The Project Gutenberg eBook of Airopaidia This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online at www.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook. Title: Airopaidia Containing the narrative of a balloon excursion from Chester, the eighth of September, 1785 Author: Thomas Baldwin Release date: December 15, 2024 [eBook #74910] Language: English Original publication: United Kingdom: J. Fletcher Credits: Tim Lindell, Robert Tonsing, and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) *** START OF THE PROJECT GUTENBERG EBOOK AIROPAIDIA *** AIROPAIDIA: OR AËRIAL RECREATION. +Descriptions+ _of_ the aërial Scenes _are illustrated with _ENGRAVINGS_, by the best Masters: two of which are_ +coloured+. _The_ one, _a circular View from the Balloon at its greatest Elevation; the_ City of Chester _appearing in the_ Center. The other, _a Specimen of Balloon Geography: being a Prospect from_ above _the Clouds, of the Country between_ Chester, _and_ Warrington _in Lancashire, with the Track of the Balloon in the Air_. _A_ third _represents the Balloon over Helsbye-Hill in Cheshire, with a beautiful View of the adjacent Country_. AIROPAIDIA: +containing the NARRATIVE of a BALLOON EXCURSION+ from +chester+, the eighth of September, 1785, taken from +minutes+ made +during+ the Voyage: H I N T S +on the IMPROVEMENT of BALLOONS, and MODE of INFLATION by _STEAM_: MEANS to prevent their DESCENT over WATER: occasional ENQUIRIES into the STATE of the ATMOSPHERE, favouring their DIRECTION: with various philosophical OBSERVATIONS and CONJECTURES.+ +to which is subjoined, MENSURATION of HEIGHTS by the BAROMETER, _MADE PLAIN:_ with extensive TABLES.+ The +whole+ serving as an +introduction+ to AËRIAL NAVIGATION: +with a copious+ INDEX. +By THOMAS BALDWIN, Esq. A. M.+ - - - - - Addita +navigiis+ sunt Multa. _Lucretius De Rerum Nat._ L. 5, V. 335. Nihil +perfectum+ simul ac +inceptum+. +Usus uni rei+ deditus, et +naturam+ et +artem+ sæpe vincit. _Cicero._ CHESTER: Printed for the Author, by J. Fletcher; and sold by W. Lowndes, No. 77, Fleet-street, London; J. Poole, Chester; and other Booksellers. 1786. Price, in Boards, 7s. 6d. TO THE PRINCIPAL INHABITANTS OF _CHESTER:_ For their +polite attention+ on the Day of Ascent, and Preservation of +order+ during the +inflation+: on which, the Success of aërial Experiments so much depends, and throu’ the Want of which, so many have already failed; for the kind Anxiety manifested during his Absence; and for their friendly +congratulations+, on his safe Return; the following Account of the Balloon-Excursion, written at their Request, is, by their Permission, with all Gratitude, Esteem and Respect, +dedicated+, by their most obliged, and most obedient Servant +the+ AIRONAUT. AN ACCOUNT OF THE PLATES; WITH DIRECTIONS FOR PLACING THEM. 1st. _An Account of the Plates._ 1. (_a_) _A Circular View from the Balloon at its greatest Elevation_, (Page 58.) The Spectator is supposed to be in the Car of the Balloon, suspended above the _Center_ of the View: looking _down_ on the Amphitheatre or _white_ Floor of Clouds, and seeing the _City of Chester_, as it appeared throu’ the _Opening_: which discovers the Landscape _below_, limited, by surrounding Vapour, to something less than _two_ Miles in Diameter. The Breadth of the _blue_ Margin _defines_ the _apparent_ Height of the Spectator in the Balloon (viz. 4 Miles) _above_ the _white_ Floor of Clouds, as he hangs in the Center, and looks _horizontally_ round, into the _azure_ Sky. 2. (_b_) _The Balloon over Helsbye-Hill in Cheshire_, at half past II. on Thursday the 8th of September, 1785. (Page 78.) It is seen in the _South-west-Quarter_. The View was taken in a _high_ Field, at the End of Sutton-Causeway. Helsbye-Hill, tho’ upwards of 600 _Feet high_, appeared from the Car of the Balloon, to be on the _same Level_ with the _Grounds below_. 3. (_c_) _A Balloon-Prospect from above the Clouds_, (Page 154,) or _Chromatic_ View of the Country between Chester, Warrington and Rixton-Moss in Lancashire: shewing the whole Extent of the aërial Voyage; with the _meandering_ Track of the Balloon throu’ the Air. 4. _The Explanatory Print_ (_d_), (Page 155:) which elucidates the former by giving the Names of the principal Places mentioned in the Excursion. N. B. _The Circular View_ is seen to the best Advantage, when placed _flat_ on a Table or Chair, and _rather_ in the Shade: the Eye looking _directly_ down upon the Picture. Whoever will be at the Trouble of viewing _distinct_ Parts of the _Balloon-Prospect_, throu’ a very small Opening, made by rolling a Sheet of Paper into the Form of a hollow Tube, and applying it close to either Eye, at the same Time shutting the other; or by looking throu’ the Hand, held a little open, and close to the Eye; may form a very accurate Idea of the Manner, in which the _Prospect below_ was represented _gradually in Succession_, to the Aironaut; whose Sight was bounded by a Circularity of Vapour, as in Section 79, 221. 2d. _Directions for placing them._ Place the _Top_ of the +circular view+, _even_ with the _Top_ of the Page. The Plate will then lye over at the Bottom, and at the _right_ Side of the Page. Fold the Bottom up into the Book, even with the Margin: and the _right_ Side in like Manner. Observe to place the _Bottom_ of each of the other Plates, even with the _Bottom_ of the Page. The Plate will then lye _over_ at the Top, and at the _right_ Side of the Page. Fold the Top _down_, into the Book, _even_ with the Margin: and the right Side, in like Manner. The circular View, to _face_ Page 58. The Balloon over Helsbye-Hill, to _face_ Page 78. The Balloon Prospect, to _face_ Page 154. The explanatory Print, to be placed _on_ Page 155: and, when unfolded, to be seen _along with_ the Balloon-Prospect. Literal and other Errors proper to be examined, and corrected with the Pen, before the Book is read. Page. 6. Note [1]—ειαδεν _write_ ευαδεν. 18. Note [6]—_Cube_ of the Velocity, &c. _write_ (as in some Copies) Square of the Velocity, &c. the Resistence will be as 3 × 3 = 9.—See Chambers’s Dictionary, under +resistence+. 23. Section 21. _Blot out_ [Signs] of Currents. 26. _Before_ All Things being thus prepared, _insert_ [_Section_] _viz._ 25. 35. Line 13.—I o’Clock, _write_ I. o’Clock. 54. Section 52.—an Extent above them of 77 Miles, _write_ an Extent of 102 Miles. See the Occasion of this Mistake in Note (_a_) Calculation SECOND, which makes the Answer 102 Miles, 1 Quarter, 320 Yards; and the Ans. to the PROBLEM being 102 1 307 ————————————————————————— gives the Prospect 13 Yards less than _that_ over the Clouds. 84. Line 4.—great Turnpike-Road, _write_ great public Road. 84. Note [26] _After_ See Moore’s Practical Navigator, _insert_ See Page 98 [34]. 98. _After_ Note [34] _add_ See Section 84, Note [26]. 118. Line 5.—from a vertical Situation only, to be seen, _write_ to be seen from a vertical Situation only:. 174. Line 1.—excessine Diminution _write_ excessive Diminution. 177. Line 9.—contain _write_ contains. 202. The Sections 259, 260, 261, are repeated. 234. Line 6.—a Yard, _write_ two Yards. 236. Line 3. _After the Words_ in Danger of breaking; _add_ the Bottom of the Balloon must be opened, or the upper Valve drawn. _And erase the Remainder of the Sentence._ 237. Line 4.—which is a Sign that the Balloon descends, _write_ (which is a Sign that the Balloon descends). 242. Line 21.—supercede, _write_ supersede. 263. Line 5.—commonly: ascend, _write_ commonly ascend:. 266. Line 21.—their Passage _write_ its Passage. 271. Line 14.—each 4 Feet _write_ each 4 Inches. 278. Lines 15 and 18.—third Tables _and_ third Table, _write_ fourth Tables _and_ fourth Table. 283. Note [119].—more than the three first Decimals _write_ more than the four first Decimals. 288. Line 5. _After_ .0000076, _insert_ which, being divided by .1, gives a Cypher less. 288. Line 11.—with 4° on .25, _write_ with 4° on 25. 290. Note [120]—at low Water.) _write_ at low Water. 292. Line 23.—there will remain the greater Height, _write_ there will remain, +secondly+; (see Section 367) the greater Height. 303. Line 6.—(viz. the 8,) _write_ (viz. the .8,). 309. Line 10. Marginal Note.—_7th Step in Section_ 366. write _7th Step in Section_ 368. 310. _After_ Line 23, _insert_ _Air_-Thermom. 56°. 311. Line 1.—By the Practice of the first Example, _write_ Practice of the second Example. 312. Line 29. _After_ The Answer, &c. _insert_, made by rejecting a Cypher,. 317. Before the last Line but two, _insert_ +end of the first stage+. 318. Line 23.—the 2d Tenth, _write_ the 1st Tenth. 319. Line 13.—, gives 7. _write_, gives 97. 322. last Line but two.—and the remaining Feet _write_ the remaining Feet. AIROPAIDIA: CHAPTER I. [Sidenote: Introduction.] Section 1. The Public have, for a considerable Time, been entertained with Accounts of aërial Voyages. Such Accounts are, in many Respects, vague and unsatisfactory: by no Means adequate to the Expectations and Wishes, which have been formed by those, who have not yet penetrated the profound Heights of the Atmosphere. [Sidenote: Mistakes to be noticed, as Examples of Avoidance.] 2. The Voyagers have, now and then, been pretty accurate in Regard to Time Place Distance and Velocity: Circumstances highly worthy of Remark, in order to estimate the Improvement already made in this wonderful Discovery, and point out its Use: but neither ought the _several Occasions of Failure_ in the Experiments to be omitted; as they will be found to arise more from a Want of Prudence and Foresight in the Managers, than from any Defect in the Machine, or the Principle on which it acts. Such Failure ought therefore to throw an additional Light and Credit on the Art: and give a Spur to Ingenuity, which, it is not to be doubted, will continue to drive forwards with the same rapid Success; nor rest, till the Art itself is brought to the highest Degree of Perfection; till airostatic Ships make the Circuit of the Globe: a +Navigation+ which, from its Novelty and Importance, deserves to be considered in a separate Treatise. [Sidenote: Aërial Voyagers defective in their Descriptions.] 3. Balloon-Voyagers have likewise been particularly defective in their Descriptions of aërial Scenes and Prospects: those Scenes of majestic Grandeur which the unnumbered Volumes of encircling Clouds, in most fantastic Forms and various Hues, beyond Conception glowing and transparent, portray to a Spectator placed as in a Center of the Blue Serene above them: contemplating at the same Instant, and _apparently_ at some Miles Distance immediately below, a most exquisite and ever-varying Miniature of the _little Works of Man_, heightened by the supreme Pencil of Nature, inimitably elegant, and in her highest Colouring. Such are the Scenes which, Ballooners all allow, constitute the true Sublime and Beautiful: inspire Ideas of rational Humiliation to a thinking Mind, and raise the most careless Mortal to an unknown Degree of enthusiastic Rapture and Pleasure. Every Beholder is a Judge of the Scenery around him: and no one, it is presumed, ever ascended into the Atmosphere on a _mild Day_, with a sound and well ballasted Balloon, that did not wish to taste the Luxury of a second Voyage. [Sidenote: Disappointment shoud excite the Ardor of the Scientific.] 4. Yet notwithstanding, as Ignorance is known to be the Parent of Fear, the Bulk of Mankind, which are by far the greater Number, will long continue to entertain absurd Apprehensions concerning it; to oppose and ridicule the Invention; as they will oppose every other Discovery, which they have neither Talents _Inclination_ or Leisure to understand. This Reflexion shoud, on the contrary, rather excite than check the Ardor of the Skilful and Scientific, to cherish and promote the Art. In the History of Airostation, each Event is yet new and _uncompared_. _Every_ Circumstance ought therefore to be carefully recorded: since it woud be unfair to fix Bounds to Science; or argue, that such Inferences, as shall demonstrate the great Utility of the Invention, may not be drawn from Circumstances which Inattention might pronounce to be most trifling and minute. [Sidenote: The Reader cautioned.] 5. The Reader is requested to observe that, this Account being addressed to the Generality, and not to the Curious and Philosophic only; many Circumstances are added, which woud otherwise have been considered as superfluous: and some it was thought proper to repeat, in order to connect the Thread of the Narration, without the Necessity of frequent Reference to the Sections. [Sidenote: Squalls of Wind the Day preceding the Ascent.] 6. An Agreement having been made with Mr. Lunardi, that he shoud resign his Balloon to Mr. Baldwin on Wednesday the 7th of September; an Advertisement to that Purpose appeared in the Chester Paper: and on Wednesday Morning, a great Number of Spectators assembled in the Castle-yard of the City of Chester: where many waited till half past IV in the Afternoon; Mr. Lunardi declaring that, on Account of the Violence and Unsteadiness of the Wind which blew from the South and South-West, it was dangerous to attempt the Inflation of his Balloon; and Mr. Baldwin continuing to assert that, if it coud be filled, he was willing to go up. The Weather was _then_ moderate: but Mr. Baldwin, thinking the Hour too late to begin the Inflation, which, judging from the two former Inflations, coud not probably have been completed till after _Sunset_; made a Proposal to Mr. Lunardi, that he shoud postpone the Exhibition till the next[1] _Day_. The latter, after some Reluctance, arising from a Fear lest the Public shoud disapprove his Conduct, politely complied with his Request, on Mr. Baldwin’s saying that he woud take the Blame on himself. CHAPTER II. +Preparations for the Voyage.+ [Sidenote: Cannon first fired at IX.] Section 7. On Thursday the 8th of September 1785, at IX in the Morning, one of the Cannons (a Six-pounder) was first fired in the Castle-yard, to inform the City and Neighbourhood, that the necessary Preparations were making to inflate the Balloon. Till VIII that Morning, the Air had been hazy: but was then clear, bright and calm _below_, with an upper Tier of light Clouds in the Zenith moving from South-West by West, and dense ones rising in the Horizon. [Sidenote: At X, the Inflation began with a small Balloon.] 8. At X o’Clock, the Process began with the Inflation of an airostatic Globe eighteen Feet in Circumference, of Silk Tiffany, made the latter End of the Year 1783, and decorated with Painting, Mottoes and Devices: in the Performance of which little Work, Mr. Baldwin was (in the modern Phrase) the sole Projector, Architect Workman and Chymist. [Sidenote: An airostatic Globe liberated as Pioneer to the great one.] 9. The Airostat was presently liberated by the Hands of Mr. Lunardi; and continuing to turn gently the same Way round its own Axis, afforded a beautiful Spectacle to the Beholders: remaining in Sight about half an Hour. It was intended to serve as a Sort of Pioneer, to delineate the Track of the great Balloon. [Sidenote: Its Fate.] 10. It fell at some Miles Distance, ’tis said unfortunately on a Hedge, and was presently torn to Pieces by the Eagerness and Avarice of the Pursuers, who expected and undeservedly obtained the Reward promised in the Letter appended to it. [Sidenote: Second Cannon at XII.] 11. At XII the Cannon fired a second Time, to announce that the Process was in a proper Degree of Forwardness. At this Time Mr. Baldwin went, with some Friends, to take an early Dinner: he also recapitulated the Articles, to be certain that Nothing was omitted. [Sidenote: Inventory for the Voyage.] 12. The following Inventory, with which he ascended, may be of Use to future Aironauts; to whom _only_ it is addressed. The Cable and Grapple are considered as Part of the Balloon. (See Section 13.) 12. Article 1. A portable Barometer,[2] with a common Syphon or Bulb, (purchased at Lausanne.) 12. 2. Martin’s Thermometer,[3] with Farenheit’s Scale[4] for the Degrees of Temperature. 12. 3. Mariner’s Compass in a double Box, to be used when the Sun is intercepted from the View by Clouds, in order to discover whether the Balloon turns round. 12. 4. Down, or small Feathers, to be loose in the Pocket, and thrown out, when enshrined in Clouds; or at any other Time, to shew the Rise or Fall of the Balloon. 12. 5. An Asses’ Skin Patent Pocket-book; as Wet spoils Paper. 12. 6. Two _red_ Lead Pencils: each Pencil ready pointed at both Ends, to save Time and Trouble: preferable to Ink, which may be spilt or frozen. The Strokes with _red_ Lead are not so easily obliterated, as when made with a _black_ Lead Pencil. 12. 7. A small sharp Knife pointed, and ready open, or which will open easily. A Pair of Scissars. 12. 8. A _wicker_ Bottle of Brandy and Water, only three Parts full, half and half: such Bottles are more secure: and such Mixture will not soon freeze. The cochuc or elastic Bottle is still better. A Cork-screw. 12. 9. _Compact_ Provisions, which do not soil the Fingers or Pocket-book, as Confectionaries, Fruit, Biscuit, Bread. 12. 10. A _boarded_ Map of the Country over which the Aironaut may be supposed to pass: the Back serving as a Table. 12. 11. Two Needles with large Eyes: the _raw_ Silk put through, and tyed on a Knot at the Ends to prevent the Needles from being lost: to be ready at the Instant wanted, to sew up any Holes within Reach, in the Balloon; the Holes being first tyed up with Twine. The Needles to be stuck into Parchment, containing a small Hank of _raw_ Silk: the Needle Silk run round the Parchment, to keep the Hank dry. The whole Hank to be tyed by one End to the Side of the Car; when above all Clouds, to shew, by the Divergency of the Threads, the Electricity of the Air. 12. 12. A few Yards of Dutch Twine, loose in the Pocket, to tye the Neck of the Balloon in descending. 12. 13. For easy Experiments; 1st, Dutch Twine, half a Mile long, on a Reel, or Pulley, or two Lengths on different Reels: also to each Reel a Flag, made of white Linen, a Yard square; and stretched by a slender Lath; one Side of the Flag being bound and stitched round it: also a Piece of Twine, two Yards long, is to be fastened by its Ends to the Ends of the Lath: a Loop is to be made in the Middle of the Twine: and to the Loop is to be applied round the Middle of the Lath another Piece of Twine, which will prevent the Lath from being bent; and will keep the Flag always stretched. By this Apparatus, Observers from below may be enabled to estimate the Height of the Balloon, as will be shewn in its proper Place. 12. 14. 2dly, To try the Density of the Air, at different Heights, _above_ the freezing Point with Water; _below_ it, with Brandy. In a Basket take two Pint-bottles, one full of Water, the other of Brandy; and six or eight empty ones: also a small Metal Tunning-dish. Let one End of a String be tyed round the Neck of each Bottle: and the other End sealed to the Top of a large Cork much tapered, to enter the Mouth easily. Round each Neck, tye a Parchment Label, large enough to contain in abbreviated Characters the Number of the Bottle; Time of Observation, Heights of the Barometer and Thermometer, while on the Ground. When an Experiment is made in the Air; pour off a full Bottle into an empty one: put the Cork into the emptied Bottle, and mark again the Time, Barometer and Thermometer: which are to be compared with an Eudiometer below, to discover the Rarity and Purity of the Atmosphere. 12. 15. A third white Linen Flag, made as above, and tyed to the upper Hoop of the Balloon, so as to hang in Sight, will give Notice of a Change in the Wind. 12. 16. A Yard of thin Ribbon, two Inches broad, tyed to the lower Hoop, will mark the Rise and Fall Of the Balloon. (12. 17. A Magnet and Iron Filings in a thin Pewter Dish with a Cover; Also The Prism and large Telescope were left, as too heavy.) And the Sextant or Quadrant coud not be procured in Time. They woud, have been of little Use, as no Horizon of the round Earth was seen during the Excursion: and it is presumed, that the circular Horizon is seldom visible, when the Balloon is at any considerable Height; the Accumulation of Vapour between the Eye and Horizon preventing it: tho’ such Vapour remains invisible to Spectators from below. 12. 18. Eight Bladders, each above half blown, and differently coloured for Ornament, tyed round the _upper_ Part of the Car, Breast high when the Aironaut stands upright: in Case the Balloon fall into Water. 12. 19. Speaking Trumpet: also a live Pigeon, in a small Basket of Matting. 12. 20. Pepper, Salt, Ginger; to try the Effects of Tastes, which have been said to become insipid on the Peak of Teneriffe. CHAPTER III. ADDRESSED TO AIRONAUTS. [Sidenote: New Kind of Cable and Reel recommended.] Section 13. The following Anchor and Cable, for greater Safety and some particular Uses, are recommended as an Improvement. A _strong_ Iron double Grapple, moving on a Swivel, fastened to a _Rope_,[5] half a Mile, or better _a Mile_ long: and, if not all; a Part of which at least, at the Distance and for the Length of ten Yards from the Grapple, shoud be of Silk, as a non Conductor: also other ten Yards, at its upper End, counting from the Reel or Pulley to which the Silk shoud be tyed. The Reel or Pulley being at least eighteen Inches in Diameter, and fixed vertically in the Center of the upper Hoop, seven Feet above the Bottom of the Car; by Means of three or four Iron Rods fastened in the Bottom of the Car, and meeting together above the Reel: the Rods so strong as to prevent the Shock which otherwise the Aironaut woud receive in alighting on the Ground. The Reel shoud have one, or two Iron Winches or Handles, one at each End of the Reel; with moveable Handles of Wood round them. The Reel may be furnished with sudden Checks; or gradual Clamps, as in a Mil, to retard the Velocity. SIGNS TO BE OBSERVED, WHEN IN THE AIR. [Sidenote: Cautions against two Extremes.] 14. The two Extremes to be avoided are, too lofty an Ascent: and too precipitate a Fall. [Sidenote: 1st. Too lofty an Ascent.] The former is to be apprehended when Balloon has swelled considerably, and strains as if ready to burst; from the Shape of an inverted Cone, or Children’s Top, changed to that of an oblate Spheroid, or Turnep. It is therefore necessary to look up at the Balloon from Time to Time: and either open the Mouth, or as it is sometimes called the Neck, _for an Instant_; or draw the Valve; which is done by pulling a Cord fixed at the Top of the Machine and running thro’ it to the Hand, till the Balloon only appears full without straining. These Operations are to be occasionally repeated during the _Ascent_. If it is required to rise still higher; gradually throw out Ballast, and repeat the Operations. The proposed Quantity of Ballast being thrown out, the Balloon will have acquired its utmost Height, and become stationary, i.e. neither rise nor fall. The self Descent of the Balloon is only in Proportion, as the inflammable Air or Gass escapes thro’ imperceptible Holes in the Silk or Seams. 2dly. +To prevent too precipitate a Fall+. [Sidenote: 2ndly. Caution against too precipitate a Fall.] 15. 1st. Tye, or compress the Mouth of the Balloon, for a Moment; which must always be opened, on observing that the Balloon is again risen to so great a Height as to _strain_, or be distended as above mentioned. 2d. In descending, throw out Ballast, when the Balloon is within a Quarter of a Mile of the Ground, but not before, i.e. at 26 Inches by the Barometer: and, if the Fall is precipitate, not less than 25 Pounds Averdupoise, Pound by Pound, or at once, if there should be Occasion. 3d. In Case of Accident, as the Escape of Gass; or if the Balloon be not furnished with +an Equatorial Hoop+; prepare to throw out all the Ballast at the above Height, but not before; as the more forcible the Fall,[6] the greater the _Resistance_ from the Air: cut away Ends of Cords; tear off Ornaments: part with Shoes, Cloaths. All which must be made _loose_ and _ready_ to throw out, at the Moment the Balloon begins to descend. Before the Landing, particular Care must be taken, that the Weight of the Aironaut be sustained, by grasping the Hands round the +opposite+ Sides of the upper Hoop; so that the Feet may not touch the Bottom of the Car. The Knees shoud likewise be bent. Repeating the above, at each Rebound of the Balloon, if any; the Aironaut will alight in the gentlest Manner: and probably the Balloon may act as a Parashute or Umbrella, which _alone_ will, at all Times, ensure an easy Descent. SIGNS WHEREBY TO JUDGE WHETHER THE BALLOON IS RISING OR FALLING. SIGNS OF RISING. [Sidenote: Signs of Ascent or Descent.] 