Chapter LXXXV: Section 429: The Expence attending the Inflation of Balloons is a

solid Objection to their frequent Use.

A Check is thereby given to every Improvement that might otherwise be expected from a Repetition of Experiments.

It is, in short, the chief Difficulty under which the +aironautic art+ at present labours.

This Difficulty, however, if once overcome, (and of which there is little Doubt) will probably bring those extraordinary Machines, into general Estimation.

What _now_ costs fifty Pounds, may _then_ be done for five: abating the Expence of the preparatory Engine.

Mons. Lavoisier, by the Application of Steam to Iron Filings enclosed in a Copper Retort, has generated inflammable Air, or light Gass:[136] and Dr. Priestley, by converting a Gun-Barrel into a Steam-Engine, has produced a Gass 13 Times lighter than common Air;[137] whereas by the present expensive Method, with Metal and Acid, the Gass for Inflation is seldom more than six Times lighter.

What has hitherto been atchieved on a small Scale, is here meant to be extended.

As no Particulars are made public, or at least, have yet come to the Author’s Knowledge, relative to the Construction of such a Gass-Steam-Engine, as may, with Safety and Effect, be applied to the Inflation of Balloons; the following Descriptions of different Models may deserve some Notice:—may possibly excite the Attention of the ingenious; and put them on contriving _easier_ Means to obtain the _same_ End.

I.

430. Let there be an Iron _Hot-hearth_, one Yard square, and two Inches thick. Let it be _set_ on a Common Brick Stove, built as near the Ground as possible, (or even below it) in the open Air. Its Chimney to consist of malleable Iron, flat at the Top, and strong enough to support a Tea-Kettle or Boiler to produce Steam: and extending at least one Yard from the End of the Hearth horizontally, before it turns up. It may rise three or four Yards high, slanting farther from the Hearth: the Form a hollow Cylinder: with a Turn-Cap at the Top, two Feet long, set on at right Angles; for the Management of the Smoke.

Supposing then the Fire-Place to face the West; the Chimney may project Eastward. The North Side is to be appropriated to the Iron-Borings or Turnings; and on the South Side is to be deposited the Dross or Calx.

A Muffle or Mould of malleable Iron is to be screwed and luted over the hot Hearth. The four Sides of the Muffle next the Hearth are to have horizontal Lips or Rims projecting half an Inch: and Screws are to be driven, throu’ Holes drilled at proper Distances, into the Hearth. The Sides are to rise upright a Couple of Inches: closing, as they rise, in the Form of a hollow Cylinder, one Foot in Diameter, and perhaps a Yard above the Hearth: which is now converted into a _Gass-Steam-Engine_.

It is proposed to strew over the _Hot-hearth_ a thin Layer of Borings, one Tenth of an Inch thick; to which Layer when _red_ hot, the boiling Steam is to be applied. The extricated Gass is to be conveyed from the Top of the Cylinder, by Means of an extended Trunk of Tin, and varnished Linen, into a Tub of cold Water kept _continually_ flowing over, into which a few Lumps of quick Lime are thrown: and from thence the Gass is to rise into the Balloon.

431. The Iron, whether Filings or Turnings, proper for Inflation, must be _bright_; wholly free from Chips, Bits of Wood, and all heterogeneous Particles: but particularly RUST, and GREASE: _less_ than a cubic Inch of the latter, woud spoil a Ton of the brightest, and otherwise the best prepared Materials. (Section 339.)

A Day or two _only_, before a Balloon is inflated; the proper Quantity of bright Iron shoud be heated +red hot+ in _Charcoal_, and suffered to go cold.

For Want of this simple Preparation of the Iron, the Gass has proved defective in Point of _LEVITY_: altho’ the Balloon appeared fully inflated.

This Misfortune happened at Birmingham, and other Places.

432. The _Desideratum_ is, _quickly_ to apply, and _remove_ the Borings, keeping the Machine _nearly_ Air-tight. For, it is now well known, that the Gass will _explode_, if one-third Part of common Air be introduced: or, if less; it may _unite_ with the _Gass_, and detract from _its_ Levity.

433. The following _Particulars_ may likewise be considered as an Improvement.

II.

1. To lay a Plate of Iron, Brass, or Copper, over the Hearth; which, if made of _cast_ Iron, will be apt to crack, in Contact with the Steam; and will also unite with and concrete the Iron Turnings or Gun-Borings into a solid Mass, that woud be separated with Difficulty.

2. To make the Dross-Pit in the Form of a hollow Wedge, narrow at the Top: screwing and luting it to the South Side of the Hearth. It shoud hold the Dross arising from a Ton of Borings; which will be sufficient for the Inflation of a Balloon, to carry one Person.

3. On the North Side is to be erected a Platform of Brick, a Yard square, _floored_ with a Plate of Iron: the inside Surface to be even with the Bottom of the Hearth.

4. The Ton of Borings is to be placed on the _Floor_, and covered with another Muffle, secured and luted to the Side of the Hearth: having a Communication of two Inches high, and one Yard wide, with the Bottom of the Hearth: as the Dross-Pit has.

5. A Brass or Copper Rake is to remain within the two Muffles: to press forward the Borings, spread them over the Hearth; stir them frequently;—by turning the Instrument, scrape them into the Dross-Pit; and apply fresh from the _Deposit_.

6. To perform these manual Operations within the Machine kept Air-tight; it will be necessary, at the exterior End of the Muffle, to fasten a strong leathern Case, made very wide and pliant, and two Yards long: into which the End of the Rake-Handle is to be inserted.

III.

434. _The Mode of Operation._

The Borings being spread on the Hearth, and _red_ hot; the Steam Pipe is to be opened, and _instantly_ shut. The Gass being _suddenly_ extricated; the Pipe is to be opened, and shut again as before: the Borings pushed into the Dross-Pit, and a fresh Supply spread. This Process to be renewed, till the Inflation is completed.

If it be thought necessary to prevent the Steam from communicating with the whole Depôt of Borings, and so evolve too much Gass; a little Brass Door with Hinges of the same, might be made to hang from the Top of the Communication between the two Muffles: which Door opening inwards, and hanging vertically, woud by the Pressure of the Gass, stop up the Open: and yet, if made strong, _not_ prevent the Operations of the Rake, at proper Times.

IIII.

435. The Machine woud be less complex, with one large Muffle, somewhat longer North and South than the Hearth; furnished with leathern Case and Rake. Put in the Borings at one End: keep the Steam-Pipe always open; with a _Hand_ at the Rake; pushing away the Dross, and pressing forwards fresh Borings.

V.

