1st Table_,
thus:
[Sidenote: Section, 356.]
To find the Expansion _with_ 4° of Heat, _on_ the _colder_ Barometer;
(which, as before, is the _upper_ Barometer) standing at Inches 29,
.5218 Tenths.
_First_, _with_ 4° _on_ 29 Inches = .0117:
_2d_, _with_ 4° _on_ .5218 Tenths _above_ 29 Inches:
In order to obtain which, begin
_with_ 4° _on_ 29 = .0117
then _with_ 4° _on_ 30 = .0121
Subtract for the Expansion _with_ —————
4° _on_ 1 Inch above 29, and there
remains .0004.
[Sidenote: Section 362.]
Then for the Expansion _with_ 4° _on_ .1 Tenth of an Inch above 29
Inches; add a Cypher and
decimal Point, viz. .00004:
[Sidenote: Section 363.]
Then for the Expansion on .5128, multiply
the two last Terms, and divide —————
the Product by the first Term
.1: the Answer is .0002|0872
Add the Expansion _with_ 4° _on_
29 Inches, just found, .0117
to the Inches of the _colder_
Barometer, viz. 29.5218
———————
Answer; Inches 29.5337 Tenths of the _colder_
Barometer, are _now_ expanded equally with the _warmer_: (rejecting the
Decimals as in Section 395.)
Place the Barometers, thus:
_Upper_ Barometer, 29.5337
_Lower_ Barometer, 30.0168
_End of the first Stage._
[Sidenote: Section 371.]
411. _By the 2d Table_, and in the 2d Column, find the _Height_ of
each Barometer, _with_ the _Standard-Heat_, in Feet and Tenths,
corresponding to the Inches and +nearest+ Tenth _above_ and _below_ the
Point required: and
First of the _upper_, at 29.5337:
The Inches and _nearest Tenth_ is above
Feet.
29.5, corresp. to 2119.7 } Difference
and below 29.6, cor. to 2031.5 } between .5 and .6
—————— } above 29 Inches.
88|.2 }
[Sidenote: Section 373.]
412. _By the 3d Table_, _with_ the _Difference_ 88 Feet, find the
_Expansion_ on the remaining Decimals, above 29.5, viz. on .0337, thus:
on 03 = 26 decimated 26.
003 = 26 2.6
0007 = 62 .62
—————
Feet 29.22
From the _Height_ corresponding to 29.5
viz. Feet 2119.7 Tenths,
subtract the 29.22, i.e. Height cor. to .0338
and there ————————— ———————
remains 2090.4|8, the _Height_ cor. to 29.5338
with Expansion of the Standard-Heat.
413. Repeat the 4 last Steps for the _lower_ Barometer, at 30.0168.
1st. The Inches and _nearest_ Tenth is _above_
30. corresp. to Feet 1681.7 } Difference of
and _below_ 30.1 cor. 1595.0 } .1 above 30
—————— } Inches.
86|.7
2d. Then with 86 Feet, find the _Expansion_ on the remaining Decimals,
above 30,
viz. .0168, thus: on 01 = 9 9.
006 = 52 5.2
0008 = 69 .69
—————
Feet 14.89
414. (3d.) From the _Height_ corresponding to
30 Inches, viz. Feet 1681.7 Tenths,
subtract the Height 14.89 corresp. to .0168,
———————
and there remains 1666.8|1, the Height corresp.
to 30.0168, with _Expansion_ of the Standard-Heat.
4th. From the _upper_ Height, at 2090.48
Subtract the _lower_ Height, at 1666.81
———————
And there remains the Height 423.67 in Feet
and Tenths of the upper Barometer, with the
Standard Temperature.
_End of the second Stage._
[Sidenote: Section 374.]
415. Detached Therm. _above_ 57°
Detached ditto, _below_ 60.2
———————
_Whole_ Heat 117.2
_Half_ Heat 58.6(0 adding a Cypher)
_Standard_ Heat 31.24
——————
which being deducted, leaves 27°.36, viz. Degrees
of Heat more than the _Standard_, for each Barometer.
[Sidenote: Section 380.]
416. By the 4th Table, find the Expansion of Air, with 27°.36, on Feet
423.67 Tenths.
[Sidenote: Section 406.]
_First_, _with_ 27°, _on_ 423.67, thus:
viz. _on_ 400 as 4000 = 262.4 decimated 26.24
20 as 2000 = 131.2 1.312
3 as 3000 = 196.8 .1968
.6 as 6000 = 393.6 .03936
.07 as 7000 = 459.2 .004592
—————————
Expansion = 27.692752
[Sidenote: Section 407.]
_Second_, _with_ .36 _on_ the _same_, thus:
on 400 as 4000 = 349.9 decimated .3499
20 as 2000 = 174.9 .01749
3 as 3000 = 262.4 .002624
.6 as 6000 = 524.8 .0005248
.07 as 7000 = 612.3 .00006123
—————————
Expansion = .37050003
Add the former 27.692752
———————————
Height in Feet 28.06325203
417. Which Height for Expansion of Air, _with more than_ the Standard
Heat, being +added+[133] to the Height, for Expansion of the Barometer,
_with_ the Standard-Heat, gives the true Height of the upper Barometer,
at the given Heat.
For _Expansion_ of _Air_ above Standard Heat,
Height in Feet 28.0
For _Expansion_ of _Barometer_,
with Standard: Height in Feet 423.6
—————
418. True Height of the _upper_ Barometer 451.6
_Lower_ Barometer 1 Foot above the Water 1.0
Height of the Top of the Cross above the
Gallery 50.0
—————
Height of the Top of the Cross above the
Tyber 502.6
Height of the same, measured the same
Day geometrically, was Feet 502.9
_End of the last Stage._
CHAPTER LXXVIII.
PRACTICE OF THE FOURTH EXAMPLE,[134] FOR MEASURING SMALL HEIGHTS.
[Sidenote: By this Example, _small_ Heights are easily measured.]
Section 419. Attached Therm. _below_, 71°.0
Attached Therm. _above_, 70 .5
—————
Subtract, and there remains .5 Tenths of a Degree of
Heat to be added to the _colder_ Barometer (which in the present Case
is the _upper_, but might possibly have been otherwise) by the 1st
Table.
_First_, _with_ 0°.5 _on_ 29 Inches. To obtain which, begin
_with_ 1°.0 _on_ 29 Inches = .002:
_with_ 0°.1 above 1°, _on_ 29 = .0002: then
_with_ 0°.5 above 1°, _on_ 29 = .001.
Prepare it for Addition to the _colder_ Barometer.
colder Barometer 29.985
Expansion _with_ .5 above 1°, _on_ 29 .001
——————
29.986
_Secondly_, _with_ .5 Tenths above 1°, _on_ .985 Tenths above 29
Inches. To obtain which, (having already found the Height from
Expansion _with_ .5 above 1°, _on_ 29 Inches, to be .001;) since the
Expansion on .985 Tenths above 29 Inches, is somewhere above 29, yet
below 30 Inches; find the Expansion _with_ .5 above 1°, _on_ 30
Inches, thus:
first, _with_ 1°, _on_ 30 = .003
2d. _with_ 0°.1 above 1°, _on_ 30 = .0003
3d. _with_ 0°.5 above 1°, _on_ 30 = .0015
Subtract the Expansion _with_ .5 Tenths above 1°, _on_ 29 Inches, from
the Expansion _with_ .5 Tenths above 1°, _on_ 30 Inches:
viz. _on_ 30 = .0015
_on_ 29 = .001
—————
The Answer is .0005, the Height from Expansion, _with_ .5 Tenths
above 1°, _on_ 1 Inch above 29, i.e. on the 30th Inch: Then, if 1 Inch
above 29 gives .0005; .1 gives .00005:
and 985
———————
multiplied 00025
as whole 00040
Numbers, 00045
————————
give .0004|925
add the former Number 29.986
and, for the three remaining Decimals,
_may_ be substituted 1 Decimal
in the fourth Place 1
———————
colder Barometer of equal Heat } 29.9865
with the _warmer_ }
420. _When the Quicksilver in each Barometer indicates the same Number
of Inches_, differing _but_ one _or_ two Tenths _at the most; (which
will frequently be the Case, in levelling flat Countries, or measuring
small Heights;—instead of the usual Method, (to find the Height of each
Barometer_ separately, _with the Standard-Heat, by the_ 2d Column _of
the 2d Table, as in Section 411;)—it will be more convenient,_
1st. _To subtract the lower Barometer from the upper. Then,_
2dly. _By the_ 3d Column _of the same Table, find the_ +difference+,
(_viz. of_ one _or_ two Tenths _at the most_) below _the Inches and_
nearest Tenth _of the_ lower _Barometer_.
_And_ lastly, _with that_ +difference+, _find by the_ 3d Table, _the
Height at the Standard-Heat, corresponding to the remaining Decimals_
above _the_ upper _Barometer_.
421.(_1st._) From the lower Barom. viz. 30.082
Subtract the upper 29.9865
———————
Remaining Decimals _above_ the upper .0955
_2d._ Find, by the 2d Table, the Height corresponding to the Inches,
and _nearest_ Tenth _above_ and _below_ the Point at which the
Quicksilver rests in the lower Barometer.
The Inches and _nearest_ Tenth is
_above_ 30 Inches, correspond. to Feet 1681.7
and _below_ 30.1, corresponding to 1595.0
——————
86.7
which is the +difference+ of .1 _below_ 30.1.
_Lastly._ Find, by the 3d Table, _with_ the +difference+, viz. 86 Feet,
_on_ the remaining Decimals, for the Height, in Feet, corresponding to
the Standard-Heat.
viz. .09 77 = 77. Feet.
.005 43 = 4.3
.0005 43 = .43
—————
Answer, Height in Feet 81.73
corresponding to .0955 above Inches 29.9865 Tenths of an Inch, of
Quicksilver in the upper Barometer thus brought to the Standard-Heat.
422. Prepare for Expansion of Air from Excess above Standard-Heat, on
the same Number of Feet:
Detached Thermom. _above_ 76°.
Detached Thermom. _below_ 68.0
————
Whole Heat 144.0
Half Heat 72.0(0 adding a Cypher)
Standard-Heat 31.24
—————
which deduct, and there remains 40.76: with which, by the 4th Table,
find the Expansion of Air on Feet 81.73:
_First, with_ 40°, _on_ 81.73, thus:
_on_ 80. as 8000 – 777.6 = 7.776
1. as 1000 – 97.2 = .0972
.7 as 7000 – 680.4 = .06804
.03 as 3000 – 291.6 = .002916
————————
7.944156
_Second_, _with_ .76 _on_ 81.73, thus:
_on_ 80. as 8000 – 1477.4 = .14774
1. as 1000 – 184.6 = .001846
.7 as 7000 – 1292.7 = .0012927
.03 as 3000 – 554.0 = .0000554
————————
Expansion .1509341
add the former Expansion 7.944156
—————————
Sum of the Expansions, viz. }
Height in Feet } 8.0950901
from Excess of Heat above Standard,
_with_ 40°.76 _on_ 81.73,
+added+ to the Height at the Standard-Heat, }
in Feet } 81.73
gives, in Feet and Tenths, the true ——————
Height of the Tarpeian Rock 89.8|2.
CHAPTER LXXIX.
A CALCULATION TO ASCERTAIN THE HEIGHT OF THE BALLOON ON THE DAY OF
ASCENT: ONE BAROMETER AND ONE THERMOMETER ONLY, BEING TAKEN UP INTO
THE CAR.
Section 423. The Question is stated from Section 36: and the Mode
of Operation taken from the _Recapitulation_ of the second Example,
Section 409.
Observation before the Ascent:
Below: Barometer 29.8; attached Thermometer 0; detached Thermometer 65°.
Above: Barometer 23¼ = 23²⁵⁄₁₀₀ or 23.25;[135] attached Thermom. 0;
detached Thermom. 65°.
There being no attached Thermometers; the _first_ Table is useless: the
Barometer below is therefore supposed to be of the same Temperature as
when above; the detached Thermometer remaining at the same Degree, viz.
65°.
State the Barometer, thus: when _below_, at 29.8
when _above_, at 23.25.
_End of the first Stage._
424. Find the Height (at the Standard-Heat) corresponding to the Inches
and _nearest_ Tenth above and below 23.25: i.e. above 23.2, and below
23.3: by the 2d Table.
Now 23.2 corresponds to 8379.7: and the Difference of .1 above, i.e.
to 23.3, is in Feet = 112|.1: by the 3d Column of the same Table.
With this Difference, consult the 3d Table: i.e. with 112, (omitting
the .1 as too minute) on the remaining Decimals above 23.2, viz. on
05, as on 5, or ⁵⁄₁₀; and the Answer is 56 Feet: which Number being
subtracted from 8379.7, the Remainder 8323.7, is the Height in Feet of
the Barometer in the Car, at the Standard-Heat.
Repeat the last Process for the Barometer on the Ground.
Now 29.8, by the 2d Table, corresponds to 1856.0; and there being
no Parts or Decimals more minute than a Tenth, viz. .8, there is no
Occasion for the 3d Table.
Subtract the Barometer in the Car, from the same when on the Ground;
and, by the 2d Table,
upper Barom. 23.25, corresp. to 8323.7, and the
lower Barom. 29.8, to 1856.0: the
Remainder is the Height in Feet —————— of the
Barometer in the Car viz. 6467.7, with the
Standard-Heat.
_End of the second Stage._
425. Detached Therm. above, at 65°
Detached Therm. when below, at 65
———
Whole Heat 130
Half Heat 65.(00 adding Cyphers)
Standard-Heat 31.24
—————
which deduct, and there remains 33.76 Degrees
more than the Standard-Heat, for each Barometer.
Then for the Expansion of Air, with such Heat more than the Standard,
consult the 4th Table: viz. _with_ 33°.76 _on_ Inches 6467.7, the
Height of the Barometer in the Car with the Standard-Heat, thus:
426. _First_, _with_ 33°, _on_ 6467.7
_on_ 6000 as 6000 = 481.1, decimated 481.1
400 as 4000 = 320.7 32.07
60 as 6000 = 481.1 4.811
7 as 7000 = 561.3 .5613
.07 as 7000 = 561.3 .05613
—————————
Expansion = 518.59843
427. _Second_, _with_ .76 _on_ 6467.7:
_on_, as before, 6000 = 1108. decim. 11.08
4000 = 738.7 .7387
6000 = 1108. .1108
7000 = 1292.7 .012927
7000 = 1292.7 .0012927
——————————
Expansion = 11.9437197
Add the former 518.59843
————————————
Total Expansion = 530.5|542197
viz. Height _by Expansion_ in Feet,
with more than the Standard-Heat,
add to Height in Feet at
the Standard-Heat 6467.7
——————
428. The true Height, in Feet and
Tenths, of the Barometer in the
Car 6998.2
Feet in a Yard 3) ——————
Yards in a Mile 1760) 2332.2 Feet.
1760 (1 Mile.
——————
Yards in a Quarter of a Mile 440 ) 572 (1 Qr.