16. 1. When the Aironaut perceives a Pressure upwards against the Soles of his Feet. 2. When some Objects, on the Surface of the Earth immediately below, diminish, and others disappear. 3. When an upper Cloud approaches or involves the Balloon. 4. When a lower Cloud leaves the Balloon. 5. When Rain Snow or Hail beat +violently+ against the Top of the Balloon. 6. When Feathers, Balloon-Flag, or Ribbon seem to be drawn forcibly downwards. 7. When Objects on Earth, or among Clouds below the Balloon, rise and present themselves _beyond those_, which, the moment before, were thought most distant. 8. When the Balloon appears broader and shorter; also fuller at the Bottom; being more distended than at the first Ascent. SIGNS OF DESCENT. [Sidenote: Signs of Descent.] 17. 1. When the Aironaut perceives the Bottom of the Car withdrawing itself from the Pressure against the Soles of his Feet. 2. When Objects on Earth, and surrounding Prospects encrease in Magnitude and Number. 3. When a lower Cloud approaches or involves the Balloon. 4. When an upper Cloud leaves the Balloon. 5. When Weather beats against the Bottom of the Car or Balloon. 6. When Feathers, Balloon-Flag, or Ribbon appear to be drawn upwards. 7. When the most distant Objects _set_, and disappear. 8. When the Balloon seems taller; and its lower Hemisphere less distended, tho’ continuing _tight_. SIGNS OF PROGRESSIVE HORIZONTAL MOTION. [Sidenote: Signs of progressive Motion deceitful.] 18. These are equivocal and deceitful. When the Aironaut has lost Sight of the Earth by intervening Clouds; the Balloon seems at Rest, and only the lower Clouds appear to move: whereas the contrary may be true, the Clouds may rest, and only the Balloon move. In this Case, Attention must be paid to the half Mile white Flag, whose Situation and Motion must be observed, with respect to the Balloon, and to the Earth before the Cloud intervened. If the Flag retains its Situation with Respect to the Balloon, it may be inferred that no Change in the Direction has happened: if its Situation alters, the Sun or Compass is to be observed: and an Estimate made of the new Current of Air by which the Balloon is affected: its Velocity, Sound, Temperature, &c. [Sidenote: To descend when lost.] 19. But to acquire a Certainty of course, it will be proper to descend below the Cloud: or move by Compass, Map, and a Knowledge of the Country: or try the long Cable (Section 13.) [Sidenote: Signs of Wind horizontal.] 20. It is likewise necessary to know the _Signs of Wind_, or Currents of Air. SIGNS OF NEW AND SUDDEN HORIZONTAL CURRENTS. When the Feathers, Balloon-Flag, or Ribbon, compared with Sun or Compass, take a new and sudden horizontal Direction. 21. +of currents from above+: properly named _Waves Torrents and Tide of Air_. [Sidenote: Signs of depressing Torrents and Tide of Air.] They are very frequent, and require to be guarded against: are sometimes or long Continuance, at other Times momentary: against the first throw out Ballast at the Height of a Quarter of a Mile, but not before, or _as hereafter directed_: when momentary, and above that Height, Nothing is to be apprehended: the Balloon will appear broader and recover its Form. CHAPTER IV. PREPARATIONS FOR ASCENT. [Sidenote: Preparations for Ascent.] Section 22. Before half past I, Mr. Lunardi had inflated his Balloon in the finest Manner; and having, with the most obliging and spirited Attention, made such Preparations, and taken such Precautions, as he thought were necessary to ensure the Success of the Expedition; sent to inform Mr. Baldwin (who continued purposely absent, that he might not disturb or precipitate the Process; but that every Circumstance shoud be conducted with Deliberation and without Hurry) that all Things were ready for his Departure. [Sidenote: The Public reminded of the Necessity of preserving order during the Inflation of Balloons.] 23. And Mr. Baldwin takes this Opportunity of returning his best Thanks to his Friends and the Public, on the Day of Ascent, for keeping +the small Circle clear+, by strictly adhering to the Words of the Advertisement, which declared, “that in order to prevent an interruption of the Process in the Inflation of the Balloon, no Persons _were_ to be admitted +within the circle+, except those Gentlemen who politely undertook +in turn+ to hold the Lines which detained the Balloon.” [Sidenote: Lead Weights placed at first in the Car, to prevent any Fatigue in holding the Lines, and the Necessity of weighing, unless at the Time of Ascent, to determine the Power of Levity.] 24. It may be proper to mention that Mr. Baldwin being resolved to prevent the disagreeable Circumstances of being _weighed_ in the Presence of Thousand spectators, at a Time when it is uncertain whether the Balloon has _acquired_ a sufficient Degree of Levity to raise his own Weight, together with the Instruments, Provisions, Ballast, and other Articles, all which are known or easily calculated; finding some Days before, his own Weight, and having calculated the rest as under[7]; he ordered his Servant, on the Day of the Excursion, to bring Lead Weights equal to the _Sum total_, with an overplus Weight of 10lb. for Levity of Ascent, and place them _gradually_ in the Car, attached for that Purpose to the Balloon, soon after the Inflation began. By which Means the Gentlemen who held the Cords were quite at Ease: nor was there Occasion to tye the Lines during the Inflation, to Posts fixed in the Circumference of the Circle; nor consequently to _cut them_ afterwards. But it will be seen that Mr. Lunardi inflated the Balloon in a superior Manner. 25. All Things being thus prepared, Mr. Baldwin stepped into the Car: and finding, that, besides his own Weight, the Provisions, Articles, Ballast, &c. the Balloon woud support an additional Weight, and _still_ rise with superior Levity; Mr. Lunardi put in 12lb. of additional Ballast, and _guessed_ the encreased Levity at 10lb. more. Additional { Ballast 12 { Levity 10 ——— 22 Added to the 234 ——— Make the Sum 256lb. All which added to the Weight of the Balloon, _by Information only_, as follows: Balloon varnished 113 Netting and Cords 18 Car and Hoops 24 Mended and added Parts 5 Grapple and Cable 4 ——— 164 With the 256 Make the total Levity of the Gass to produce an Equilibrium, equal to 420lb. The Weight of a Quantity of Air equal in Bulk to the Balloon, being secluded; and the Gass substituted in its Room. [Sidenote: Weight of Articles.] 26. The Calculation of the Weight of Articles was, as follows: Pounds Articles. Averd. Ounces. 1. Eight coloured Bladders[8] (Section 13, Art. 18) 1 – 0 2. Preparations against extreme Cold. +A Winter Dress.+ Flannel or woollen Socks } Cap } Gloves } Drawers } 0 – 14 Under Stockings } ———— Waistcoat } 3. Brandy, Water, Flask, and Refreshments 1 – 8 4. Barometer (portable) 0 – 12½ 5. Thermometer 0 – 3 6. Dial-Compass (a Mariner’s Compass in a double Box, will traverse better) 0 – 3½ 7. Two white Flags, 0 – 4 with Dutch Twine on two Reels furnished with Swivels 2 – 8 8. Asses Skin Pocket Book, Blank Cards, Pencils, Knife and Scissars 0 – 4½ 9. Map of Cheshire boarded, the superfluous Parts cut away 0 – 3 10. Speaking Trumpet 0 – 8½ 11. Mr. Lunardi’s Flag 3 – 8 12. Basket and eight Pint Bottles labelled, one full of Brandy, another of Water 8 – 3 ——————— 20 – 0 [Sidenote: Weight of Ballast.] 27. The Ballast consisted of three Bags of dry Sand, and two red grit Stones, taken while in the Car, _additional_. 1st Bag tyed up weighed 12lb. 2d Ditto 12 3d untyed Ditto 20 1st red Grit 7 2d red Grit 5 —— In all 56lb. CHAPTER V. ASCENT WITH 20lb. OF LEVITY. [Sidenote: Ascent at 40M. past I, with 20lb. of levity.] Section 28. At 40 Minutes past I, the Balloon having a Levity which not less than 20 Pounds Weight woud counterpoise, Mr. Baldwin was liberated by the Hands of Mr. Lunardi, who suffered no one to approach the Car: and he ascended, amidst Acclamations mixed with Tears of Delight and Apprehension, the Misgivings of Humanity, and other usual Sensations of Surprize, which, in a brilliant and numerous Assembly, will long continue to accompany a Spectacle so novel interesting and awful, as that of seeing a Fellow Mortal separated in a Moment from the Earth, and rushing to the Skies. [Sidenote: Employments of the Aironaut.] 29. The Balloon well inflated, tower’d aloft in an upright and perpendicular Direction, with a quick Motion, and an accelerated Velocity. The Aironaut having stood up, for a Minute or two, waving his Hat in the left, and saluting the Spectators with Mr. Lunardi’s coloured Flag in the right Hand; put on his Hat, and having fastened the Flag-Staff horizontally among the Lines of the Balloon, immediately betook himself to different Employments, before he woud indulge in looking over the Brink of the Car; lest the Novelty of the Prospect shoud call off his Attention from _Things of Moment_. [Sidenote: Sensation of rising described.] 30. The Force of Ascent was, from the first, plainly _palpable_: the Sensation being that of a strong Pressure from the Bottom of the Car, upwards against the Soles of the Feet. [Sidenote: Caution against the vitriolic Acid Liquor.] 31. His first Point being to guard against a Deluge of acidulous Liquor, which, he was told, had fallen, to the Quantity of three Quarts, on the Head and Shoulders of a former Aironaut, from the Trunk or Bottom of the Balloon, which ended in a wide circular Opening of eighteen Inches Diameter; he found that when the Weight either of himself, or of the Ballast, was not exactly in the Center of the Car; the Opening of the Balloon woud, without any Trouble, hang so as to lie on the Outside of the Car: but he did not perceive more than a few Drops issue from the Mouth: which happened a few Minutes after he arose. [Sidenote: Attitude, and farther Employments.] 32. This Difficulty vanishing; he changed his erect into an inclined Posture between sitting and kneeling; sometimes with the right Knee near the Bottom and Center of the Car: and having both Hands quite free, the Balloon being subject to no _sensible Motion_; he reconnoitred all the Lines and Cords: coiled the Rope or Cable to which the Anchor or grappling Iron was fixed: tyed fast its proper End to the upper Hoop: observed and felt the superior Thickness of the Cord leading to the Valve: coiled it, in order that it might be free to act: placed the untyed Bag of Ballast near the Outside of the Car: also the tyed Bags at proper Distances to preserve the Equilibrium: unwrapped one of the white Flags, tyed it to the String on one of the Reels, and just threw it an Inch or two over the Side of the Car: then placed his Watch, _open_ Knife, Scissars, Thermometer and Compass on his right Hand: the Barometer being swung above in Sight towards the left. [Sidenote: Change of Attitude, and Observation of the reddish Vapour.] 33. He then stood on his Feet, with a Design to look down: but his Attention was drawn to the Opening of the Balloon, which began to breathe out by Intervals a visible _reddish Vapour_; in Form like that which is seen at the Top of a Brewery, only that the under Surface was not jagged but smooth, altho’ wavy and uneven. The Particles which composed it were so large as to be distinctly visible: and appeared, as if endued with a very strong repelling Power, from the great and seemingly equal Distances, of about half a Quarter of an Inch, from each other. It was observed by a scientific Spectator from below, that the Parts of the Balloon, which reflected the Sun’s Rays, appeared of a bright Copper-Colour: but the _reddish_ Vapour issuing from its Mouth put on the Form of a lambent Flame. A similar Appearance had been observed by him, in a former Ascent of the same Balloon, the Neck or Mouth being then likewise open; and also by others, who declared they saw the Balloon on Fire. The Change of the +red+ into Flame-Colour, when seen at a great Distance, may it not be owing to this, that the direct Rays, being mingled with those which are intercepted between the Eye and the Object, became in Part absorbed, and in Part refracted; and therefore coud not reach the Sight? [Sidenote: The Gass not offensive.] 34. This gentle Evaporation of inflammable Air, or Gass, continued: disappearing at the Distance of four and five Inches below the Opening: nor did it offend the Smell; not descending within its Influence. [Sidenote: Attention to the Balloon, and Dimensions of the Car and Hoops.] 35. He then looked upwards at the Balloon, and perceived that it was considerably swelled in its Dimensions: and that the Distention had raised the Bottom-Opening of the Balloon half way between the two Hoops: i.e. from his Hip to his Shoulder, as he stood upright. The Height from the Bottom of the Car (which was a thin circular Board four Feet and a half, Diameter, placed on a strong Netting, and covered with green Bays) to its Top or the lower Hoop, was three Feet; with the Netting continued round between the lower and upper Hoop. [Sidenote: Stationary, and Notes made.] 36. He was aware that the Swelling of the Balloon, and copious Vapour then issuing from it, denoted the Moment when it began to lose its ascensional or elevating Power; and that its accelerated Motion was diminishing. He therefore looked at his Barometer and Watch, which was 53 Minutes past I.[9]; took up his Pencil, and on a Card (marked before he left the Earth, as follows: Chester-Castle-Yard. Thursday, the 8th of Sept. 1785, I. o’Clock, Barometer 29⁸⁄₁₀, Therm: 65 in the Shade towards the North;) he wrote “Rose at 40 Minutes past I.” He then looked again at the Barometer, which continued falling for some Minutes, and fluctuating up and down within the Space of an Inch or more. It first began to rest at 23¼, and a little after at 23½. Having looked again at his Watch, he put down “57 Minutes past I. became stationary: Barometer 23¼: Therm: still 65, sometimes lying in the Shade, and sometimes exposed to the Sun: the Balloon turning round frequently thro’ East to South.” [Sidenote: Fluctuation of Barometer.] 37. The Fluctuation of the Barometer, he imagined to arise from continued Exertions of the Gass within the Balloon, opposed by the atmospheric Air, which varying in Density and Temperature woud give an unequal Resistance to the Balloon: and both Gass and Air being elastic, the Power of Ascent would act by Intervals, and communicate its Pulsations to the Quicksilver in the Tube. His own irregular Motions in the Car would increase the Fluctuation. [Sidenote: The Compass traversed, but was useless.] 38. The Compass likewise traversed backwards and forwards, pointing due North, and unaffected by the Turns of the Balloon: but was useless, as the Sun shone bright the whole Time of the Excursion.[10] [Sidenote: Aironaut first looked down at Leisure.] 39. Thing’s taking a favourable Turn, he flood up, but with Knees a little bent, more easily to conform to accidental Motions, as Sailors when they walk the Deck: and took a full Gaze before, and below him. [Sidenote: Scenes below described.] But what Scenes of Grandeur and Beauty! A Tear of pure Delight flashed in his Eye! of pure and exquisite Delight and Rapture; to look down on the unexpected Change already wrought in the Works of Art and Nature, contrasted to a Span by the +new perspective+, diminished almost beyond the Bounds of Credibility. Yet so far were the Objects from losing their Beauty, that +each+ was +brought up+ in a new Manner to the Eye, and distinguished by a Strength of Colouring, a Neatness and Elegance of Boundary, above Description charming! The endless Variety of Objects, minute, distinct and separate, tho’ apparently on the same Plain or Level, at once linking the Eye without a Change of its Position, astonished and enchanted. Their Beauty was unparalelled. The Imagination itself was more than gratified; _it was overwhelmed_. The gay Scene was Fairy-Land, and Chester Lilliput. He tried his Voice, and shouted for Joy. His Voice was unknown to himself, shrill and feeble. There was no Echo. [Sidenote: Let down the white Flag, 2 Furlongs, equal to half the Length of the Twine on one Reel.] [Sidenote: Its Uses.] 40. He then returned to an Employment which, tho’ irksome, he imagined would contribute to the Amusement and Information of Spectators below, if it coud be completed while he continued in Sight; as it woud furnish them with Ideas of Height and Distance, altogether new and interesting, _as will be seen in their proper Place_: and unwound half the Reel; the white Flag hanging out to the Length of 440 Yards or a Quarter of a Mile. [Sidenote: The Reel defective.] 41. The circular Motion of the Balloon was communicated to the Loop in the Middle of one Side of the Lath or Reel, round which from End to End the Twine was wrapped, and by which it hung on his Finger, and pressed it to a Degree of Pain.[11] [Sidenote: The Employment again suspended.] The Work was again suspended. He coud not long withstand the Temptation of indulging his Eye with a View of the glorious and enchanting Prospect. [Sidenote: The Beautiful preferred to the Sublime, in Prospects.] 42. But the Beautiful among the Objects below was still more attractive than the Sublime among those around. [Sidenote: Inverted Firmament what.] On looking down South by West, the Balloon often turning gently to the right and left, and giving the Aironaut an Opportunity of enjoying the circular View without a Change of Attitude; innumerable Rays of Light darted on the Eye as it glanced along the Ground: which, tho’ of a gay green Colour, appeared like an inverted Firmament glittering with Stars of the first Magnitude. 43. This splendid Appearance was owing to the Rays of the Sun reflected from certain Pits or Ponds of Water, of which there is one at least in most Fields or Inclosures throughout the County: but particularly in the low Grounds of Leach-Eye and Dodleston. [Sidenote: Broad Turnpike Road a narrow Foot Path.] The Object that next drew his Attention, _while ascending_, was the Overley Turnpike-Road, which is remarkably wide, (resembling the Emilian Way across the Atrian Fens, between Bononia and Ferràra in Italy) raised over Saltney Marsh, leading to North-Wales and Holyhead: composed of Sea-Sand cast up above high Water Mark. This appeared like a narrow Foot-Path well trodden, of a _white_ Colour, and strait as if drawn by a Line. [Sidenote: River Dee red.] 44. Nothing however raised his Curiosity more than the Change in Colour of the River _Dee_, Avon ddû, (i.e. _Thee_) which in the British Language signifies the _black River_, from the Appearance of its Waters, when seen from an Eminence running in their deep Channel between the Mountains of Wales; but which glides by Chester with a Silver Stream. This River,—Thanks to the cool Climate; not like the _green_ Mincius of Virgil!—had now acquired the unvaried Colour of _red Lead_. Nor coud he discover even the Appearance of Water; but merely that of a _broad red_ Line, twining in Meanders infinitely more serpentine than are expressed in Maps. [Sidenote: Cause of the Change conjectured.] Whether the Change arose from the Transparency of its Waters, when seen at the Height which was _apparently_ 7 Miles, _as will be noticed hereafter_, though the Barometer made it scarcely a Mile and Half, is uncertain. He was at first inclined to think, that the Rays, having suffered a double Refraction, were reflected to the Eye, from the reddish Sand which forms their Bottom, tho’, at the Depth of 7 Yards at an Average, above the Cause-Way, or _artificial_ Cascade near Chester Bridge: or possibly the Water of Rivers when seen at a certain Distance, may act as Water composing Clouds when view’d from below, at a certain Height and Angle; reflecting only the _red_ Rays: the rest being refracted, or absorbed. The Colours of Objects shone more brilliant and lively at that amazing Height, than if seen on a Level with themselves. Nor did the Eye seem to want the Aid of Glasses: as every Thing, that coud be seen at all, was seen distinct. [Sidenote: The City of Chester _blue_.] 45.The _Redness_ of the River Dee was curiously contrasted by a Change equally novel but more pleasing, in the Colour of the City of Chester, when seen directly from above, on a Scale not larger than the Plan of it, in Burdett’s Map. The Town was entirely _blue_. The highest Buildings had no apparent Height: their Summits were reduced to the common Level of the Ground. Nor was the Cathedral distinguished; nor any Tower or Spire discerned. The Whole had a beautiful and rich Look; not like a Model, but a coloured Map. The Roofs of all the Houses appeared, as if covered with _Lead_, in the most elegant Taste. Strangers may wish to be informed, that in most of the Northern Counties, the Buildings are covered with _blue Stones_ called +Slates+[12] found in the Mountains; instead of artificial _red_ Tiles, as in London, and the South of England. CHAPTER VI. BALLOON VERGING TO THE SEA. [Sidenote: Sympathy of the Spectators, on seeing the Aironaut verging towards the Sea.] Section 46. Before a farther Description of aërial Scenes is attempted, it woud be improper not to mention a Circumstance which happened on the first Ascent of the Balloon: and too strongly called forth the tender sympathetic Feelings, by raising, in the Minds of the Spectators, _alarming Apprehensions_ for the Safety of the Aironaut, on seeing the Balloon move gently towards the Sea. They were however, in a great Measure, soon relieved from their Anxiety: for, by rising into another Current, he escaped the Danger: skirting the Coasts of the River Mersey; which coud not be seen from the Balloon at the Distance of little more than a League, tho’ the Sun was supposed to shine the whole Time on the Water. The upper Current was, in Fact, rendered visible to the aërial Traveller, for more than two Hours before, and at the Time of his Ascent; by lofty Clouds of the second Stratum, flying in a safe Direction. CHAPTER VII. [Sidenote: Aërial Scenes continued.] Section 47. A Few Seconds of Time before the Balloon had attained its greatest Height; the Velocity of Ascent being every Instant retarded by the Escape of Gass thro’ the Opening;—the _remarkable Stillness_ which prevailed in so elevated a State of the Atmosphere, _apparently_ many Miles above all visible Vapour, far beyond the Sight of every living Creature, and where the human Voice was no longer heard from below; the larger Objects, with which the Surface of the distant Earth was covered, as Rivers Woods Inclosures, diminishing to the View, yet encreasing in their Beauty;—coud not but make a lively Impression on the Mind of the Aironaut. The striking Contrast and Novelty of his Situation filled him with unusual and pleasing Sensations. He had just left, for the first Time, his native Earth, where he had continued for a while the central Object to some _thousand_ Spectators; whose Eyes, he knew, were still turned towards him; that he was still the Subject of their Conversation: yet no human Figure met his Sight; no human Sound vibrated on his Ear. An universal Silence reigned! an empyrèan Calm! unknown to Mortals _upon Earth_. The Sky was painted with a purer, and more transparent Azure. The Sun shone hot, and with a brighter Lustre. His Beams were _white_ and sparkling: not surrounded with Haze or Vapour: but too fierce for the human Eye to look upon a second Time with Pleasure.[13] [Sidenote: Objects which filled the Mind of the Aironaut with Wonder and Delight.] 