436. Further: it has since occurred, that a Machine in the Form of a +gun-barrel+, _extended in all its Dimensions_, will probably answer _every_ Intention.

And of this Kind are the hollow cylindrical Tubes, of _different_ Lengths, and about a Foot in Diameter,[138] which are _cast_, for the Conveyance of Steam, from the Boiler of a Steam-Engine.

Such a one, (previously lined with a Cylinder of Copper, or malleable Iron, to prevent the Adhesion of the Borings, when reduced to a Calx by the Admission of Steam;) might be placed horizontally over a Stove, (with or without a Chimney) and surrounded with _red_ hot Coals.

The Ton of Borings might be deposited at one End of the Tube; and, by Means of the Air-tight flexible leathern Case, be pressed with a Rake, _gradually_ into the Fire, and _beyond_ it when calcined.

Care must be taken to make the _Apparatus_ nearly Air-tight.

The Steam shoud pass into the Tube, from _below_: and the Gass be conducted towards the Balloon throu’ another Iron Cylinder, nearly equal in Diameter and at right Angles with the first; lying also in an horizontal Direction; along the Ground.

The Tubes might be _forged_ or _cast_, so as to form but one rectangular Piece.

The further End of the second Tube shoud communicate with a _third_, made of Tin, and bent downwards about a Foot; thence at right Angles, for six Inches: then to rise up, also at right Angles, the Length of six Inches more.

The Tin Tube is to descend into a Cistern of cold Water, made to flow over continually, by a fresh Supply; and into which, a few Lumps of Quicklime shoud be thrown.

The Gass, which will press upwards throu’ the Water, is to be received into an inverted Funnel, and thence (as in Section 339, Art. 2.) conveyed to the Balloon.

VI.

437. The following Alterations woud supersede the Use of the Rake, and _leathern_ Cases: the latter of which, by any accidental Crack or Flaw in the Leather, might admit a sufficient Quantity of common Air to produce an Explosion.

The cylindric Form of the Copper, or malleable Iron (to be used as a Lining for the Tube) is to be changed, into that of a half Cylinder, or inverted Muffle: and to be perforated with small Holes.

This Muffle is to be _nearly_ filled with a Ton of Iron Borings: (the Ends to be made up, to prevent the Borings from falling out into the Tube;) the Muffle itself is to be supported by a Cradle[139] of the same Form, made of +strong+ Copper Wire,[140] like the _open_ _Iron-Wire_-Fenders: and the whole is to be thrust into the Tube.

The Length of the Muffle depends on the Quantity of Borings that are intended to be used.

The Ends of the Tube shoud not be made so strong as the Tube itself: that, if an Explosion happens, they _may_ give way first, and prevent a Rupture of the Tube: not that any Danger is to be apprehended, that such an Event will take Place, so long as the Steam-Pipe is attended to, by a proper Person: the above Caution being only given, to prevent a Possibility of Rupture.

Each End shoud be cast, or forged with a hollow Handle; and shoud screw into the Tube.

The Length of the Tube shoud be such, that the Person who attends the Steam-Pipe, shoud feel no Inconvenience from the Heat of the Fire.

Nine Feet woud therefore be a proper Length: the conducting Tube the same.

Within six Inches from each End of the Tube which holds the Borings, a Hole, half an Inch in Diameter shoud be drilled across the Middle of the Tube, in an horizontal Direction.

Into these, an Iron Axis is to be fitted, (so as to take out _occasionally_) and pass throu’ the Tube: each End of the Axis is to project outwards a Couple of Inches, and to be made _square_, for the Socket of a strong Iron Winch or Handle.

Each Axis to be furnished with a strong Chain, of equal Length with the Tube; one End of which Chain is to be riveted, or otherwise fixed, to the Middle of the Axis; and the other, to be fastened _occasionally_ to one Extremity of the Cradle and Muffle: the second Axis and Chain in like Manner, to the other Extremity.

The Muffle is to be placed in the Cradle: both are then to be thrust into the Tube, and fastened to the Chain at the farther Axis: in which Position the Muffle may be filled with Borings, and gradually drawn into the Tube; till the same End has reached the Center of the Fire. The nearer End is then to be hooked by the nearer Chain, already wrapped round the nearer Axis: and the light Iron Caps to be screwed on each End of the Tube.

438. The Boiler for Steam may be fixed on any Part of the Tube near the Fire, and near the opposite Axis; so that one Person may attend both the Steam-Pipe, and Axis. The Steam to be conveyed throu’ a small Orifice made in the Bottom of the Tube, between the same Axis and the Fire.

439. As soon as the Materials, above the Center of the Fire, are supposed to be _red_ hot, the Steam-Pipe is to be opened for a Moment and +shut again+. The extricated Gass will be instantly +heard+, rushing throu’ the Vessel of _cold_ Water; and as instantly +seen+ to swell the varnished Linen-Trunk as it passes into the Balloon.

The Steam-Pipe is to be regulated by these infallible Signals: and the Process continued, till that Quantity of Borings, that was in the Center of the Fire, and consequently _red_ hot, is supposed to be calcined.

At which Time, the Handles are to be applied to the Axis, and the Cradle and Muffle drawn 5 or 6 Inches forward into the Fire.

When drawn too far; Recourse must be had to the second Axis.

440. If great Expedition is required, two or three Conductors from the same Tube may be used: and, at the Distance of six or seven Feet from the Fire, _Tin-Conductors_ may be added; taking Care that they are _made_, _applied_, and _continued Air-tight_.

THE END.

An _alphabetical_ +index of the contents+:

Referring to the +sections+ and +notes+, but _not_ to the _Pages_.

A. Section.

Absorption of Water by Air, _Experiment to prove_ the, 247

Accumulation of Air, _mediocèanal_, 259, 260

Aërial Scenes _described_, 39, 47, 51, 56

Air gives +form+ to _Things_, 53

- _gentle_, its Effect on the _Surface_ of the Balloon, 201

- _calm_, its _Effect_ on the _Surface_ of the Balloon, 202

- _pure_, cool, defloguisticated, perpetually descending, 252

- _descending Torrents_ of, on Etna and Teneriffe, 265

- _Reception and Dispersion of_, what, 280

Air Bottle Balloon, _its Use_, 311

- - - _preferred_ to an _interior_ Balloon, 314

Aironaut _Employments_ of the, in the Balloon, 29

- - _Attitude_ of the, in the Balloon, 32, 33

- - _lost over a Country_ well-known when _below_, 177

- - to _try_ different Heights, to find a _favorable Wind_, 309

- - to _wait_, in the _Calm above_ the Clouds, for a _Wind_, 309

Airostat, a small one _first_ liberated, 8

Altitude _apparent_, from the Balloon when _stationary_, 49

- - _barometric_, 49, _b_.