440
———
32 Yards.
The Height of the Balloon 1 Mile, 1 Quarter, 32 Yards, and 2 Feet.
_End of the last Stage,
and of the Mensuration of Heights._
N. B. A _thermometric_ sliding Rule, for the Expansion of Quicksilver,
and of Air, may possibly, from the foregoing Tables, be so contrived
and adapted to the Barometer, as to tell the Height by Inspection,
while in the Car of the Balloon.
CHAPTER LXXX.
HINTS, ON THE CHEAPEST METHOD OF INFLATING BALLOONS, WITH DESCRIPTIONS
OF DIFFERENT MODELS FOR A GASS-STEAM-ENGINE.
Section 429. The _Expence_ attending the Inflation of Balloons is a
solid Objection to their frequent Use.
A Check is thereby given to every Improvement that might otherwise be
expected from a Repetition of Experiments.
It is, in short, the chief Difficulty under which the +aironautic art+
at present labours.
This Difficulty, however, if once overcome, (and of which there is
little Doubt) will probably bring those extraordinary Machines, into
general Estimation.
What _now_ costs fifty Pounds, may _then_ be done for five: abating the
Expence of the preparatory Engine.
Mons. Lavoisier, by the Application of Steam to Iron Filings enclosed
in a Copper Retort, has generated inflammable Air, or light Gass:[136]
and Dr. Priestley, by converting a Gun-Barrel into a Steam-Engine, has
produced a Gass 13 Times lighter than common Air;[137] whereas by the
present expensive Method, with Metal and Acid, the Gass for Inflation
is seldom more than six Times lighter.
What has hitherto been atchieved on a small Scale, is here meant to be
extended.
As no Particulars are made public, or at least, have yet come to
the Author’s Knowledge, relative to the Construction of such a
Gass-Steam-Engine, as may, with Safety and Effect, be applied to the
Inflation of Balloons; the following Descriptions of different Models
may deserve some Notice:—may possibly excite the Attention of the
ingenious; and put them on contriving _easier_ Means to obtain the
_same_ End.
I.
430. Let there be an Iron _Hot-hearth_, one Yard square, and two Inches
thick. Let it be _set_ on a Common Brick Stove, built as near the
Ground as possible, (or even below it) in the open Air. Its Chimney
to consist of malleable Iron, flat at the Top, and strong enough to
support a Tea-Kettle or Boiler to produce Steam: and extending at least
one Yard from the End of the Hearth horizontally, before it turns up.
It may rise three or four Yards high, slanting farther from the Hearth:
the Form a hollow Cylinder: with a Turn-Cap at the Top, two Feet long,
set on at right Angles; for the Management of the Smoke.
Supposing then the Fire-Place to face the West; the Chimney may project
Eastward. The North Side is to be appropriated to the Iron-Borings or
Turnings; and on the South Side is to be deposited the Dross or Calx.
A Muffle or Mould of malleable Iron is to be screwed and luted over the
hot Hearth. The four Sides of the Muffle next the Hearth are to have
horizontal Lips or Rims projecting half an Inch: and Screws are to be
driven, throu’ Holes drilled at proper Distances, into the Hearth. The
Sides are to rise upright a Couple of Inches: closing, as they rise, in
the Form of a hollow Cylinder, one Foot in Diameter, and perhaps a Yard
above the Hearth: which is now converted into a _Gass-Steam-Engine_.
It is proposed to strew over the _Hot-hearth_ a thin Layer of Borings,
one Tenth of an Inch thick; to which Layer when _red_ hot, the boiling
Steam is to be applied. The extricated Gass is to be conveyed from
the Top of the Cylinder, by Means of an extended Trunk of Tin, and
varnished Linen, into a Tub of cold Water kept _continually_ flowing
over, into which a few Lumps of quick Lime are thrown: and from thence
the Gass is to rise into the Balloon.
431. The Iron, whether Filings or Turnings, proper for Inflation,
must be _bright_; wholly free from Chips, Bits of Wood, and all
heterogeneous Particles: but particularly RUST, and GREASE: _less_ than
a cubic Inch of the latter, woud spoil a Ton of the brightest, and
otherwise the best prepared Materials. (Section 339.)
A Day or two _only_, before a Balloon is inflated; the proper Quantity
of bright Iron shoud be heated +red hot+ in _Charcoal_, and suffered to
go cold.
For Want of this simple Preparation of the Iron, the Gass has proved
defective in Point of _LEVITY_: altho’ the Balloon appeared fully
inflated.
This Misfortune happened at Birmingham, and other Places.
432. The _Desideratum_ is, _quickly_ to apply, and _remove_ the
Borings, keeping the Machine _nearly_ Air-tight. For, it is now well
known, that the Gass will _explode_, if one-third Part of common Air be
introduced: or, if less; it may _unite_ with the _Gass_, and detract
from _its_ Levity.
433. The following _Particulars_ may likewise be considered as an
Improvement.
II.
1. To lay a Plate of Iron, Brass, or Copper, over the Hearth; which, if
made of _cast_ Iron, will be apt to crack, in Contact with the Steam;
and will also unite with and concrete the Iron Turnings or Gun-Borings
into a solid Mass, that woud be separated with Difficulty.
2. To make the Dross-Pit in the Form of a hollow Wedge, narrow at the
Top: screwing and luting it to the South Side of the Hearth. It shoud
hold the Dross arising from a Ton of Borings; which will be sufficient
for the Inflation of a Balloon, to carry one Person.
3. On the North Side is to be erected a Platform of Brick, a Yard
square, _floored_ with a Plate of Iron: the inside Surface to be even
with the Bottom of the Hearth.
4. The Ton of Borings is to be placed on the _Floor_, and covered with
another Muffle, secured and luted to the Side of the Hearth: having a
Communication of two Inches high, and one Yard wide, with the Bottom of
the Hearth: as the Dross-Pit has.
5. A Brass or Copper Rake is to remain within the two Muffles: to
press forward the Borings, spread them over the Hearth; stir them
frequently;—by turning the Instrument, scrape them into the Dross-Pit;
and apply fresh from the _Deposit_.
6. To perform these manual Operations within the Machine kept
Air-tight; it will be necessary, at the exterior End of the Muffle, to
fasten a strong leathern Case, made very wide and pliant, and two Yards
long: into which the End of the Rake-Handle is to be inserted.
III.
434. _The Mode of Operation._
The Borings being spread on the Hearth, and _red_ hot; the Steam Pipe
is to be opened, and _instantly_ shut. The Gass being _suddenly_
extricated; the Pipe is to be opened, and shut again as before: the
Borings pushed into the Dross-Pit, and a fresh Supply spread. This
Process to be renewed, till the Inflation is completed.
If it be thought necessary to prevent the Steam from communicating with
the whole Depôt of Borings, and so evolve too much Gass; a little Brass
Door with Hinges of the same, might be made to hang from the Top of
the Communication between the two Muffles: which Door opening inwards,
and hanging vertically, woud by the Pressure of the Gass, stop up the
Open: and yet, if made strong, _not_ prevent the Operations of the
Rake, at proper Times.
IIII.
435. The Machine woud be less complex, with one large Muffle, somewhat
longer North and South than the Hearth; furnished with leathern Case
and Rake. Put in the Borings at one End: keep the Steam-Pipe always
open; with a _Hand_ at the Rake; pushing away the Dross, and pressing
forwards fresh Borings.
V.
436. Further: it has since occurred, that a Machine in the Form of a
+gun-barrel+, _extended in all its Dimensions_, will probably answer
_every_ Intention.
And of this Kind are the hollow cylindrical Tubes, of _different_
Lengths, and about a Foot in Diameter,[138] which are _cast_, for the
Conveyance of Steam, from the Boiler of a Steam-Engine.
Such a one, (previously lined with a Cylinder of Copper, or malleable
Iron, to prevent the Adhesion of the Borings, when reduced to a Calx
by the Admission of Steam;) might be placed horizontally over a Stove,
(with or without a Chimney) and surrounded with _red_ hot Coals.
The Ton of Borings might be deposited at one End of the Tube; and, by
Means of the Air-tight flexible leathern Case, be pressed with a Rake,
_gradually_ into the Fire, and _beyond_ it when calcined.
Care must be taken to make the _Apparatus_ nearly Air-tight.
The Steam shoud pass into the Tube, from _below_: and the Gass be
conducted towards the Balloon throu’ another Iron Cylinder, nearly
equal in Diameter and at right Angles with the first; lying also in an
horizontal Direction; along the Ground.
The Tubes might be _forged_ or _cast_, so as to form but one
rectangular Piece.
The further End of the second Tube shoud communicate with a _third_,
made of Tin, and bent downwards about a Foot; thence at right Angles,
for six Inches: then to rise up, also at right Angles, the Length of
six Inches more.
The Tin Tube is to descend into a Cistern of cold Water, made to flow
over continually, by a fresh Supply; and into which, a few Lumps of
Quicklime shoud be thrown.
The Gass, which will press upwards throu’ the Water, is to be received
into an inverted Funnel, and thence (as in Section 339, Art. 2.)
conveyed to the Balloon.
VI.
437. The following Alterations woud supersede the Use of the Rake, and
_leathern_ Cases: the latter of which, by any accidental Crack or Flaw
in the Leather, might admit a sufficient Quantity of common Air to
produce an Explosion.
The cylindric Form of the Copper, or malleable Iron (to be used as a
Lining for the Tube) is to be changed, into that of a half Cylinder, or
inverted Muffle: and to be perforated with small Holes.
This Muffle is to be _nearly_ filled with a Ton of Iron Borings: (the
Ends to be made up, to prevent the Borings from falling out into
the Tube;) the Muffle itself is to be supported by a Cradle[139] of
the same Form, made of +strong+ Copper Wire,[140] like the _open_
_Iron-Wire_-Fenders: and the whole is to be thrust into the Tube.
The Length of the Muffle depends on the Quantity of Borings that are
intended to be used.
The Ends of the Tube shoud not be made so strong as the Tube itself:
that, if an Explosion happens, they _may_ give way first, and prevent
a Rupture of the Tube: not that any Danger is to be apprehended, that
such an Event will take Place, so long as the Steam-Pipe is attended
to, by a proper Person: the above Caution being only given, to prevent
a Possibility of Rupture.
Each End shoud be cast, or forged with a hollow Handle; and shoud screw
into the Tube.
The Length of the Tube shoud be such, that the Person who attends the
Steam-Pipe, shoud feel no Inconvenience from the Heat of the Fire.
Nine Feet woud therefore be a proper Length: the conducting Tube the
same.
Within six Inches from each End of the Tube which holds the Borings, a
Hole, half an Inch in Diameter shoud be drilled across the Middle of
the Tube, in an horizontal Direction.
Into these, an Iron Axis is to be fitted, (so as to take out
_occasionally_) and pass throu’ the Tube: each End of the Axis is to
project outwards a Couple of Inches, and to be made _square_, for the
Socket of a strong Iron Winch or Handle.
Each Axis to be furnished with a strong Chain, of equal Length with
the Tube; one End of which Chain is to be riveted, or otherwise fixed,
to the Middle of the Axis; and the other, to be fastened _occasionally_
to one Extremity of the Cradle and Muffle: the second Axis and Chain in
like Manner, to the other Extremity.
The Muffle is to be placed in the Cradle: both are then to be thrust
into the Tube, and fastened to the Chain at the farther Axis: in which
Position the Muffle may be filled with Borings, and gradually drawn
into the Tube; till the same End has reached the Center of the Fire.
The nearer End is then to be hooked by the nearer Chain, already
wrapped round the nearer Axis: and the light Iron Caps to be screwed on
each End of the Tube.
438. The Boiler for Steam may be fixed on any Part of the Tube near
the Fire, and near the opposite Axis; so that one Person may attend
both the Steam-Pipe, and Axis. The Steam to be conveyed throu’ a small
Orifice made in the Bottom of the Tube, between the same Axis and the
Fire.
439. As soon as the Materials, above the Center of the Fire, are
supposed to be _red_ hot, the Steam-Pipe is to be opened for a Moment
and +shut again+. The extricated Gass will be instantly +heard+,
rushing throu’ the Vessel of _cold_ Water; and as instantly +seen+ to
swell the varnished Linen-Trunk as it passes into the Balloon.
The Steam-Pipe is to be regulated by these infallible Signals: and the
Process continued, till that Quantity of Borings, that was in the
Center of the Fire, and consequently _red_ hot, is supposed to be
calcined.
At which Time, the Handles are to be applied to the Axis, and the
Cradle and Muffle drawn 5 or 6 Inches forward into the Fire.
When drawn too far; Recourse must be had to the second Axis.
440. If great Expedition is required, two or three Conductors from the
same Tube may be used: and, at the Distance of six or seven Feet from
the Fire, _Tin-Conductors_ may be added; taking Care that they are
_made_, _applied_, and _continued Air-tight_.
THE END.
An _alphabetical_ +index of the contents+:
Referring to the +sections+ and +notes+, but _not_ to the _Pages_.
A. Section.
Absorption of Water by Air, _Experiment to prove_ the, 247
Accumulation of Air, _mediocèanal_, 259, 260
Aërial Scenes _described_, 39, 47, 51, 56
Air gives +form+ to _Things_, 53
- _gentle_, its Effect on the _Surface_ of the Balloon, 201
- _calm_, its _Effect_ on the _Surface_ of the Balloon, 202
- _pure_, cool, defloguisticated, perpetually descending, 252
- _descending Torrents_ of, on Etna and Teneriffe, 265
- _Reception and Dispersion of_, what, 280
Air Bottle Balloon, _its Use_, 311
- - - _preferred_ to an _interior_ Balloon, 314
Aironaut _Employments_ of the, in the Balloon, 29
- - _Attitude_ of the, in the Balloon, 32, 33
- - _lost over a Country_ well-known when _below_, 177
- - to _try_ different Heights, to find a _favorable Wind_, 309
- - to _wait_, in the _Calm above_ the Clouds, for a _Wind_, 309
Airostat, a small one _first_ liberated, 8
Altitude _apparent_, from the Balloon when _stationary_, 49
- - _barometric_, 49, _b_.
Anchor and Cable, 13
Apogay Winds, what, 241
Apparent Height _proportioned_ to the _barometric_ Height, 49
Appearance of a Plain _below_, the Size of a moderate Carpet, what,
179, 189
Appearance of a Plain _below_, the Size of a Handkerchief, what,
181, 187
Appearances at _different_ Altitudes, _from the Balloon_, 213
Articles, _Weight_ and _Number_ of, 26
Ascent, to _check_ and _promote_, 14
- - _Preparations_ for, 22
- - of the Balloon at 40 Minutes past I. o’clock, 28
- - with _twenty Pounds_ of _Levity_, 28
- - of Balloons, Causes to _limit_ the, 279
- - _proper Times_ for, 285
- - _new_ Mode of, to _determine_ the _Height_, 299
Atmosphere _gross_, when seen throu’, _from below_, 55
- - Depression of the, 232
- - State of, _favorable_ to the _Direction_ of Balloons, 268
- - Conjectures concerning the _Warmth_ of the _superior_, 275
- - probably _respirable_ at _great Altitudes_, 277
- - _Height_ of, 290
- - _Weight_ of, in _England_, 290
Attention to the Balloon _necessary_, 35
Aurora Borealis, Conjectures concerning _Appearance_ of, 274
B.