48. A Chearful Serenity filled the Breast of the Aironaut. In an erect Posture, and with the utmost Composure he gazed around: reflecting with Wonder and Delight on a Situation, where the +Beautiful+ and +Sublime+ were seen united, in a Manner perfectly novel and engaging. [Sidenote: Novel situation illustrated by a familiar Comparison.] If it be allowed, for the Sake of Illustration, to compare _great_ Things with _small_; he found himself suspended in the central Concave of an unmeasurable Crater Bowl or Bason; and considerably above the Rim or Margin, so as to peep fairly over it: for by looking _straight before him_, while the Balloon continued gently turning on its vertical Axis, he coud see quite round into the +Blue+. The Earth was the _Miniature-Picture_[14] painted on the Bottom of the Bowl, on the Inside. The Sides of the Bowl next the Bottom were rather obscure: as the Objects, on the Surface of the Earth not immediately under the Eye, being foreshortened, were indistinct, either on Account of their immense Distance, or by mere Accumulation of Vapours, and mixed with Haze and Cloudiness. [Sidenote: The Comparison carried on.] From thence to the Top of the Bowl, was fantastically grouped, spotted, and dash’d with Clouds dense and luminous, in the strangest and most grotesque Forms; still smaller and more numerous, as the Eye was more extended: The Rim or Margin ending, not in a fringed Border; but in a plain smooth Line; to represent the amazing Distance, at which, the upper Surfaces of _Clouds in Perspective_ lost all their rugged mountainous and fringed Shapes; and terminated even and smooth: making a perfect horizontal Ring in the Heavens, somewhat below the Eye of the Observer. The whole formed a glorious _Concave_: and the Imagination was lost in the surrounding distant Azure.[15] [Sidenote: _Apparent_ Altitude of the Balloon when stationary.] [Sidenote: The _apparent_ Heights proportioned to the _barometric_ Height.] 49. Considering more attentively the Dimensions of this vast Amphitheatre; as he long continued _apparently_ in the _same_ Spot, and seemed to himself a mere Atom floating _invariably_ in the Center of the empty Space; yet as a sole thinking Being there, whose Mind was bent on estimating the Extent of his View, so accurately defined by the circular Horizon of dense accumulated Vapour; and judging, as of other Distances, by _the natural Eye_ alone; pointing downwards on Objects which were only distinguishable when immediately below it, frequently no more than the Circuit of a Mile on the Earth’s Surface, the _vertical Boundary_ of the profound Abyss; all else being obscured by Haze, or removed from Sight by Volumes of intervening Cloud; he coud not divest himself of the Idea, but that the _apparent_ Depth below him was at least _seven_ Miles: _three_ from the Earth to the upper Surface of the superior Clouds,[16] and _four_ above them.[17] OBJECTION REMOVED. [Sidenote: _Improbability_ of a concave Appearance of the Clouds and Earth, _lessened_, by a familiar Illustration.] 50. Some may find a Difficulty in conceiving, how the whole Prospect of Clouds and Earth together coud put on a _concave_ Appearance: both of which were in Reality _convex_, with Respect to the Situation of the Observer in the Car. A familiar Illustration may help to remove the Objection. Imagine a Person placed in the Center of a Plain, or Carpet; extended every Way beyond the Reach of the Eye. If in that Situation he was gradually elevated; the _distant_ Parts of the Carpet woud _seem_ to rise with him: and those Figures of the Pattern woud alone be distinguished, that lay immediately below the Eye: the more remote becoming dim and faint. The whole would put on the Form of a concave Bowl; as soon as he had risen to so great a Height, as plainly to perceive the Figures of the surrounding Pattern more and more foreshortened, in Proportion to their Distance from the Center of the Carpet. CHAPTER VIII. Section 51. The Perspective of the Clouds was entirely new; and remarkable both for Beauty and Grandeur. The lowest Bed of Vapour that _first_ put on the Appearance of Cloud was of _a pure white_; in detached Fleeces; encreasing as they rose. They presently coalesced, and were aggrandized into +a Sea+ _of Cotton_, but more _white_; and _dazling_: tufted here and there by the light Play of Air, and gentle Breezes in every Direction: but where undisturbed, the Whole became an extended Firmament or _white_ Floor of thin Cloud, thro’ whose Intervals the Sun must shine with fiercer Gleam. The upper Surface was quite even: not blended with the Air above, but defined and separated with the utmost Exactness; being condensed by the Coolness, and checked in their Ascent, by the Levity of the superior Regions. Thro’ this _white_ Floor uprose in splendid Majesty and awful Grandeur, at great and unequal Distances, a vast Assemblage of _Thunder-Clouds_: each Congeries consisting of whole Acres in the densest Form. [Sidenote: Circular Boundary of the _celestial_ Prospect from the Balloon _above_ the clouds.] 52. Their conglomerate and fringed Tops rising, at different Distances, in circular Order, one above the other, to the Number of _thirty_: till they became imperceptible from their remote Situation: the Eye commanding an Extent of 102 Miles.[18] Their Form was, as if Pieces of Ordnance were discharged perpendicularly upwards into the Air: and that the Smoke had consolidated, at the Instant of Explosion, into Masses of Snow or Hail: had penetrated thro’ the upper Surface or _white_ Floor of common Clouds, and there remained visible, and at Rest. Some indeed had not wholly lost their Motion: continuing still to be lifted up. Others ponderous and sleepy, nodded, by mere Weight, their monstrous Heads. It seemed as if they had persisted in mounting upwards, till they coud rise no higher: their lower Parts pressing perpendicularly against the upper, which gradually swelled them out on _all Sides_. By partial and temporary Movements of the Air, some broad _unwieldy_ Caps lost the _vertical_ Direction of their Columns. The Columns likewise underwent a similar and gradual Change: rolling from their Pedestals or spiral Bases; and, at Times, assuming +every organized Shape+ that Fancy coud suggest. [Sidenote: Opinion of Philosophers.] 53. The imperceptibly slow yet perpetual Changes they underwent, strongly called to Remembrance, the Opinion of the great Berkeley,[19] as well as of the ancient Philosophers, that AIR GIVES FORM TO THINGS: scarcely a Breath of which seemed, however, to disturb their general Order. The Constitution of these enormous Masses was such as to reflect _some_ of the Sun’s Rays, and to transmit _others_ in a Variety of Colouring. [Sidenote: The Colours of the Thunder Clouds.] 54. The Parts next the Sun were of a _snowy_ Whiteness. Then of a _bright luminous Yellow_ melting into a _dusky Sulphur_: afterwards of a _Purple_. The Rays being now shorn; a Degree of Opacity and Transmission took Place throu’ half the Substance of the Cloud, which seemed of a _transparent Blue_ like the _Onyx_. [Sidenote: Delightful Tints visible only from the Balloon.] 55. These _delightful Tints_ must be ever eclipsed to a Spectator on the Surface of the Earth, looking upwards throu’ the gross Atmosphere that surrounds it; but highly _interesting_ to one who is suspended in a ratified and unencumbered Medium of the etherial Regions, where the Eye darts without Resistance above Clouds, and all visible Vapour. [Illustration: _A VIEW from the_ BALLOON _at its GREATEST elevation see Page IIII.a._ Publish’d May 1ˢᵗ. 1786, by T. Baldwin Chester.] Note: the Print, representing a circular View from the Balloon at its greatest Elevation, is taken from a Scene described in the above Chapter. CHAPTER IX. OTHER AËRIAL SCENES DESCRIBED. [Sidenote: Balloon Shadow traced on the Clouds.] Section 56. During the Time that the Balloon from being stationary at 23¼ (corresponding to the Height of about a Mile and a half) began to _decline_, which it must have done with a brisk Motion, imperceptible to the Aironaut at the Time, tho’ since recognized, on Account of the great Opening at the Bottom; he traced its _Shadow_ over the Tops of Volumes of Clouds below. It was at first small: in Size and Shape like an Egg: but soon encreased to the Magnitude of the Sun’s Disk; and woud have made a solar Eclipse to a Spectator looking from the Cloud: still growing larger, as the Balloon descended, or Clouds arose. But his Attention was presently called to another equally novel, but more captivating Appearance; that of an _Iris_ encircling the whole _Shadow_, at some Distance round it. The Colours were remarkably brilliant. This _celestial Phantom_ attended the Aironaut for a few Minutes: conforming, as a Vessel at Sea, to the Change of _Surface_; now plainly visible, now indistinct and disappearing; as it passed _throu’_ the _luminous_ or _shadowy Wave_ of Clouds _apparently_ at Rest. [Sidenote: The Iris, a Frame to the pictured Land, vanishes.] 57. The Clouds, in which this Phenomenon continued, were of the superior or second Stratum in Height, as in fair Weather; rare; of a transparent _Blue_ and purest _White_, alternate. At the End of four Minutes they dispersed, so as to admit an unexpected Sight of the pictured Land thro’ +them+, and thro’ the Place of _the Balloon-Shadow_; whose Form first vanishing, _the Iris_ remained, for a few Seconds, complete, and in resplendent Beauty. 58. _Írides_, of the same Kind, tho’ of less vivid Colours, are seen round the Moon, in a mild Evening; as thin light Clouds move slowly under it.[20] [Sidenote: Sun hottest when the Balloon was stationary.] 59. The Sun shone brighter and fiercer, when the Balloon was at its greatest Height: the _Heat_ piercing throu’ his Cloths, (which were of a _dark_ Colour;) while the Aironaut _stood_ with his Face from the Light. [Sidenote: Lunardi’s Flag thrown out, at the Height of a Mile.] The Mouth remaining open, it continued to descend, as appeared by the Barometer which had risen nearly to 24 Inches: at which Instant Mr. Lunardi’s _coloured_ Flag was thrown out, for the Information of a Friend; and that Spectators below might judge what was nearly the perpendicular Height of a Mile in the Air, according to Halley’s Table. [Sidenote: The Flag was seen to descend for 3 Minutes.] 60. The Flag was seen by the Aironaut descend for three Minutes: at which Time it became invisible. It fell, _not_ perpendicularly; but in large Spirals, and by Jerks; darting first on one Side, then on the other. The Resistance of the Air made it act as a Parashute. The Flag was instantly pursued, and taken up in a Field one Mile distant from Chester. The Descent of the Balloon must have been retarded, being four Pounds and a half lighter. [Sidenote: The Dove turned out.] 61. The Pigeon was then taken out of the Basket of Matting: Thermometer 54; Barometer 25³⁄₁₀. It trembled much. Being turned loose, it looked frequently up at the Car; but flew downwards in cylindrical Gyrations eight or ten Yards in Diameter, according to the Turn of its Head to the right, which seemed to rest in an oblique Attitude: the Wings and Tail continuing extended as much as possible, but without Motion, during its Descent. The Bird was out of Sight in a few Minutes: but continued, as _the Owner_ observed, full half an Hour, in the Air. CHAPTER X. [Sidenote: 4th Cannon heard.] Section 62. At 10 Minutes and a half past II. o’Clock, the fourth or last Cannon, a Six-pounder (to announce, by preconcerted Agreement, that the Balloon began to be invisible to Spectators in Castle-Yard, Chester) was distinctly heard by the Aironaut; but had no Effect on the Balloon: did not agitate it in the least: the contrary of which was expected. For the same Cannon, discharged the third Time at the Distance of 30 Yards from the Balloon, when it had risen a few Feet from the Ground; affected it so strongly, that the Aironaut was +then only+ obliged to keep himself upright, by holding the Cords with his Hands. [Sidenote: Balloon first invisible to the Inhabitants of Chester.] 63. At 17 Minutes past II. was heard the Sound of a Number of Voices, which it was then imagined came from Chester, as the farewel Salute after the last Cannon: but it was afterwards known that the Balloon did not become wholly invisible, till that Shout. [Sidenote: Distance of the Balloon calculated.] 64. From an Observation made by a Spectator in the Castle-Yard, just half an Hour intervened between the Discharge of the third, and of the last Cannon; as therefore the Report was half a Minute, or 30 Seconds[21] longer in reaching the Balloon; the Distance of the Balloon at the Time of the Report was _nearly_ six Miles and a half. [Sidenote: Chester seen as a _small_ Model.] 64. The single thin white Cloud of the first or lowest Order in Height that rendered Chester invisible to the Aironaut, was observed several Minutes before, _apparently_ to pass under the Balloon, retire from it, to approach, and expected to invelope, the _blue_ City of Chester: which for a long Time had been kept in View, and seen _obliquely_, under the _common_ Perspective, with a small Degree of Elevation above the Level of the Ground: suggesting to his Mind the curious and complete Model of Paris, exhibited some Years ago _on a small Table_, in many Towns of Europe. [Sidenote: The Sight _doubly_ deceived in the Distance.] The Cloud appeared, four Miles Distance at least from the Aironaut; below; and as if touching the City. The contrary Supposition, it seems, took Place, among the Inhabitants there: who thought, a Cloud, a Mile above them, had surrounded and inveloped the Balloon. [Sidenote: Condiments tasted as usual.] 65. The Pepper Salt and Ginger were tasted, and found to retain their usual Pungency: contrary to what Travellers have reported to happen on the Peak of Teneriffe. [Sidenote: Silk electric.] The small Hank of yellow raw Silk tyed to the upper Hoop, and hanging down from it, appeared _rough_, as if electric: and, tho’ drawn thro’ the Hand, continued _furred_ as before. [Sidenote: _White_ Flag wholly hung out from the Car.] 66. It was now thought a proper Time to finish the original Work of unwinding the remaining Part of the half Mile of Twine: which proved equally tedious, as at the first; and took up a considerable Time. When completed, the _white_ Flag was extended exactly half a Mile from the Car. [Sidenote: Cattle discovered from the Balloon.] [Sidenote: Ballast thrown out,] 67. Perceiving that the Balloon was descending very _briskly_, by the Appearance of Cattle in the Corner of a Field; first, _one_ of the two solid Weights was cast down: then the _other_. [Sidenote: Time in falling estimated.] A Return of Sound to the Balloon, from the lighter which weighed five Pounds, was heard in 130 Countings of a Watch, which made 120 of the same full Beats in a Minute. Before the Weight became invisible; it _appeared_ to move a good Deal out of the Perpendicular: owing either to an under Current; or to a Deception of Sight, respecting the horizontal Motion of the Balloon in a different Direction, during the Descent of the Stone. The other must have fallen in soft Grass, or otherwise: as it was not heard. CHAPTER XI. Section 68. At 28 Minutes past II. the solid Weights before mentioned were thrown out. At 29 Minutes the Barometer had fallen to 25 Inches. [Sidenote: Balloon reascending.] A Handful of Feathers were sent adrift, which fell quick: demonstrating _likewise_ the Ascent of the Balloon, a second Time: but, tho’ 12 Pounds lighter, it did not seem to regain its original Height: judging +merely+ from this Circumstance, that no more Gass escaped _visibly_ from the Mouth. [Sidenote: Apparent Size and Situation of the _white_ Flag.] 69. It is somewhat remarkable, that, on repeated Enquiries from unprejudiced Persons, the _white_ Flag, when suspended from the Car above 440 Yards, appeared 4 Yards long: and when at the end of the _half Mile_ Twine, seemed about 8 Yards long, to Spectators from below, in different Places: that sometimes it appeared before, and sometimes behind the Balloon: while to the Observer in the Car, it seemed regularly to follow the Balloon: unless when a _new_ Motion was impressed upon the latter: at which Time the _white_ Flag was situated almost under the Car: or when the Balloon changed its Direction; the Flag being _then_ not always _discoverable_. When seen _edgewise_ or _foreshortened_; it woud _appear_ to be _nearer_ the Car than it really was. [Sidenote: Effect of the _white_ Flag on the Balloon.] 70. As there was a Peculiarity attending the Situation of the _half Mile_ Flag, which may prove of singular Use in Airostation; it ought not to be passed over in Silence. The half Mile Flag hanging loosely from the Car; not perpendicularly under, but following it, frequently at an Angle of about 45 Degrees; shews that the Flag met a Resistance from the Air, unfelt by the Balloon: which out strip’d it, in Proportion to the _greater_ Surface which the Balloon exposed to the Wind. Taking also into the Account, that the Balloon remained in Equilibrio; while the Flag was subject to the Force of Gravity: which Force was restrained from Exertion, otherwise than as a _Vis Inertiæ_, to keep it always in a perpendicular Situation. The Resistance of the Air, acting in an horizontal Direction against the _Vis Inertiæ_ of the Flag, must have a Tendency to drive it back: which being ineffectual; the Flag must consequently _rise_; and in rising _will retard the Balloon_. A Power may therefore be communicated to a Balloon, in the Direction of the Wind, which shall _retard_ its Progress throu’ the Air: a Subject which seems capable of farther Prosecution. CHAPTER XII. [Sidenote: Beautiful Effects of the _white_ Vapour on the Prospects below.] Section 71. From 28 Minutes after II, till the Balloon had passed over the _Forest_ of +Delamere+, and the steep Crag of +Helsbye-Hill+; thin light semi-transparent Vapours, which seemed to be collecting at a _vast Depth below_; moving slowly in all Directions; rising to great Heights, falling, melting away, and again condensing;—(the Land, one while covered with a +white+ _Veil_; then _caught_ thro’ Openings for a few Seconds; the Objects appearing more distinct and _coloured_, from being seen in detached Groupes and single _Pictures framed_ and _enshrined_ in fleecy +Vapour+; _now again_ discovered by a Glance of the Eye, and _then_ repeatedly escaping from the Sight;)—+wonderfully+ heightened the Grandeur, Gaiety and _inimitable_ Beauty of the _ever varying_ Prospects. An Illustration taken from Scenes _abroad_. 72. Appearances of a similar Kind are frequent in the _noble and venerable_ Structures appropriated for divine Worship _abroad_: whose Walls are decorated with the _finest Paintings_; the Subjects solemn and _engaging_; suited to inspire a _chearful Devotion_. While the inferior Clerics perfume the Garments of the _Priests_ officiating and offering Incense before the _high Altar_; which is ornamented with _full-Length Portraits_ in the richest Drapery, of Persons whether male or female, reputed of sound Morals and exemplary Piety; accompanied by Guardian Saints and happy Angels;—Columns of _white_ Smoke, wafted from _Silver_ Censers, rise to a certain Height in slow _majestic_ Movement, before the Eyes of the _kneeling_ Suppliants, who are _instantly shut out_ from the _enchanting_ View; till the Clouds dispersing, shew by _Intervals_, a Glympse of the _celestial_ Prospect, and of the _higher_ Orders of Beings, who _look down_ with _Complacency_ upon them; and seem _actually_ +descending+ throu’ Openings of the Clouds which _appear_ at Rest. CHAPTER XIII. [Sidenote: 2d Balloon-Iris.] Section 73. At 33 Minutes after II, the Balloon-Shadow was _again_ the Center of a brilliant _Iris_, painted at some Distance round it on Clouds below. [Sidenote: Bottle filled with _light_ Air.] 74. One of the Pint-Bottles for light Air was prepared (as in Article 14, of Section 12;) and dropped from the Car. The _Water_ it contained was poured down, to observe the Effects of _Air_ and _Light_ on the Drops. The Air did _not_ at that Height oppose a Resistance sufficient to break the Stream into _small_ Drops. Nor did they seem to coalesce: remaining, while they continued in Sight, of the same Size; some very large, others less so; and at the same _relative_ Distance, as when they first left the Bottle. The Colours seemed _stronger_ than usual. It may be _here_ observed that none of the Bottles were returned; tho’ found, and a Reward promised. The Country People, as soon as they saw a Bottle; imagining it must contain some Liquor, immediately contrived to open it: by which Procedure, the Intention of the Experiment was frustrated. The Bottles, which are _dangerous_ Companions even without Liquor, shoud, notwithstanding, be left in the Car: at least till the Time of _landing_ the Balloon. [Sidenote: Burton and Flint seen at the _first_ rising.] 75. While the Balloon was _first_ rising; a gentle Motion of the lower Current of Air carried it immediately towards the Sea. (Section 46.) At which Time, the Aironaut by a _Glance_ discovered the Mouth of the River Dee, four and five Miles wide, _yawning before him_: the Prospect extending to the Sea, as far as the _Smoke_ from the Lead-Works near a Place called Flint on the Welch Coast; and to Burton-Head on the Wirral Side; distant ten Miles from Chester. He has since been informed; that the Balloon seemed to +rest+, for a few Minutes, in the Air: and then _return slowly_ over Chester. [Sidenote: Balloon in a _quiescent_ Bed of Air.] It is therefore more than probable, that as the Balloon continued to ascend; it was _becalmed_ in a _quiescent Stratum_ or Bed of the Atmosphere, which existed for a certain Depth or Thickness, between the lower and upper Current: and that the Direction of the Balloon was changed; the Instant it arrived within the Influence of the _upper_ Current. [Sidenote: Of _rowing_ the Balloon to any Point of the Compass.] Consequently, with a proper Apparatus to ascend and descend _at Will_, without Loss of Gass or Ballast; the Balloon woud have remained suspended _invariably_ at the same Height, and _vertically_ over the same Spot of Earth: or, with propulsive Machinery; might, on the same Level, have been _rowed_ to any Point of the Compass. [Sidenote: The Balloon, influenced on its Approach towards _Water_.] 76. In passing _only_ +across+ Trafford Meadows, three Miles from Chester; the Balloon lost its usual progressive Motion over the Country: for more than a Quarter of an Hour, following the Course of the River Goway to the West North-West, and towards the Sea, as at Chester: turning gently backwards and forwards round its own Axis, near the Villages of Great and Little Barrow: and making Curves over the Meadows, whose Breadth at those Places was about a Mile. [Sidenote: Its Progress marked.] The Balloon then returned into its former Direction: inclining, _again_, towards a Brook and Meadow near Alvanley: passed Eastward a little to the left of Manley (_white_) Mill: crossed the Forest of Delamere, and Crag of Helsbye, (about twice the Height of Shooter’s Hill, near London;) whose lofty Summit was _apparently_ reduced to a common Level with the Valley made by the River Wever, and with the adjacent Sea Marsh. Nor coud it have been distinguished by a Stranger, as an _Eminence_. [Sidenote: Hills and Vallies on a Level.] Indeed, the Wood near Kingsley, which grows on a sloping Ground, skirting the Hill, and _from_ the Sun, put on a _dusky_ Hue; and the Tops of the Trees a _darker Green_: this Difference of _Colour_, conveyed the _faint Resemblance_ of a rising +Slope+. A _real_ Knowledge of the Country probably contributed to aid the Imagination in this Distinction. Note: the Print representing a View of the Balloon over _Helsbye Crag_, refers to a Scene in the above Chapter. CHAPTER XIV. [Sidenote: 39 Minutes past II, Frodsham Town and Bridge seen.] Section 77. At 39 Minutes after II, Thermometer 60, Barometer 23¾, corresponding to the Height of a little more than a Mile,[22] _the Vapours dispersing_, discovered the Town of Frodsham, and Bridge over the Wever distant from the Town one Mile: the Balloon still continuing at a vast Height; having risen imperceptibly from the Time that the Ballast was thrown down. From a Conversation held the next Morning at Frodsham, with some intelligent Persons who had descried it gliding gently throu’ the Air; the Balloon appeared so extremely _minùte_, that it was thought impossible to be the +one+ expected the same Day to rise at Chester with an Aironaut. [Illustration: R. Newton } Arm. design et pinx. Stothard delin. T. Baldwin} Sharp sculps. _The_ BALLOON _over HELSBYE HILL in_ CHESHIRE _see page IIII b._ Published May 1ˢᵗ. 1786, by T. Baldwin Chester.] [Sidenote: Half Mile _white_ Flag like a Feather.] To use their own Expression, “_it coud not have been larger than a Bladder, if they had seen it on the Ground_.” The same Persons observed the _white_ Flag, like a _Feather_ about 8 Yards Distance from the Balloon. A second Air Bottle was thrown down. [Sidenote: Course of the Balloon traced to shew the Manner in which it was affected by the _Water_.] 