Anchor and Cable, 13

Apogay Winds, what, 241

Apparent Height _proportioned_ to the _barometric_ Height, 49

Appearance of a Plain _below_, the Size of a moderate Carpet, what,
179, 189

Appearance of a Plain _below_, the Size of a Handkerchief, what,
181, 187

Appearances at _different_ Altitudes, _from the Balloon_, 213

Articles, _Weight_ and _Number_ of, 26

Ascent, to _check_ and _promote_, 14

- - _Preparations_ for, 22

- - of the Balloon at 40 Minutes past I. o’clock, 28

- - with _twenty Pounds_ of _Levity_, 28

- - of Balloons, Causes to _limit_ the, 279

- - _proper Times_ for, 285

- - _new_ Mode of, to _determine_ the _Height_, 299

Atmosphere _gross_, when seen throu’, _from below_, 55

- - Depression of the, 232

- - State of, _favorable_ to the _Direction_ of Balloons, 268

- - Conjectures concerning the _Warmth_ of the _superior_, 275

- - probably _respirable_ at _great Altitudes_, 277

- - _Height_ of, 290

- - _Weight_ of, in _England_, 290

Attention to the Balloon _necessary_, 35

Aurora Borealis, Conjectures concerning _Appearance_ of, 274

B.

Ballast of what it consisted, 27

- - when to be _first_ thrown out, 21

- - in Hand, ready to throw out, 91

- - thrown down, 67, 95

- - thrown over _nearly_ 32 Pounds, 103

- - poured down at once 20 Pounds, 183

Balloon going to Sea, 75, 87, 90

- - in a quiescent Bed of Air, 75

- - of rowing it to any Point, in a Calm, 75

- - drawn aside out of the Perpendicular, 103

- - shrunk to its former Shape, 123

- - alternately rising and falling, 125, 138

- - in the Air five Hours and a Quarter, 207

- - sustained above Water, how, 294, 295

- - best Form of, 307

- - Double, what, 314

Balloons their Defects, and further Improvements, 303

- - Air-tight Varnish for, 320, 325

Barometer, and Thermometer, when stationary, 36

- - Fluctuation of the Quicksilver in the, 37

- - Mensuration of Heights by the, 350

Beautiful preferred to the Sublime, in Prospects, 42

- - Appearance, 43

Bladders necessary, 26

- - began to _crackle_, 116

Bottles of Air thrown down, Caution, 74, 77, 84

Breath not affected, nor visible, during the Excursion, 126

Breeze Sea-, 88, 92, 257

C.

Cable, and Anchor or _Grapple_, 13

- - to be fastened to a _Center above_ the Car, 297

Calculations of the _Distance_ seen from the Balloon, 52, _a_.

- - of the Height of _Mountains_, 171, _a_.

Calm _above_, and Wind _below_, at the same Time, 168

Canal artificial, Duke of Bridgewater’s, Appearance of, 166

Cannon first discharged at IX. o’clock, 7

- - the second Time, at XII., 11

- - the third Time, at 40 Minutes and a half past I., 64

- - the last Time, at 10 Minutes and a half past II., 62

Car and Hoops, their _Dimensions_, 35

Caution to keep the Circle clear during the Inflation, 23

- - against the _Dropping_ of Water _out of_ the Balloon, 31

- - on Landing, 98

- - _not_ to open the upper Valve, 122

Charts Balloon, first suggested, 168

Chilliness _first_ perceived, 92; again, 109

- - _felt_ near moist Places, 283

Circularity of Prospect, 79, 221

Circumstance, _each_ to be recorded, 4

Circumstances _apparently superfluous_, mentioned and repeated,
why, 5

Clouds, an upper Tier _seen_ to move in a safe Direction, 7, 46

- - Perspective of the, 51

- - _appearing_ in rapid Motion, 163

- - View of the, taken from above them, 130, 171

- - Colouring of the, 172

- - _highest visible_, 213

Cochuc-Varnish, 320

Cold, its Effects on the Balloon, 94

Colour of the Rivers, _red_, 44

- - of the City of Chester, _blue_, 45

- - of Thunder-Clouds, 54

- - of upper Clouds, 57, 172,

Colours, _primary_, of Objects beneath, 129

Columns of Air, depressing, observed by the Ancients, 239

Compass, the properest Kind of, 38, _a_.

Conclusions, useful, 159

Conjunction of the Planets _preceding_ a Hurricane, 211

Contemplation of the Prospect, 113

Course of the Balloon traced, to shew the Manner in which it was
affected in passing over Water, 78

Curls and Streams of Air, Smoke and Vapour, 250, _b_.

Currents of Air, horizontal, 20

- - from _above_, to be guarded against, 21

Currents _under_, of Air, 87

- - of Air, blowing _to and from_ great Towns, 250

- - of Air, _contrary_, at different Heights, at the same Time,
267

- - the Balloon rising throu’ _different_, 106

D.

Defects in the Composition for Balloons, _remedied_, 320

Depressing Torrents of Air, 254

Depression of the Atmosphere, 232

- - over _moist_ Places in _fair_ Weather, 243

- - of the Atmosphere proved from History, 253

- - _nocturnal_, of the Atmosphere, 267

- - corroborating Proofs of a, 268

Depth below, conveys no Idea of Distance, 157

Depths, Mensuration of, with Barometers, &c. 348, 368, _a_, _a_.

Descent of the Balloon, to _retard_ the, 15

- - Signs of the, 17, 159, 181

- - at _first rapid_, with a rushing Noise, 96, 97

- - Proof of _gentle_, 100

- - Change in _visible_ Objects, during the, 182

- - of Balloons over Water, _enquired_ into, 229, 230

- - - - - - Means to prevent, 294, 295

Description of the Ascent, 47

Diameter of the Prospects _above_ and _below_, 52, 79

Diminution of Objects, _excessive_, when seen from the Balloon, 223

- - - - Laws respecting the, 224

Direction of the Balloon, Hints for the. 315

Distance seen from the Balloon, Calculations of the. 52, _a_.

- - of the Balloon from _Chester_, at the Report of the 4th
Cannon, 64

- - Idea of, from _Experience_, 158

- - what is the _greatest_, to be seen from the Summits of the
_highest_ Mountains, 171, _a_.

- - at which an Object can be distinguished by a _good_ Eye, 175,
_a_.

- - of the Balloon-_Course_, 191

- - at which, the Balloon was seen, 227

- - and Height of a Balloon, found by a Quadrant, 310

Dove turned out of the Car, 61

E.