Ballast of what it consisted, 27
- - when to be _first_ thrown out, 21
- - in Hand, ready to throw out, 91
- - thrown down, 67, 95
- - thrown over _nearly_ 32 Pounds, 103
- - poured down at once 20 Pounds, 183
Balloon going to Sea, 75, 87, 90
- - in a quiescent Bed of Air, 75
- - of rowing it to any Point, in a Calm, 75
- - drawn aside out of the Perpendicular, 103
- - shrunk to its former Shape, 123
- - alternately rising and falling, 125, 138
- - in the Air five Hours and a Quarter, 207
- - sustained above Water, how, 294, 295
- - best Form of, 307
- - Double, what, 314
Balloons their Defects, and further Improvements, 303
- - Air-tight Varnish for, 320, 325
Barometer, and Thermometer, when stationary, 36
- - Fluctuation of the Quicksilver in the, 37
- - Mensuration of Heights by the, 350
Beautiful preferred to the Sublime, in Prospects, 42
- - Appearance, 43
Bladders necessary, 26
- - began to _crackle_, 116
Bottles of Air thrown down, Caution, 74, 77, 84
Breath not affected, nor visible, during the Excursion, 126
Breeze Sea-, 88, 92, 257
C.
Cable, and Anchor or _Grapple_, 13
- - to be fastened to a _Center above_ the Car, 297
Calculations of the _Distance_ seen from the Balloon, 52, _a_.
- - of the Height of _Mountains_, 171, _a_.
Calm _above_, and Wind _below_, at the same Time, 168
Canal artificial, Duke of Bridgewater’s, Appearance of, 166
Cannon first discharged at IX. o’clock, 7
- - the second Time, at XII., 11
- - the third Time, at 40 Minutes and a half past I., 64
- - the last Time, at 10 Minutes and a half past II., 62
Car and Hoops, their _Dimensions_, 35
Caution to keep the Circle clear during the Inflation, 23
- - against the _Dropping_ of Water _out of_ the Balloon, 31
- - on Landing, 98
- - _not_ to open the upper Valve, 122
Charts Balloon, first suggested, 168
Chilliness _first_ perceived, 92; again, 109
- - _felt_ near moist Places, 283
Circularity of Prospect, 79, 221
Circumstance, _each_ to be recorded, 4
Circumstances _apparently superfluous_, mentioned and repeated,
why, 5
Clouds, an upper Tier _seen_ to move in a safe Direction, 7, 46
- - Perspective of the, 51
- - _appearing_ in rapid Motion, 163
- - View of the, taken from above them, 130, 171
- - Colouring of the, 172
- - _highest visible_, 213
Cochuc-Varnish, 320
Cold, its Effects on the Balloon, 94
Colour of the Rivers, _red_, 44
- - of the City of Chester, _blue_, 45
- - of Thunder-Clouds, 54
- - of upper Clouds, 57, 172,
Colours, _primary_, of Objects beneath, 129
Columns of Air, depressing, observed by the Ancients, 239
Compass, the properest Kind of, 38, _a_.
Conclusions, useful, 159
Conjunction of the Planets _preceding_ a Hurricane, 211
Contemplation of the Prospect, 113
Course of the Balloon traced, to shew the Manner in which it was
affected in passing over Water, 78
Curls and Streams of Air, Smoke and Vapour, 250, _b_.
Currents of Air, horizontal, 20
- - from _above_, to be guarded against, 21
Currents _under_, of Air, 87
- - of Air, blowing _to and from_ great Towns, 250
- - of Air, _contrary_, at different Heights, at the same Time,
267
- - the Balloon rising throu’ _different_, 106
D.
Defects in the Composition for Balloons, _remedied_, 320
Depressing Torrents of Air, 254
Depression of the Atmosphere, 232
- - over _moist_ Places in _fair_ Weather, 243
- - of the Atmosphere proved from History, 253
- - _nocturnal_, of the Atmosphere, 267
- - corroborating Proofs of a, 268
Depth below, conveys no Idea of Distance, 157
Depths, Mensuration of, with Barometers, &c. 348, 368, _a_, _a_.
Descent of the Balloon, to _retard_ the, 15
- - Signs of the, 17, 159, 181
- - at _first rapid_, with a rushing Noise, 96, 97
- - Proof of _gentle_, 100
- - Change in _visible_ Objects, during the, 182
- - of Balloons over Water, _enquired_ into, 229, 230
- - - - - - Means to prevent, 294, 295
Description of the Ascent, 47
Diameter of the Prospects _above_ and _below_, 52, 79
Diminution of Objects, _excessive_, when seen from the Balloon, 223
- - - - Laws respecting the, 224
Direction of the Balloon, Hints for the. 315
Distance seen from the Balloon, Calculations of the. 52, _a_.
- - of the Balloon from _Chester_, at the Report of the 4th
Cannon, 64
- - Idea of, from _Experience_, 158
- - what is the _greatest_, to be seen from the Summits of the
_highest_ Mountains, 171, _a_.
- - at which an Object can be distinguished by a _good_ Eye, 175,
_a_.
- - of the Balloon-_Course_, 191
- - at which, the Balloon was seen, 227
- - and Height of a Balloon, found by a Quadrant, 310
Dove turned out of the Car, 61
E.
Earth removed from _Sight_, 170
Echo none _above_, 39
Eknèfiai Winds, what, 241
- - a dry Wind, 267
Electricity of the Air, 65
Elliptic Solid, the Form of the Balloon an, 160
Employments of the Aironaut, 32
Engines _Steam_, Models of, for Inflation, described, 429
Equatorial Hoop, its Use, 161, 315
Evaporation of _Steam_, 249
Expansion of the Balloon, by what Manouvre, 132
Experiment to prove whether the _superior_ Atmosphere be _hazy_,
tho’ the Sun continue _shining_, 47, _a_.
Experiments necessary, in order to improve the Modes of
_Direction_, 296
Examples in the Mensuration of _Heights_ with Barometers. See Table.
Example 1st, Practice of the, 351
- - - Recapitulation of the, 385
- - 2d, Practice of the, 386
- - - Recapitulation of the, 409
- - 3d, Practice of the, 410
- - 4th, Practice of the, to determine _small_ Heights, 419
- - 5th, Practice of the, to determine the Height of the Balloon,
423
F.
Fish _Dìodon-Globe_, a _Model_ for Balloons, 377
Flag _white_, hung out a Quarter of a Mile in Length, 4
- - hung out half a Mile, in all, 66
- thrown _down_ at a Mile high, 59
- Descent of the, 60
- _white_, its Effect on the Balloon, 70
- - Progress of the Balloon marked by the. 91
- - _impeding_ the Balloon, 103
- - the remaining one unfolded, 105
- - shewed a Change in the _Direction_ of the _Wind_, 105
Flights with the Balloon, for three Hours longer, 193
Flying-Coach, 149
Foot Roman, the _Measure_ of a, 49, _b_.
Form of the Balloon at its _greatest_ Altitude, 14
- - - the _same_ at each Descent, 159
G.
Gass not offensive during the _Voyage_, why, 34
- procured by Means of _Acid_, 338
Gass procured by Means of _Steam_, 429
Geography Balloon, _first_ suggested, 167
Globe-Fish, a _Model_ for Balloons, 377
Grapple or Anchor, 13
Gums Copal, Sandarac, Mastic, &c., 326
H.
Heat of the _Sun_, _greatest_, while in the Car, 59
Height _apparent_, proportioned to the _barometric_ Height, 49
- - of the Balloon, when _stationary_, at the _first_ Ascent,
viz. 2332 Yards, 52, _a_.
- - in the Balloon, conveys no Apprehension of falling, 156
- - of _principal_ Mountains, noted, 171
- - of a Mountain, seen at a _Distance_, calculated, 171, _a_,
_a_.
- - to which Balloons will _probably_ ascend, 278
- - fixed, Method of ascending to any, 299
- - of the Balloon, to ascertain by a _Quadrant_, 310
- - _preparatory_ Instruments to observe the, 350
- - of the Balloon measured, 425
Heights to measure, Densities to estimate, 299
- - of the Atmosphere, while they encrease in an _arithmetical_
Progression, the Densities are said to encrease in
_geometrical_ Progression: the Meaning of such Terms, 301, _a_.
Hemisphere _upper only_, of a Balloon to be inflated, 315
Hoop equatorial, its Use, 161, 315
Horizontal Motion, Signs of, _deceitful_, 18
Hours proper for the Ascent of _Balloons over Water_, 254, 255, 261
Hygrometer _Horse-Hair_, the _best_ Kind, 217
I.
Illustration of the Scenery, 72
Improvement during the Process of Inflation, 24
Improvements how to be made in the propulsive Machinery, 319, 330
- - in the Process of Inflation by Acid, suggested, 339
- - suggested in the Process by Steam, 429
Incorrectness of Maps, 81
Inflation began at X. o’clock, with a small Balloon, 8
- - Degree of, to be limited, 278, 317
- - Process of, 339
- - by Means of Acid, Expence saved in the, 347
- - by Means of Steam, Expence saved in the, 429
Inflation by Means of Steam, Model and Mode of, 429
- - by Steam, preferred to the Process by Acid, 429
Information derived from the Shape of the Balloon, 159, 160
Inventory of the Voyage, 12
Iris 1st, round the Shadow of the Balloon, 56
- 2d, 73
- 3d, 136
Iron _bright_ and _fresh_, proper for inflation, 431
L.
Landing, Manouvres during the, 98
- - first, near _Frodsham_ in _Cheshire_, 100
- - second, near _Warrington_ in _Lancashire_, 188
- - Precautions to secure a safe, 297
- - in _windy_ Weather, Precautions to secure a safe, 298
- - _improved_ Mode of, 317
Latitudes variable, _light Airs_ playing in Eddies, common in the,
241
Level of the _lowest_ Stratum of Clouds in _fair_ Weather, 93
- all Inequalities of Surface reduced to the _same_, 111
Light of a _red_ Colour, Conjectures concerning the, 222
M.
Machinery _propulsive_, to be used in the _Calm_, _above Winds_, 319
Magnitude of Objects, Laws respecting the, 224
Manouvres seen at a _great_ Distance, 140
Map consulted, 174
Mast, a light _hollow_, 315
Meanders of the River _encreased_ to the _View_, 81
Mensuration of Heights and _Depths_ by Barometers, 348
Methods to ascertain the _true_ Height, 350
Method, the cheapest to inflate by Steam instead of Acid, 429
Mistakes to be noticed, to prevent Repetition, 2
Motion encreased, progressive not perceived, 165
Motion of Air, called _Reception and Dispersion of Air_, what, 280
Mountains, Names and Heights of principal, 171, _a_.
- - their Use, 265
Mouth of the Balloon, _closed_, 102
N.
Neck of the Balloon, how to place it, 31
- - _first_ tyed, 125
- - risen near _eight_ Feet upwards, 119
- - an _Attempt_ to reach it, 121
- - held _Air-tight_ in the _Hand_, 125
Notes made during the Voyage, 36
O.
Objects diminishing as the Balloon arises, Description of, 109
Objects, all _terrestrial_, disappearing, 163
Order preserved during the Inflation, 23
P.
Parashute or Umbrella, 15
- the Balloon formed a vast, 184
Perspective new, 39, 229
Place where the Balloon alighted, 100, 187
Points, the plainest generally most essential, frequently
overlooked, 4, 338
Preparations for Ascent, 22
Prospects _most beautiful_, at what Height, 93
- below noted, 128
Pulley or Reel, 13
R.
Rain _warm_ in Winter, accounted for from the Theory of
Accumulation, 270
Reception and Dispersion of Air, 280
Reel or Pulley, its Defects remedied, 41, _a._
Respiration easy during the Excursion, 114
Resistence of the Air, as the _Square_ of the Velocity of the
falling Body, 15, _a._
Rising, Signs of, 16, 30
Rivers, _no Appearance of_ Water in the, 110
Rule, general for measuring Heights, copied, 384
Rusty Iron, _improper_ for Inflation, 398
S.
Sail, three seen in the _Liverpool_ Channel, 108
- _triangular_ Latteen, _purposely to retard_ the Balloon, 315
- Anemòmeter, what, 315
- Weights to be added to the, 316
- Vane-, what, 318
Scenes aërial, described. See Sublime.
Sea-Breeze discovered, 88
- - its Duration, 256
- - its Extent, 257
Sensation of _rising_ described, 30
Sensations accompanying the Balloon, 141, 154
Shadow of the Balloon _traced_ on the Clouds, 56, 73, 136
Shadows, their Length, _at Noon_, calculated, 84
- - - - - _at half past III._ calculated, 100
- - encreased, seemed to raise the Objects, 127
Shape of the Balloon _altered_, 118
Sign of Descent, 181
Signs to be observed in the Management of Balloons, 14, 15, 17, 20
Situation novel, peculiar to the Balloon, 221
Sound of the Gass throu’ the upper Valve, 134
- in the Air, an _uncommon_, 162
Sounds immediately under the Balloon, their Effects, 175, _a._
Spirits raised by the Purity of the Air, 155
Spunges of Air, 247
Squalls of Wind, the Day preceding the Ascent, 6
Stationary, the Balloon, 36, 122
Steam, Mode of Inflation by Means of, 429
Storms of _Collection_ and _Dispersion_, 232, 263
Sublime and beautiful Scenes, 3, 39, 47, 48, 49, 51, 71, 84, 112
Sun, when hottest, 59
Sympathy of the Spectators, 46
T.
Table the 1st. See Mensuration.
- - for Expansion with Heat, from 1 to 40 Degrees, on Inches of
the Barometer, from 9 to 32 Inches, 363
- the 2nd, shewing the Variations of the Barometer, at each Inch
and Tenth of the Quicksilver, from 1 to 32 Inches, the Air
being at the freezing Point, 371
- the 3d, for easy Calculations, from the 2d Table, 373
- the 4th, shewing the Expansion with Heat, from 1 to 100
Degrees, on any Number of Feet in the Air, 381
Tastes not altered, on Account of the Height, 65
Thermometer warmer _above_ than _below_, 126
Thermometers compared, 12, _c._
Thunder-Clouds described, 52
- - under the Balloon, 172
Tide of Air in the Atmosphere, 291
Tides highest, 288, 289
Time, noted, 7, 8, 11, 22, 28, 36, 62, 63, 68, 73, 77, 85, 100,
101, 124, 162, 174, 186, 203, 206
- of Ascent, 28
Time, in which the Excursion was performed, viz. two Hours and a
Quarter, 191
- Noon, a dangerous one, for Balloons to pass an Arm of the Sea,
256
- the best, pointed out, 256
- Noon and full Tide, improper: Midnight and low Water, proper
Hours for Ascent, over Water, 287
Torrents of Air mediocèanal, depressing, 257, 258, 259
- - - - - accumulating, 260
Transparency circular, of Vapour, 222
Twine cut, lest it should prove a Conductor of Electricity between
the Balloon and Earth, 103
U.