78. The Town of Kingsley being to the East; Frodsham-Bridge half a Mile to the West; the Conflux of the Rivers Wever, and the _wide_ Mersey falling into the Sea one Mile farther Westward; the Balloon proceeding in its usual Course over the Country in the _upper_ Current; began to be _impeded_, on its vertical Approach +across+ the Meadows to the Wever; was actually stopped; and being _entangled_ by the _River_, evidently changed its former Direction: imitating, if possible, _its_ Meanders; or at least making Gyrations in Circles of different Diameters, at the same Time turning different Ways round its Axis: describing Curves, something similar to that of the Moon round the Earth in her Orbit; or of Saturn, Jupiter, and Mars, as those _Curves_ are delineated in the _Prints_ of Long’s Astronomy:[23] the Course of the River being its _changeable_ Center. 79. It is to be observed, that if the Balloon had continued to pursue its _former_ Course; no Danger was to be apprehended of its falling on the Sea, or on the broad Branch of the River Mersey towards Warrington. On the contrary, it must have gone into the Heart of the adjoining County, and passed near Manchester. It is likewise worthy of remark; that unless a Fragment of light Vapour intervened for a few Seconds; the Country immediately below the Observer was _continually_ illuminated by the Sun’s Rays: tho’ none but the larger Objects were distinguishable at the Bottom of the profound Abyss, _more_ than two Miles in Diameter at one View: that being the utmost Boundary of the circular Prospect below. [Sidenote: Circularity of Prospect below, bounded by _Vapour_.] 80. The _Sea_ tho’ known to be _near_ by the Dashing of its Waves upon the Shore, which were plainly heard, was totally eclipsed: as if by Haze or Vapour, which began to be accumulated only at a certain Height _below_ the Balloon; yet in such a Manner as _not_ to prevent the solar Rays from penetrating throu’, and shining bright upon the Water. 81. There was now sufficient Leisure to trace the incredible Variety of most beautiful _Curves_, into which the Stream had worked the Bed of the River Wever in a Course of _Time_, and in the Compass of a few Miles: an Appearance which _demonstrates_ the Incorrectness of +Maps+. Some _actual_ Clouds presented themselves in detached Groupes over the Land: and the _Land_ itself _shone_ plainer throu’ the Intervals, than in Places near which _no_ Clouds appeared. [Sidenote: Sight of Warrington.] 82. On reconnoitring the scattered Town of Frodsham, which like Chester was of a _light_ +Blue+; the Balloon moving _by Intervals_ round its Axis, the Prospect seemed to _open_ on a _sudden_; and the Aironaut coud discover the Town of Warrington: the Plan of which was small, neat, but of a _darker Blue_, inclining to _Grey_: the Slates[24] there used being almost peculiar to the County of Lancaster. 83. From this _Enlargement_ of the Prospect over Land, he imagined that the Balloon was either _gently_ descending; or that it appeared throu’ the _clear_ Intervals of _actual_ Clouds _below_ him. [Sidenote: Pleasurable Circumstance peculiar to the Balloon.] 84. He had Time however to make the following Remarks. Cattle, if grazing in the Meadows, were not distinguishable; or at least were not distinguished. It was in vain to look for Sheaves of Corn, or Hattocks on the Ground: possibly from a Sameness of _Colour_ like the growing _Stalks_, and _Field_: or _protruding_ but a small Degree of +Elevation+; tho’ the _Shadow_ even at _twelve o’Clock_[25] was something _longer_ than the _perpendicular_ Height of +each+ Object.[26] Noises of Carriages along the great public Road; especially Waggons and Carts +heavily+ laden; (the Gratings of whose _Wheels_ against the _Stones_ seemed uncommonly _harsh_;) were discriminately heard, tho’ not _discoverable_ by the Eye. Numbers of human Voices were almost +continually+ huzzaeing: except while +stationary+ at the first Rise; when +all around+ was wrapt in the Sublimity of +Silence+; which afforded a pleasurable Contrast;—diffusing a +delicious Calm+. A third Bottle of Air was thrown out. CHAPTER XV. [Sidenote: Balloon over Aston-House, at 4 Minutes past III, and near a Mile high.] Section 85. At 4 Minutes past III, the Balloon remained _vertically_ over the River, and over the elegant Mansion called Aston. [Sidenote: Wind _below_.] 86. A Wind was heard +below+ for a few Seconds: and the Air felt a _little cool_. Thermometer 55, or Temperate: Barometer 25½, corresponding to the Height of near a Mile.[27] [Sidenote: The Balloon going to Sea, determined the Aironaut to _descend_, in Hopes of finding a Sea-Breeze in _Time_.] 87. The Balloon continuing its eccentric Movements from _Side to Side_ across the Meadows; yet still gliding _down_ the River, in a North-West by North Direction, almost at right Angles to that which it _before_ had held; consequently _towards_ the Sea, and in a Line which continued must pass throu’ the Center of the Channel: some Step it was necessary to take, and +soon+. By throwing out Ballast, the Balloon woud instantly rise: but it woud probably, as _before_, rise into +a Calm+, and therefore _descend_ nearly in the same Line: which woud merely _protract_ the Time till the Balloon had reached the Center of the Channel: where, having no Resource, the Ballast being then expended; there might be some Risque in waiting for a Vessel, tho’ the Balloon woud not for +several Hours+, have lost its _levitating_ Power, so as to have sunk with the Aironaut. To him however it immediately occurred, that there might be an +under+ Current of Air, as usual in the Middle of the Day, blowing from Sea to Land: and, that if the Balloon was made to descend +quickly+ into the Sea-Breeze; it might, in a few Minutes, be carried so _far_ within the Country, as to be _soon beyond_ the Influence of the _Sea_ and _River_: and +then+, by throwing out some Pounds of Ballast, woud return into the _upper_ Current, and pursue a _safe_ Course towards Manchester; or even towards Prescot and Liverpool, if an easterly Wind prevailed _above_. 88. In Consequence of these Expectations; he looked downwards _towards_ the Sea, _then_ wholly _invisible_; tho’ the Murmuring of its Waves was _more_ plainly heard. [Sidenote: Smoke blown to Land by a Sea-Breeze.] +Thick Smokes+ were distinguished issuing from _different_ Places along the Marsh near the Coast: and _apparently_ skirting the Ground, as if impelled by a _brisk_ Wind from the Sea. 89. No Time was to be lost. The Balloon having reached the Cascade; and continuing to move more regularly along the Course of the River, past the _Bridge_, and proceeded to _Rock-Savage_. [Sidenote: The Balloon still going to Sea, the Mouth was opened.] 90. The Neck or _Mouth_ which remained shut, by its own Pressure against the Outside of the upper Hoop, as _it_ lay over it; was instantly brought within the Hoop, and set +wide open+ in a perpendicular Situation. Not more than a Couple of Minutes had elapsed before Sounds were more audible and louder. Cattle and Corn in the Fields became visible. [Sidenote: Ballast in Hand ready to throw out.] 91. The Observer very deliberately stooping to put down his Card and Pencil; with his _left_ Hand grasping the Hoop of the Car, and with his Right holding a Sand-Bag, to throw over as he approached the Earth; found that the Balloon was _influenced_ by an +under+ Current blowing from the Sea: and marked his Progress by the half Mile +white+ Flag; whose Stretcher having acquired a Position parallel to the Plane of the Horizon, placed the Flag in an excellent Point of View: the Balloon _towing_ it _apparently_ with a _slow_ Motion, over the distant Tops of the _dark-green_ Trees. CHAPTER XVI. BALLOON DESCENDING. [Sidenote: Air chilly. Therm. 55; Barom. 26½.] Section 92. No sooner had the Balloon _descended_ within the Influence of the _Sea Breeze_, than it became +instantly+ _condensed_ by a certain +chilliness+ which +then+ began to prevail. [Sidenote: Balloon in the _under_ Current.] 93. This Height has _since_ been considered as the +Level+ of +fleecy Vapour+, +Scud+, or lowest Stratum of Clouds, in +bright+ and +warm+ Weather.[28] No _visible_ Clouds were presented _near_ the Spectator. On the contrary, they seemed to _shrink back_ to the Distance of a Mile round the Eye; and then _immediately_ appear above it, the Balloon continuing to descend. Nor did any _circular_ Horizon of the Earth shew itself; till the Balloon had reached below this Level: viz. Barom. 26½, Thermom. 55. i.e. Temperate. Prospects were most +extensive+ and beautiful at this Altitude: which the Barometer estimates at full half a Mile.[29] Looking again at the Barometer, scarce a Minute afterwards; it had risen to 27. [Sidenote: Sudden Effect of cool moist Air on the Balloon.] 94. The Condensation by Chill and Moisture, and quick Contraction of _its_ Dimensions acted like a _Charm_ on the _Balloon_. In a Moment; as if dropped from the Clouds, the +Sea+ suddenly presented itself.[30] It seemed +near+, and of a +red+ Colour. _Circular_ Landscapes of the _distant_ Countries filled the Eye. Almost the whole Extent of the Channel was a perfect Calm: and rather _dazled_ the Sight. But from the Peninsula of Hale to that of Runcorn, and upwards, a _partial_ +Breeze+ from the North-West _ruffled_ the Surface (which was there of a _dark_ and menacing Complexion;) and seemed in its Course to have reached and _influenced_ the Balloon: whose Descent proving _more_ rapid than was expected; the Sand-Bag tyed up, weighing 12 Pounds, was opened, and the Sand _dispersed_. [Sidenote: Ballast thrown down, 12lb. and 12lb.] 95. The Aironaut continuing as before to _stand_ upright in the Car, and having resumed his Card and Pencil; Thermometer _again_ at 55°, on finding the Descent not _sufficiently_ retarded, wrote swiftly, “+no more remarks, mind the ship+:” meaning the Balloon: and briskly stooping for the second Bag of Sand, weighing likewise 12 Pounds, _dispersed_ it by _Handfulls_ in the same Manner. [Sidenote: Descent at first rapid.] 96. The circular Mouth of the Balloon continuing wide open, at about 18 Inches Diameter; so much _cool_ and _moist_ Air rushed in during the Descent; that, tho’ its Momentum or acquired Motion was retarded by _Dispersion_ of the Ballast, it had not yet recovered an +actual levity+: being too near the Ground before the second Bag was discharged. _Presuming_ however that 24 Pounds Weight of Ballast thrown out, was sufficient to break the Fall, tho’ in a cool moist _condensing_ Atmosphere of _pure defloguisticated_ Air; the Event of _landing_ was _waited for_. [Sidenote: A _depressing_ Torrent of Air on the Balloon.] It has been _since_ imagined that a _heavy_ +depressing+ torrent of _cool_ Air took Place from the North-West at a certain Height over the Water, and _assisted_ the Descent of the Balloon. [Sidenote: The Balloon descended with a _rushing_ Noise.] 97. In order to judge with what Rapidity the Balloon descended, when so +low+ as to be within the Influence of the _under_ Current, while the _cool moist_ Air rushed in at the Bottom, and most probably pressed out the Gass; the following Intelligence has been communicated by a Person of Veracity. [Sidenote: Anecdote shewing the Rapidity of Descent, at first.] As two credible Farmers were working, with their Servants, in the +harvest+; on hearing a hollow, rushing Sound in the Air, which they took to be a _Whirl-wind_, or _distant Thunder_, and which seemed every Moment to encrease and approach them; they all retreated under a large Oak. While there, they first perceived the swift Descent of the Balloon. Two, who were afraid of Thunder, then began to take Courage, boldly exclaiming they shoud never fear Thunder again, since the _Falling_ of a Balloon coud be attended with so _terrible_ a Noise. CHAPTER XVII. BALLOON STILL DESCENDING. Section 98. The Car, gliding _over_ Trees in the _farther_ Hedge-Row of a Grass Field, glanced on the Ground. [Sidenote: Caution on Landing.] The Aironaut, being _prepared_ for the Event, supported a _Part_ of the Weight of his Body by his Hands, grasping the _upper_ Hoop. The Balloon _stooping_, and declining from the North-West Breeze, drew the _upper_ Hoop out of the Perpendicular: by which Means, the Bottom of that Division of the Barometer-Frame which contained the _Tube_, pressed against the Bottom of the Car on the Ground, was _separated_ from the remaining Half of the Frame, and fell on the _Grass_. [Sidenote: More Ballast parted with, viz. seven Pounds.] The Balloon, then rising with an elastic _Bound_, elevated the Car a few Yards, and descended to the Ground, but _more_ gently than before: rose again; and the Aironaut perceiving that the progressive Motion of the Breeze was bringing the Balloon near a _third_ Hedge; took up his Knife, (which lay by him _ready open_ for Use) and _cut away_ the remaining Half of the _Barometer-Frame_; threw out the _Basket with the Bottles_, and _Tunning Dish_; the _Speaking Trumpet_; the _Woollen Gloves_, the remaining half Mile of _Twine on the Reel_.[31] The Car _cleared_ the Hedge, and _slightly_ for an _Instant_ touched Ground, the _third_ Time. [Sidenote: Farmers offering their Assistance.] 99. During these Operations; the Aironaut had observed different Persons in Motion towards him, who proved to be several _Farmers_ and _Labourers_ who had run themselves out of Breath to _overtake_ the Balloon. One asked the Aironaut, whether he intended to alight; and was answered, “_Not for any Time_.” [Sidenote: Proof of the _gentle_ Descent.] 100. The Car alighted each Time so _smoothly_, that neither the _Watch_ nor _Thermometer_ that lay near each other on the _green_ Bays at the Bottom, were displaced. Nor was the _Glass Tube_ containing the Quicksilver, separated from the Division of the Frame in which it was originally fixed: but the whole was brought back, a few Days after, in a perfect State: except a small Hole, made in Consequence of the inverted Situation of the _Mercury_ in Vacuo, _which_ fell against the Top of the exhausted Tube. [Sidenote: Balloon landed near Frodsham.] The Car _first_ landed at 28 Minutes past III, in a Field belonging to a Farm called Bellair, in the Township of Kingsley, near two Miles East by South from the Town of Frodsham, and twelve from Chester. END OF THE FIRST PART. AIROPAIDIA. THE SECOND PART OF AN AËRIAL EXCURSION FROM CHESTER THE EIGHTH OF SEPT. 1785. CHAPTER XVIII. RE-ASCENT OF THE BALLOON. Section 101. Bellair-Meadow: half past III o’Clock:[32] Thermom. at 55: _bright_ Sun: _few_ Clouds in Sight. [Sidenote: Balloon rapidly re-ascending.] The Balloon being now 31 Pound lighter; taking a Direction +from+ the Sea-Breeze into the Country, and _again_ towards Aston-Hall[33]; mounted up like a Sky-Rocket, with accelerating Velocity: its upper Parts _nodding_ from Side to Side, as if to _shake off_ the _resisting_ Column of Air immediately above it. [Sidenote: The Neck tyed.] [Sidenote: Drawing the Valve, while Mouth of the Balloon is _open_, shewn to be _dangerous_.] 102. There being no proper Opportunity of closing the Mouth of the Balloon on its _near_ Approach to the Sea, or during the _Swiftness_ of its Descent; tho’ there had been _frequent Inclination_ to attempt it; this _little_ but +essential+ Work was instantly resolved upon. And the more so, as the Mouth had continued open _from_ the first: and as Mr. Lunardi did not _happen_ to mention this Circumstance: the Utility of which, tho’ _too late_ to be put in Practice, had, but a few Minutes before, very plainly suggested itself. His Directions were, to _open_ the Valve in order to descend: which woud _possibly_ have _encreased_ the Rapidity of Descent: and, by _introducing_ a thorou’ Air _upwards_, while the Motion of the Balloon was in a _contrary_ Direcion, might have occasioned a _dangerous Rupture_ of the lower Parts of the Balloon, _which_ actually took Place in a preceding Excursion. [Sidenote: The Balloon drawn _sideways_.] 103. The Balloon, tho’ rising _quick_, seemed _not_ to be wholly disengaged from the Ground, but to have received a Check; and to _lean_ a little out of the Perpendicular: particularly the Car, which was evidently drawn a _different_ Way _from_ the Balloon. [Sidenote: The half Mile _white_ Flag impeding the Balloon.] On perceiving that the half Mile _white_ Flag, fastened to the _upper_ Hoop of the Car, sensibly impeded the Elevation of the Machine, by _trailing_ along the Ground, (the Balloon being yet within the Influence of the Sea-Breeze, or _lower_ Current of Air;) the Question was, whether it woud not be imprudent to suffer the Balloon to rise near half a Mile, before the _white_ Flag; was _disentangled_ and free to follow it. For as neither the _Twine_, nor the _lower Cords_ of the Balloon were of Silk; the Twine having lain on the Trees or +moist+ Ground, might become a +conductor+ from the Earth to any Stratum of Air that had +less+ or +more+ than what is called its natural Quantity[35] of the +electric+ Fluid. [Sidenote: Twine _cut_, lest it shoud prove a _Conductor_ of _Electricity_.] Adding to the above, a Wish to rise higher the _second_ Time than the first; stooping for the Scissars, the String was _cut_: reserving a Remainder to tye the Neck of the Balloon; which was immediately done by gathering the Parts of the Balloon into the Hand, wrapping a Couple of Yards loosely round, and tying them on a +slip+ or +bow+ Knot: one End of which was +purposely+ left hanging three Feet downwards, to _untye_ instantly on Occasion. [Sidenote: Additional Levity of one Pound.] This additional Levity of _nearly_ one Pound, gave the whole Quantity of Ballast thrown over in a _few_ Minutes, _nearly_ 32 Pounds. [Sidenote: Remarks on the Balloon.] 104. The intelligent Farmer who stood near the Balloon, when it alighted at Bellair, had observed it for some Time _before_ near the Sea, and marked its Return, as coming _apparently_ from _Overton_. At first, which was _more_ than five Minutes before it came to the Ground, it seemed to him as if it coud not have been _larger_ than a Bladder. He saw it reascend, first _sideways_, then upright; moving from the Sea. Afterward it rose _rapidly_, and rather _towards_ the Sea and Warrington, distant twelve Miles. [Sidenote: _Apparent_ Size of the Balloon, when seen from _below_.] He watched it for a Quarter of an Hour: and caught it by Intervals, near and above a Cloud in the _blue_ Sky, at so great a Height that it looked like a _Lark_: and at last: so _small_ that the People who stood near him coud none of them regain a _Sight_, when they had once lost it. 105. The remaining _white_ Flag was unfolded, and tyed to one of the Balloon-Cords attached to the _upper_ Hoop, at a proper Distance to _play_ freely in the Wind: and, notwithstanding all that has been said to the contrary, shewed _instantaneously_ and _plainly_ the corresponding Changes made by the Wind in different Directions. And, as the Breeze was accompanied with a Sensation of _Coolness_ against the Face of the Aironaut, looking towards that Quarter from whence the Wind came, as indicated by the Flag; (which Quarter was not in a Line with the Path of the Balloon;) the Flag must have shewn that the Change was made by the _Air_ in _its peculiar_ progressive Direction, and not by _its_ Resistance or Progress in the Track of the Balloon. [Sidenote: _Balloon_ moving in a Direction _different_ from that of the _Air_.] 106. It is probable that the _Momentum_ of the Balloon, acquired by its centrifugal or accelerating Force upwards, might have kept it in _one_ Direction, while it continued to rise throu’ _different_ Currents. CHAPTER XIX. BALLOON STILL RE-ASCENDING. [Sidenote: Balloon vertical over Aston, for 8 Minutes.] Section 107. The Balloon being now _wholly_ unconfined, continued to _rise_ with _great_ Rapidity: crossed the Meadow in the Sea-Breeze, and remained as _before_, for 6 or 8 Minutes,—by Intervals _gently_ turning on its Axis—almost wholly _vertical_ over Aston-Hall, but rather more to the _Eastward_ of it. The Country still exhibited _bright gay_ and +extensive+ Prospects. 108. _Three_ Sail of _Vessels_ appeared in the +Channel+: and _four more_ were sailing down the River Wever, _apparently_ just under the Balloon, diminishing to _mere Cockle-Shells_, or like _Boats_ which have _no_ Rigging. Shouts continued. Corn and Cattle were visible in the Fields and Meadows. Aston, tho’ a _large_ and _elegant Mansion_, appeared like a _House_ which Children _build_ with _Cards_. [Sidenote: Chilliness felt at the same Height in re-ascending.] 109. A Chilliness in the Air was again perceived in rising, as he imagined, to the _same_ Height at which he felt it in _descending_, indicated by the Thermometer at 55°. (Sect. 92.) He then found himself inclined to taste the _Brandy and Water_, ready mixed by his Order, and to eat a Biscuit: but on putting the Liquor to his Lips; thought it _too_ strong, so drank none, nor eat any Thing. 110. The _three_ Sail, and the +Channel disappeared+. [Sidenote: River _red_.] The River put on a deep _red_ Colour, like the Dee. Its Meanders seemed to _encrease_; as its Width _diminished_ to a _broad_ Line. Its Water was _lost_ to the Sight. Corn and Cattle were no longer distinguishable. The House at Aston was yet a beautiful tho’ minute Object: the Balloon moving several Times round it; as if loth to quit _that_ and the River. The Cascade was become a _white_ Line: and the _fine_ Bridge below, a _yellow Straw_ crossing the broad _red_ Streak. Of the _four_ Vessels in the Wever, _not_ an _Atom_ visible. The Shouting entirely ceased. [Sidenote: Rocks Woods and Meads reduced to a _coloured Plain_ of the _mellowest_ Tints.] 111. The _blue_ scattered Houses, wide public Road called Sutton-Causeway over Frodsham Marsh, the Meadows Fields and Woods, the _lofty_ Hills, Helsbye Crag and Halton-Tower, were _reduced_ to _one common_ Level; and diminished to the Size and Semblance of a _coloured_ Map, but it was the _superb_ and _finished Colouring_ of +Nature+. [Sidenote: Balloon higher than at the _first_ Ascent.] 112. Ceasing to look _down_ on the smooth +Lawns+ _below_, which were _now_ of the richest and _fullest_ Patterns, seen as throu’ the _small_ or inverted End of a common Perspective-Glass, and _spun_, as it were, to a _fine Thread_; Pleasure and Delight, tho’ of another Kind, fill’d the Imagination of the Beholder: who, raising his Eyes on a Level with himself, so as to look _straight before_ him; found that the Balloon had _already_, and almost beyond his own Belief, soared to so amazing a Height in the Atmosphere, as to raise him _far_ above the +Rim+ of the immense Bowl or Crater; and that it was still _stealing_ with _Rapidity_ upwards. [Sidenote: Contemplation of the Prospect.] 113. During the Contemplation of this magnificent Prospect, a _perfect_ Calm took Place, and _soothing Silence_ reigned. And thus; for _a while_ detached, _far_ detached from Earth, and _all_ terrestrial Thoughts; wrapt in the _mild Azure_ of the _etherial_ Regions; suspended in the Center of a vast and almost endless Concave; come, as a _mere_ +Visitor+, from _another_ Planet; surrounded with the stupendous Works of _Nature_, yet _above_ them;—the +glorious Sun+ except, which enlivened +all+, and shone with pure celestial Lustre;—a peaceful +Serenity+ of _Mind_ succeeded; an +enviable+ EUROIA.