Earth removed from _Sight_, 170

Echo none _above_, 39

Eknèfiai Winds, what, 241

- - a dry Wind, 267

Electricity of the Air, 65

Elliptic Solid, the Form of the Balloon an, 160

Employments of the Aironaut, 32

Engines _Steam_, Models of, for Inflation, described, 429

Equatorial Hoop, its Use, 161, 315

Evaporation of _Steam_, 249

Expansion of the Balloon, by what Manouvre, 132

Experiment to prove whether the _superior_ Atmosphere be _hazy_,
tho’ the Sun continue _shining_, 47, _a_.

Experiments necessary, in order to improve the Modes of
_Direction_, 296

Examples in the Mensuration of _Heights_ with Barometers. See Table.

Example 1st, Practice of the, 351

- - - Recapitulation of the, 385

- - 2d, Practice of the, 386

- - - Recapitulation of the, 409

- - 3d, Practice of the, 410

- - 4th, Practice of the, to determine _small_ Heights, 419

- - 5th, Practice of the, to determine the Height of the Balloon,
423

F.

Fish _Dìodon-Globe_, a _Model_ for Balloons, 377

Flag _white_, hung out a Quarter of a Mile in Length, 4

- - hung out half a Mile, in all, 66

- thrown _down_ at a Mile high, 59

- Descent of the, 60

- _white_, its Effect on the Balloon, 70

- - Progress of the Balloon marked by the. 91

- - _impeding_ the Balloon, 103

- - the remaining one unfolded, 105

- - shewed a Change in the _Direction_ of the _Wind_, 105

Flights with the Balloon, for three Hours longer, 193

Flying-Coach, 149

Foot Roman, the _Measure_ of a, 49, _b_.

Form of the Balloon at its _greatest_ Altitude, 14

- - - the _same_ at each Descent, 159

G.

Gass not offensive during the _Voyage_, why, 34

- procured by Means of _Acid_, 338

Gass procured by Means of _Steam_, 429

Geography Balloon, _first_ suggested, 167

Globe-Fish, a _Model_ for Balloons, 377

Grapple or Anchor, 13

Gums Copal, Sandarac, Mastic, &c., 326

H.

Heat of the _Sun_, _greatest_, while in the Car, 59

Height _apparent_, proportioned to the _barometric_ Height, 49

- - of the Balloon, when _stationary_, at the _first_ Ascent,
viz. 2332 Yards, 52, _a_.

- - in the Balloon, conveys no Apprehension of falling, 156

- - of _principal_ Mountains, noted, 171

- - of a Mountain, seen at a _Distance_, calculated, 171, _a_,
_a_.

- - to which Balloons will _probably_ ascend, 278

- - fixed, Method of ascending to any, 299

- - of the Balloon, to ascertain by a _Quadrant_, 310

- - _preparatory_ Instruments to observe the, 350

- - of the Balloon measured, 425

Heights to measure, Densities to estimate, 299

- - of the Atmosphere, while they encrease in an _arithmetical_
Progression, the Densities are said to encrease in
_geometrical_ Progression: the Meaning of such Terms, 301, _a_.

Hemisphere _upper only_, of a Balloon to be inflated, 315

Hoop equatorial, its Use, 161, 315

Horizontal Motion, Signs of, _deceitful_, 18

Hours proper for the Ascent of _Balloons over Water_, 254, 255, 261

Hygrometer _Horse-Hair_, the _best_ Kind, 217

I.

Illustration of the Scenery, 72

Improvement during the Process of Inflation, 24

Improvements how to be made in the propulsive Machinery, 319, 330

- - in the Process of Inflation by Acid, suggested, 339

- - suggested in the Process by Steam, 429

Incorrectness of Maps, 81

Inflation began at X. o’clock, with a small Balloon, 8

- - Degree of, to be limited, 278, 317

- - Process of, 339

- - by Means of Acid, Expence saved in the, 347

- - by Means of Steam, Expence saved in the, 429

Inflation by Means of Steam, Model and Mode of, 429

- - by Steam, preferred to the Process by Acid, 429

Information derived from the Shape of the Balloon, 159, 160

Inventory of the Voyage, 12

Iris 1st, round the Shadow of the Balloon, 56

- 2d, 73

- 3d, 136

Iron _bright_ and _fresh_, proper for inflation, 431

L.

Landing, Manouvres during the, 98

- - first, near _Frodsham_ in _Cheshire_, 100

- - second, near _Warrington_ in _Lancashire_, 188

- - Precautions to secure a safe, 297

- - in _windy_ Weather, Precautions to secure a safe, 298

- - _improved_ Mode of, 317

Latitudes variable, _light Airs_ playing in Eddies, common in the,
241

Level of the _lowest_ Stratum of Clouds in _fair_ Weather, 93

- all Inequalities of Surface reduced to the _same_, 111

Light of a _red_ Colour, Conjectures concerning the, 222

M.

Machinery _propulsive_, to be used in the _Calm_, _above Winds_, 319

Magnitude of Objects, Laws respecting the, 224

Manouvres seen at a _great_ Distance, 140

Map consulted, 174

Mast, a light _hollow_, 315

Meanders of the River _encreased_ to the _View_, 81

Mensuration of Heights and _Depths_ by Barometers, 348

Methods to ascertain the _true_ Height, 350

Method, the cheapest to inflate by Steam instead of Acid, 429

Mistakes to be noticed, to prevent Repetition, 2

Motion encreased, progressive not perceived, 165

Motion of Air, called _Reception and Dispersion of Air_, what, 280

Mountains, Names and Heights of principal, 171, _a_.

- - their Use, 265

Mouth of the Balloon, _closed_, 102

N.

Neck of the Balloon, how to place it, 31

- - _first_ tyed, 125

- - risen near _eight_ Feet upwards, 119

- - an _Attempt_ to reach it, 121

- - held _Air-tight_ in the _Hand_, 125

Notes made during the Voyage, 36

O.

Objects diminishing as the Balloon arises, Description of, 109

Objects, all _terrestrial_, disappearing, 163

Order preserved during the Inflation, 23

P.

Parashute or Umbrella, 15

- the Balloon formed a vast, 184

Perspective new, 39, 229

Place where the Balloon alighted, 100, 187

Points, the plainest generally most essential, frequently
overlooked, 4, 338

Preparations for Ascent, 22

Prospects _most beautiful_, at what Height, 93

- below noted, 128

Pulley or Reel, 13

R.