Useful Conclusions, 159
Utility of Balloons, 332, 333
Utility _general_, of Balloons, 338
V.
Valve upper, emits the _lightest_ Gass, 124
- _first_ tried, 133
- -Swing, or Umbrella-Pendulum, as _propulsive_ Machinery,
communicates a _progressive_ Motion to the Balloon, 319
Vane-Sail, 318
Vapour, Observation of the _reddish_, 33
- _white_, _beautiful_ Effects of, 71
- - began to be accumulated at a _certain_ Height, 80
Vapours, their _Transparency_, 222
Varnishes, 320, 325
Velocity of the Balloon, 192
Vessels, the _four_ and the River Wever _disappeared_, 110
View _circular_, from the Balloon at its _greatest_ Elevation, 55
- of the Balloon over _Helsbye-Crag_,77
- of the Clouds, _from_ above _them_, 171
- _from_ the Balloon of the Country between Chester and
Rixton-Moss, 192
Vis Inertiæ, 70, 316
W.
Warmth of the superior Atmosphere, 275
- of the Air above Plains and cultivated Countries, 276
- of the Air over the _Sea_, at certain Times and Seasons, 276
- descending from _above_, 284
Water poured down, to observe the Effects of Air upon it, 74
- Balloon influenced on its Approach to, 76, 78
- Balloon above the Influence of, 131
- the Descent of Balloons over, 229
- the Causes of their Descent over, 230
- Absorption of, by Air, 247
- a curious Phenomenon seen on its Surface, 249, 250, _b._
- Means to prevent the Descent of Balloons over, and within its
Influence, 294, 295
Waves of Air, 21
- of the Sea, the Dashing of, heard; the Sea being invisible, 80
Weather, about the Time of the Excursion, 211
Weighing during the Inflation avoided, how, 24
Weight of Provisions and Articles, 24
- of the Balloon, and its Apparatus, 25
Wind heard below, 86
Winds, the Eknèfiai and Apogay, what, 241
- the Directions in which they blow, 253, _a._
- the Eknèfiai productive of Cold, 253, _a._
- _Land_- and _Sea_-, 253, _a._
- contrary, at different Heights, their Use to waft Balloons to a
given Point, 268
Wings, their Use, first to retard, second to direct, 315
Winter-Dress, preparatory, 26, 338
- -Prospect from the Balloon, 169
FOOTNOTES:
[1] Ποιησον δ᾽ Αιθρην, δος δ᾽ Οφθαλμοῖσιν ιδεσθαι·
Ἐν δε Φαει και ολεσσον, επει νυ τοι ευαδεν οὑτως.
Homer’s Iliad, Book 17, Line 646.
[2] Phil. Trans. Vol. LXVII, for 1777, Part II, Page 513, containing
Sir G. Shuckburgh’s Rules for the Mensuration of Heights with the
Barometer. Also Vol. LXVIII, for 1778, Part II, Page 681:
[3] And Page 688.
[4] It were to be wished that the Divisions of the Thermometer by
Farenheit were become general throughout Europe, in preference to
those by Reaumur yet retained _abroad_; which Divisions of Reaumur
are not sufficiently minute to mark the least sensible Change in the
Temperature, are subject to frequent Mistakes, and the Inconvenience
of adding in the Notation, the Words _above_ or _below_ the Cypher,
zero, or Point of Congelation: besides their being in Conversation
not easily compared with those of Farenheit; each Degree of the
latter having to that of the former nearly the Proportion of 18 to
11: since Farenheit from the freezing Point upwards to boiling Water
has 212−32=180°, and Reaumur to the same Height, 110° Divisions: Mr.
Saussure says as 4 to 9; in which there is an evident Oversight: see
his curious and philosophic Investigation of the Atmosphere in “Essais
fur L’Hygrometrie.” 4to. A Neuchatel, 1783.
Frequent Mention being made of the Thermometer graduated according to
Farenheit’s Scale, in different Parts of the following Account; it may
not be amiss to shew the corresponding Points according to Reaumur,
taken from “Thermometre universel de Comparaison, extrait du Journal de
Physique de M. L’Abbé Rozier.”
Farenheit, Reaumur.
54 13 & 4-9ths above the Cypher.
55 14 ditto, nearly.
57 15 2-9ths ditto, nearly.
59 16 4-9ths ditto, nearly.
60 17 1-9th ditto.
65 20 1-9th ditto, nearly.
[5] The Strength of the Rope, or Cable, if its Length does not exceed
10 or 12 Yards, ought to be such as to support a weight, greater than
the Weight of the Balloon and it’s Appendages, for the Resistance made
by the Grapple against the Balloon acted on by the Wind is immediate:
The Rope ought therefore to be made of Indian-Gut, as most elastic,
or Silk, as lightest. But if the Rope be half a Mile, or a Mile long;
the Resistance is gradual: the Balloon descending for some Minutes;
and having an open Space to move in through the Air: the Rope or Cable
acting as a Radius, and the Levity of the Balloon and Opposition of the
circumambient Air preventing it from falling with any Violence.
The shorter Cable may be used at the Height of 10 Yards; in aid of the
longer, to prevent it from rising; or to moor it, by winding the Reel,
and hauling down the Balloon close to the Ground.
[6] The Resistance being as the Square of the Velocity; therefore if
the Velocity be increased 3 Times, the Resistance will be as 3×3=9,
i.e. will be increased 9 Times.
[7]
Pounds Averdupois.
Weight of the Aironaut 160
Provisions and Articles
calculated at 20
Sand-Ballast prepared in Bags 44
Levity for Ascent 10
———
_Sum total_, 234
[8] Ancient Warriors among the Arabs, Spaniards, Romans, Gauls, and
Germans, being frequently obliged to pass deep Rivers, never undertook
a Campaign without them. For the above Anecdote, and many curious
Experiments on Air, see Sam. Reyheri, _Dissertatio de Aëre_, tertium
edita. Kiliæ. 1673.
[9] Equal Time with a Regulator corrected by an Observation.
[10] Being a Dial-Compass, the Dipping of the Needle was frequently
checked by the Glass at the Top. A Mariner’s Compass is the best.
[11] [Sidenote: The Defect of the Reel remedied]
The Loop shoud have been furnished with a +Swivel+: or the Lath or Reel
shoud have been a Kind of Pulley, a Foot in Diameter, and two Inches
wide. The Hook of which having also a Swivel might have been held in
the Hand: and thus the Twine woud have run off in a short Time with the
greatest Readiness; the Swivel conforming to the circular Motion of the
Balloon.
[12] +Slate+ (according to Cronstedt) is the +Whetstone+ _of fine
Particles_, composed of Glimmer, Quartz; and, in some Species, of a
martial argillaceous Earth, See “Essay on Mineralogy” by Mendes Da
Costa, Sect. 264.
[13] [Sidenote: Method of discovering Haze round the Sun, in bright
Weather.]
_To know whether the Air is hazy, tho’ the Sun continues shining._
The Method taken for that Purpose was by placing the Hand so as to
cover his Disk or Body, and then observe the Glory blazing round him;
which may, in general, be seen to issue in great Abundance, in Rays of
a _golden Colour_: occasioned by a Haziness or Vapour which pervades
the _lower_ Regions of the Air, most frequently in the hottest and
calmest Weather, and in the hottest Climates. The Accumulation of
these Vapours, before they are formed into Clouds, are often so great
as to intercept the Sun’s Rays, or dye them the Colour of Blood: an
Appearance frequent in Virginia, and also throughout the torrid Zone.
In the _Campania_ of Rome, for Instance, the Italians have a peculiar
Name for such Kind of Weather, when the Sun is neither _visible nor
invisible_: Il Sole si vede, e’ non si vede.
By Degrees the Hand is to be removed so as just to have a Glance of the
Sun’s Limb. And it frequently happens that the Air is exceedingly hazy;
tho’ not a Cloud appears above the Horizon.
[14] Esse in +Imaginibus+ quâpropter _Causa_ videtur _Cernendi_, neque
posse +sine his+ Res ulla videri.
Lucretius de Rerum Natura. L. 4. V. 238.
[15] Notwithstanding what has been said; +this+, to the great and
to the sordid Vulgar, woud still appear a solitary, helpless, and
deplorable Situation. But such are not captivated with the golden Lines
of +Epictetus+, (Chap. 13. Line 3. see Mrs. Carter’s Translation.)
“ΠΑΝΤΑ ΘΕΩΝ μεστα και ΔΑΙΜΟΝΩΝ·—Βλεπων τον ΗΛΙΟΝ και Σεληνην, και
Ἀστρα, και ΓΗΣ απολαυων και ΘΑΛΑΣΣΗΣ, ἐρημος εστιν ου μαλλον ἠ και
ἀβοηθητος·” Nor are they +practically+ influenced by the better Words
of a much finer Writer: “The Earth is full,” &c. &c. And “If I take the
Wings of the Morning,” &c. &c.
[16] There being, at first, no Clouds, as usual, to occupy the Place of
the lowest Stratum.
[17] It has been said that the _apparent_ Height from the Balloon to
the Ground was 7 Miles, viz. 4 to the Summit of the Clouds, and 3
below: and the _barometric_ Height was about a Mile and half, viz. 2332
Yards, _a Calculation of which will be given_.
If then we divide that Height or Distance into 2 such Parts, that the
greater shall be to the less as 4 to 3; we obtain the Length of each
Part; i.e. the barometric Height from the Balloon to the Summit of the
Clouds, and thence to the Earth; which is done thus:
Suppose the whole Distance to be any Line, as A. B. to be divided in C.
Then, as 7 is the whole Line, and 4 the greater Part; say, as the whole
7 is to the greater Part 4, so is the whole Distance to a fourth Term
proportional, which will be equal to the greater Distance sought:
Whole Distance in Yards. Greater Distance in Yards.
Thus 7, : 4 :: 2332 : 1332⁴⁄₇ Ans.
4
—————
7 ) 9328
2332 the whole. 1332⁴⁄₇
1332⁴⁄₇ being the greater Distance found; take the greater from the
whole, and then will remain the lesser Distance wanted, viz. 999³⁄₇:
the 1332⁴⁄₇ = the greater Distance, and 999³⁄₇ = the lesser Distance:
and adding the Fractions ⁴⁄₇ ³⁄₇ = 1 to the 999; we have 1332 Yards for
the greater Distance, or Height of the Balloon above the Summit of the
superior Clouds: and 1000 Yards for the less Distance, or Height from
the Earth to the Summit of the superior Clouds.
Note. _The Line A. B. here selected is the_ famous Measure _of
(half) a_ +mathematical+ _Rhinland and Roman_ +Foot+, _according to
Snellius_. (_See_ Geographia Generalis _of Varenius, published by_
Newton. _Lib. 1. Cap. 2. De variis Mensuris._)
[18] PROBLEM.
To find the circular Boundary of the _celestial_ Prospect over the Tops
of the superior Clouds, from the Balloon at the Height of near a Mile
and half above the Surface of the Earth, viz. 2332 Yards. The Height
from the Earth to the upper Surface or Floor of Clouds being 1000
Yards; and the Height above the Floor to the Balloon being 1332 Yards.
_On the Curvature of the Earth and Clouds, and Elevation of the Eye
above their circular Horizon._
Rule. To the Earth’s Diameter, equal to 7940 geographical Miles, add
_the Height_ of the Eye above its Surface: multiply the Sum by that
Height: then the square Root of the Product gives the Distance at
which an Object on the Surface of the Earth can be seen by an Eye
so elevated. Note the Diameter of the Earth, in Feet, is 41798117,
according to Newton. (See Practical Navigator, by J. Moore, 7th Ed.
Page 251.)
FIRST.
Double 1000 Yards, the Height from the Earth to the Clouds for an
Addition to the Diameter of the Earth, whose Surface is now considered,
as extended to the concentric Floor of Cloud.
1000
1000
————
2000
SECOND.
13932702(⅓) Diameter of the Earth in Yards.
2000 Addition to the Diameter.
————————
13934702 Sum, to which add
1332 the Height of the Eye or of the
———————— Balloon above the Floor of Cloud.
13936034 Sum, which multiply into
1332 the Height of the Eye above the
———————— Floor.
27872068
41808102
41808102
13936034
Extract the ———————————
Square . . . . . 1760) Yards in a Mile.
Root 18562797288 (136245 (77 Miles.
1 12320
—— ———————
23) 85 13045
69 12320
——— ———————
266) 1662 Yards 440) 725 (1 Quarter of a Mile.
1596 440
———— ———
2722) 6679 285 Yards.
5444
————— Ans. 77 Miles, 1 Qu. 285 Yards.
27244) 123572
108976
——————
272485) 1459688
1362425
———————
97263
[Sidenote: Circular Boundary of the _terrestrial_ Prospect from the
Balloon on a _clear_ Day.]
PROBLEM.
To find the circular Boundary of the _terrestrial_ Prospect, on a clear
Day, from the Balloon at the Height of near a Mile and half, viz. 2332
Yards: the Earth’s Diameter being
equal to 13932705⅔ Yards,
add 2332 the Height of the Eye or
———————— Balloon.
13935037 the Sum, multiply into
2332 the Height of the Eye, &c.
————————
27870074
41805111
41805111
27870074
———————————
Extract the . . . . . 1760) Yards in a Mile.
square Root 32496506284 (180267 (102,
1 1760 say 102½ Miles, Ans.
—— ————
28) 224 4267
224 3520
——— ————
3602) 9650 747 Yards, Remainder.
7204
————
36046) 244662
216276
——————
360527) 2838684
2523689
———————
314995 Remainder.
[19] See his “Minute Philosopher.”
[20] Ullòa in his voyage to South-America relates, that in passing over
the +Deserts+, Írides are frequently seen by Travellers round _their
own Heads_ as the Center of the _Iris_; and visible only to themselves.
But what Analogy the _Balloon Iris_ bears to them, Time and future
Experiments may discover. See his “Voyage to South America, Vol. 1. Pa.
442.”
[21] As Sound travels 1142 Feet in a
Second, it must have moved in 30 Seconds
————
Feet in a Yard 3 )34260 = Feet
Yards in a Mile 1760 )11420( 6 Miles
10560
—————
Yards in a Quarter of a Mile 440)860( 1 Quarter
440
—————
Answer 6 Miles, 1 Quarter, and 420 Yards.
[22] Equal to 2085 Yards; or 1 Mile, 325 Yards.
[23] Long’s Astronomy. Pages 227, 229.
[24] Also called the _Horsham Stone_, from a Place so named, in Surrey,
where great Quantities are found.
[25] PROBLEM.
To find the _Length_ of the _Shadow_ from a Person of _middle_ Stature,
(five Feet and a half High) viz. at XII o’Clock, on the 8th Day of
September, 1785, at Chester, whose North Latitude is 53° 12′; (and 3°
11′ West Longitude from London.)