[36] An Idea of which it is not in the Power of Language to convey, or to describe. CHAPTER XX. [Sidenote: Breathed freely. Thermometer 60.] Section 114. Respiration at so great an Altitude was perfectly free and _easy_: _forced_ Trials being made for Information on that Point: a Sensation of Levity seemed _rather_ to be communicated by the Air to the Lungs: but this might be the Effect of the Imagination. It was however a _curious_ Circumstance to find the Breath _not_ visible; the Thermometer rising +again+ to 60. Nor did the Pulse seem to be quicker than _usual_, in this elevated tho’ _inactive_ Situation. [Sidenote: Thunder-Clouds as before.] [Sidenote: Fairy Landscapes striking.] 115. The Perspective of a vast Series of Thunder-Clouds of a _sulphúreous_ and _metallic_ Tinge, placing themselves in Ranks, each beyond the other, in _bright_ and tremendous Order, and a Sort of _Battle-Array_, beyond Conception _grand_ yet _beautiful_; coud not pass _under_ him without Notice. The immense circular and visible Distance of the +nebulous+ Horizon, extended +now+ 102 Miles _at the least_ round the Eye, as already mentioned (Sect. 52); was a grand Source of the Sublime. Nor did the contracted View of the Landscape below fail, in Turn, to _regain_ an Attention to its _indiscriminate_ yet _pleasing_ Scenery. 116. +On a sudden+ he was called back to himself. [Sidenote: Bladders _crackling_.] Several of the +Bladders+, which were tyed round the Car, in Case the Balloon shoud _alight on_ the Sea, and were +dry+ on the Outside, began at the same Instant to +crackle+; being greatly distended by the Air within. When pressed with the Hands and Fingers, they felt extremely hard, and _ready_ to _burst_. [Sidenote: Balloon _bloated_.] On looking upwards at the Balloon, it appeared +greatly+ inflated: the external Pressure of the surrounding Air being _much lessened_, in so elevated and _rarified_ a State of the Atmosphere. [Sidenote: Balloon _quilted_ by internal Pressure.] 117. The Balloon _pressed_ in an unusual Manner _throu’_ the Meshes of the Net, quite round. [Sidenote: Balloon shorter and broader.] 118. The Shape was much altered by this Distention of the Sides: and its _perpendicular_ Diameter _shorter_ than before. [Sidenote: Neck 8 Feet above the Car.] 119. The Neck or _Mouth_, which was _tyed_, had actually risen _upwards_, and was +then+ near _eight_ Feet _above_ the Bottom of the _Car_. [Sidenote: Neck cut off in a former Excursion.] 120. It was not known till afterwards, that Mr. Lunardi on his second aërial Voyage from Liverpool, had been obliged to cut off the _lower_ Part of the _Neck_, weighing upwards of _two_ Pounds and a _half_, in order to lighten his Descent near Tarporley in Cheshire; and that he had not _Silk_ sufficient to repair the Loss. CHAPTER XXI. [Sidenote: An Attempt to reach the Twine by _climbing_ on the Car.] Section 121. In vain did the Aironaut strive to reach the _Neck_ of the Balloon, from the _Car_. Attempting to put his Feet on the _opposite_ Sides of the _lower_ Hoop, by grasping the _upper_ with his Hands; he coud not in _that_ Situation raise himself so high _as before_; nor let go his Hold with _either_ Hand. He then stepped _down_ into the Car. The Agitation of _which_, brought within the Reach of his Hand, the loose _End_ of the Twine (_purposely tyed on a Bow or Slip Knot_) that had stuck to one of the Side-Cords, and held the _Center_ of the _Neck_ rather _out_ of the Perpendicular. CHAPTER XXII. BALLOON AT ITS GREATEST HEIGHT. [Sidenote: Mouth of the Balloon opened.] Section 122. Being cautious how he suffered the +lightest+ Gass to escape throu’ the Top of the Balloon, which must have happened in drawing down the String of the Valve; yet apprehending the +Possibility+ of an immediate Rupture at its +present greatest+ Elevation;—glancing his Eyes _around_ to take a +farewel+ View;—he _pulled_ the Twine, that tyed the +Neck+. [Sidenote: Balloon _shrunk_ to its usual _Shape_.] 123. _Instant_ Relief was given to the Balloon: which shrunk into the Shape which it had assumed in the former Ascent, when the Gass began to issue in visible Vapour, the _Neck_ likewise _lowering_ itself to the Height of his Shoulders, as in Section 35. [Sidenote: Mouth _opened_ at 41 Minutes past III.] 124. On stooping he found the Time 41 Minutes after III, and the Thermometer 57. [Sidenote: No _visible_ Vapour escaped.] Nor was he surprised that no _visible_ Vapour escaped; as he had imagined that much _common_ Air had been pressed into the _Mouth_ of the Balloon: and which, being _heavier_ than Gass, woud _go out first_. [Sidenote: Why the _Valve_ at the Top is not to be _opened_.] On that Ground he was confirmed in his Resolution _not_ to open the Valve at the top, which always emits the _lightest_ Gass. [Sidenote: The _Neck_ being made _Air-tight_, the Balloon rose _again_.] 125. As soon however as the Neck of the Balloon reached his Shoulder, he _gathered_ the Silk in his Hand, and held it _Air-tight_ tho’ untyed, to prevent Evaporation of much _real_ Gass: presuming that if any Levity remained; the Balloon woud presently _rise_ again, and _swell_. And he was pleased to find the Event answer his Expectations. CHAPTER XXIII. AIR WARMER ABOVE THAN BELOW. Section 126. It was a Matter both of Surprize and Pleasure to observe that the Thermometer had risen +again+ to 60, when the Balloon had soared _above_ the Sea-Breeze; as the Aironaut had expected to feel the extreme Rigour of Winter; and had made Preparations against _intense_ Cold. Nor did he find any Difficulty in Respiration _during_ the Excursion; which may possibly be accounted for from the _Warmth_ of the Air. [Sidenote: The Breath not visible during the Excursion.] That the Breath[37] was _not_ visible at _any_ one Time, and particularly while the Balloon was elevated above the _under_ Current, might it not be owing to the uncommon +dryness+ of the Air, which woud _dissipate_ the Vapour at the Instant of _Exposure_? [Sidenote: Encreased Shadows seem to raise the Objects.] 127. It was remarked, some little Time _before_, and _during_ the _last_ Glance of the Prospect taken at the _highest_ Elevation, that the House at Aston was still visible, and the _dark coloured_ +Line+ forming its +diminutive+ Shadow seemed _thicker_ in Proportion to the _Plan_, than when the Mansion was _first_ seen before the Re-ascent. And it had a _sensible_ Effect in _apparently raising_ it above the _common_ Level. [Sidenote: Prospects _below_ noted.] 128. The Circuit of the _Land-Abyss below_ was also greatly _contracted_: and a Haziness inclining to a _dark Green_ seemed to cover the _outward_ Verge _round_ the _Lawn_. The _red_ River Wever only appeared. The Channel and _broad_ Branch of the River Mersey towards Warrington, had long since vanished. [Sidenote: _Down_ View like the Pattern of a Turkey-Carpet.] The Lawn itself, which composed the Ground-View, was full of _innumerable_ Enclosures _almost_ +close+ to each other; with _much_ Wood:—dwindling to the Pattern of an elegant Turkey-Carpet: which, according to Principles of Mahommedan Faith, tho’ wrought in _gay_ and _vivid_ Colours, is _made_ to exhibit +no exact+[38] _Resemblance_ to the Works either of Art or Nature. [Sidenote: The Earth _glowing_ with _primary_ Colours only.] 129. The Colours, of which the Ground Work was _principally_ formed (except +white+; also the _roughened_ Sea, which _alone_ was +black+; and Shadows, which _constantly_ gave a _transparent_ +violet+) were four simple and _primary_ ones, viz. +red+, +yellow+, +green+, and +blue+: all which seemed to +glow+, tho’ in a _less_ Degree, like the Colours of the Prism. This unmixed _Coloration_ of Objects, to be seen from a vertical Situation _only_, to be seen without _Refraction_, is a new singular and _pleasing_ Phenomenon. [Sidenote: _Cromátic_ view of the Earth, an Appearance peculiar to the Balloon.] 130. A View, taken _above_ the Level of the Clouds, may, from this Circumstance, without Impropriety, be called a +chromatic view+ or the Earth: of which, the _Print_ is an Example: delineating the Extent of the aërial Excursion; and placed at the End of the _second_ Part, including the Re-ascent. CHAPTER XXIV. BALLOON ABOVE THE INFLUENCE OF WATER. [Sidenote: Balloon above the Influence of the Waters and Sea-Breeze.] Section 131. The Balloon pursued its former _gentle_ Course in the _upper_ Current of Air moving from the South West, and Aston House: and had risen _above_ the Influence of the _Waters_ and _Sea-Breeze_. [Sidenote: Balloon repeatedly swelling.] 132. In Consequence of having _held tight_ the Neck of the Balloon, the Gass _within_ began _again_ to expand, and the Machine became _more bloated_ than when _stationary_ at the first Ascent: the Bottom of the Balloon being drawn up to the Height of his Hand, when the Arm was stretched, and himself on Tip-toe. [Sidenote: The Valve first tried.] 133. Tho’ the late Descent, at the last +Opening+ of the Balloon, had been rapid; which was known _chiefly_ by the Want of Reaction from the Bottom of the Car against the Soles of the Feet; yet being still _far above all_ Clouds; fearless of the _Currents_, _Rocks_, and _Shoals_, to which +all maritime+ _Navigation_ is subject; he took the Opportunity of trying the upper Valve; _purposely_ to know the Effect. So retaining the Bottom of the Balloon in his _right_ Hand, he drew the Valve Cord with his _left_. Immediately he heard it _click_: which proved that it was quite open, and in good Order. [Sidenote: The Valve answered.] 134. He tried the Valve three Times _smartly_, and deliberately. The Escape of the inflammable Air or Gass was like the _growling_ Sound made in a Mill by the Grinding of the Mill-stones, but by no Means so loud. CHAPTER XXV. THIRD BALLOON-IRIS [Sidenote: Balloon-shadow.] Section 135. The _successive_ Operations of untying the Neck, and _repeated_ Trials of the Valve, brought the Observer so low, that he coud trace the _Image_ of the Balloon on the _upper_ Surface of _light silvery_ Clouds beneath him. [Sidenote: Third Balloon-Iris.] [Sidenote: Iris remained.] [Sidenote: The Earth disappeared.] 136. _Iris_, a bright _celestial_ Nymph, his _former_ Attendant, deck’d in gay Attire as usual for the Bow, made her _third_ Appearance: instantly _encircling_ the Balloon. Nor was her Stay so short as before; as if to _recompense_ the Aironaut for the lost Sight of Earth and all _terrestrial_ Objects, which then began to _disappear_. 137. In less than _a Minute_ after the _Deflation_; the Neck of the Balloon continuing to be held tight in the Hand; the Balloon _quickly_ encreased in Bulk, and soared _aloft_, as before. [Sidenote: Balloon alternately rising and falling.] 138. It continued _rising_ as long as the Hand coud _reach_ to hold the Neck _tight_: and, on loosing it _an Instant_, made a rapid Descent: on Account of the _Gass_ which escaped, and of the atmospheric _Air_ which rushed in by the _same_ Opening at the Bottom. [Sidenote: The Play of _fast_ and _loose_ repeated.] 139. The alternate Play of +fast and loose+, was frequently and _successfully_ repeated: the Balloon always rising till it swelled out of the Reach of the Hand: at which Time it was let go: and the Neck (as well as the Balloon) descending; was _presently_ caught in the Hand, and made _Air-tight_ as before. [Sidenote: Manouvres seen at the Distance of 15 Miles.] 140. These Manouvres were performed, at a Height _far_ above the Level of _all_ Clouds, and in Sight of Numbers of People: some of whom were at least 15 Miles distance: yet coud plainly, from an Eminence called _Hoole-Mill_ Field, a Couple of Miles from Chester, discover the Balloon at an amazing Height, darting up and down several Times; or as they expressed themselves, “_quivering and warping in the Air_.” CHAPTER XXVI. SENSATIONS ACCOMPANYING THE BALLOON. [Sidenote: Situation safe and pleasant.] Section 141. The alternate Elevation and Descent of the Balloon gave sufficient Leisure to reflect on the +security+ and +pleasure+ of his Situation, thus _wafted_ on the _Pinions_, and _merging_ in the _Ocean_ of Air. Indeed the whole Excursion was a Continued Scene of Pleasure. The Eye and the Imagination were beyond Measure delighted. 142. If there had been any Thing to wish for, it was the _living_ Pencil of +Angelica+,[39] or some other celebrated Painter: in order to gratify the World with the _bright Miniatures_ and _Colouring_ of so much _variegated_ Beauty. 143. As it woud be difficult, if not impossible, by _mere_ Description, to convey an adequate Idea of the different +Sensations+ experienced while in the Car; (for Pleasure is itself unspeakable;) yet the Fancy may possibly, without Censure, be a Moment _indulged_, in its Allusions to such familiar Subjects as approach nearest to +them+: so as not to leave the _public_ Mind _wholly_ in the Dark, with Respect to the above Points of natural and general Curiosity. [Sidenote: The _Swing_ a favourite Amusement.] 144. Most young People, whenever they have Opportunity, amuse themselves on the +slack rope+, or Swing: the Pleasure _encreases_ in Proportion to the _Loftiness of Ascent_ they are _able_ to acquire. [Sidenote: The Mogul enjoys the Air without Fatigue, by Means of the _Swing_.] 145. In the East, where the Heat of the Climate forbids robust Exercises; the _Swing_ is considered as a princely Diversion: and of which the +Mogul+ himself _condescends_ to partake. He is swung by Slaves: and thus enjoys the _pure_ Air _without_ Fatigue. [Sidenote: The Balloon and Swing compared.] 146. The Ascent of the Balloon is not unlike what is felt, in the _ascending_ half of the Swing: and the Descent is attended with that agreeable Sensation known to those who _sink_ throu’ the _descending_ half. [Sidenote: A favourite Diversion among the Russians.] [Sidenote: Artificial Declivity of _waved_ Ice.] 147. A Diversion similar to the above is peculiar to the _North of Europe_, practised by the Russians, particularly the Inhabitants of Zarsko Zelo; and accompanied with a Sensation _so delightful_, that they seek it in the _open_ Air, amidst the _utmost Severity_ of the _Frost_. It is a Sort of Boat or _Car_, in which they _glide_, for a considerable Distance, _down_ an _artificial_ Declivity of _waved_ and _polished_ Ice: being drawn up by Servants; they launch precipitately forwards, and _down_ again as before. [Sidenote: Amusements of Gestation in common with the Balloon.] 148. _Sledges_ drawn _swiftly_ over the undulated Surface of a _snowy_ Country, a favourite Diversion in many Parts of Germany, in Lapland, and Siberia: Skaiting on _level_ Ice; the Motion of a Vessel on _smooth_ Water; of a _fleet_ Horse; also of Wheel-Carriages rolling over +even+ Gravel, or a _grassy_ Plain, are each a _Luxury_ of the same Kind; and _grateful_ to the Nerves. [Sidenote: Vertical Flying-Coach.] 149. There is yet another Amusement, which is said to be of _German_ Extraction, still frequent in the North of England, called the _vertical_ +Flying-Coach+.[40] Two Persons are required to turn the Machine (when full): which moves like the four Sails of a Windmill: a Seat being placed at the End of each Sail. 150. The _Pleasure_ communicated to the _Nerves during_ the Descent, is to some Constitutions so _exquisite_, as to be full as much as the human Frame can support: others are affected by it in a _gentler_ Manner. These different Diversions, flowing from the same Principle in common with the Balloon, viz. that of _being carried with a gentle Motion_, are _one or other_ suited to all Ranks and Ages. 151. The Pleasure of the double Slack Ropes, when seated in the Car appended between them, is perhaps in itself _superior_ to that of most others. 152. The _vertical Flying-Coach_[41] compleats the _Circle_, of which the Slack Rope describes but the lower _Half_. [Sidenote: Balloon and Vertical Flying-Coach compared.] 153. The Sensations communicated by the Motion of the Balloon, come nearest those of the vertical flying Coach, tho’ _more_ gentle, and if possible, _more_ pleasing. [Sidenote: No Sickness or Giddiness in the Balloon.] At Sea, the most experienced Mariner is sometimes _sick_ or _giddy_. 154. Nothing of the Kind happens in the Balloon: where an infinite Variety charms the Imagination. [Sidenote: The Spirits raised.] 155. The Spirits are raised by the _Purity_ of the Air[43], and _rest_ in a _chearful_ Composure. [Sidenote: The Greatest Height conveys no Fear of falling.] 156. Even when _stationary_ above the Clouds, the _Height_ conveys with it no _Danger_ of _falling_: any more than _when_ in a Vessel at Sea, (as off the West-India Islands, for Example) the _Fish_ are seen gliding over the clear _white rocky_ Bottom, at the Depth of twenty Fathom: as the Aironaut seems perfectly unconnected with the Earth, and unconcerned about it. [Sidenote: The Depth below the Clouds gives no Idea of Distance.] 157. Nor does the Depth _below the Clouds_ give an Idea of _Distance_. On the contrary, the _smooth chequered Lawns_ which form the Surface of the Earth, are presented to the Eye, as on a _Level_ with the _Clouds_ themselves: _at least_ +come up+ to their +undersides+, and appear so much a Part of _them_; that the _Clouds_ occupy the Place of _Earth_: and the Aironaut seems able to descend from the _Car_ upon the _Clouds_, and to walk from Side to Side over the _empty_ Space, as over a Sheet of _transparent_ Ice, across a _River_, whose Depth is equal to the _small_ but indefinite Thickness of the Clouds. 158. It is from _frequent_ +experience+ only that the _Diminution of Objects_ presuppose their _Distance_. CHAPTER XXVII USEFUL CONCLUSIONS. [Sidenote: Change in the _Form_ of the Balloon while descending: with Conclusions drawn from the Change.] Section 159. It was remarkable that, the lower Parts of the Balloon regularly adopted a _similar_ Form at each Descent: not unlike a _Ship’s Bottom_; looking up, at the Head or Prow, while on the Stocks: the _Neck_ of the Balloon forming a beautiful _central_ Pillar; in Shape like that of a _Speaking Trumpet_ inverted. [Sidenote: Time of Descent discovered by the Form of the Balloon.] And hence may be derived a Piece of _useful_ Information: as the _precise_ Time of descending is discovered by bare _Inspection_ of the Machine. [Sidenote: Balloon adopting the Form of an elliptic Solid.] 160. Another Conclusion seems likewise deducible from the above, that if the Balloon is so burdened, as to _descend_ while it retains the Form of an +elliptic solid+;[44] it will descend more rapidly, than if it contained less Gass: the Force of Descent in both Cases being supposed the same. For if the Diminution of Gass be so great as _not_ to fill the upper Hemisphere of the _Balloon_; the Resistance of the atmospheric Air _below_ woud probably give _it_ the Appearance of a _Concave_ or Umbrella, which woud greatly _check_ the Descent: viz. in Proportion to the Square of the Number of Feet of which the Surface was composed. [Sidenote: An equatorial Hoop prefered to a Parashute.] 161. Hence also the evident Utility of an +equatorial hoop+ for Balloons: in Preference to a Parashute, which woud be only an Incumbrance. CHAPTER XXVIII. [Sidenote: An uncommon Sound in the Air.] Section 162. At 40 Minutes past III, when the Balloon was _apparently_ some Miles above the Level and Summit of the Clouds; a +sudden+ and uncommon _Sound_ was heard for three or four Seconds only. A Sort of _hollow_ Wind seemed issuing from a Plain of Clouds in the North-East Quarter, greatly below the Balloon: which as +suddenly+ ceased. [Sidenote: An unusual Motion communicated to the Balloon.] The Instant the Sound was heard; a gentle Motion was _impressed_ on the _Balloon_, as if by a Hand touching _it_ near the _Top_. 163. Clouds to the North-East appeared, for the first Time, in _rapid_ Motion towards the Balloon. They _sailed_ directly _under_ it: filled up the Chasm, and drew a _white_ Veil over _all terrestrial_ Objects. [Sidenote: Conjecture in the Cause of the Motion.] 164. It has been _since_ imagined, that a fresh Wind _descended_ from the South-West Quarter in the upper Current, and was heard in the North-East, being ecchoed from the upper Tier of Clouds _below_: and that the Balloon, finding less Resistance than the +range+ of Clouds, soon overtook and passed them: particularly as the lower Part of the _white_ Flag vibrated only in the usual Direction. 165. The _encreased_ progressive Motion of the Balloon was _not_ perceived (Section 18): being considered as at _Rest_, and the _apparent_ Motion _referred_ to the _Clouds_. CHAPTER XXIX. [Sidenote: A narrow Ditch the Duke of Bridgewater’s Canal.] Section 166. In a few Minutes, a Side-Break throu’ the Clouds discovered a long ill-formed narrow Line or Ditch, something less than a Foot in Breadth, extending several Ways: and which from its Proximity to Places that were known, and coming into View; viz. the Country about Norton and Halton-Castle; proved to be the Duke of Bridgewater’s Canal. [Sidenote: A Glympse of Runcorn Gap.] +Suddenly+ came in Sight the _spacious_ +open+ of the Mersey above Runcorn Gap: which appeared of a +ruddy+ Colour, and _very_ near: as if the Balloon had again _felt_ the Influence of the _River_. [Sidenote: _Balloon-Geography_ first suggested for _Maps_.] 167. A new System, that of _Balloon-Geography_ here suggested itself: in which the Essentials of _Proportion_ and _Bearings_ woud be far more accurate, than by the present Method, both for _Maps_ and _Charts_, viz. To make Drawings by +sight+, from the Car of a Balloon with a _Camera Obscura_, aided by a Micrometer applied to the under Side of _the transparent_ Glass. [Sidenote: Air presumed to be warm with South-West Wind long continued.] The Season proper for such an aironautic Expedition, would be _any_ _calm bright_ Day: the Wind having blown from the South West Quarter, for some Days before, which is _frequently_ the Case: the Air, at _such_ Conjuncture probably remaining +warm+, to the Height of a Mile or more, unless in the very Midst of Winter. [Sidenote: Balloon Geography for _Charts_.] 168. And particularly for Charts, which in a _maritime_ Country are _most_ useful: as Balloons have an extraordinary Predilection to become _stationary_ over Channels and Rivers; altho’ a very _strong_ Gale of Wind, shoud continue the _whole_ Time to blow in an horizontal Course directly +under+ the Balloon. [Sidenote: Balloon in a Calm with a _strong_ Wind _below_.] Of which Event the Writer of this Account was an _Eye-Witness_, in the Case of Mr. Lunardi: who was _detained_ above 20 Minutes over the _broad Bend_ of the River Mersey, near Ince, in Cheshire, the Day he _landed_ between Tarporley and Beeston-Castle, ascending from the New Fort at Liverpool. He quitted his Station by the Escape of Gass, and descended into the _Stream_ of Wind, which continued as _violent_ as before. CHAPTER XXX. Section 169. The Summer Scenes of Fairy-Land below, being soon eclipsed by the _quick_ Intervention of a _Range_ of Clouds; the +sudden+ Contrast of which was highly pleasing to the Imagination; a Prospect of +mid winter+ instantaneously succeeded. [Sidenote: The Center filled up in an Instant.] 170. The Earth’s _Surface_ throu’ an immeasurable Crater of Vapour accumulated round the Aironaut, who was suspended, and seemed fixed in the Center above it, _no longer existed_. And, if it will not be allowed, that a _new_ Earth, and a _new_ +sky+ appeared; at least, let the Imagery and Resemblance of what was really seen, be taken from that +earth+, which in Fact did _not_ appear. A +world+ of _Clouds_, +greater+ than the +one+ below, became, for the first Time the _sole_ Object that engrossed the Sight. (See Section 144.) [Sidenote: View of the Clouds taken from _above them_.] 171. The Balloon was _apparently_ raised some Miles above the _Surface_ of a _concave shallow_ Plate, or Shell, or rather an immense Plain, _which_ was in general smooth and well defined: but the _dense_ tonìtruous Masses, rising here and there _above_ the Rest, greatly resembled steep and +rugged mountains+ seen in Perspective, at different Distances from 5 and 10 to at least a hundred Miles.[45] An unvaried deep cerùlean and pellucid Azure, without a Cloud above, enclosed the +novel earth+: whose Surface, whether Valley, Plain, or +mountain+ _in Appearance_; seemed as if covered to a prodigious Depth, by successive Falls of Snow, driven and polished by the Winds and Frost, and dazzling to the Sight: the Sun still shining above all, with +white+, unremitting and invigorating Rays.