Rain _warm_ in Winter, accounted for from the Theory of
Accumulation, 270

Reception and Dispersion of Air, 280

Reel or Pulley, its Defects remedied, 41, _a._

Respiration easy during the Excursion, 114

Resistence of the Air, as the _Square_ of the Velocity of the
falling Body, 15, _a._

Rising, Signs of, 16, 30

Rivers, _no Appearance of_ Water in the, 110

Rule, general for measuring Heights, copied, 384

Rusty Iron, _improper_ for Inflation, 398

S.

Sail, three seen in the _Liverpool_ Channel, 108

- _triangular_ Latteen, _purposely to retard_ the Balloon, 315

- Anemòmeter, what, 315

- Weights to be added to the, 316

- Vane-, what, 318

Scenes aërial, described. See Sublime.

Sea-Breeze discovered, 88

- - its Duration, 256

- - its Extent, 257

Sensation of _rising_ described, 30

Sensations accompanying the Balloon, 141, 154

Shadow of the Balloon _traced_ on the Clouds, 56, 73, 136

Shadows, their Length, _at Noon_, calculated, 84

- - - - - _at half past III._ calculated, 100

- - encreased, seemed to raise the Objects, 127

Shape of the Balloon _altered_, 118

Sign of Descent, 181

Signs to be observed in the Management of Balloons, 14, 15, 17, 20

Situation novel, peculiar to the Balloon, 221

Sound of the Gass throu’ the upper Valve, 134

- in the Air, an _uncommon_, 162

Sounds immediately under the Balloon, their Effects, 175, _a._

Spirits raised by the Purity of the Air, 155

Spunges of Air, 247

Squalls of Wind, the Day preceding the Ascent, 6

Stationary, the Balloon, 36, 122

Steam, Mode of Inflation by Means of, 429

Storms of _Collection_ and _Dispersion_, 232, 263

Sublime and beautiful Scenes, 3, 39, 47, 48, 49, 51, 71, 84, 112

Sun, when hottest, 59

Sympathy of the Spectators, 46

T.

Table the 1st. See Mensuration.

- - for Expansion with Heat, from 1 to 40 Degrees, on Inches of
the Barometer, from 9 to 32 Inches, 363

- the 2nd, shewing the Variations of the Barometer, at each Inch
and Tenth of the Quicksilver, from 1 to 32 Inches, the Air
being at the freezing Point, 371

- the 3d, for easy Calculations, from the 2d Table, 373

- the 4th, shewing the Expansion with Heat, from 1 to 100
Degrees, on any Number of Feet in the Air, 381

Tastes not altered, on Account of the Height, 65

Thermometer warmer _above_ than _below_, 126

Thermometers compared, 12, _c._

Thunder-Clouds described, 52

- - under the Balloon, 172

Tide of Air in the Atmosphere, 291

Tides highest, 288, 289

Time, noted, 7, 8, 11, 22, 28, 36, 62, 63, 68, 73, 77, 85, 100,
101, 124, 162, 174, 186, 203, 206

- of Ascent, 28

Time, in which the Excursion was performed, viz. two Hours and a
Quarter, 191

- Noon, a dangerous one, for Balloons to pass an Arm of the Sea,
256

- the best, pointed out, 256

- Noon and full Tide, improper: Midnight and low Water, proper
Hours for Ascent, over Water, 287

Torrents of Air mediocèanal, depressing, 257, 258, 259

- - - - - accumulating, 260

Transparency circular, of Vapour, 222

Twine cut, lest it should prove a Conductor of Electricity between
the Balloon and Earth, 103

U.

Useful Conclusions, 159

Utility of Balloons, 332, 333

Utility _general_, of Balloons, 338

V.

Valve upper, emits the _lightest_ Gass, 124

- _first_ tried, 133

- -Swing, or Umbrella-Pendulum, as _propulsive_ Machinery,
communicates a _progressive_ Motion to the Balloon, 319

Vane-Sail, 318

Vapour, Observation of the _reddish_, 33

- _white_, _beautiful_ Effects of, 71

- - began to be accumulated at a _certain_ Height, 80

Vapours, their _Transparency_, 222

Varnishes, 320, 325

Velocity of the Balloon, 192

Vessels, the _four_ and the River Wever _disappeared_, 110

View _circular_, from the Balloon at its _greatest_ Elevation, 55

- of the Balloon over _Helsbye-Crag_,77

- of the Clouds, _from_ above _them_, 171

- _from_ the Balloon of the Country between Chester and
Rixton-Moss, 192

Vis Inertiæ, 70, 316

W.

Warmth of the superior Atmosphere, 275

- of the Air above Plains and cultivated Countries, 276

- of the Air over the _Sea_, at certain Times and Seasons, 276

- descending from _above_, 284

Water poured down, to observe the Effects of Air upon it, 74

- Balloon influenced on its Approach to, 76, 78

- Balloon above the Influence of, 131

- the Descent of Balloons over, 229

- the Causes of their Descent over, 230

- Absorption of, by Air, 247

- a curious Phenomenon seen on its Surface, 249, 250, _b._

- Means to prevent the Descent of Balloons over, and within its
Influence, 294, 295

Waves of Air, 21

- of the Sea, the Dashing of, heard; the Sea being invisible, 80

Weather, about the Time of the Excursion, 211

Weighing during the Inflation avoided, how, 24

Weight of Provisions and Articles, 24

- of the Balloon, and its Apparatus, 25

Wind heard below, 86

Winds, the Eknèfiai and Apogay, what, 241

- the Directions in which they blow, 253, _a._

- the Eknèfiai productive of Cold, 253, _a._

- _Land_- and _Sea_-, 253, _a._

- contrary, at different Heights, their Use to waft Balloons to a
given Point, 268

Wings, their Use, first to retard, second to direct, 315

Winter-Dress, preparatory, 26, 338

- -Prospect from the Balloon, 169

FOOTNOTES:

[1] Ποιησον δ᾽ Αιθρην, δος δ᾽ Οφθαλμοῖσιν ιδεσθαι·
Ἐν δε Φαει και ολεσσον, επει νυ τοι ευαδεν οὑτως.
Homer’s Iliad, Book 17, Line 646.

[2] Phil. Trans. Vol. LXVII, for 1777, Part II, Page 513, containing Sir G. Shuckburgh’s Rules for the Mensuration of Heights with the Barometer. Also Vol. LXVIII, for 1778, Part II, Page 681:

[3] And Page 688.