FIRST,
To find the Sun’s Altitude at XII.
From 90°. 00′ Subtract
The Latitude 53. 12
———————
The Remain. 36. 48 is the Complement of Latitude,
to which add (from the Tables)
Sun’s N. Decl. 5. 29
———————
The Remain. 42. 17 is the Sun’s Altitude (viz. at XII.)
SECOND,
For the Shadow say,
As the Sine of the Sun’s Altitude 42° 17′
To the Person’s Height, viz. 66 Inches,
So is the Co-Sine of the Sun’s Altitude,
To the Length of the Shadow.
For the Sine of the Sun’s Altitude 42° 17′ in the Table
of artificial Sines, is the Logarithm 9.82788, which, subtracted
from the arithmetic Complement, viz. 9.99999 (supposing
the last Figure a 10) becomes, .17212
Then for the Person’s Height, viz. 66 Inches:
in the Table of Logarithms is the corresponding
Number, 1.81254
And for the Co-Sine (had by subtracting the Altitude
42.17 from 90.00) viz. 47.43: among the artificial
Sines is the Logarithm, 9.86913
————————
The above Sums added, are 11.86079
which logarithmic Number (deducting the _Initial_ 1 as useless) viz.
1.86079, in the Table of Logarithms, corresponds to 72.57, equal to 72
Inches, for the Length of the Shadow at XII.
Reducing then the Numbers 66 and 72, to the lowest Denomination, thus
6)⁶⁶⁄₇₂ = ¹¹⁄₁₂ the Proportion which the _Length_ of the _Shadow_ bears
to the _Height_ of the _Object_ is thereby obtained: that is
[26] If the _Length_ of the Shadow be divided into 12 Parts, the Height
of the Object would be 11 of those Parts.
See Moore’s Practical Navigator. See Page 98 [34].
PROBLEM.
An +easy+ Way to find the Proportion which the _Length_ of the Shadow
bears to the _Height_ of an Object is, +AT ANY TIME WHEN THE SUN
SHINES+, to fix a Plummet Line and +frame+ _upright_ in the Ground;
measure the _Length_ of its _Shadow_, and compare _it_ with the
_Height_ of the +frame+.
[27] Equal to 3 Quarters of a Mile and 121 Yards.
[28] i.e. When the Barometer _below_ is at 30 Inches, and Thermometer
_below_ at 60° viz. about 1000 Yards high in _fine_ Weather, and 500 in
_changeable_.
[29] Being 1083 Yards, i.e. half a Mile, and 203 Yards.
[30] It was High Water at Chester and Frodsham-Bridge, at 38 Minutes
past I.
[31] Articles parted with, to check the _first_ Descent at Bellair,
near Frodsham: and to ascend the _second_ Time.
To check the _first_ Descent. Pounds. Ounces.
Ballast, at twice: 24 0
To clear Trees and Hedges, and
_re-ascend_:
Barometer and Frame, 0 12½
Basket with Tunning Dish and
Bottles (except the Flask with
Brandy and Water) 4 10
Half Mile of Twine on the Reel 1 0
Speaking Trumpet 0 8½
Woollen Gloves 0 1
———————
31 0
24 0
———————
Remains for Re-ascent 7 0
[32] The Sun’s Azimuth from the North Point _Westward_, being 118.26′:
its Supplement to 180° is 61°.34′ South westerly: i.e. South West by
West, half West _nearly_.
[33] The _Length_ of the Shadows being more than _double_ the Height of
the +Objects+: see [34].
[34] To find the Length of the Shadow at half past III. (See Section
84, Note _a_.)
{Lat. of Chester, 53° 12′}
Given {Sun’s Dec. 5 29 } To find Sun’s Alt.
{Hour III, 30M. 52 30 }
This is the Case of an oblique spheric Triangle, wherein are two Sides
and one Angle between them given, to find the Sun’s Azimuth, and the
Sun’s Co-Alt.
Side 84. 31 } Sum of Sides 121. 19
Side 36. 48 } Diff. of Sides 47. 43
(3½ Hour) Angle contained 52. 30
Half ditto 26. 15 } 63. 45
Half Sum of Sides 60. 39 } Co. 29. 22
Half Difference ditto 23. 51 } 66. 9
THE FIRST PREPARATIVE PROPORTION.
As Sine of ½ Sum of Sides 60. 39 0.05966 Co-Ar.
To Sine of ½ Difference of Sides 23. 51 9.60675
So Co-Tangent ½ contained Angle 63. 45 10.30703
—————— ————————
To T. of ½ Diff. of the other two Angles 43. 15 9.97344
SECOND PREPARATIVE PROPORTION.
As Co-Sine ½ Sum of Sides 29. 21 0.30968 Co-Ar.
To Co-Sine ½ Diff. 66. 9 9.96123
So Co-Tangent ½ contained Angle 63. 45 10.30703
————————
To T. ½ Sum of other Angles 75. 11 10.57794
Half Diff. before found 43. 15
——————
Sum, is greater Angle 118. 26 = Sun’s Azim.
Diff. is lesser Angle 31. 56 = S’s right Asc.
Then by first Axiom in Trigonometry, to know the Sun’s Altitude say,
As Sine Sun’s right Asc. 31. 56 0.27659
To Sine Co-Lat. 36. 48 9.77744
So Sine of the contained Angle 52. 30 9.89947
———————
To Co-Sine of the Sun’s Alt. 63. 57 9.95350
from 90.
——————
Sun’s Alt. 26. 3
Having Sun’s Alt. to find the Shadow,
As Sine Sun’s Alt. 26. 3 0.35738 Co-Ar.
To Person’s Height, 66 _Inches_, 1.81954
So Co-Sine of the Sun’s Alt. 63. 57 9.95350
————
To Length of Shadow, 135 _Inches_, 2.13042
Then 6(⁶⁶⁄₁₃₅ = ¹¹⁄₂₂ - | - ³⁄₆ or ½, i.e. as 22 to 45: supposing the
Length of the Shadow divided into 45 Parts; the _Height_ of the Object
woud be 22 of those Parts; or not quite _half_ the _Length_ of the
Shadow, at half past III.
See Section 84, Note [26].
[35] See “Priestley on Electricity.”
[36] Εὔροια.
[37] [Sidenote: An Account of the _Breath_ being visible at Sea, when
the Thermometer was at 61.]
The Breath is said to become _visible_ at Sea or Land at any
Temperature of the Thermometer not _exceeding_ 60°: tho’, in Latitude
41°, and Westward of the Azores Islands, being in Sight of the Peak of
+st. george+, (which probably equals, if not exceeds, the Height of
Teneriffe) the Observer has seen his _own Breath_, and _that_ of the
Sailors on Deck, when the Thermometer in the _Shade_ was at 61: the Air
(in January) being _then remarkably_ damp.
[38] This Assertion may seem to contradict what was said in Section 44:
When—“every Thing, that coud be seen at all, was seen +distinct+:” but
it only proves that the Balloon had attained a greater Altitude during
the Re-ascent, and that the +shadows+ were _much lengthened_, as the
Evening advanced.
[39] Angelica Kauffman.
[40] It consists of a Frame, made by placing two strong Posts, moveable
at Pleasure, each nine or ten Feet high, upright in the Ground, at the
Distance of two Yards: the Posts being well secured by broad Pedestals,
to keep them firm: a strong horizontal Iron Axis goes throu’ the Top
of the Posts; and throu’ the Centers of four Arms or Levers at their
Junction.
Between the four corresponding Ends of each two Arms, (which Arms are
also strengthened by Beams from one to the other), are fixed four Seats
or Boxes, well secured, each holding three or four Persons, and moving
on Iron Pivots, near the Top of the Boxes, so as always to preserve the
_vertical_ Equilibrium.
[41] [Sidenote: Recommended to _Invalids_.]
Why not recommend the Use of that Machine to Invalids? who woud
find Refreshment in the +open+ Air: as its Rotation communicates a
gentle Motion to the System,[42] without the least Fatigue; _rather_
encreasing the _Animal_ Spirits.
[42] Particularly the Stomach and Diaphragm. See “Berdoe’s Enquiry.”
[43] Talis Aër qualis Spiritus. See “_Health’s Improvement_,” by Dr.
Moffet, Chapter 3, Of Air, Page 79.
[44] Or Solid of _least_ +resistance+, see Chambers’s Dictionary, with
the Supplement.
[45] It will be found, that, on comparing the _two_ Calculations in
Section 52, Note (_a_), _corrected_; the circular _Distance_ from
the Eye, above the Clouds, was 102 Miles, 1 Quarter, 320 Yards:
while _that_ above the Earth, seen from the same elevated Situation,
(supposing the Day to have been +clear+ for such a View,) was 102
Miles, 1 Quarter, 307 Yards: whose Difference is only 13 Yards:
that is, the _Distance_ above the Clouds to the _nebulous_ Horizon,
was _rather_ more extensive, than _that_ above the Earth to the
_terrestrial_ Horizon.
It may not, to some Readers, be deemed either unentertaining, or
foreign to the Subject; if the Distance of the _Prospect_ from the
Balloon at its greatest _barometric_ Altitude, viz. 2332 Yards, or a
Mile and Half within 33 Yards, be compared with the Distance which may
be seen from the _Summit_ of the principal Mountains in different Parts
of the Globe.
1. Cotopàzy, a Mountain in the Province of Quito, in America, and under
the equinoctial Line, is _said_ by Ullòa (Vol. 1. Page 422) to be 3126
Toizes or Fathom, i.e. 6252 Yards, or 3 Miles and a Half and 92 Yards
in Height.
2. White Mountain, called by the French Mount Blanc, near Geneva, is
considered by Sir G. Shuckburgh (Phil. Trans. Vol. 67, Part 2d, Page
598, for the Year 1777) as the highest Land in Europe, Asia, or Africa
(known to Europeans) and calculated by him at 5220 Yards, or 3 Miles
within 60 Yards above the Level of the Mediterranean Sea.
Mons. Bourit just returned from his last Tour, see his “Description de
Glacieres” in 1773, makes the White Mountain but 5102 Yards in Height,
(which is 30 Yards lower than Teneriffe) including the 410 Yards for
the Level of the Lake of Geneva above the Mediterranean.
3. The Peak of Teneriffe in the Canary Islands, which, _in approaching
towards it_, Authors agree, may be seen at the Distance of 120 Miles at
Sea, if the Weather is clear; (Modern History, Vol. 14th, Page 451;)
and, in _returning from it_, is discoverable at the Distance of 150
Miles, according to Glas’s History of the Canaries (Page 234);—has been
estimated by Dr. Heberden in Madeira (Guide to the Lakes, Page 187) at
5132 Yards, or 3 Miles within 148 Yards.
Glas remarks farther, that in sailing from Teneriffe, the Peak, at the
Distance of 150 Miles is very little darker than the _azure_ Sky, on
Account of the great Quantity of Vapour intercepted between the Eye and
the Mountain: and _not_ because it ceased to be an Object too small
for the Sight; or was in Fact, below the Horizon, and only raised by
Refraction of the Vapour.
With Respect to the Peak of St. George, situated in the Island called
_Pico_, one of the Azòres; the Writer of this Account asserts, from the
Mouth of an able and experienced Officer in his +Majesty’s+ _Navy_,
who, during the last War, cruized some Weeks off those Islands; that
the latter has frequently observed the Peak, at the Distance of 120
Miles, and coud then distinguish a _third_ Part of its Height _down_
the Mountain. Section 126, Note (_a_), see also [46] below.
4. Etna is 3877 Yards above the Mediterranean: (according to Brydone’s
Tour throu’ Sicily and Malta, Vol. 1. Page 211) or 2 Miles and 357
Yards.
5. Blue Ridge, the highest Mountain in the Island of Jamaica, is,
according to Dr. Clark, who measured it in November last, 3080 Yards,
or 1 Mile and three Quarters, above the Level of the Ocean.
The +distance+ to be +seen+ is considered as terminating the Radius of
a Circle, whose Center is the +eye+ of the Observer, on _each_ Mountain.
_Height of the Mountains._ +distance+ _to be_ +seen+
_from them in Miles_.
_Cotopàzy_ 3 Miles and a Half and }
92 Yards, (for the Process, } 167½ and 405
see Section 52, Note (_a_)). } Yards.
_White Mountain_ 3 Miles within } 153¼ and 13
60 Yards. } Yards.
_Peak of Teneriffe_ 3 Miles within } 152 within 72
148 Yards. } Yards.
_Mount Etna_ 2 Miles and 357 } 132 and 127
Yards. } Yards.
_Blue Ridge_ 1 Mile and 3 Quarters. } 117¾ and 30
} Yards.
_Balloon_ 1 Mile and half within } 102¼ and 307
33 Yards. } Yards.
As it is well known that Objects of the _greatest_ Magnitude appear
but as +blue air+ at even a _less_ Distance than 100 Miles; to
which add the Difficulty of Journies, and Ascent to the Summit of
these astonishing Mounds of Earth; and all this for the Sake, not
of a complete +down prospect+, subject to _a perpetual Variety_,
but merely an _imperfect Side-View_: the +pleasure+ and +ease+ of
attaining still _more_ stupendous Heights at _any_ Place and Time, by
Means of the +balloon+, are strikingly in Favor of that Invention.
And, notwithstanding the confessed Merit of Dr. Black’s Project with
the _Farciminàlis_ of a Calf, and Mr. Cavallo’s Soap Bubbles with
inflammable Air; (see his History of Aerostation, Page 34;) if the
Emperor had been alive who offered a Reward for the Invention of a _NEW
PLEASURE_; the _first_ Prize had been due to the Brothers Montgolfier,
and a _second_ to the Brothers Roberts.
[46] As therefore it may be supposed that the Peak of St. George, in
_receding_ from it, woud _vanish_ at the Distance of 150 Miles; its
Height may _easily_ be ascertained geometrically thus:
[Illustration]
See the Figure annexed.
Let M be the Summit of the Mountain: and let the Line M T drawn to the
Circumference of the Circle at T, be the _evanescent_ Distance of the
Mountain in the Horizon, viz. 150 Miles.
Join T C, viz. a Line drawn from the _Tangent_ to the Center of the
Circle, which Line will therefore represent the Semidiameter of the
_Earth_, viz. 3958 Miles, according to Newton.
Draw a Line from C to M, which will pass throu’ some Point of the
Circumference as H, the Base of the Mountain.
Then, in the Triangle M T C, as the Angle at T is a right Angle
(Euclid’s Elements, Book 3, Proposition 18;) and the Sides M T, and T
C, containing the right Angle, are _known_; the _third_ Side C M is
readily found: (being a Corollary to the 47th Prop. 1st Book Euclid:)
viz. having the two Sides of a right Angle Triangle given to find the
_third_. Therefore
RULE.
Multiply the Sides containing the right Angle, each into itself: viz.
150 and 3958: add the Products into one Sum: from which extract the
_square Root_; _equal_ to the Length in Miles, of the _third_ Side
required.