[47] CHAPTER XXXI. [Sidenote: Brilliant Colouring of _dense_ Clouds.] [Sidenote: Aironaut lost in the _blue Fields_ of Air, by the Intervention of Clouds below him: which prevented all _farther_ Knowledge of his Situation, and also a Sight of the Earth itself.] Section 172. A Thunder Cloud in most grotesque Form;—of superior Magnitude, Density, and +brightness+—a _celestial Colouring_; and whose _Shade_ was itself a _Colour_ of semi-transparent and transcendent _Blue_ and _Violet-Purple_;—remaining for several Minutes, _exactly under_ the Balloon, _tempted_ the Aironaut to descend into it; and, if possible, investigate its Structure and Composition. Blanchard, he knew, had passed throu’ +many+ without Danger: any Fears that might otherwise have been entertained on that Head were therefore groundless: particularly as Gass, i.e. _inflammable Air_ and the _electric Fluid_ (supposing an electric Atmosphere had surrounded the Thunder Cloud) mutually _repel_ each other. He however declined the Trial: among other Reasons which then offered; that the temporary and apparent Rest of both Balloon and Clouds portended _his_ Situation to be over the Center of _some Water_: so that if _Gass_ had been let out in order to _descend_; _enough_ might _not_ have remained to make Choice of a proper Place to _land_. 173. Some Minutes after; on the _Retreat_ of the Clouds, or _progressive_ Motion of the Balloon; he found himself suspended over the most _enchanting_ Meanders of a Rivulet. Where he coud not tell. CHAPTER XXXII. [Sidenote: The Aironaut was lost, tho’ in Sight of a Country well known _when below_.] Section 174. He _thought_ himself again over the Wever. [Sidenote: At 47 Minutes past III, over a _red_ Rivulet.] At 47 Minutes after III, the Prospect _beneath_ opened, just wide enough to shew, that he was suspended in the open Space over the Center of some Rivulet. The Map of the Country which had been so carefully studied, was _now_ consulted for the first Time, but coud not bring to his Recollection any Traces of the extraordinary Curves which then met his Eye. They bore not the least Resemblance to any Part of the River Mersey. No River like that below him had ever presented itself. Its _Doublings_ were so various and _fantastic_ as to exceed the Limits of Credibility. [Sidenote: The Neck of the Balloon tyed some Time _before_ to prevent the Descent.] 175. He was still stationary, at an immense Height, without the _least_ Inclination to descend: having _some Time before_ taken the Precaution to tye _again_ the Neck of the Balloon, as soon as he had perceived it did _not_ inflate, as at first, to any _dangerous_ Degree. No Towns, no Houses appeared. No _public Roads_ were discoverable. No Voices were heard.[48] The Country beyond the Rivulet began to disclose itself: but was quite _new_ to him at that _Altitude_, and seemed as if almost covered with Wood. 176. His _Watch_ shewed the Time of the Day, and the Sun alone _sufficiently_ indicated the Point of the Compass. The _white_ Flag manifested _no_ Change in the Wind. But whether he was near Liverpool, Wigan, or Manchester, he coud not discover. [Sidenote: The Country _below_ unknown to the Aironaut, _when_ in the Balloon.] 177. He was entirely +lost+ in the _blue Fields_ of Air; far above the Summits of the Clouds; tho’ the Balloon was in Sight of the Earth, and of Numbers who were gazing at it. 178. The _Colour_ of the new Rivulet was full as +red+, as any he had seen before. He thought it might be an insignificant Brook, which tho’ curiously curved, was too small to be inserted in the Map. Still he continued over it: turning and returning _gently_ in small Curves. 179. He presently passed _Northward_ of the Rivulet _over_ a woody Country, in which he coud discover _no_ Variety of _Colouring_ either in the Ground Work or Enclosures; the whole having a _dark green_ Cast. [Sidenote: Unusual Objects below.] An Appearance of a very distant and remote _Plain_ then presented itself; the Size of a moderate Carpet: of a _ruddy_ Colour; and surrounded by a _green_ Border. Being an unusual Object it continued to engage his Attention. 180. Not far from the first, another of the same Kind, of a more dusky Cast, but _less_ and somewhat nearer, that is _more under_ him, then attracted his Notice. He wished to _decipher them_, but in vain. [Sidenote: The Prospects opened, which demonstrated his Descent, owing to the Loss of Gass.] 181. The Sun shone +bright+ on both: and in a very few Minutes, the _circular_ Prospects _encreased_: which was now become a _regular_ and undeniable Signal that the Balloon had begun to _descend_. (Section 17.) The _latter_ Plain appeared, at the first, about the Size of a common _Handkerchief_. The Balloon continued to descend. [Sidenote: The same Spot perpetually varying to the Eye of the Aironaut.] 182. In a Couple of Minutes, the Plain appeared intersected +closely+ every Way, like the _Coat_ of a _ripening Melon_. Descending a little _lower_; it seemed covered with a _Net_, the _Meshes_ of which were distinct. And _lower_ still; it extended itself _greatly_ on _all_ Sides: (at which Time a certain Degree of _Chilliness_ prevailed:) and was then _again mistaken_, and looked upon as a +dry+ _Heath_, deeply overrun with Shrubs of the same Name. [Sidenote: Ballast thrown out gradually.] 183. The Descent of the Balloon being _rather_ quicker than was expected, or desired; it was deemed expedient to have Recourse to the _last_ Bag of Sand, which lay open, and weighed 20 Pounds. It was accordingly thrown out, a Handful at a Time. [Sidenote: The remaining Ballast thrown out _at once_, in all 20lb. weight.] But that Method not seeming _sufficient_ to _check_ the Descent, when at the Height of 150 or 200 Yards; _all_ the Sand was poured out, and the Bag thrown down. [Sidenote: Gentle Landing of the Balloon.] This had the desired Effect: and the Balloon continuing to descend with a Motion _uniformly retarded_, alighted, as the +down+ _of a Thistle_, in the gentlest Manner, without +any+ _Rebound_. [Sidenote: Anchor and Cable not made use of.] 184. There being scarcely a _Breath_ of Air abroad, the Aironaut made no Use of his Anchor and Cable: but continued as from the first, +standing+ _upright_ in the Car; which, having moved a Yard or two _only_ along the Ground, rested in a perpendicular Situation. The Balloon, suspended over him like a _vast_ Umbrella, +levitated+ _vertically_ in the grandest Manner. 185. He was _alone_ when he alighted: but, in a _few_ Minutes, found himself surrounded by the Country-People, who had waded _above Ancle-deep_, and came running from all Parts, to see the +wonder+, and contribute their _Assistance_. [Sidenote: Landed at 53 Minutes past III. Thermometer 59.] 186. He _landed_ exactly, at 7 Minutes before IV: Thermometer 59: but +where+ he coud _not_ tell. The first Question was “Pray where am I?” And the Answer;—in _Lancashire_. On asking the nearest Distance to a Turnpike-Road; the People said he was within _two Fields_ of one, and offered to conduct him thither. He accepted their Offer, and shared _his Liquor_ among them. CHAPTER XXXIII. Section 187. The Balloon alighted _near_ the _Middle_ of a +moss+; called +rixton-moss+, a Place he had never before heard of. [Sidenote: Rixton-Moss, its Magnitude.] It was a large Tract of unenclosed +wet+ Land, above four Miles long and above two broad, intersected by Ditches or Water Courses, which divide the Moss into Fields of a _moderate_ Size. The whole is surrounded by _tall_ Forest Trees. This was the _lesser_ of the two dusky Plains, which appeared about the Size of a Handkerchief, and which he wished to decipher, but in vain. 188. Rixton-Moss is situated five Miles North North East of Warrington, and a little to the left of the Turnpike Road leading from thence to Manchester, and 25 from Chester. [Sidenote: Chat-Moss in Lancashire.] 189. He has since been informed that the other Plain, about the Size of a moderate _Carpet_, was no _less_ a Place than +chat moss+, a vast _Tract_ of barren _wet_ Land, _many_ Miles in Extent. [Sidenote: The _Rivulet_ seen when _above_, was the River Mersey near Warrington.] 190. Curiosity tempted him to make particular Enquiry concerning the Rivulet over which he hung, _admiring_ the Beauty of its serpentine Meanders; and, from a Description given of his Manouvres over _Lymm_, situated to the East of Warrington, and from a peculiar Curve, appearing in the Form of a _true Lover’s Knot_, when over the Gunpowder Water-Mills, he was convinced the _Rivulet_ coud have been no _other_ than the broad Branch of the River +Mersey+. [Sidenote: The Excursion performed in two Hours and a Quarter.] 191. The +aërial excursion+ was performed in two Hours, and a Quarter, within two Minutes. The Distance of the Balloon-Course, if traced along the Ground, 30 Miles. Section 130. [Sidenote: Balloon, unknown to the Aironaut, going at the Rate of 30 Miles an Hour.] 192. In comparing the Dates at Bellair and Rixton-Moss; it is certain that the Balloon, excluding the Force of _Ascent_, must have moved _forwards_, during some Part of the Re-ascent, at least at the Rate of 30 Miles an Hour: tho’ the Aironaut, for the most Part, imagined he was gliding throu’ a serene Atmosphere. Probably the progressive Motion was encreased, from the Time the unusual Sound was heard, in Section 162. Note: The Print, representing a +chromatic+ View above the _Level_ of the Clouds, of the Country from _Chester_ to _Rixton-Moss_, is to front the _left_ Page, at the End of this Chapter. END OF THE RE-ASCENT. CHAPTER XXXIV. THE SEQUEL. [Sidenote: Flights with the Balloon for +three+ Hours longer.] Section 193. The Sequel contains an Account of _several Flights_ made, in Presence of the Aironaut, by different Persons, during _three_ Hours, in the Car of the Balloon, viz. from the Time he alighted, till _after_ +sunset+. [Illustration: _A_ +Balloon Prospect+ _from ABOVE the_ CLOUDS _see page IIII c._ Publish’d May 1ˢᵗ. 1766, by T.Baldwin Chester.] [Illustration: The +Explanatory+ Print. _see Page IIII. d._] Rixton-Moss, +Lancashire+, IV. o’Clock P.M. The Afternoon being _fine_, the Sun _bright_, and the Air _calm_; finding the Country People remarkably civilized and kind; and having dispatched a Messenger on Foot to return in a Post Chaise from Warrington; the Aironaut was resolved to gratify the Curiosity of his numerous Followers, and give the young People a Taste for Balloons, by treating them successively with an Airing. 194. Indeed it was no inconvenient Method of removing and conducting the Machine: and _possibly_ different Positions of the Balloon might furnish a _useful_ Hint. [Sidenote: The Aironaut indulged the People of the Country with _Flights_ in the Balloon.] Having asked aloud _who chose to ride_, several answered in the Affirmative. So having pitched upon a young Fellow of less Weight than himself; bid him get up, between the Cords, over the Hoop, into the Car; stand near the Middle, and hold an opposite Cord in each Hand. He obeyed with the greatest Alacrity: and seemed to be _a noisy bold_ Adventurer. [Sidenote: The Aironaut _first_ quitted the Car; but continued to _conduct_ the Balloon.] 195. The _Aironaut_ then got out; and having suffered the Balloon to rise; fastened the End of the Cable to _central_ Meshes of the Net, at the Bottom of the Car: ordering the strongest and tallest Man to hold the Cable, and let it go by Degrees till the Anchor or grappling Iron _alone_ remained in his Hand. [Sidenote: Behaviour of different Adventurers.] The Balloon now rising _above_ the Height of the Trees, and giving the Adventurer a new and extensive Prospect of the Country; he became _silent_; _pale_; his _Countenance_ the _Picture_ of _Distress_; looking _down_ as if for _Help_. The Conductor repeatedly bid him take Courage. But, in vain. By lowering the Car _within_ the Height of the Trees, he seemed to _recover_ from his _Dismay_. CHAPTER XXXV. Section 196. The Route of the Balloon being now throu’ a _flat woody_ Country, with _tall_ Trees growing in the Hedge Rows; a Difficulty occurred, how to conduct the Cable, when the Balloon was _above_ or _between_ the Trees, without entangling: which gave the Conductor much Trouble, as he was frequently obliged to walk round a Field, the Balloon being held in the Center, before he coud espy a proper Opening. [Sidenote: March of the Balloon.] The Procession marched slowly forward: and the young Man was carried among _his Peers_ in Triumph through the Air, across the Turnpike-Road, into the Middle of an open Grass Field, where he descended; took a Companion _less heavy_, and left the Car. This Stripling was a good Deal surprised the Instant he rose above the Trees; but ventured to look around: and appeared on the _whole_ much delighted. 197. A great Concourse of People were now collected. Accidental Carriages halted: joined the Cavalcade, and partook of the Diversion: the _greater_ Part following the Balloon throu’ the _open_ Fields adjoining the Road. [Sidenote: Caution to prevent the Escape of the Balloon.] The Conductor _generally_ preferring the beaten Track; yet _suspecting_ the Balloon with its Adventurer in the Car, might _designedly_ be suffered to _escape_, took the Precaution to have the Grapple held by _nearest_ Relations to the Person in the Car. 198. The Gass evaporating; a smart young Fellow, who seemed ready for the Jaunt, stepped in: on which the former resigned his Place. But he was no sooner raised a few Yards above his Companions, than the _florid_ Colour forsook his Cheeks; he _trembled_; bent himself _double_ with Fright; and the Balloon was obliged to be hauled down. [Sidenote: A Venus in the Car of the Balloon.] 199. A fond Mother then requested that her Child, a fine blooming Girl, might ascend: boasting of her Courage, and comparing it with that of the Person who had none. The _Venus_ smiled, and mounted her Car with great Spirit. [Sidenote: Politeness of the neighbouring Gentlemen.] 200. Some Ladies and Gentlemen of the Neighbourhood who had watched the Balloon, while it hung at an immense Height over Lymm, and the Gunpowder Works on the River Mersey, came, in their Evening Walk, to meet it: joined the Procession; gave the Aironaut _polite_ Invitations to their Houses, and shewed him every possible Civility. [Sidenote: Effect of Air in _Motion_ on the Surface of the Balloon.] 201. The Resistance made by the _Surface_ of the Balloon, against the _least Breath_ of Air moving _horizontally_, was _frequently_ tried by occasionally holding the Grapple: and it was a decided Point, that the _least Motion of the Air_ was sufficient, together with the Action of _Levitation_, to prevent the Person, who held the Grapple when the Cable was extended, from transporting the Balloon against the Current: nay it was with Difficulty he coud remain in the _same_ Place: the Balloon sometimes pulling him forwards, and almost off his Feet. [Sidenote: Effect of _calm_ Air on the Surface of the Balloon.] 202. When the Air was perfectly _calm_, which frequently happened while the Balloon migrated with different Passengers, as the Evening was the finest in the World, and the Country flat and woody in the Hedge-Rows; it was with _Difficulty_ that the Conductor coud draw the Balloon after him, faster than the Rate of a moderate _Walk_: viz. three Miles an Hour. CHAPTER XXXVI. [Sidenote: Sun set at 34 Minutes past VI.] Section 203. The Sun set at 34 Minutes past VI. and, tho’ it was _then_ near that Time, the Post-Chaise was _not_ arrived. 204. On Enquiry for a dry smooth Meadow, he was recommended to proceed a little farther, to a Place on the Road within three Miles of Warrington. 205. Having by this Time gratified the Curiosity of the Country in admitting Boys and Girls to the Age of six or seven Years, into the Car; and being arrived after Sun-set at the Place appointed, viz. _Milton’s Croft-Green_; he ordered the Balloon to be laid on its Side along the Ground: having removed the Car, and opened the Mouth; the inflammable Air or Gass, was soon pressed out by Means of a _long Pole_ rolled _across_ it by two Men, standing one at each End of the Pole: beginning at the Top or upper Valve, which was held down close to the Ground; and ending at the Mouth or Neck. It was then rolled up, put into the Car; and the whole Apparatus placed on the Top of the Chaise which arrived the Moment wanted. [Sidenote: Balloon put up at 53 Minutes past VI.] 206. The Operation was completed at 53 Minutes past VI: the Conductor having accompanied the Balloon on Foot exactly +three+ Hours. [Sidenote: Balloon in the Air five Hours and a Quarter.] 207. The Balloon had therefore continued _floating_ in the Air, with different Persons, in the whole, for the Space of five Hours and a Quarter. The Conductor, promising to accept the very polite Invitation offered him by Mr. _Stanton_, a Gentleman who is principally concerned in the Gunpowder-Works upon the Mersey; called at his House, and partook of some Refreshments. He then drove to Warrington, where he was met by a Person whom Curiosity had inspired to follow the Balloon _on Foot_ from Chester, as long as he coud keep it _in View_. 208. Mr. Lunardi likewise with great Civility dispatched his Servant to assist the Aironaut in _the Care_ of the Balloon; but he did not arrive in Time; not reaching Warrington till VIII. at Night: having lost Sight of the Balloon about _Daresbury_, four Miles from Warrington. 209. Nor was it visible to any, at least very few, of the Inhabitants of that Town, which was equally hidden from the Aironaut: who, _then_ ignorant of his Situation, must have remained a considerable Time suspended above the Clouds; which concealed both the Town and River. He saw Warrington but twice when +above+: for a short Time, at a great Distance, and a _mediate_ Altitude. 210. The following Day he returned to Chester: was met by the Militia-Music, and ushered with loud Huzzaes into his native City. On his safe Arrival; besides the private and sincere Congratulations of his Relations and Friends; the Bells rang: his Flags were carried in Procession, and every public Demonstration of Joy was shewn on the Occasion. TO THE INHABITANTS OF CHESTER THANKS. END OF THE EXCURSION THROU’ THE AIR. AIROPAIDIA. CHAPTER XXXVII. +OBSERVATIONS, HINTS, and CONJECTURES, on the SUBJECT of the BALLOON and EXCURSION FROM CHESTER THE EIGHTH OF SEPT. 1785.+ OF THE WEATHER, IN THE VICINITY OF CHESTER, ABOUT THE TIME OF THE EXCURSION. Section 211. For more than ten Days _before_ the Balloon-Voyage, the Wind had blown (_interruptedly_ on Account of the Sea-Breeze) from South and South by West. Monday the 5th of September: A Conjunction of the Planet Mercury and the Moon, at +one+ in the Afternoon. Tuesday the 6th: A violent Hurricane in the South of England, at London, Portsmouth, &c. The same Day at Chester North-North-West, and distant from London 182 Miles; South-Breeze; Rain most of the Day. Thermometer at Noon in the Shade, 62: and 14 Divisions colder each Night, than the _following_ Day, at an Average of five Years. Barometer, below _Much Rain_, viz. at 28 Inches ⁹⁄₁₀ths. Wednesday the 7th: Violent Squalls from South and South-West, with hazy Air, till half past IV in the Afternoon. Thermom. 58; Barom. Changeable, viz. 29½. Thursday the 8th, which was the Day of the Excursion: Much bright Sun. (On Enquiry) calm _below_ till half past III in the Afternoon, then West Sea-Breeze: South-West Breeze _above_ till half past IV. Calm bright Evening. Also the upper Stratum of Clouds thin and _white_, in _quick_ Motion, when seen from _below_ till Noon: at which Time the Sky was almost cloudless: and, from _above_ the upper Stratum, were seen, interspersed, Multitudes of detached Thunder-Clouds in large Masses, rising at Intervals, in the _Middle_ of the upper Surfaces of white Clouds, and stretching _above_ them. Friday and Saturday moderate: South and South-West Breeze. Sunday the 11th. The Planet Mercury stationary. Cloudy Morn. South-West Breeze. Thermom. at 60 at Noon. Barom. _above_, Changeable, viz. at 29½. +Much thunder+ and Rain in the Afternoon. 212. Quere, Had the _Thunder_-Clouds on Thursday, tho’ not remarked by any from +below+, yet visible to a great Extent from the Balloon _above_ them,—any Connexion with the _Thunder_ that happened +three+ Days after? [Sidenote: Weather, to be prognosticated, by _Sight_, from the Balloon] Answer: It appears to the Observer, that the _Thunder_ was _gradually_ collecting in the Air from _Thursday_ till Sunday: and if so; will not Balloons, when more _frequent_, prognosticate the Weather, _by Sight_, better than any other known Methods? CHAPTER XXXVIII. ON CERTAIN APPEARANCES AT DIFFERENT ALTITUDES OF THE BALLOON. [Sidenote: Of the highest visible Clouds which are always _white_.] Section 213. The highest visible _white_ Clouds, often seen in detached Streaks, during the finest and also in the worst Weather, (if not intercepted by lower Clouds) and which, when melting away, are known in some Counties by the common Appellation of Horse-Tails; and, suspended over Great-Britain, are frequently _marbled_ or dappled by the Wind; putting on the Appearance of white Waves, like Sea-Sands ruffled and left by a rapid Tide;—had been disturbed, separated, and almost _melted_ down by the _Storm_ the Day preceding the Excursion. Two of them _only_ were still visible in Streaks, near the Sun’s Place, at the first Ascent. They seemed without Motion, and became afterwards _invisible_. Saussure, the celebrated Professor of Philosophy at Geneva, is very exact in his Definition, Description, and Height of these Appearances: and thinks it _probable_, their Situation may be “_at least fifteen English Miles above the Surface of the Earth_.” “Car quand je considere ces fines Pommelures, &c.” “For when I consider these delicate Dapplings, which, in a Series of fair Weather, begin to cover the azure Vault of Heaven with a white and transparent Gauze, and which portend Rain a long Time before it happens; I am led to believe they occupy a very elevated Situation in the Atmosphere” (Essais sur l’Hygrometrie, P. 271.) It seems however that _Crosbie_, in his Excursion from Dublin on the 25th of January 1785, pierced throu’ and soared above these _fine Webs_, at the Height of 16 Inches by the Barometer in a _frosty_ Air. [Sidenote: Of the _Chilliness_ perceived at a certain Height.] 214. It has been already noted, that at a certain Height, a Kind of +chilliness+ was perceived, not ascertainable by the Thermometer. The Sensation was _suddenly_ impressed four Times, in ascending and descending to and from the same Height, viz. about 26 and 27 Inches, equivalent to between 500 and 1000 Yards above the Surface of the Earth at the first Ascent. From the Uniformity of Effect at the same Height; the Sensation may be ascribed to the same Cause, viz. the Level of the first or lower Tier of Clouds: altho’ the Aironaut did not pass throu’ any visible Cloud or Vapour, during the Excursion. See Section 93. [Sidenote: Remarkable Appearances of Earth and Clouds.] 215. At the same Height likewise, tho’ the Observations have not been set down at large; the Appearances of the Earth and Clouds were very remarkable. During the Ascent of the Balloon, between the Altitudes of 26 and 27 Inches; the _circular_ Prospects of the subjàcent Earth _instantly_ contracted, and, during the Descent, about the same Height, _instantly_ enlarged themselves to the Eye of the Aironaut. 216. At the same Height mentioned before, the _circular_ Prospects of the Clouds appeared on the same horizontal Plane with the Eye: tho’ at the Distance of a Mile. See Section 49. In _this_ Situation, the Observer endeavoured to discover the Thickness of the _Stratum_ of Clouds: but was always baffled by a Deception of Sight worth recording. The _Strata_ were plainly composed of three or more Heights of Clouds, _sailing_ at great Intervals, one above the other: all which regularly _vanished_, as he approached their respective Levels: as if _instantly_ thrown into the Circumference of a Circle, whose Radius was a Mile. During the Ascent, in passing their supposed Level, the Clouds _instantly_ appeared _far below_ him: and during the Descent, as far _above_. 