[4] It were to be wished that the Divisions of the Thermometer by Farenheit were become general throughout Europe, in preference to those by Reaumur yet retained _abroad_; which Divisions of Reaumur are not sufficiently minute to mark the least sensible Change in the Temperature, are subject to frequent Mistakes, and the Inconvenience of adding in the Notation, the Words _above_ or _below_ the Cypher, zero, or Point of Congelation: besides their being in Conversation not easily compared with those of Farenheit; each Degree of the latter having to that of the former nearly the Proportion of 18 to 11: since Farenheit from the freezing Point upwards to boiling Water has 212−32=180°, and Reaumur to the same Height, 110° Divisions: Mr. Saussure says as 4 to 9; in which there is an evident Oversight: see his curious and philosophic Investigation of the Atmosphere in “Essais fur L’Hygrometrie.” 4to. A Neuchatel, 1783.

Frequent Mention being made of the Thermometer graduated according to Farenheit’s Scale, in different Parts of the following Account; it may not be amiss to shew the corresponding Points according to Reaumur, taken from “Thermometre universel de Comparaison, extrait du Journal de Physique de M. L’Abbé Rozier.”

Farenheit, Reaumur.
54 13 & 4-9ths above the Cypher.
55 14 ditto, nearly.
57 15 2-9ths ditto, nearly.
59 16 4-9ths ditto, nearly.
60 17 1-9th ditto.
65 20 1-9th ditto, nearly.

[5] The Strength of the Rope, or Cable, if its Length does not exceed 10 or 12 Yards, ought to be such as to support a weight, greater than the Weight of the Balloon and it’s Appendages, for the Resistance made by the Grapple against the Balloon acted on by the Wind is immediate: The Rope ought therefore to be made of Indian-Gut, as most elastic, or Silk, as lightest. But if the Rope be half a Mile, or a Mile long; the Resistance is gradual: the Balloon descending for some Minutes; and having an open Space to move in through the Air: the Rope or Cable acting as a Radius, and the Levity of the Balloon and Opposition of the circumambient Air preventing it from falling with any Violence.

The shorter Cable may be used at the Height of 10 Yards; in aid of the longer, to prevent it from rising; or to moor it, by winding the Reel, and hauling down the Balloon close to the Ground.

[6] The Resistance being as the Square of the Velocity; therefore if the Velocity be increased 3 Times, the Resistance will be as 3×3=9, i.e. will be increased 9 Times.

[7]
Pounds Averdupois.
Weight of the Aironaut 160
Provisions and Articles
calculated at 20
Sand-Ballast prepared in Bags 44
Levity for Ascent 10
———
_Sum total_, 234

[8] Ancient Warriors among the Arabs, Spaniards, Romans, Gauls, and Germans, being frequently obliged to pass deep Rivers, never undertook a Campaign without them. For the above Anecdote, and many curious Experiments on Air, see Sam. Reyheri, _Dissertatio de Aëre_, tertium edita. Kiliæ. 1673.

[9] Equal Time with a Regulator corrected by an Observation.

[10] Being a Dial-Compass, the Dipping of the Needle was frequently checked by the Glass at the Top. A Mariner’s Compass is the best.

[11] [Sidenote: The Defect of the Reel remedied]

The Loop shoud have been furnished with a +Swivel+: or the Lath or Reel shoud have been a Kind of Pulley, a Foot in Diameter, and two Inches wide. The Hook of which having also a Swivel might have been held in the Hand: and thus the Twine woud have run off in a short Time with the greatest Readiness; the Swivel conforming to the circular Motion of the Balloon.

[12] +Slate+ (according to Cronstedt) is the +Whetstone+ _of fine Particles_, composed of Glimmer, Quartz; and, in some Species, of a martial argillaceous Earth, See “Essay on Mineralogy” by Mendes Da Costa, Sect. 264.

[13] [Sidenote: Method of discovering Haze round the Sun, in bright Weather.]

_To know whether the Air is hazy, tho’ the Sun continues shining._

The Method taken for that Purpose was by placing the Hand so as to cover his Disk or Body, and then observe the Glory blazing round him; which may, in general, be seen to issue in great Abundance, in Rays of a _golden Colour_: occasioned by a Haziness or Vapour which pervades the _lower_ Regions of the Air, most frequently in the hottest and calmest Weather, and in the hottest Climates. The Accumulation of these Vapours, before they are formed into Clouds, are often so great as to intercept the Sun’s Rays, or dye them the Colour of Blood: an Appearance frequent in Virginia, and also throughout the torrid Zone.

In the _Campania_ of Rome, for Instance, the Italians have a peculiar Name for such Kind of Weather, when the Sun is neither _visible nor invisible_: Il Sole si vede, e’ non si vede.

By Degrees the Hand is to be removed so as just to have a Glance of the Sun’s Limb. And it frequently happens that the Air is exceedingly hazy; tho’ not a Cloud appears above the Horizon.

[14] Esse in +Imaginibus+ quâpropter _Causa_ videtur _Cernendi_, neque posse +sine his+ Res ulla videri.

Lucretius de Rerum Natura. L. 4. V. 238.

[15] Notwithstanding what has been said; +this+, to the great and to the sordid Vulgar, woud still appear a solitary, helpless, and deplorable Situation. But such are not captivated with the golden Lines of +Epictetus+, (Chap. 13. Line 3. see Mrs. Carter’s Translation.)

“ΠΑΝΤΑ ΘΕΩΝ μεστα και ΔΑΙΜΟΝΩΝ·—Βλεπων τον ΗΛΙΟΝ και Σεληνην, και Ἀστρα, και ΓΗΣ απολαυων και ΘΑΛΑΣΣΗΣ, ἐρημος εστιν ου μαλλον ἠ και ἀβοηθητος·” Nor are they +practically+ influenced by the better Words of a much finer Writer: “The Earth is full,” &c. &c. And “If I take the Wings of the Morning,” &c. &c.

[16] There being, at first, no Clouds, as usual, to occupy the Place of the lowest Stratum.

[17] It has been said that the _apparent_ Height from the Balloon to the Ground was 7 Miles, viz. 4 to the Summit of the Clouds, and 3 below: and the _barometric_ Height was about a Mile and half, viz. 2332 Yards, _a Calculation of which will be given_.

If then we divide that Height or Distance into 2 such Parts, that the greater shall be to the less as 4 to 3; we obtain the Length of each Part; i.e. the barometric Height from the Balloon to the Summit of the Clouds, and thence to the Earth; which is done thus:

Suppose the whole Distance to be any Line, as A. B. to be divided in C. Then, as 7 is the whole Line, and 4 the greater Part; say, as the whole 7 is to the greater Part 4, so is the whole Distance to a fourth Term proportional, which will be equal to the greater Distance sought:

Whole Distance in Yards. Greater Distance in Yards.
Thus 7, : 4 :: 2332 : 1332⁴⁄₇ Ans.
4
—————
7 ) 9328
2332 the whole. 1332⁴⁄₇
1332⁴⁄₇ being the greater Distance found; take the greater from the
whole, and then will remain the lesser Distance wanted, viz. 999³⁄₇:
the 1332⁴⁄₇ = the greater Distance, and 999³⁄₇ = the lesser Distance:
and adding the Fractions ⁴⁄₇ ³⁄₇ = 1 to the 999; we have 1332 Yards for
the greater Distance, or Height of the Balloon above the Summit of the
superior Clouds: and 1000 Yards for the less Distance, or Height from
the Earth to the Summit of the superior Clouds.