From the _third_ Side, subtract that Part, viz. C H, which is equal
to the Semidiameter T C already found: and the Remainder H M is the
_Height of the Mountain_.
Thus: 150 Miles. 3958 Miles in the Semidiameter of
150 3958 the Earth.
——— ————
7500 31664
15 19790
————— 35622
22500 11874
Square of the ————————
greatest visible 15665764 Square of the Semidiameter
Distance. add 22500 of the Earth.
————————
Extract the sq. Root, 15688264 ( 3960.84 Square Root.
9 3958 subtract.
—— ————
69) 668 Rem. 2.84 Answer in Miles.
621
———
786) 478.2
471 6
—————
79208) 6664.00 continued to 2 Decimals.
6336 64
———————
792164) 32736.00 ditto.
31686 56
————————
104944
To find the .84 Part of a Mile; multiply
1760 Yards in a Mile,
Decimal Parts of a Mile to be reduced .84 into Yards.
————
7040
14080
——————
1760)1478.40(0
Subtract 1478
————
282
Answer: the Height of the Mountain is 2 Miles 282 Yards.
[47] Rays flowing from the Sun seem to be +red orange+ or +yellow+,
according to the Quantity of Vapours floating in the Atmosphere,
which absorbs the most refrangible ones: and the fewer the Vapours
the more does the Sun’s Light approach to a perfect and intense
+white+, according to the Doctrine of Newton: which seems to receive
Confirmation from the Purity of the Solar Light, when seen _above
Clouds_ and _Vapours_, in the Balloon: where the Sun shines not so much
with a _golden_ as with a _sparkling_ +silver+ Light.
[48] +Sounds immediately under+ the Balloon, seemed, as if originated
_near_ the Ear, and _louder_ than they would have been heard, at
the Distance of some Yards _only_, when on a Level with themselves:
augmenting rather than decreasing, during the _Ascent_ of the Balloon,
till it arrived to a Height indicated by the Barometer at 27 Inches.
Presently afterwards, the Balloon still rising; the Sounds _died away_:
much sooner indeed than was expected.
The like was observed in _descending_ from a State of perfect
Tranquillity and Silence: _Sounds_ from _below_, when about the same
Height, _suddenly rushing_ on the Ear.
It must be considered that by _this_ Time, the +shadows+ were much
encreased; tho’ at half past II, they were _more_ than double in Length
to the Height of each Object.
The Trees woud therefore spread a +shade+ _across_ the Road.
The +tops+ of the _Houses_ likewise, being Part of them in the Shade;
and either _thatched_ with Straw, or covered with Slates of a _dusky_
Hue; woud prevent their _throwing off_ any _striking_ Colour.
Possibly the _Encrease_ of Shade _alone_, might give the Face of the
Country _below_, a _dark-green_ Cast.
It is certain that the Height of the Balloon must have been very great,
to prevent the Sight of public and _Turnpike-Roads_, _above_ which it
_frequently_ passed, and which had been +plainly+ seen _before_ the
_Re-ascent_.
For suppose the Road but 5 Yards wide, which is less than the Truth; if
it be allowed that an Object may be distinguished by a _sharp_-sighted
Person, when its _Distance_ from the Eye does not _exceed_ 5156 Times
the Diameter of the Object; i.e. when the Object does not subtend a
_less_ Angle at the Eye than _30 Seconds_ of a Circle, (Smith’s Optics,
Article 97) which is the _smallest_ visible Point, and equal to the
8000th Part of an Inch on the _Retina_;—by multiplying 5 Yards, viz.
the Diameter of the public Road, into 5156 (or, in round Numbers, into
5000) Times its Distance from the Eye in the Balloon; the Product is
25000 Yards: which Product being divided by 1760, the Number of Yards
in a Mile, amounts to 14 Miles, and 360 Yards.
Supposing farther, that a _common_ Eye can _only_ see an Object at
_half_ that Distance; the Height woud _then_ be 7 Miles.
The _Improbability_, therefore, (on Account of the _Warmth_ of the
Air at that Height, viz. 60°;) of having _soared_ to so great an
Altitude, seems to point out, that the +shadows+ must have contributed
a _principal_ Share, in preventing a Sight of the public and _Turnpike_
Roads.
[49] The +magnitude+ of an Object _decreases_, as the +squares+ of its
Distance from the Eye _increase_.
At whatever Distance, for Example, the Eye can see any Object clearly;
as at the Distance of a Foot, or a Yard, if the Object be removed to
_twice_ that Distance; it will appear 4 Times smaller than it did
before: 2 multiplied into 2, equals 4, which is the Square of 2: in the
same Manner, if the Object be removed to thrice the Distance from the
Eye, it will appear 9 Times as small, as at the first Distance: for 3
into 3 gives 9, the Square of 3: and so of any farther Distance.
[50] See “Berkeley’s New Theory of Vision, Section 67.”
[51] Dr. Smith having Recourse to _intervening Objects_; the Writer
cannot assent to the Validity of his Argument, illustrated by a
well-known Figure, to solve the Appearance of the _horizontal Moon_.
See “Priestley’s History of Light and Colours, Page 712.”
[52] Phil. Trans. for 1785, Part 1, Page 287.
[53] Cavallo’s Treatise on Air, Page 576. Vitriolic Acid Air, Alkaline
Air, and other elastic Fluids, are instantly +absorbed+ by _Water_;
(Page 673.) Inflammable Air, and fixed Air, are likewise +absorbed+ by
+water+. (Page 434).
[54] Nam fit, ut interdum tanquam demissâ Columnâ
In Mare de Cœlo descendat.—Lucr. L. 6. V. 425.
_Una_ Eurus Notusque ruunt, creberque Procellis
Africus. Also
Omnia Ventorum _concurrere_ Prælia vidi. +Virgil.+
[55] Franklin’s Account of Whirlwinds and Waterspouts, in his
Miscellaneous Tracts. Lowthorp’s Abridgement of Phil. Trans. Vol. 2.
Page 103. Varenius Geogr. Gen. C. 21, Pag. 265. A clear Account of the
Effects of a +depression+ is to be met with in “the History of Jamaica,
in 3 vols. vol. 3. Page 800, on _Trade and Land Winds_.”
[56] Mons. Maupertius has found, that the extreme Cold at Tornea,
in the northern Regions beyond the Artic Circle, came directly from
_above_: see “La Figure de la Terre,” Page 59. Il semble que le vent
souffle—de tous Côtés à la Fois; et il lance la _Neige_ avec une telle
Impetuosité, qu’en un Moment tous les Chemins font perdus. “It seems
that the Wind blows from all Points of the Compass at once,” &c.
[57] The Doctrine of smokey Chimnies distinctly treated of under the
Article +smoke+, in the Encyclopædia Britannica, may receive some
Improvement, from Circumstances which ascertain the sudden Descent,
Elevation, and quick Depression of _Columns_ or rather _Torrents_ of
Air, viz. by widening the Tubes, and covering their Tops.
[58] It is thought more _candid_, and will to _many_ be more
_satisfactory_; to make occasional References to different Authors who
have treated distinctly on a Subject, and leave the Reader to draw his
own Conclusions by applying to their _express_ Words;—than, either
to insert abundant Quotations; or _weave_ their Thoughts into the
_Texture_ of the Work: which must encrease its Bulk, without producing
any Thing either new or instructive.
[59] Once, particularly, in the Month of January, at Lausanne:
Farenheit’s Thermometer at 7 only: the Country covered with Snow; and
a North Wind beating +violently+ on the Lake, which continued liquid
without Ice: owing, perhaps, in _Part_, to subterranean Heat, and
Exhalations.
[60] The Depression and Reverberation of the Wind near Rivers, and its
Descent from Mountains, _a Point to be discussed_, may furnish a Hint
and Reason, why Rain falls more in one Place, than in another not far
distant: and why in the same Place it falls in different Quantities, at
different Heights, irregularly.
[61] Cavallo’s Treatise on Air, Page 446.——
[62] 442.——
[63] 441.——
[64] 442.
[65] It is _light_ in Consequence of its _Warmth_, when compared with
the _cooler condensed Air_ above it.
[66] In the same Manner that Curls and Streams of Air _descended_ into
the Bason over the rising _Steam_, and interrupted the Regularity of
_its_ Elevation; in the _larger_ Towns, during Winter (_the Weather
being moderate_) the Pressure of Air on all Sides, from without,
produces a constant Breeze towards the Center of the Town: as may
be discovered, not only by the Smoke in its Deviation from the
Perpendicular, as it issues from the Chimneys; but by all who are
inclined to make the Trial; for, on leaving the Town, they will _meet_
the Breeze.
In calm Weather, during Summer, the contrary Event happens: but more
particularly in _hot_ Climates. For the Country being hotter than the
Town; a _Depression_ of the Atmosphere takes Place, and scatters the
Smoke on all Sides round the Town.
The Cities in Italy, and other hot Climates, on Account of the
Buildings, and _desirable_ Narrowness of the Streets, form _one_
contiguous _Shelter_, _Arbor_, or grand _Parasol_: For which Reason,
the Nobility leave the Country, and reside in the Towns during Summer:
there finding a Coolness and Refreshment unknown on the _scorching_
Plains.
A _Reception_ and _Dispersion_ of Air takes Place; _as will presently
be mentioned_.
The same ocular Proof and Process in the Evaporation of Steam, accounts
at once, for a curious Phenomenon constantly observable on all Waters;
viz. _a narrow_ +smooth+ _irregular Surface of considerable Length,
nearly in the Direction of the Wind, yet unaffected by it_: all which
is probably nothing more than _rising_ Volumes of _elastic invisible_
Steam; _resisting_ the _two_ nearest _descending Waves_ of +air+; and
preventing them from approaching the _Surface_ of Water, over which the
Steam is compressed; and _there_ producing a _temporary_ +calm+.
[67] Phil. Trans. for 1777, Page 470. Thibet in Lat. 31, _cold_ with
Snow and Frost.
See Ullòa’s Voyage to South-America, Book 6, Chapter 7; where he
describes the snowy Mountains, under the Equator.
As the Weather, near the Equinoctial, is more regular, its Changes
closely following those of the Moon; and also the Winds and Hurricanes
more violent; the Truth of the foregoing Theory will receive the
strongest Confirmation by tracing the Effects of +depressing torrents
of air+, in the Island of Jamaica, extracted from the Author already
mentioned.
“The cool Vapour _rushes_ from the Mountains towards the hot dry Air,
which hovers over the Savannahs or Vallies.
The Rain falls heaviest in the Mountains. Vol. 3, Page 600.
The _Land-Wind_ after Rain, proceeds from that Quarter whence the Rain
has fallen _heaviest_; and seems to _rush_ from above.
In Spain and North-America, the Wind _rushes down_. Page 601.
When the _Land_ is _most_ heated, the Sea-Breeze blows almost _all_
Night. Page 602.
The Barometer subsides from 1 Inch to 1½ _at_ the full Moon, or just
_after_ it.
Wind blows from the Mountains all round the Island: and still a
Sea-Breeze over the Mountains: to the Low-Lands, none, 604.
(In Jamaica likewise the Wind blows off the Island _every way_ at once,
so that no Ship can any where come in by Night, or go out but early in
the Morning, before the Sea-Breeze sets in. See Abr. Phil. Tr. Vol. 3,
P. 548.)
_Mountain Air rushes down in a continual Current to every Part of the
Coast, the Stream descending incessantly throu’ the Night: while heavy
cold Air descends to the Mountain Tops_, 604.
With a _West_ Wind below there is an _East Scud above_, 605.
_Mountains_ +cloudy+, _low Lands_ +sunny+. 606.
In +all+ _the River-Courses of Jamaica, there is a sensible Current
of Air. Rain never comes without some Wind: and the Showers almost
invariably follow the very Meanders of the larger Rivers_, 608.
Rain always cools: the Thermometer falling, after a Shower, from 6 to 8
Degrees, 610.
(And Iron rusts least in rainy Weather: [the Air being then +driest+,]
descending from the _upper_ Regions. Abr. Ph. Tr. V. 3, P. 546.)”
It is said also that “in Jamaica the Clouds gather, and _shape_
according to the Mountains: so that _old Seamen_ will tell you each
_Island_ towards Evening, by the _Shape_ of the Cloud _over_ it.”
The Sea-Breeze, being counterpoised by _Descent_ of the _etherial Air_,
produces a +calm+.
The same Author likewise says, that “the Clouds begin to gather about 2
or 3 o’Clock in the Afternoon _at the Mountains_, and do not _embody_
first in the Air, and after settle there, but _settle_ first and
_embody_ there: the rest of the Sky being clear till _Sun-set_. So
that they do not pass _near_ the Earth in a _Body_, and only _stop_
where they meet with Parts of the Earth elevated _above the rest_;
but +precipitate+ _from a very great Height_, and in Particles of an
_exceeding rarified Nature_; _so as not to obscure the Air or Sky at
all_: that great Variety of beautiful Colours in the Canopy of Heaven
being raised to a much greater Distance [he means Height] in Jamaica
than it is here.” Abr. Ph. Tr. V. 3, P. 557.
(Prognostics of Weather, at certain Periods of the Moon, are mentioned
by Captain Langford. Lowthorp’s Abr. Phil. Trans. Vol. 2, Page 105.)
[68] The Depression of a _Torrent_ of Air in the Form of an hyperbolic
Solid, _contracting_ as it _descends_ to the Earth, in Proportion as
its _Density_ encreases; may furnish a Hint towards the Solution of a
Difficulty how to account for the Augmentation of vesiculous Vapours
into large solid Drops, frequent during _Summer_-Showers.
[69] Mons. Saussure’s valuable “Essais sur L’Hygrometrie,” throw new
Light on the Doctrine of Rarefaction and Condensation not unfavourable
to the Hypothesis here advanced. Page 260.
[70] Ice, when exposed to marine acid Air, is dissolved by it, as fast
as if it touched a red hot Iron. See Cavallo’s Treatise on Air, Page
727. Also Priestley’s Experiments and Observations, Vol. 1, Page 148.
[71] “The +water+ remains +transparent+ or colourless, tho’ saturated
with marine acid Air, and by a very gentle Degree of Heat, the Gass may
be again expelled from it, as it is expelled from Spirit of Salt.”
This Observation is applicable to the Transparency of Vapours, in the
Air, tho’ mixed with the marine Acid exhaled from the Sea: for when
the acid or Sea Air is mixed with Alkaline or Land Air, they instantly
_combine_; lose their Elasticity, and form a _white_ visible Substance
or _Cloud_. Cavallo, Page 728. Priestley’s Exp. and Obs. Vol. 2, Page
293.
[72] On the Descent of Air in _Thunder-Gusts_, see “Chalmer’s Account
of the Weather in South-Carolina, Vol. 1, Page 1, to 39.”
[73] “Historia Ventorum, Pag. 54, Art. 34.”
[74] Book V. Chapter 2d.
[75] Vol. 1. Page 184.
[76] Page 195.
[77] History of the Canary Isles, Page 252.