217. Quere: Is it not from the same Cause, that all Vapour is _generally_ invisible to a certain Height and Distance from the Eye? It being incontrovertible that more Vapours rise about +noon+, than at any other Hour, particularly at Sea, while the Sun continues to _shine_; which, notwithstanding, are wholly _invisible_, till arrived at a _certain_ Height? [Sidenote: Visibility of Vapours by mere Distance.] And hence the Visibility of Vapours by _mere_ Distance, which contains a sufficient Number of Particles to intercept and refract the Light, without Cold, Condensation, or _actual_ Accumulation: viz. by Refrangibility of those primary Rays of Light, which Air and Vapour united are most _apt_ to reflect or transmit. Mons. Saussure has proved by his Horse-Hair comparàble Hygrometer, that “the Air shews Signs of _greatest_ Humidity an Hour after Sunrise, and of _least_ Humidity, between three and four in the _Afternoon_.” But the Air being _then_ also the hottest, will _dissolve_ or evaporate the greatest Quantity of Vapours, and raise them _above_ the Hygrometer (which by its _Heat_ will not retain, but on the contrary repel and _dissipate_ them) to great Heights in the Atmosphere. See “Essais sur l’Hygrometrie, C. 6, P. 315.” 218. In general then: Is not the _Cause_ of the above Deceptions, _not_ an _Absence_, but a _Transparency of Vapour_ to a certain Distance: (just as the Zenith _appears_ +cloudless+, when the Air is _overcast_ around;) beyond which Distance, the _Number_ and relative Proximity of Particles with Respect to the Eye, is such, as to intercept the Rays of Light: _when only_, they put on the _Colour_ of Air, and Form of Vapour and Cloud? And hence the probable Reason, why +no+ _circular_ Horizon of the Earth’s Surface was presented during the Excursion, Section 79: and why it seldom has or can present itself to Aironauts or _Mountaineers_, at any _considerable_ Height above the Region or Level of Clouds, even tho’ Clouds do _not_ appear in the Air, either to themselves, or to Spectators _below_. This Point seems capable of Illustration by Analogy, from the Impossibility of encreasing the _Magnitude_, and at the same Time, _Distinctness_ of distant Objects, seen throu’ a _common_ Telescope; on Account of the Quantity of Vapours between them and the Eye _Which_ +vapours+ may be magnified till the Object appears confused and obscure; and even at last become substituted in the Place of the Object, under the Form of Opacity and _Cloudiness_. 219. The _greater_ the Height of the Balloon, the more _contracted_ was the Circle of Vapour below it; and the more limited the Prospect of the Earth’s Surface below the Vapour. 220. It seemed probable that the Sun shone as _bright_ on the Countries around the Observer, as on Objects immediately below him: which Objects coud not have been illuminated by the Sun’s Rays, darting throu’ the +apparent+ and _contracted_ +opening+ under him; as the Rays which shone on the Balloon, fell beyond the _Opening_, _obliquely_ on Clouds which caught the Shadow of the Balloon. 221. The extreme _Rarity_ or _Tenuity_ of the Vapours was _evident_ from the _progressive_ Course of the Balloon, which was _always_ in the Center of a _circular_ Opening, limiting the lower Prospects; except when the Spectator lost all Sight of the Earth, by dense, watry, intervening Clouds. [Sidenote: Novel Situation peculiar to the Balloon, again described.] This _august_ central Situation, +always changing yet still the same+, had the most striking Effect on the Senses and Imagination. Yet, however pleasing the Recollection of this +glorious appearance+; however _strongly_ impressed, accurately described, or richly painted; it must fall infinitely short of the original +sensation+. Unity and Sameness were there contrasted with _perpetual Variety_: Beauty of Colouring; Minuteness, and consummate Arrangement;—with _Magnificence_ and _Splendor_: _actual_ Immensity;—with _apparent_ Limitation:—all which were _distinctly_ conveyed to the Mind, at the _same_ Instant, throu’ the Intervention of the Organs of Sight: and, to complete the Scene, was added the Charm of +novelty+. CHAPTER XXXIX. CONJECTURES ON THE CAUSES OF THE CIRCULAR TRANSPARENCY TO A CERTAIN DISTANCE BELOW THE BALLOON, AND OF THE RED LIGHT FROM THE SEA AND RIVERS, WHEN SEEN ABOVE THE LEVEL OF THE SUPERIOR CLOUDS. [Sidenote: On the circular Transparency.] Section 222. Quere: As Red is the heaviest and Blue the lightest Colour; and as _red_ Rays blended at a certain Angle with _blue_ Rays, produce Opacity: further; as +red+ is the _predominant_ Colour reflected from Water, while in the Form of _dense_ Cloud, for Instance at the Rising and Setting of the Sun; and +blue+ the Colour always reflected from the light Medium of Air or Sky; Does not this Mixture of least and most refrangible Rays, which, when aided with the intermediate primary ones, causes a _Transparency_ near and round the Eye of a Spectator placed either on Earth or among the Clouds; produce, at a greater Distance and different Angle, such a Degree of Opacity, as actually to give the Idea of Clouds surrounding him at a Distance? The latter Part at least is true, that Vapour and Air, which are _naturally_ qualified to _transmit_ +red+ and +blue+, rather than any other Light, will, at a certain Angle, when _blended_, produce an +opacity+. (See the Letter sent by +Newton+ from Cambridge to Dr. Derham, in order to be presented to the Royal Society,—in “Miscellanea Curiosa, Vol. 1, Page 109.”) [Sidenote: On the red Light from the Sea and Rivers.] Quere: May not the Rivers below act as a Prism; as Clouds, about Sun-set or Sun-rise, do to a Spectator on Earth, and reflect only the primary Colour +red+, the _heaviest_ and least refrangible Ray? It being also considered that Refraction cannot change the primary Colour: nor are Rays, in the Direction from below to the Zenith, refracted; tho’ seen from a rarer into a denser Medium. Possibly, a Pencil of Rays, in coming up from the River below may be stripped or drained by the double Absorption of the Atmosphere and River, and the Colour +red+ only, suffered to reach the Eye: “being the last to quit its Basis the Water.” (See Morgan’s Observations on the Light of Bodies, &c. &c. Phil. Trans. for the Year 1785, Part 1, Vol. 75, Chap. 91.) CHAPTER XXXX. ON THE EXCESSIVE DIMINUTION OF OBJECTS ON THE SURFACE OF THE EARTH, TO A SPECTATOR SITUATED ABOVE THE REGION OF CLOUD, AT THE BAROMETRIC HEIGHT OF NEAR A MILE AND HALF, PERPENDICULAR. [Sidenote: Recapitulation of the Scenery below.] Section 223. The Earth’s Surface was presented to the Eye throu’ a _circular_ Opening as already described. This Opening discovered a _Plain_, smooth and level as a Die: a Sort of _shining_ Carpet, enriched with an endless Variety of Figures depicted _without_ Shadow, as on a Map: what was really Shadow forming a separate Colour, and not considered at the Time, as _Shadow_. The Objects were distinctly marked, and perfectly known to be Miniatures of the Face of Nature. All was _Colouring_: no Outline: yet each Appearance curiously defined by a striking Contrast of simple Colours, which served to distinguish the respective Boundaries with most exact Precision, and inconceivable Elegance. +Red+ Rivers, +yellow+ Roads, Enclosures +yellow+ and _light_ +green+, Woods and Hedges _dark_ +green+, were the only Objects clearly distinguishable, and their Colouring extremely vivid. The Sun’s Rays reflected from the Surface of the Sea, and other Waters, dazzled the Sight. +All+ living Creatures were invisible. 224. The Area of each Inclosure, computed to contain a certain Number of Acres, was seen from above under the Form of a Miniature Picture of a certain Magnitude or visible Extension, perpetually diminishing, as the Eye recedes to a greater Distance. And the Case is similar, whether the Miniature be seen from _above_, or _along_ the Ground. The Miniature also lessens as the Distance encreases, according to a certain Proportion so exactly;[49] That, 1. If the _Distance_ and _Magnitude_ of a tangible Object be known by Mensuration; a Judgment is formed, and Laws laid down, for its corresponding _Miniature_ on the Eye. 2. If the _Miniature_ be seen, and _Distance_ known by Mensuration; the Mind forms a Judgment of its tangible _Magnitude_. 3. And lastly, if the _Miniature_ be seen, and _Magnitude_ of a tangible Object is known by Mensuration; the Mind makes an Effort, to the Estimation of its Distance from the Eye. These are some, among many Modes of Comparison, by which the Mind acquires a tolerable Degree of Proficiency, in estimating _Distances_ of familiar Objects, _known_ from the Appearance of their respective Miniatures on the Fund or Bottom of the Eye. And so far most Theories agree. But such _ocular_ Test is only true, while the Comparison is made in _nearly_ the same Medium. For an Object, if seen at the same Distance _along_ the Ground, will appear less as it rises above it; and least in the Zenith; as the Sun and Moon, at Setting or Rising, appear _large and oval_; but at their greatest Elevation, are _small_ and _round_: because being seen, when passed out of a Medium impregnated with Vapours, which in some Measure intercept the Rays of Light: for the +fainter+[50] a distant Object appears, the _greater_ it is apprehended to be.[51] Possibly indeed an Object at the same Distance, if brighter at one Time than another, will _contract the Pupil_ in Proportion to its Brightness: which may have the same Effect, as if the Object had made a _smaller_ Miniature on the Retina; and will regularly strike the Mind with an Idea of _Magnitude_, _only_ equal to its corresponding _Contraction_; i.e. less, when the Object is bright, and greater when faint. 225. If a like Reasoning be applied to the Ascent of Balloons; and it be said that they do not rise so high as is imagined, because their Magnitude is diminished, merely from being elevated into a Portion of the Atmosphere _least_ impregnated with Vapours; it will follow, that to a Spectator in the Balloon; known Objects on the Surface of the Earth below,—being seen from a rarer into a denser Medium, also into one which contains a great Quantity of Vapours;—shoud appear _larger_, than when seen along the Ground, at a Distance equal to its Height in the Balloon: all which is contrary to Matter of Fact: particularly if the Barometer gives a proper Estimate of the Height, of which there is little Doubt: a proper Allowance being made, _in certain Cases_, on Account of the Refraction: for, as before mentioned, (Section 44) Objects seen from the Balloon at a Mile and Half _barometric_ Height, continued, with invariable Uniformity, to suggest the Idea of at least seven Miles. 226. By a general Comparison of Enclosures, and of separate Buildings when they coud be distinguished from the Balloon above the Region of Cloud, with the most distant Extremities, (on the horizontal Level) of Fields or Houses situated along the Sides of Hills or Mountains, at a known Distance by Miles, making Allowance for their being seen in a straight Line;—the latter seemed at least five Times _larger_ than the _former_: supposing them at equal Distances. To give an Instance. Supposing the most distant Extremities of a known Building or Enclosure, situated on the Side of a Hill or Mountain, presented a Miniature of a _familiar_ Magnitude to the Eye of the Spectator on the Ground, at the known Distance of a Mile and Half; the same Object when seen from the Balloon at the same _barometric_ Height, appeared full five Times less. This Comparison was made by Memory, the Morning after the Excursion, tho’ suggested while in the Balloon, from the wonderful Minuteness of all Objects then presented to the Eye. The Author being likewise familiarized to judge of Heights; having been on several of the chief Mountains in Europe: also, of comparative Distances, from his Situation near a large City, in a populous, enclosed Country; on a high Plain, within View of the Sea, Mountains, Hills, Enclosures, Buildings, and Objects whose Magnitude and Distances were known. 227. The Balloon itself, a Globe twenty-five Feet in Diameter, was seen in the Air on the Day of Ascent, at the Distance of 19 Miles. [Sidenote: The Magnitude of Objects seen from the Balloon compared with those of the Sun or Moon near the Meridian, when seen from below.] 228. The Reason already given, for the Solution of the famous Question concerning the apparent Magnitude of the horizontal Moon, seems no less applicable to Objects on the Earth’s Surface, when seen from the Balloon: which _Diminution_ of Objects _below_ confirms the Defect of Dr. Smith’s Hypothesis. For, as they appeared _extremely bright_; being shone on by the Sun, and seen throu’ the Air in a perpendicular Line, containing the least possible Quantity of Vapour; the Brightness must have exceeded that of the same Objects, when seen along the Ground: and consequently the Miniatures of the former must have been less than the latter, and also their respective Distances _seem greater_. CHAPTER XXXXI. CONJECTURES ON THE CAUSES WHICH INFLUENCE THE DESCENT OF BALLOONS IN THEIR PASSAGE OVER WATER. [Sidenote: Recapitulation of Facts.] 1. Conjectures concerning the regular Tendency of the Balloon to _descend_ on its _Approach_ towards +water+. 2. Its _greatest_ Descent, when in the Zenith, over the Middle of Rivers. 3. Recovery and _Re-ascent_ to the former Level, as it _recedes_ from them. Section 229. Article 1. On the first Ascent in the Castle-Yard, Chester, the Balloon gently moved towards the River Dee, and the Sea. And woud probably have gone out to Sea, if the ascensive Power had not presently raised it above the Influence of the Water; into an upper Current of Air, which was visible at that Time, and for two Hours before the Ascent, by the Motion of superior Clouds in a safe Direction towards the Land. 229. 2. The Balloon was _affected_ in passing across the River Goway, and Trafford Meadows, which are a Mile wide: first moving Westward, and again towards the Sea; making several Curves: then resting and _lingering_ between Great and Little Barrow: as the Aironaut was _well_ informed by Persons of _Veracity_, who observed it: his Attention being engaged at that Time by other Objects. 229. 3. A proportionable Effect was observed in _crossing_ a small Brook near Alvanley. 229. 4. The River Wever and its broad Meadows above Frodsham-Bridge actually stopped the farther Progress of the Balloon: tho’ its Course was _merely_ +across+ the River. The Deviation was gently tho’ _invariably_ towards the +sea+: and, if not _timely_ prevented, the Balloon must have fallen in the Middle of the Channel. 229. 5. The same Case woud have happened on the Re-ascent at Bellair; if the _levitating_ Force had _not_ as at first, overcome the Influence of the +waters+, and lifted the Balloon into the _same_ upper Current, which continued to move in its former safe Direction. 229. 6. Different Branches of the Duke of Bridgewater’s Canal near Preston-Brook might _possibly_ affect it in a small Degree: and, tho’ Clouds a little afterwards, secluded the Aironaut from a Sight of the Earth; yet the Balloon was known to hang, for some Time, over the Mersey near Warrington. 229. 7. The Balloon descended and alighted on the Middle of a large Tract of wet Moss Ground. The Writer saw Sadler’s Balloon rise at Manchester, the 11th May, 1785, and descend near Blencow-Bridge, at the Conflux of _two_ Rivers. The above Facts give sufficient Indications of the constant Tendency which Balloons have, to descend on Water. CHAPTER XXXXII. Section 230. Three Causes seem generally to concur in producing the Effect of Descent, over Water. 1. The Water itself. 2. The Air above it. 3. Change of Temperature, Section 231. Article 1. So long as Gass escapes from the Balloon; it will be instantly and _reciprocally_ attracted, throu’ the _Crevices_, by the Moisture contained in the _Air_, particularly over _Rivers_: its specific _Gravity_ within the Balloon, woud be encreased,[52] and consequently the Balloon itself rendered less buoyant: The Gass woud, on the contrary, be repelled by _electric_ Air: which woud lessen its Tendency to escape, throu’ the Pores of the Silk. But it is _presumed_ that Air-tight Balloons will be little affected by _external_ Moisture. 231. 2. Moist Air over Water being generally cooler than over the adjacent Land, will, so long as the Gass continues at its former Temperature, assist and raise the Balloon _thus_ moving into a _denser_ Stratum: but no sooner is the Balloon contracted by the external Cold, than it descends into a Medium of Air, whose specific Gravity is proportionable to the contracted Bulk of the Balloon, and rests when equal to it. 231. 3. Water is also a Conductor of Electricity, tho’ a feeble one: and there is moreover a strong chemical Affinity between +water+, inflammable Air, Gasses, Floguiston, and Electricity.[53] 231. 4. Water will therefore +conduct+ the Gass to itself: i.e. will draw the Balloon _downwards_, and with accelerating Velocity; as the Attraction is stronger, the nearer the Water. 231. 5. But if the Air over the Water be warmer than that over Land; then the Balloon, moving into a warmer Medium, as over the Sea in frosty Weather, most undoubtedly descends: till the included Gass has received the additional Encrease of Temperature from that of the Air, at which Time it will have a Tendency to reascend, and will rest suspended in Equilibrio, as in the former Case. The above Causes however may be considered, as _trivial_. The first may be avoided by making the Balloon _Air-tight_: and the second easily guarded against by throwing out a little _Ballast_. The _only_ formidable one, if any, is +the depression of the atmosphere+. This it will be necessary to consider with some Degree of Attention. CHAPTER XXXXIII. Section 232. Whoever consults Antiquity,[54] or is acquainted with modern Mèteorism, will ascent to the Truth of the Facts there recited, viz. That the Storms of +dispersion+ called _Prester-John_, and _Ox-Eye_ over Table Bay at the Cape of Good-Hope (not to mention those of +collection+, as _Whirlwinds_[55] and _Waterspouts_;) _descend_ on Sea and Land from the _middle_ Regions of the Air, often _perpendicularly_ +downwards+: and then blow violently from a Center, to all Parts of the Compass at once: a necessary Consequence of their beating _forcibly_ upon the Land or Water. The Ancients maintained that the Origin, of Wind was a mere _Depression_ and _Percussion_ from the Cold of the middle _Region_: and it shoud be remarked that their Observations were made on the _Continent_, and in _warm_ Climates. Now what is seen to Excess in the _hottest_ and _coldest_ Climates;[56] most probably takes Place, in a less Degree, in temperate ones. Therefore, on a Change of Weather, the upper Atmosphere _descends_: whether its Effects are _Cold_, as in Winter; _Warmth_, as in Spring; _Wind_ or _Wet_; at the proper Seasons of the Year. 233. The Balloon, with which Dicker Junior ascended at Bristol, April 19, 1784, on a +windy+ Day, proved the Truth of the Conjecture: for tho’ the Aironaut threw out most of his Ballast; yet after each Ascent and Recovery, he was repeatedly darted _downwards_ +even+ with the Ground.[57] 234. A similar Event happened to Crosbie, in his Passage over the Sea from Dublin to England; for, tho’ he too discharged his Ballast, the Wind kept him _down_ and +even+ with the Water. The Weather at that Time seems to have been an Εκνέφιας, Procella, Percussion, Squall, or Tornado, i.e. a Storm of +depression+, and +dispersion+. 235. The Eknèfiai Winds come from cool Points on each Side the North. Bacon also observes that all +boisterous+ Winds, as Procella, Typho, and Turbo, have the evident Direction of a Precipice, or Projection _downwards_, more than other Winds: they seem to rush down like a Torrent or Cascade: and are then reverberated or beat back from the Earth, in all Directions. Stubble, Corn, or Hay in the Meadows are raised, and spread around in the Form of an +extended canopy+, (_inverted Cone_, _elliptic Solid_, and _hyperbolic Curve_.) See “Bacon’s Historia Ventorum”, Pag. 43, ad Articulum 10.[58] 236. If then it be allowed to reason from that Analogy which took Place in most of the Cases already mentioned; the _gentler_ Depression. of Balloons over Water in _milder_ Weather, may be owing to a Cause somewhat similar, tho’ not so evidently an immediate Object of the Senses, viz. _an actual tho’ invisible Descent of Air upon the Water_. 237. Blanchard in his Passage over the Sea from Dover to Bologne in France, when near the Middle of the Channel, suffered an unexpected Depression, and at the same Time was nearly +becalmed+. A +calm+ also took Place on the Irish Sea: which must have prevented Crosbie from landing,—without _Wings_, or some _propulsive_ Machinery, connected with the Balloon. 238. Lunardi rose from Liverpool when the Wind blew _boisterously_: yet was _becalmed_ twenty Minutes over the _broad_ Turn of the Mersey near Ince, when above the Level of the Wind: and, descending into the same Stream of Wind, was hurried along towards Beeston-Castle in Cheshire. CHAPTER XXXXIV. [Sidenote: Depressing Columns of Air known to the Egyptians.] Section 239. The Existence of depressing Columns of Air was well known to a People more ancient than either Romans or Greeks. 240. The sultry Climate of Egypt, whose Situation is that of an extensive Meadow watered by a _broad_ River, and enclosed by Mountains to the East and West; consequently not subject to general horizontal Currents of Air, except along the Line of its Meridian,—is _the Country_, wherein Columns of +cool+ Air descending on the Water, woud be soon observed. And they, in Fact, were almost the only People who applied the Observation to common Life: having, according to Herodotus, as well as later Writers, built lofty Structures +open at the top+. By which Means the cool Air +rushing+ downwards greatly refreshed the Inhabitants. The ancient Pantheon, at present called All Saints Church, now standing at Rome; built in the lowest Situation of a Street named the Piazza di Navona is on this Construction: and the Hint probably taken from an Egyptian Model. 241. In all inland Countries, whose Lakes are frequently surrounded by Mountains, as Bala-Pool in North-Wales; those of Westmoreland and Cumberland; the Lake of Geneva in Swisserland;—the Air rushes +forcibly+ on the Surface of the Water in descending Torrents: this the Writer has frequently observed.[59] (In other Languages, the Words applicable to Wind on a Lake, or the Ocean, signify Descent: as, Καταβαινω, and Επικειμαι· also the Northerly or _descending_ Wind corresponded to the Εκνὲφιας while the Southerly or _ascending_ Wind answered to the Απογη.) All this, which may be allowed to take Place in _bad_ Weather, may perhaps be excepted to, in _fine_, and still more so, in the _finest_ Weather. As the slightest Change is first observable on the Surface of Water, whether on Lakes or the Ocean, the _Descent of Air_ in the finest Weather is familiar to Mariners by the Appellation of +light airs+, playing in Eddies: and particularly in the _variable_ Latitudes; i.e. between 32 and 42: to these the Writer can also witness: as well as on small and large inland Lakes, by partial _Dimplings_ and _Rufflings_ of the Surface. OBJECTION TO THE THEORY REMOVED. 