Note. _The Line A. B. here selected is the_ famous Measure _of
(half) a_ +mathematical+ _Rhinland and Roman_ +Foot+, _according to
Snellius_. (_See_ Geographia Generalis _of Varenius, published by_
Newton. _Lib. 1. Cap. 2. De variis Mensuris._)

[18] PROBLEM.

To find the circular Boundary of the _celestial_ Prospect over the Tops of the superior Clouds, from the Balloon at the Height of near a Mile and half above the Surface of the Earth, viz. 2332 Yards. The Height from the Earth to the upper Surface or Floor of Clouds being 1000 Yards; and the Height above the Floor to the Balloon being 1332 Yards.

_On the Curvature of the Earth and Clouds, and Elevation of the Eye
above their circular Horizon._

Rule. To the Earth’s Diameter, equal to 7940 geographical Miles, add _the Height_ of the Eye above its Surface: multiply the Sum by that Height: then the square Root of the Product gives the Distance at which an Object on the Surface of the Earth can be seen by an Eye so elevated. Note the Diameter of the Earth, in Feet, is 41798117, according to Newton. (See Practical Navigator, by J. Moore, 7th Ed. Page 251.)

FIRST.

Double 1000 Yards, the Height from the Earth to the Clouds for an Addition to the Diameter of the Earth, whose Surface is now considered, as extended to the concentric Floor of Cloud.

1000
1000
————
2000

SECOND.

13932702(⅓) Diameter of the Earth in Yards.
2000 Addition to the Diameter.
————————
13934702 Sum, to which add
1332 the Height of the Eye or of the
———————— Balloon above the Floor of Cloud.
13936034 Sum, which multiply into
1332 the Height of the Eye above the
———————— Floor.
27872068
41808102
41808102
13936034
Extract the ———————————
Square . . . . . 1760) Yards in a Mile.
Root 18562797288 (136245 (77 Miles.
1 12320
—— ———————
23) 85 13045
69 12320
——— ———————
266) 1662 Yards 440) 725 (1 Quarter of a Mile.
1596 440
———— ———
2722) 6679 285 Yards.
5444
————— Ans. 77 Miles, 1 Qu. 285 Yards.
27244) 123572
108976
——————
272485) 1459688
1362425
———————
97263

[Sidenote: Circular Boundary of the _terrestrial_ Prospect from the Balloon on a _clear_ Day.]

PROBLEM.

To find the circular Boundary of the _terrestrial_ Prospect, on a clear Day, from the Balloon at the Height of near a Mile and half, viz. 2332 Yards: the Earth’s Diameter being

equal to 13932705⅔ Yards,
add 2332 the Height of the Eye or
———————— Balloon.
13935037 the Sum, multiply into
2332 the Height of the Eye, &c.
————————
27870074
41805111
41805111
27870074
———————————
Extract the . . . . . 1760) Yards in a Mile.
square Root 32496506284 (180267 (102,
1 1760 say 102½ Miles, Ans.
—— ————
28) 224 4267
224 3520
——— ————
3602) 9650 747 Yards, Remainder.
7204
————
36046) 244662
216276
——————
360527) 2838684
2523689
———————
314995 Remainder.

[19] See his “Minute Philosopher.”

[20] Ullòa in his voyage to South-America relates, that in passing over the +Deserts+, Írides are frequently seen by Travellers round _their own Heads_ as the Center of the _Iris_; and visible only to themselves. But what Analogy the _Balloon Iris_ bears to them, Time and future Experiments may discover. See his “Voyage to South America, Vol. 1. Pa. 442.”

[21] As Sound travels 1142 Feet in a
Second, it must have moved in 30 Seconds
————
Feet in a Yard 3 )34260 = Feet
Yards in a Mile 1760 )11420( 6 Miles
10560
—————
Yards in a Quarter of a Mile 440)860( 1 Quarter
440
—————
Answer 6 Miles, 1 Quarter, and 420 Yards.

[22] Equal to 2085 Yards; or 1 Mile, 325 Yards.

[23] Long’s Astronomy. Pages 227, 229.

[24] Also called the _Horsham Stone_, from a Place so named, in Surrey, where great Quantities are found.

[25] PROBLEM.

To find the _Length_ of the _Shadow_ from a Person of _middle_ Stature, (five Feet and a half High) viz. at XII o’Clock, on the 8th Day of September, 1785, at Chester, whose North Latitude is 53° 12′; (and 3° 11′ West Longitude from London.)

FIRST,

To find the Sun’s Altitude at XII.
From 90°. 00′ Subtract
The Latitude 53. 12
———————
The Remain. 36. 48 is the Complement of Latitude,
to which add (from the Tables)
Sun’s N. Decl. 5. 29
———————
The Remain. 42. 17 is the Sun’s Altitude (viz. at XII.)

SECOND,

For the Shadow say,
As the Sine of the Sun’s Altitude 42° 17′
To the Person’s Height, viz. 66 Inches,
So is the Co-Sine of the Sun’s Altitude,
To the Length of the Shadow.

For the Sine of the Sun’s Altitude 42° 17′ in the Table
of artificial Sines, is the Logarithm 9.82788, which, subtracted
from the arithmetic Complement, viz. 9.99999 (supposing
the last Figure a 10) becomes, .17212

Then for the Person’s Height, viz. 66 Inches:
in the Table of Logarithms is the corresponding
Number, 1.81254

And for the Co-Sine (had by subtracting the Altitude
42.17 from 90.00) viz. 47.43: among the artificial
Sines is the Logarithm, 9.86913
————————
The above Sums added, are 11.86079

which logarithmic Number (deducting the _Initial_ 1 as useless) viz. 1.86079, in the Table of Logarithms, corresponds to 72.57, equal to 72 Inches, for the Length of the Shadow at XII.

Reducing then the Numbers 66 and 72, to the lowest Denomination, thus 6)⁶⁶⁄₇₂ = ¹¹⁄₁₂ the Proportion which the _Length_ of the _Shadow_ bears to the _Height_ of the _Object_ is thereby obtained: that is

[26] If the _Length_ of the Shadow be divided into 12 Parts, the Height of the Object would be 11 of those Parts. See Moore’s Practical Navigator. See Page 98 [34].

