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.