[78] As the superior Clouds, during the Balloon Excursion, did not much
exceed the Height of 1000 Yards; supposing then the Clouds at an equal
Height above the Sea, near Teneriffe; one ought to conclude, either,
that the Peak was not so high as Glas represents it; or, that the Level
of the Clouds was less than half the Height of the Mountain.
[79] See “Royal Astronomer, by R. Heath, Page 321, on _Trade Winds and
Monsoons_.”
[80] One Pound of Nitre only, producing by mere Heat, 6 cubic Feet of
Air. “Cavallo, Page 332, and 811, Experiments on Gun-Powder.”
[81] “See Recherches surles Modifications de l’Atmosphere. No. 715.”
Ph. Trans. Part 2, for 1777. Col. Roy’s Experiments, Sect. 2d, Page
689, 744, 753, 764.
[82] The different Phenomena of the _Aurora Borealis_ may be owing to
the Ascent and Motion of the Apogay, in the _middle_ Region, over the
Stratum of Eknèfiai or _Ground_-Winds.
The Effects of _Tides in the Air yet to be_ mentioned, must not,
however, be wholly excluded.
The Aurora Borealis is seen in _Spring_, _Autumn_, and _Winter_:
sometimes _culminating_, sometimes moving in _Streams_ and _Waves_
in the _superior_ Regions of the Atmosphere: when culminating; as if
rising out of Clouds in the North.
This Appearance may be owing to warm moist Air perpetually generating
between the Tropics, and rolling over the cold _dry_ Stratum of
Eknèfiai Winds, which cut off its Communication with the Earth: till
accumulating over the Poles, it enlightens the Atmosphere, converting a
six _Month’s Night_ into Day; and returns to the Surface silently: or
in Lightning, whenever it is communicated to the Earth, throu’ _Vapour
descending_ by its own specific Gravity; or along with _depressing_
Torrents of Air, known to be accompanied by frequent +flashes+.
When the Vapour is _condensed_ in its Descent, by passing throu’ a
Stratum of the Eknèfiai Winds; it becomes _overcharged_ with the
electric Matter, _surrounding_ and _adhering_ to it; and deposits the
Overplus in Lightning, on its Approach to _other_ Clouds, or to the
_Earth_.
It is visible in the Form of a Vapour, when the Vapour to which it
adheres, becomes overcharged with electric Matter, by Descent into a
_cool_ Eknèfiai Stratum below: there forming a luminous and transparent
Atmosphere: the Particles of Light and Vapour being repelled to great
Distances from each other at so _rare_ a Height.
It culminates above the Vapour, because less heavy than the
circumambient Air: and may be subject to the Attraction of other
Planets.
The Aurora Borealis is also seen to issue in Streams and Waves of
Light, with inexpressible Velocity, on its Return to the South, in a
lower Stratum, as it _passes throu’_ Interstices, between the Vesicles
of warm Vapour, raised and dispersed by the turbulent Apogay Winds, in
the middle Region.
During Summer, the middle Region becomes blended with the lower, throu’
Defect of Cold: and the electric Matter is supposed to be communicated
to the Earth, silently, and continually; but by Lightning, when a lower
and colder Atmosphere condenses and overcharges the Vapour, and cuts
off the Communication.
It cannot be seen but in escaping from Vesicle to Vesicle: nor, during
Summer, after Sunset, on Account of the Twilight.
[83] Air is not unfit for Respiration, by having lost its _vital_
Principle, but because it has imbibed _Floguiston_, which cannot
_easily_ be separated from it, but by Agitation in Water. Cavallo, on
Air, Pages 479, 670.
[84] For if Moisture be one Cause, which keeps the Particles of Air
at greater Distances from each other; this Cause decreases at _great_
Altitudes.
If also the _Elasticity_ decreases in Proportion, not only to the
Height, but the Driness; its Particles must, on both Accounts, approach
each other, at great Altitudes: tho’, from the Altitude only; they woud
separate according to the Rule, viz. that the Rarity of the Air is
proportionable to the Relaxation of the Force compressing it.
So that at the Height of 8 or 10 Miles, a Quantity of Air taken from
the Surface of the Earth, woud occupy 6 Times its former Space:
supposing the Air both below and above to be of the _same Kind_, as
well as of the _same mean_ Temperature of 55, on the Thermometer. See
“Martin’s Philosophical Grammar, Page 178.”
[85] Chalmer describing a Whirlwind, which is a _Storm_ of +collection+
and _Ascent_ of +hot+ Air, &c. by Rarefaction, says, “as the Wind
ceased, presently after the Whirlwind passed, the +branches+ and
Leaves of various Sorts of Trees, which had been carried into the Air,
continued to +fall+ for +half an hour+; and, in their Descent, appeared
like Flocks of Birds of different Sizes.”
This Circumstance proves that Columns of +hot+ Air must have been
raised in a Body, in Succession, to so considerable a Height, that
_Branches_ of Trees carried up by them, took _half an Hour_ in falling.
[86] It may be from this Principle, that in the East, Liquids are kept
_cool_ by being hung in the Shade, in the _open_ Air, suspended in _wet
Cloths_: there being a continual Breeze and Succession of +cool dry+
_Spunges_ (as it were) of Air, in Contact with the _wetted_ Cloths,
whose Moisture will thus be more quickly evaporated.
[87] Historia Ventorum, Pag. 48, Art. 33.
[88] “Cum enim (Venti) Choreas ducant, Ordinem Saltationis nosse
jucundum fuerit. Art. 18.”
[89] On the Action of the Sun and Moon over Animal Bodies, by Dr. Mead,
Miscell. Cur. Vol. 1. P. 372, 373.
[90] For these Observations see Gassendus’s Natural Philosophy. De
Chales’s Navigator. And Astro-Meteoro-Logica, per J. Goad.
[91] See Maclaurin’s Newton, Page 376.
[92] Air at a Medium is 800 Times _rarer_ than Water: so that if 800
Times the Quantity of Air _naturally_ contained in a Vessel whose
Dimensions are those of a cubic Foot, were pressed into it by a Syringe
or _Condenser_, the Air woud differ nothing from Water in Density.
[93] See Wilson on Climate, Chap. 15. Pages 46, 54.
[94] 55.
[95] By reducing 10 Feet 6 Inches, and 6 Feet 7 Inches, into Inches,
and dividing by common Divisors, as 3 and 2; it is found that 10 Feet
6 Inches, will be to 6 Feet 7 Inches, as 3 to 2 nearly: that is, as 15
Miles to 10 Miles.
[96] White’s Ephèmeris, Page 38, for the Speculum Phenomenorum, or
Mirror of the Heavens.
[97] See the Book which gives an Account of Walker’s Eidouranion.
The _intelligent_ Reader will easily distinguish the Effects,
attributed to the Planets, viz. their mutual Attractions, owing to
natural Causes only;—from the futile Ravings of judicial Astrology.
[98] See London Chronicle, 26th July, 1785.
[99] To find the Direction of an upper Current, without the
Inconvenience of rising above the Level which the Aironaut has fixed on.
This the Abbé Bertholon has hinted at, by Means of a smaller Balloon.
The Dimensions of which, must however be so large; that, allowing for
the Evaporation of Gass, it will _just_ rise with the Weight of a
Quantity of Cord, a Mile and half, for Instance, in Length: and have
sufficient Room left within, to admit of the Expansion of Gass without
Rupture.
The Pioneer-Balloon may be taken up, _empty_, and filled with Gass
necessarily escaping from +the mouth+ of the _great Balloon_, when
stationary: and may be sent up with a Cord, fastened to the Center
above the Car of the _great Balloon_, to reconnoitre the _superior_
Currents: or it may be only filled _in Part_; and made to _descend_,
and _discover_ the _lower_ Currents.
See “Des Avantages de Ballons, &c. Page 72.”
[100] As the _Heights_ of the Atmosphere encrease in an _arithmetical_
Progression; the Densities are said to encrease in a _geometrical_
Progression: which is a mathematical and pedantic Mode of Expression.
For _arithmetical_ Progression _here_ means no more than the Height of
1, 2, 3, 4, 5, 6, &c. &c. Yards, Fathoms, Roods, or any other equal
Interval.
If then at the Height of one Yard, the Balloon has acquired (suppose)
the Levity of 1 Pound; then, if this Levity encreases in geometrical
Progression; (as twice 1 is 2,) it will, at the Height of 2 Yards, have
encreased to 2 Pounds: and, as twice 2 is 4;) it will, at the Height
of 3 Yards, have encreased to 4 Pounds: and, as (as twice 4 is 8;)
it will, at the Height of 4 Yards, have encreased to 8 Pounds: and,
(as twice 8 is 16;) it will, at the Height of 5 Yards, have encreased
to 16: and, (as twice 16 is 32;) the Levity will, at the Height of 6
Yards, have encreased to 32 Pounds; and so on, _doubling_ the preceding
Number; at the Height of each Yard, Fathom, Rood, Mile, &c. &c.
[101] _Whiston’s_ Tacquet’s Euclid, Book XI. Definition of a _right_
Cylinder, Art. 3, Page 166.
[102] Archimedes’s Theorems. Proposition 33, 34; at the End of
_Whiston’s_ Euclid, Page 42.
[103] Inferred in the Chester Chronicle, Sept. 30, 1785.
[104] The Writer not having yet been able to procure it from the London
Booksellers.
[105] See Chambers’s Dictionary under the Article +resistence+.
[106] See his “Navires des Anciens.”
[107] See “Gordon’s Principles of Naval Architecture.”
Also the Balzaes and Guaraes, in Ullòa’s Voyage to America, Book 4,
Chapter 9, Vol. 1, Page 183.
[108] Mons. Carra proposed to ascend with two Balloons. One, a seventh
Part less than the other, is to be connected by a Rope, throu’ a Pulley
fixed in the equatorial Hoop of the great Balloon, to a Reel in the
Center of the Car: in descending, the Reel is to be unwound: the great
Balloon and Car will therefore descend, while the small Balloon remains
in the Air. The Scheme is certainly practicable. See the Cut in the
London Magazine for June, 1784.
[109] See “Lewis’s Commerce of the Arts.”
[110] See Priestley’s numerous Experiments: and that Library of
_curious Investigation_, the Philosophical Transactions.
[111] And _Magnitude_ of distant Objects.
Bacon says that Objects are more _visible_ in an East Wind, and Sounds
more _audible_ in a West Wind; being heard at a _greater_ Distance.
“Historia Ventorum, P. 37, Art. 31.”
[112] See Le Roi’s Uses of the airostatic Globe _at Sea_, in his
“Navires des Anciens, Page 225.”
[113] The _natural Figure_ of the _Dìodon-Globe-Fish_, a coloured
Print of which is given in “Martyn’s new and elegant Dictionary of
natural History:” where it is described as follows: “The Form of the
Body is usually oblong: but when the Creature is alarmed, it possesses
the Power of _inflating_ its Belly to a globular Shape of great
Size;”—seems to furnish a Hint for the proper Figure of a Balloon, when
the Art is more improved.
The Balloon, as far as it is meant to resemble the upper Part of the
Fish, is to be made stiff, with Pasteboard or _Papier-mâchè_ varnished;
for, being strong, and in a permanent Form, it is more capable of
continuing Air-tight: the lower Parts being _flaccid_, will be
inflated, as the Balloon rises, and deflated during the Descent.
Rowers, and propulsive Machinery, are to be fixed within the Fish, in
Place of the Fins: and Goods of +greater+ Weight placed in a covered
Car below: the Air-Bottle-Balloon being fixed between both.
[114] And by _Kunckel’s_ or _Canton’s_ Phosphorus, See “Priestley’s
History of +light+. Pages 585, 370.”
[115] This was owing to the cool Air rushing in to supply the Tendency
to a Vacuum by the Expansion of hot Steam, with the extricated Gass.
The Accident proves that no Danger is to be dreaded from +expansion+ of
the Gass.
[116] From _Bersham-Forge_ near _Wrexham_, where there is always a
sufficient Quantity.
[117] The _detached_ Thermometer might be protected from the _Sun_, by
being swung a few Inches _below_ the Car of the Balloon by means of an
_Opening_ made purposely throu’ the Center of the Car.
[118] _Foundation of the first Table._
(Ph. Tr. for 1777, Part 2d, Page 567.)—It was found by
Experiment that the Decimal .000262
was the Expansion _on_ 30 Inches of Quicksilver, _with_
each Degree of Temperature from freezing to boiling
Water: also, the Decimal .000042
was the Expansion _on_ 30 Inches of the Glass Tube
(containing the Quicksilver), _with_ each Degree of ———————
Temperature: therefore by Addition, .000304
or by taking only 4 Decimals, .0003
is the Expansion _on_ 30 Inches of Quicksilver, and the Glass Tube
containing it, _with_ each Degree of Temperature.
_Construction of the first Table._
Thus any vertical Number, shewing the Expansion, may be readily
_formed_, by _doubling_, _first_, the Number immediately under each
Inch for the Expansion below it: and _afterwards_, by adding the Number
immediately under each Inch, to the Expansion last found.
Note: The vertical Columns, below each Inch of Quicksilver shew the
Expansion _on_ that Inch, _with_ corresponding Degrees of Temperature
indicated by the Thermometer in the Column to the left Hand. Example:
to find the Expansion _on_ 30 Inches of Quicksilver _with_ 1 Degree
of Temperature: the Answer in the Table is .003: i.e. such Expansion
raises the Quicksilver the 3000th Part of an Inch.
[119] There is seldom Occasion to take more than the four first
Decimals out of the Table, the Remainder being of _little value_.
[120] _The Foundation of the second Table._
This Table is calculated from Briggs’s Logarithms: each Number, in the
second Column, being nothing more than the Logarithm—corresponding to
the Point, (in the _first_ Column,) at which the Quicksilver stands
in the barometric Tube,—subtracted from the Logarithm of 32 Inches
multiplied by 6.
_Construction of the second Table._
This Table consists of three _vertical_ Columns only: tho’ _here
tripled_, for the greater Convenience of Inspection.
The first or left Hand Column shews, in Inches and Tenths (from ten
Inches) the Gradations of the Quicksilver in the barometric Tube,
beginning as low as one Inch above the Surface in the Cistern, and
proceeding throu’ all the intermediate Points, to the unusual Extent
of 32 Inches:[121] supposing likewise that the Tube is elevated in the
Atmosphere, so that the contained Quicksilver, when exposed to the
Temperature of 31°.24 of Farenheit, rests at each Point in the Table.
The second vertical Column gives the different Heights in Feet and
Tenths, to which the barometric Tube must be raised above its Level at
32 Inches, in order that the contained Quicksilver, if exposed to the
Temperature of 31°.24 of Farenheit, may stand at each Point indicated
in the first Column.
The third vertical Column, gives, likewise in Feet and Tenths, the
+difference+ between each two adjoining Heights in the second Column,
corresponding to a single Tenth (of Quicksilver): which single Tenth
is the Difference between each two adjoining Tenths of an Inch in the
first Column.