PROBLEM.

An +easy+ Way to find the Proportion which the _Length_ of the Shadow bears to the _Height_ of an Object is, +AT ANY TIME WHEN THE SUN SHINES+, to fix a Plummet Line and +frame+ _upright_ in the Ground; measure the _Length_ of its _Shadow_, and compare _it_ with the _Height_ of the +frame+.

[27] Equal to 3 Quarters of a Mile and 121 Yards.

[28] i.e. When the Barometer _below_ is at 30 Inches, and Thermometer _below_ at 60° viz. about 1000 Yards high in _fine_ Weather, and 500 in _changeable_.

[29] Being 1083 Yards, i.e. half a Mile, and 203 Yards.

[30] It was High Water at Chester and Frodsham-Bridge, at 38 Minutes past I.

[31] Articles parted with, to check the _first_ Descent at Bellair, near Frodsham: and to ascend the _second_ Time.

To check the _first_ Descent. Pounds. Ounces.
Ballast, at twice: 24 0
To clear Trees and Hedges, and
_re-ascend_:
Barometer and Frame, 0 12½
Basket with Tunning Dish and
Bottles (except the Flask with
Brandy and Water) 4 10
Half Mile of Twine on the Reel 1 0
Speaking Trumpet 0 8½
Woollen Gloves 0 1
———————
31 0
24 0
———————
Remains for Re-ascent 7 0

[32] The Sun’s Azimuth from the North Point _Westward_, being 118.26′: its Supplement to 180° is 61°.34′ South westerly: i.e. South West by West, half West _nearly_.

[33] The _Length_ of the Shadows being more than _double_ the Height of the +Objects+: see [34].

[34] To find the Length of the Shadow at half past III. (See Section 84, Note _a_.)

{Lat. of Chester, 53° 12′}
Given {Sun’s Dec. 5 29 } To find Sun’s Alt.
{Hour III, 30M. 52 30 }

This is the Case of an oblique spheric Triangle, wherein are two Sides and one Angle between them given, to find the Sun’s Azimuth, and the Sun’s Co-Alt.

Side 84. 31 } Sum of Sides 121. 19
Side 36. 48 } Diff. of Sides 47. 43
(3½ Hour) Angle contained 52. 30
Half ditto 26. 15 } 63. 45
Half Sum of Sides 60. 39 } Co. 29. 22
Half Difference ditto 23. 51 } 66. 9

THE FIRST PREPARATIVE PROPORTION.

As Sine of ½ Sum of Sides 60. 39 0.05966 Co-Ar.
To Sine of ½ Difference of Sides 23. 51 9.60675
So Co-Tangent ½ contained Angle 63. 45 10.30703
—————— ————————
To T. of ½ Diff. of the other two Angles 43. 15 9.97344

SECOND PREPARATIVE PROPORTION.

As Co-Sine ½ Sum of Sides 29. 21 0.30968 Co-Ar.
To Co-Sine ½ Diff. 66. 9 9.96123
So Co-Tangent ½ contained Angle 63. 45 10.30703
————————
To T. ½ Sum of other Angles 75. 11 10.57794
Half Diff. before found 43. 15
——————
Sum, is greater Angle 118. 26 = Sun’s Azim.
Diff. is lesser Angle 31. 56 = S’s right Asc.

Then by first Axiom in Trigonometry, to know the Sun’s Altitude say,
As Sine Sun’s right Asc. 31. 56 0.27659
To Sine Co-Lat. 36. 48 9.77744
So Sine of the contained Angle 52. 30 9.89947
———————
To Co-Sine of the Sun’s Alt. 63. 57 9.95350
from 90.
——————
Sun’s Alt. 26. 3

Having Sun’s Alt. to find the Shadow,
As Sine Sun’s Alt. 26. 3 0.35738 Co-Ar.
To Person’s Height, 66 _Inches_, 1.81954
So Co-Sine of the Sun’s Alt. 63. 57 9.95350
————
To Length of Shadow, 135 _Inches_, 2.13042

Then 6(⁶⁶⁄₁₃₅ = ¹¹⁄₂₂ - | - ³⁄₆ or ½, i.e. as 22 to 45: supposing the Length of the Shadow divided into 45 Parts; the _Height_ of the Object woud be 22 of those Parts; or not quite _half_ the _Length_ of the Shadow, at half past III.

See Section 84, Note [26].

[35] See “Priestley on Electricity.”

[36] Εὔροια.

[37] [Sidenote: An Account of the _Breath_ being visible at Sea, when the Thermometer was at 61.]

The Breath is said to become _visible_ at Sea or Land at any Temperature of the Thermometer not _exceeding_ 60°: tho’, in Latitude 41°, and Westward of the Azores Islands, being in Sight of the Peak of +st. george+, (which probably equals, if not exceeds, the Height of Teneriffe) the Observer has seen his _own Breath_, and _that_ of the Sailors on Deck, when the Thermometer in the _Shade_ was at 61: the Air (in January) being _then remarkably_ damp.

[38] This Assertion may seem to contradict what was said in Section 44: When—“every Thing, that coud be seen at all, was seen +distinct+:” but it only proves that the Balloon had attained a greater Altitude during the Re-ascent, and that the +shadows+ were _much lengthened_, as the Evening advanced.

[39] Angelica Kauffman.

[40] It consists of a Frame, made by placing two strong Posts, moveable at Pleasure, each nine or ten Feet high, upright in the Ground, at the Distance of two Yards: the Posts being well secured by broad Pedestals, to keep them firm: a strong horizontal Iron Axis goes throu’ the Top of the Posts; and throu’ the Centers of four Arms or Levers at their Junction.

Between the four corresponding Ends of each two Arms, (which Arms are also strengthened by Beams from one to the other), are fixed four Seats or Boxes, well secured, each holding three or four Persons, and moving on Iron Pivots, near the Top of the Boxes, so as always to preserve the _vertical_ Equilibrium.

[41] [Sidenote: Recommended to _Invalids_.]

Why not recommend the Use of that Machine to Invalids? who woud find Refreshment in the +open+ Air: as its Rotation communicates a gentle Motion to the System,[42] without the least Fatigue; _rather_ encreasing the _Animal_ Spirits.

[42] Particularly the Stomach and Diaphragm. See “Berdoe’s Enquiry.”

[43] Talis Aër qualis Spiritus. See “_Health’s Improvement_,” by Dr. Moffet, Chapter 3, Of Air, Page 79.

[44] Or Solid of _least_ +resistance+, see Chambers’s Dictionary, with the Supplement.

[45] It will be found, that, on comparing the _two_ Calculations in