For Example: Suppose the Quicksilver in the barometric Tube, in the
first Column, stands at
Inches 16.1 answering to 19570.4 } Height in Feet
And again at 16.2 answering to 19398.4 } in the Atmosphere.
———————
_Difference_ of .1 in Feet: remaining = 172.0
which sixteen Inches two Tenths, is a single Tenth more than sixteen
Inches one Tenth, and will therefore answer to a _less_ Height in
the Atmosphere by that single Tenth; considering that the lower the
Quicksilver falls in the Tube, the higher must the Barometer itself
be raised in the Atmosphere, in order that the Quicksilver may rest
at the lower Points of the Tube. If therefore a _less_ Height in the
Atmosphere be required which shall answer to one Tenth more than 16
Inches two Tenths; subtract the Height answering to 16.2 from the
Height answering to 16.1, i.e. subtract the _less_ Height from the
_greater_, and the Remainder gives that _less_ Height in the third
Column, answering to the Height of one Tenth more than 16 Inches 2
Tenths, of the Barometer.
[121] _The Barometer, (to which the Scale of Heights is applied, in the
2d Column of the 2d Table) is supposed to be sunk within the Surface
of the Earth, till the Quicksilver rests at 32 Inches, as appears from
the last Article in the table, viz. 32 Inches, 0.00 Feet. 32 Inches is
therefore the Foundation of the Table, and corresponds, according to
Shuckburgh, to 1647 Feet, under the Surface of the Sea, at low Water._
This Depth _then being_ the imaginary Level _pointed out by the
Quicksilver, at the_ unusual _Extent of 32 Inches_; _each_ interior
_Inch and Tenth of Quicksilver will correspond to a_ superior
_Elevation of the Instrument, in Feet and Tenths above that Level, and
will include the Mensuration of the deepest Mines._
_For the_ mean _Pressure of the Barometer, at low Water, from 132
Observations in Italy and England, is 30.04 Inches: the Temperature of
the Barometer being at 55°, i.e. Temperate, and that of the Air at 62°._
[122] _Foundation of the Table for Tenths._
The Height, in _Feet_, corresponding to the Expansion on the Tenth of
an inch of Quicksilver with the Temperature of 31°.24 (as in the 3d
Column of the 2d Table) are reduced by this Table into a ten Times
less Number of Feet; and the Tenth of an Inch (of Quicksilver) is also
again divided into _ten_ more Parts: in order to shew, in a ten Times
less Number of _such_ Feet, the Expansion corresponding to any of those
Parts into which the _Tenth_ of an Inch (of Quicksilver) has been
divided.
_Construction and Use of the Table for Tenths._
1. The Figures in the left vertical Column shew the Height in _Feet_,
(from 81 to 130) corresponding to a single Tenth of an Inch of
Quicksilver, viz. to the higher of two adjoining Tenths, as in the 3d
Column of the 2d Table.
2. The Figures, along the upper horizontal Line, shew the Number of
Parts into which the Tenth of an Inch has been divided.
3. The Figures, at the Point of Meeting, express, in a ten Times less
Number, of _the Feet_ in the left vertical Column, the Expansion
corresponding to any of those Parts, into which the Tenth of an Inch
(of Quicksilver) has been divided.
Thus: 90 is a _Number of Feet_ called 9 Tenths of 100: but the _Tenths_
are _Feet_, and not Tenths of a Foot.
[123] The Standard Temperature was 31°.24, which not being exactly 1
Quarter, another Decimal is added, (for Ease in Computation,) by which
31.24 becomes 31.25, i.e. by dividing one Degree of Heat into 100
Parts, and taking 25 of those Parts, or dividing the 100 by 25, the
Answer is 4, i.e. ¼ of the whole 100: or (31)¼.
[124] _The Foundation of the fourth Table._
(Ph. Tr. for 1777, Part 2d, Pages 564, and 566,)—From the _Mean_ of
a Series of Experiments with a Manòmeter, or Instrument to measure
the _Rarity_ and Density of the Atmosphere, depending on the Action
of _Heat_ and Cold, it was found, that when the _Portion of a Tube_
containing Air (at the Temperature of freezing by Farenheit, and
Pressure of 30½ Inches[125] by a common Barometer) was divided into
1000 Parts; the Volume of _Air_ within it, encreased _nearly_ in a
certain Proportion, as each Degree of Temperature encreased; viz. at a
Mean, 2.43, or simply (by rejecting the 2d Decimal as too minute) 2.4:
that is, a 1000 Parts of Air became by Expansion with one Degree of the
Thermometer, equal to 1002.43: i.e. the Portion of Air occupying 1000
Parts, did, with the Addition of one Degree of Heat, occupy 1002.43
Parts: that is (by rejecting the 2d Decimal 3 as too minute) occupied
two Parts and 4 Tenths more than the thousand.
_Construction of the fourth Table._
Supposing therefore that the Portion of the Tube containing Air, was
one Foot in Length of Height, divided also into a thousand Parts; one
Degree of Heat would encrease or expand it two Parts and four Tenths
more than the thousand Parts into which the Foot was divided.
CAUTION.
_The fourth Table properly consists of only nine horizontal Columns
of thousands, in Breadth; which Columns are extended in Length to one
hundred Lines, corresponding to 100 Degrees of Heat._
_The Table is here divided, in order that it may conform to the Size of
the Pages: by which Means the Formation of each vertical Number by the
following Rule, (which renders the Table_ self-evident_) might without
this Caution, have been attended with some Difficulty._
The vertical Columns _below_ the Figures expressing each thousand,
shew the Expansion of Air _on_ each respective thousand, _with_ the
corresponding Degrees of Temperature indicated by the Thermometer in
the vertical Column to the left Hand.
Example the first: to find the Expansion of Air _on_ one thousand Feet,
_with_ one Degree of Temperature; the Answer in the Table is 2.4, or
2.43: i.e. 2 Feet and 4 Tenths of a Foot, rejecting the 2d Decimal as
too minute.
Example the second: to find the Expansion _on_ 8 thousand Feet, _with_
99 Degrees of Heat: the Answer is 1924.56: and so of the Rest.
Thus _any_ of the _vertical Numbers_ shewing the Expansion, may be
readily _formed_, by _doubling_, _first_, the Number immediately under
each thousand in the horizontal Line, for the nine first thousands,
(of which the Breadth of the Table properly consists, exclusive of the
thermometric Column) for the Expansion below it: and, _afterwards_,
for each Expansion immediately below the former, by adding, to the
Expansion _last_ found, the Number immediately under its respective
thousand.
First Example: to find the vertical Number for the Expansion under the
first thousand, viz. 1000, _with_ 2 Degrees of Heat: the Number under
1000 is 2.43: double this: and the Answer is 4.86.
Second Example: suppose the Expansion _last_ found be that _on_ one
thousand Feet _with_ 24 Degrees of Heat; viz. 58.32: and the Expansion
_on_ the same thousand, _with_ one Degree of Heat more, viz. on 25
Degrees, be required; add the Expansion
_on_ one thousand Feet, _with_ 24 Degrees, viz. 58.32
to the Expansion _on_ the same 1000, _with_ 1 Degree, viz. 2.43
—————
and the Answer is, by Addition, 60.75
Third Example: supposing the Expansion _last_ found to be the Expansion
_on_ 9000 Feet _with_ 99 Degrees of Heat, which in the Table is 2165.1.
It is required to find the Expansion _on_ the same 9000 Feet, with 100
Degrees of Heat; add to the Expansion last found,
viz. 2165.13, the Expansion on the same 9000 Feet,
viz. 21.87 with one Degree of Heat, and
———————
2187.00 is the Answer by Addition.
_Any vertical Number shewing the Expansion may_ likewise _be_ found,
first, _by multiplying the first Figure, or Number, of the_ given
_thousand Feet (in the horizontal Line,) into the Answer or Expansion
on the_ first _thousand Feet, with one Degree of Heat: for Example_;
To find the Expansion on 9000 Feet with one Degree of Heat.
_The Expansion on 1000 Feet, with 1 Degree of Heat (from whence, all
the other Expansions are derived) being 2.43; multiply that Number
by 9, the first Figure of the given thousand Feet, and the Answer or
Expansion with 1 Degree of Heat, is 21.87: hence all the Answers or
Expansions_, immediately _under the horizontal Line of thousands, are_
formed.
_Then 2dly, any other vertical Number or Expansion may be_ formed _by
multiplying the Expansion_ immediately _under the_ given _thousand
Feet in the horizontal Line, into the_ given _Number of Degrees: for
Example_;
To find the Expansion on 9000 Feet, with 50 Degrees.
_The Expansion with one Degree on 9000, is 21.87: therefore the
Expansion with 50°, is 50 Times more, viz. 1093.50, and so of the Rest._
_These different Methods serve to prove the Answers, and to elucidate
the Table._
[125] _These Experiments were made with the Manòmeter when the
Atmosphere was half an Inch heavier than in the Experiments to prove
the Expansion of Quicksilver, the Barometer_ then _standing at 30
Inches only._
[126] There is _seldom_ Occasion to take more than the first Decimal
out of the Table.
[127] “RULE.
“_Precept the 1st. With the Difference of the two Thermometers that
give the Heat of the Barometer (and which for Distinction sake, are
called the attached Thermometers) enter Table I, with the Degrees
of Heat in the Column on the left Hand, and with the Height of the
Barometer in Inches, in the horizontal Line at the Top; in the common
Point of Meeting of the two Lines will be found the Correction for the
Expansion of the Quicksilver by Heat, expressed in decimal Parts of
an English Inch; which added to the coldest Barometer, or subtracted
from the hottest, will give the Height of the two Barometers, such as
would have obtained, had both Instruments been exposed to the same
Temperature._
“_Precept the 2d. With these corrected Heights of the Barometers enter
Table II, and take out respectively the Numbers corresponding to the
nearest Tenth of an Inch; and if the Barometers, corrected as in
the first Precept, are found to stand at an even Tenth, without any
further Fraction, the Difference of these two tabular Numbers (found
by subtracting the less from the greater) will give the approximate
Height in English Feet. But if, as will commonly happen, the correct
Height of the Barometers should not be at an even Tenth, write out
the Difference for one entire Tenth, found in the Column adjoining,
intitled_ Differences; _and with this Number enter Table III, of
proportional Parts in the first vertical Column to the left Hand, or in
the 11th Column; and, with the next Decimal, following the Tenths of
an Inch in the Height of the Barometer (viz. the hundredths) enter the
horizontal Line at the Top, the Point of meeting will give a certain
Number of Feet, which write down by itself; do the same by the next
decimal Figure in the Height of the_ _Barometer (viz. the thousandths
of an Inch,) with this Difference, striking off the last Cypher to the
right Hand for a Fraction; add together the two Numbers thus found
in the Table of proportional Parts, and their Sum subduct from the
tabular Numbers, just found in Table II; the Differences of the tabular
Numbers, so diminished, will give the approximate Height in English
Feet._
“_Precept the 3d. Add together the Degrees of the two detached or
Air Thermometers, and divide their Sum by 2, the Quotient will be
an intermediate Heat, and must be taken for the mean Temperature of
the vertical Column of Air intercepted between the two Places of
Observation: if this Temperature should be 31°¼ on the Thermometer,
then will the approximate Height before found be the true Height; but
if not, take its Difference from 31°¼, and with this Difference seek
the Correction in Table IV, for the Expansion of Air, with the Number
of Degrees in the vertical Column on the left Hand, and the approximate
Height to the nearest thousand Feet in the horizontal Line at the Top;
for the hundred Feet strike off one Cypher to the right Hand; for the
Tens strike off two; for the Units three: the Sum of these several
Numbers added to the approximate Height, if the Temperature be greater
than 31°¼, subtracted if less, will give the correct Height in English
Feet. An Example or two will make this quite plain._”
[128] There is no Occasion to take more than four Decimals out of the
Table.
[129] See Section 368, Note (_a_).
[130] Section 368, Note (_a_) on Note (_a_).
[131] Taking one Decimal _only_ out of the Table.
[132] +The question+: In the upper Gallery of the Dome of St. Peter’s
Church at Rome, and 50 Feet below the Top of the Cross, the Barometer,
from a Mean of several Observations, stood at Inches 29.5218 Tenths:
the attached Thermometer being at Degrees 56.6 Tenths; and the
Air-Thermometer at 57 Degrees: at the same Time that another, placed
on the Banks of the River Tyber, one Foot above the Surface of the
Water, stood at 30.0168, the attached Thermometer at 60°.6, and the
Air-Thermometer at 60°.2: what, was the Height of the Building above
the Level of the River?
[133] See Section 375. 2dly. If the Moiety, _Half-Heat_, or mean
Temperature of the Air, _is equal_ to the Standard-Temperature, to
which the two Barometers are brought, by the 2d Table; the fourth
Table, for _Expansion of Air_, is needless: the Height already found,
in the 2d Table, being the _true_ Height of the _upper Station_.
3dly. If the Moiety, _Half-Heat_, or mean Temperature of the Air, is
_less than_ the Standard-Temperature of 31°.24; subtract the mean
Temperature from 31.24; and with the Remainder find the Expansion, as
usual, by the 4th Table: subtract the Sum, (which is a corresponding
Height in Feet and Tenths) from the Height in Feet and Tenths of the
_upper_ Barometer, at the _Standard-Temperature_, in the 2d Table: and
the Remainder will be the _true_ Height of the _Mountain_ or _upper
Station_. Section 384, Note _a_.
[134] +The question+: Near the Convent of St. Clare, in a Street
called _La Strada dei Specchi_, at Rome, the _lower_ Barometer stood
at 30.082, its attached Thermometer 71 Degrees, and detached ditto
at 68 Degrees: on the Tarpeian Rock, or West-End of the famous Hill
called The Capitol, the _upper_ Barometer was at 29.985, its attached
Thermometer 70°.5, and detached ditto 76°: what was the Height of the
Eminence?
[135] Sadler’s _Practical Arithmetic_, Page 293.
[136] The Writer has not hitherto been so fortunate as to meet with the
original Memoir, containing the Particulars of this curious Experiment
by Mons. Lavoisier.
[137] Dr. Priestley’s Experiments and Observations relating to Air and
Water. Ph. Tr. for 1785, Vol. 75, Part 1, Page 279.
[138] The Diameter may be enlarged.
[139] By Means of the Cradle, _both_ are more easily moved: the Muffle
is prevented from adhering to the Tube; and Steam is admitted to the
Borings.
[140] Copper sustaining a _red_ Heat, better than Iron; the latter of
which, _calcines_ with Steam, or, in cooling.
Transcriber’s Notes:
• Text enclosed by underscores is in italics (_italics_).
• Text enclosed by pluses is in small caps (+small caps+).
• Obvious typographical errors have been silently corrected.
• Archaic language and spelling is left as-is, except “AERIAL” was
printed with dots above the ‘A’ and ‘E’, this was assumed to be a
typesetter's limitation and replaced with “AËRIAL", to match the
lower case usage.
• Errata have been applied, as much as I understood them.
• Numbers for sections 259–261 are repeated.
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