242. It may be objected to the above Theory, that the Wind plainly blows in an horizontal Direction, as may be seen from the Motion of Clouds and Trees. To which it may be answered, that if Clouds are not beside the Question; as it is not asserted that a single Column of Air presses from so great a Height to the Earth; (tho’ it be the Case in Squalls;) yet it is extremely difficult to determine whether Clouds move in a Direction exactly parallel to the Plane of the Horizon: and it is much more probable that they are in a perpetual Change, _encreasing_ or _melting_; rising or falling, according to the _Pressure_ and specific Gravity of the _Medium_ in which they float; its Tendency to Moisture or Driness, Cold or Heat; also the different Combinations and Decompositions, with Respect to which, the Atmosphere is in perpetual Variation. The Motion of Trees, if carefully attended to, seldom shew Effects of a regular horizontal Current. And since the more _powerful_ the Wind; the more evident and accurate may be the Observation; it will be found, that the _first_ general Effect is an oblique Depression, succeeded by a Recovery or instant Exaltation: then a momentary Pause, or actual Retreat of the Wind; and in a few Seconds, a Return of the depressing Torrent. But the strongest, and, at the same Time, an irrefragable Proof, is by _Appeal_ to Men of _Science_ in the Navy, or to skilful Pilots, who are conversant with Winds and Waves; who have weathered Storms off Cape Hatteras in Latitude 36; (where probably the Wind is perpetual;) or have made an East-India Voyage:—whether, if a Gale blew in an horizontal Direction +only+; the Ocean coud produce such an Inequality of Surface: or whether when the Sea runs +mountains+ _high_; the tremendous Surges must not arise from the _violent_ Action of Winds repeated at Intervals, sometimes _descending_ perpendicularly; but oftener in forcible elastic Torrents of oblique +depression+, and instant _Resilition_? CHAPTER XXXXV. [Sidenote: A _gentle_ Depression of Air over _moist_ Places in _fair_ Weather.] Section 243. Intimations of depressing Columns in moderate Weather, are the _sluggish_ Clouds, which often make their _first_ Appearance, and remain longest, nay almost continually, _over_ and _along_ great Rivers, and Chains of Mountains, both during a Calm, or from whatever Point the Wind blows. And hence the greater Quantity, Violence, and Continuance of Wind and Rain, which then _descend_:[60] also of the _greater_ Purity of the Air _during_ such Descent. 244. As, therefore, it is plain that atmospheric Air +descends+ _frequently_, both in bad and fine Weather; if a Cause can be assigned so general, as to make it probable, that such +depression+ does almost continually take Place:—tho’ at present the Effect is only evident to the Senses, by actual Experiment in the Passage of Balloons throu’ such Columns;—it will be sufficient to put Balloonists on their Guard against the Effects of such _Depression_. 245. In order to investigate the Theory of Depression; it may not be unacceptable, particularly to those who have not had Leisure to peruse the Experiments on Air, by Dr. Priestley, or the Collection on the same Subject by Cavallo;—just to extract a few short Quotations, on the chemical Affinities of Air and Water. 246. Article 1. “Water, as Rain, imbibes only the pure Air of the upper Regions, leaving the lighter and floguisticated Air to ascend.”[61] 246. 2. Felìcè Fontana says, “Common Air receives an Encrease of Bulk and _Elasticity_ from being shaken in Water.”[62] 246. 3. Air absorbs Water, and Water absorbs Air:[63] and the Absorption of Air by Water is promoted by Agitation: it also absorbs twice as much _defloguisticated_ Air, as common Air:[64] the whole Bulk of the Air absorbed being equal to one-twelfth of the Bulk of the Water: yet the Bulk of the Water seems but _little_ encreased: the Air being contained within the Interstices of the Water. 247. The following is a pretty and an easy Experiment, to shew how the +absorption of water by air+ takes Place, under the immediate Inspection of the Observer. Admitting the Sun’s Light into a Room, throu’ one Window only; pour a Pint of _boiling_ Water into a large Bason: hold the Bason, which will not be half full, next the Light, in such a Manner, that the Sun may shine on the Water and Bason; yet the Eyes be shaded by the Top of the Window Frame. Incline the Side of the Bason towards the Light, so that the Water may rise even with the Top. The Eye being placed just above the upper Side of the Bason, farthest from the Light; look on the Water. You may then observe the Surface of the Water next the Light, refract the Sun’s Rays, and produce the primary Colours, particularly the +red+ and +green+: which tho’ _transient_, _continue_ to be _seen_ in Succession; as Vapours rise above the Surface of the Water. Their _first_ Ascent is plainly discoverable: remaining above its Surface, in the Form of _small Dust_, gently agitated, not _separately_ but as a _whole_. Nor do they seem to rise into Steam, till assisted by the Action, and Contact of _dry Air_, which like _dry_ Spunges, _licks off_ and absorbs the small Dust already accumulated by the Force of the Heat from below, and then becomes visible under the Appearance of Steam, flying off in distinct hollow Vesicles. The more _still_ the Air of the Room, the more slowly will the Spunges of Air come in Contact with the Body of small Dust.—Besides the small Dust already mentioned; the Heat will detach solid Globules of Water; which will remain floating on the Surface of the Body of Water: till the dry Air descends and transports them with it; the Air at the same Instant dissolving the solid Globules into hollow Vesicles. But the most extraordinary Phenomenon, and which cannot be mistaken, is, that as soon as a Spunge of Air has dipped into the Surface of Water, and received its Lading; the Vesicles continue to accumulate, till another fresh Spunge descends in a similar Form, which may be traced upon the Surface of the Water, and seen in its Shadow, or rather in Beams of Light at the Bottom of the Bason, at the Instant it has flown off with its Burden: for that Part of the Surface of the Water transmits new Rays of Light, on Removal of the Vapour carried away by the Dip and Play of Air. 248. The Removal of the Vapour, likewise exhibits a curious Appearance on the Surface of the Water: which seems as if divided into irregular Parcels detached from each other; like the reticular Daplings visible on the under Side of Clouds elevated to the highest Stratum of the Atmosphere, and there evaporating or dissolving. 249. So powerful is the Attraction between Air and Water; that, while the Steam is rising above and round the Sides of the Bason; _Waves of fresh Air_, by Intervals, press the exterior Parts of the Steam _inwards_, in order to get at the Surface by descending into the Bason. This Operation is best discovered, when the Bason is held _even_. And the whole Process may be observed more distinctly, if the Bason is raised and fixed on a Frame, near the Height of the Eye of the Observer, standing upright: who will then be able to trace minutely the exact Form of the Steam, and Insinuation of the Waves of Air into the Center of each Curl, or rising Curvature: an Appearance, similar to which, may be seen in _Water_ flowing from a small Orifice in a close Vessel; the fresh Air forcibly entering in an opposite Direction; forming a visible Cavity and Curvature in the Center of the Stream. See Halley’s Experiments on Evaporation in the open Air, and in a close Room, in Lowthorp’s Abridgement of the Phil. Trans. Vol. 2, P. 108. Having once remarked the foregoing Process at Leisure; the same may be seen over any open Vessel of Water just warm enough to emit visible Steam: but the Air shoud be as _still_ and _calm_ as possible: the Steam never rising from all Parts of the Surface at once; but a depressing Spunge of Air always descends to the Surface, the Instant a Lamina of Vapour has been detached. Such is the regular and invariable Process of Evaporation. The same Process may be distinctly traced over the Surface of a Piece of Water or River, the Air being perfectly calm, in a gentle Frost, at Sunrise, particularly in Autumn, while the Water retains a Warmth superior to that of the Air. 250. Hence it follows that _as much light_[65] and _warm_ Air as is raised with the Steam by Evaporation from the Surface of any Water; _so much heavy_ and _cool_ Air is +instantaneously+, constantly, and forcibly +depressed+ upon its Surface, in order to supply the Vacancy, restore the Equilibrium, and continue the Evaporation.[66] 251. Now, besides the mutual Affinity that Water has to almost all Kinds of Air, and to Floguiston; added to its Power of Absorption; and as the +sea+, particularly in Summer, also +rivers+ and _damp_ +meadows+ are generally _cooler_ than the Lands and Countries bordering on them; Currents of _damp cool_ Air press forwards to supply the Defect or Vacancy caused by Heat, Rarefaction and Elevation of _dry warm_ Air, which is necessarily, and almost constantly rising into the Atmosphere, from heated Lands, Plains, and gentle Eminences _long shone_ on by the Sun. 252. Consequently the pure, cool, defloguisticated Atmosphere, is almost continually descending from above; sometimes imperceptibly, often forcibly, on the Surface of the Sea, the Channels of Rivers, Meadows, and all wet Land. Which Depression acts, in Proportion to its Strength, on the Balloon; and always with a sensible Effect: for, being in Equilibrio with the Air at all stationary Heights; the _least_ Depression of the Atmosphere makes the Balloon descend, considerably. 253. This Reasoning is, in many Cases, applicable to the Air, and consequently the Weather and Cold of Mountains. Nor can it otherways be accounted for, why the Snow is perpetual, and the Cold so intense, on Mountains under the Equinoctial, and between the Tropics: but which admits an easy Solution on the above Hypothesis.[67] CHAPTER XXXXVI. Section 254. The Subject of +depressing torrents+ requires an accurate Investigation: as it will serve to point out the proper Time of Day or Night, when an Aironaut ought so to calculate his Voyage, as to arrive over the Middle of the Channel, or Arm of the Sea, at some particular Hour: in order to wait for a Sea Breeze which may waft him to the other Side. A Point not difficult to be ascertained. Also, this Idea of +depression+, if properly considered and digested; may prove a sufficient Foundation on which to establish a new Theory of the _Weather_, so ill determined at present, from its _aggregate Weight_ or _Elasticity_ only, as indicated by the Barometer. 255. If a Conjecture may be formed on a Subject, material in itself, yet of which so little is actually known; woud not _the proper Time_ of undertaking a Voyage over the Channel be such, that the Aironaut shoud find himself three Parts of the Way across, by +nine+ _o’Clock_ in the Morning? 256. In _warmer_ Climates, where the Seasons are more regular; the _Land-Breeze_ blows to Sea from Midnight till X. in the Morning: at which Time, the _Sea-Breeze_ blows to Land; continues till V. or VI. in the Evening; and is succeeded by a +calm+, which lasts till Midnight. Whence it follows, that during the Time of the Sea-Breeze, there is a constant Tendency towards a +gulph of air+, _along the Middle_ of the Channel: the Equilibrium of which is as constantly supplied by a _Depression_ of the upper and in general cooler Strata of Air; and therefore a _dangerous_ Time for the Passage of Balloons. On the contrary, during the Night, and till ten in the Morning, there is an _Accumulation_ of Air, _along the Middle of the Channel_: which consequently is a proper Time to ensure a _safe_ Passage; by the Assistance of +wings+, or some +propulsive+ Machinery. [Sidenote: Of the horizontally calm mediocèanal depressing Current.] 257. The Deficiency or Vacuity being supplied from the etherial Regions; it might be taken for granted, that such Ether must be _considerably_ lighter than the adjacent common Air on an equal Level, and therefore _proportionably_ dangerous for the Passage of Balloons. But if it be considered that such Air, acting as a +wedge+, or more probably in the Form of an hyperbòlic Solid,[68] to fill up the Vacuity, descends with Rapidity from a _colder_ Atmosphere impregnated with aqueous Vapours _invisible from below_; and that both the Air and Vapour have reciprocal Affinities and Attractions, electric and mechanical, with the Body of Water beneath them; and are often rendered still cooler by its constant Agitation and _Evaporation_; also, that the Supply being immediate and cotemporary, with the +double tide of air+ flowing from the _middle_ over the _opposite_ Shores;—there possibly may be little or no Difference between the aggregate or _barometric_ Gravity of _such_ Columns, and those which are formed by the Sea-Breeze on either Side of them: therefore the Descent of Balloons is owing, among other Causes, to an almost perpendicular actual Depression of the superincumbent Atmosphere.[69] Following up the Idea of a Sea-Breeze, blowing, at a Medium, for 20 Miles over Land; altho’ the Stratum of the +lower current+ of Air, or Sea Breeze, may not exceed +half a mile in depth+, measuring from the Ground upwards; nearly equal to 26 Inches of the Barometer _above_, the Thermometer also _above_ being at 55, i.e. _Temperate_:—yet this Observation may prove of essential Service, while the +upper current+ of Air, i.e. the general Wind blows +towards+ the Sea, (which will be found to take Place more _frequently_ than is, at present, imagined;) or while the Balloon is influenced that Way; as was the Case with Sadler and his Companion when over the Nore: who, on his accidental and sudden Descent, fortunately found Safety in the +sea-breeze+. Which Breeze was sought for, and made Use of by the Author, when in the Balloon, near Frodsham, in Cheshire. For, as the Sea-Breeze is pretty general, Aironauts shoud not be too apprehensive: as they have it in their Power, by proper Management, to drop into the Breeze—for +either shore+: if they are provided with a Machinery to waft themselves across the intermediate _depressing_ or _accumulating_ +mediocèanal column of air+: which Space, between the two Shores, is, as before hinted, frequently +becalmed+. 258. Further: as the above Theory of a _mediocèanal_ Depression seems to receive additional Confirmation from _each_ Balloon Experiment; Lunardi _descending_ on the 5th of October last, when near the Middle of the Bay of Edinburgh or Firth of Forth;—it may be found _prudent_, to keep the Balloon continually rising, till the Aironaut is _one-third_ of the Passage _over_. 258. 2. For if the general Wind in the upper Current be not strong; the Aironaut may expect to be _becalmed_, with Respect to the horizontal Direction of the Current, the Instant he finds, by the Rise of the Barometer, that the Balloon _descends_; i.e. when it is acted upon by the depressing Column: in which Case, the _higher_ he has soared, the _safer_: as he will have more Room and greater _Latitude_ for Exertion by Means of the Machinery: which Machinery will be greatly _aided_ by the Force of the descending Column or Gravity; and will act on a similar Principle with the Ferry-Boats over the River Po in Italy; which are a Sort of horizontal Pendulum. For the Aironauts will continue to _descend_, at the same Time that their _Wings_ furnish the Means of a progressive Motion. Therefore, before the Time that the Balloon has reached the Surface of the Water; they will have crossed the depressing Column; and find themselves wafted _gently_ by the _new_ Sea-Breeze setting in towards the opposite Shore. 259. If the Aironaut _rises up_ to Sea with a Wind blowing from the Land on each of the opposite Sides of the Channel, and arrives above the Middle of the Channel, while the same Wind remains; it is probable that the Balloon will continue to rise higher as he proceeds towards the Middle, _where_ the +mediocèanal accumulation+ has for some Hours taken Place; and therefore he need not be under any Apprehension of falling: but, as before, it being probable he will also be _becalmed_; the Necessity of propulsive Machinery is equally urgent, in order to pass the Center of the _Accumulation_: after which, the Balloon will ride Home to the opposite Shore in the new Sea-Breeze, by _that_ Time, just beginning to set in. 260. With the Assistance of propulsive Machinery, it is imagined the Aironaut may be enabled in a few Minutes to force throu’ the calm mediocèanal Accumulation, or Depression: after which, he will have little Occasion to make Use of it. 261. +Sunrise+ is, probably, the +safest+ Time of all, to ascend towards the Sea, with an _Air-tight_ Balloon: arriving with the Assistance of the Wings, throu’ the _calm_ mediocèanal Accumulation: and there waiting till the new _Sea-Breeze_ sets in to the _opposite_ Shore. CHAPTER XXXXVII. [Sidenote: Difficulties, proposed by Mons. Sauffure stated; and their Solution attempted.] Section 259. It may be observed here, that the two Difficulties proposed by Sauffure, are, in a great Measure, removed; in admitting the Doctrine of mediocèanal _Depression_, and consequent alternate _Accumulation_, In a distinct Chapter, treating of the Variation of the Barometer, which he allows has Need of farther Explanation; he asks (Page 308) what Reasons can be assigned, why the _East_ Winds, which are _cold and dry_, make the Barometer _descend_, in England and Holland: yet, the _West_ Winds, which are _moist and temperate_, make it _rise_? The East Winds _here_ blow chiefly in Spring. Now it is universally agreed, that the Sea, is sooner heated by the Sun than the Land: and on Account of the marine Acid exhaled,[70] is also less cold,[71] during that Season, in the same Latitude. In Spring, therefore, the great Atlantic or Western Ocean, being _less_ cold than England, Holland, and Eastwards; the Air pendent over the most extensive Tract of _dry and cool Land_ in the World, rushes Westwards to supply the Equilibrium of _warm light_ Air rising upwards, and causing a temporary mediocèanal Accumulation: which (altho’ the specific Gravity of the cold Air is greater) must produce an actual Deficiency in the aggregate Weight of the Atmosphere over England and Holland: consequently the Barometer falls. Again: the West Winds which blow at other Seasons; if, in Winter; are not frequent, except about Noon after frosty Nights which have equalized the Air for the Transmission of vigorous Sunshine: and shoud be looked upon as (what they are really observed to be) _low_ partial Sea-Breezes, or +eddy+ _Currents_, insinuating themselves near the Surface, and setting Eastwards frequently against the upper and more general Winds; and therefore produce a temporary Accumulation. If, in Summer; the Supply of cool Air to the heated Land, being made not only from the _Northern Ocean_, and lofty _Mediterrànean Mountains_; but also from the _Atlantic Breezes_; the latter, tho’ _moist and temperate_, must also tend towards an Accumulation of the Atmosphere over England and Holland: and therefore the Barometer rises. CHAPTER XXXXVIII. [Sidenote: Facts and Observations tending to confirm the Doctrine of Accumulation and depression.] Section 260. Before the Subject of mediocèanal Accumulation and Depression of Air, is wholly quitted; it may be well mention and compare a few Facts and Observations, which will elucidate the Doctrine; and in their Turn, receive Light from it. 261. If, in the Middle of a _hot sunny_ Day, Vapours lighter than the Air, were to rise from the Ocean, (which they will continue to do, in hollow Vesicles or Bladders, till the Expansion breaks the Bubble, at which Time the Water woud fall to the Earth, if not drank up by the Attraction of _dry_ Spunges of Air;) there woud be a constant Wind blowing from _Land to Sea_, to fill up the Chasm: but at such Time, the Land is more heated than the Sea: therefore hot Air and Vapour arise from both; and the Breeze, on the contrary, blows from _Sea to Land_; consequently if the Vacuities were not _continually_ supplied from the etherial Regions, and from the Ocean, all Animals woud actually die, for Want of Air, as in a _hot close_ Room. Such Supply is therefore constantly made, by Depression of the Atmosphere, and Absorption of the Water. 262. What happens on a great Scale, above the Ocean, as _before_ hinted; probably, happens on a smaller, over Channels or Arms of the Sea: and on a still smaller; over and along Rivers, Brooks, wet Meadows, and damp Grounds. 263. In the variable Latitudes on the Atlantic Ocean; _cool fresh_ Air is supplied from above, by descending Vortices of Wind and Showers: i.e. _Storms_ of +collection+.[72] 264. It may be remarked, in Confirmation of the above Doctrine, that triangular or Latteen Sails are used, and more useful, in a Mediterranean Sea, surrounded by high Lands, from which the Wind suddenly descends in Squalls; than in the open Atlantic, where the Wind is more equal. 264. 2. Perhaps there cannot be a better Account of the depressing Torrent of Air, than that which Bacon has given, in describing the Motion of Wind on the Sails of Ships, in a _Squall_. “All Wind acting on the Sails of a Vessel, tends to depress or sink it. Wherefore _in strong Gales_, they first haul down the Yards, and take in the Topsails: afterwards all the Sails: cut away the Masts: throw the Lading overboard, the Guns, &c. to lighten the Vessel, and keep her above Water.”[73] CHAPTER XXXXIX. [Sidenote: Torrents of Air on _Etna_, and _Teneriffe_.] Section 265. With Respect to Mountains: on reading what Travellers have written, particularly Ullòa;[74] they seem to answer the Intention of supplying cool Air to the surrounding Plains, or Continents; by Depression and Condensation: and also, if on Islands; to the Sea itself. 266. Brydone, in his Tour throu’ Sicily and Malta, in 1773;[75] giving an Account of his Ascent to the Top of Etna, says, that at the Foot of the Crater, the Snow was frozen hard and solid:[76] and that the Crater was so hot; it was impossible to descend into it. Further: “that the Smoke rolled down from the Sides, like a Torrent: till of equal Gravity with the Air, when it shot off horizontally; forming a long Track, according to the Direction of the _Wind_: which there rose to a +violent+ Degree: so that it was with Difficulty he coud settle the Barometer for an Observation.” He also adds “that _Clouds_ began to _gather_ round the _Mountain_; but were _dispelled_ by the Wind.” Now from the foregoing Theory is it not probable to suppose, that a _Torrent of Air rushed_ continually down from the etherial Regions, not only to supply the Fire of the Crater; but also the Vacuity caused by the perpetual Elevation of Vapours and heated Air from below: the Torrent likewise _depressing_ into the Track with itself, the Volumes of Smoke which were seen to roll directly down the Sides of the Mountain: that this descending Torrent of Air, in its Progress, dispelled the Clouds forming round the Sides of the Mountain, by the Ascent of warm Vapours condensing, as they rose, on their Approach to the cold Mountain: the Smoke shooting _horizontally_, from that Height _only_, at which an _horizontal Current of Air_ began to take Place? For it can hardly be imagined that the Air at the Top of Etna, found to be “_electrical_,” and which must have been replete with a Mixture of Floguiston, inflammable Air, Gasses, and other aërial Fluids highly rarefied, heated, +dry+, (and consequently lighter,) _at the Instant_ of rising out of the glowing Cauldron, became so condensed as to fall like Water, without partaking of the Motion of a _violent_ Wind, supposed to blow in an horizontal Direction. 267. Glas, in his Account of Teneriffe,[77] reports, that the Clouds are generally half as high as the Peak, above the Sea,[78] i.e. according to him, near the Height of a Mile and Half: “_below_ which Clouds, the _North Easterly Winds_ +generally+ prevail: and, at the same Time, _above them_, we find a _fresh Westerly_ +Gale+: which I believe to be the Case _in every Part of the World when the_ +trade wind+ blows.” In Page 253, he says, that in ascending above the Level of the Clouds, he found the Air sharp, cold and piercing: and the Wind blew strong from South West, and West South West: so that the Wind blew towards the Mountain from three different Points at least, viz. the Trade Wind, from North East below the Clouds; just above them, from South West: and still higher, a fresh Gale, from West. “The Air on the Top of the Pike was thin, cold, piercing; and of a dry parching Nature, like the South Easterly Winds which I have felt in the great Desert of Africa, or the Levanters in the Mediterranean: or even not unlike those dry easterly Winds which are frequent in the Northern Parts of Europe, in clear Weather, in the Months of March or April,” Page 257. This dry Wind answers to the Eknèfiai (before mentioned) i.e. _Wind descending_ +from the clouds+. Glas further observes (Page 250) that the Clouds, in fine Weather, descend gradually towards Evening, and rest on the Woods till Morning: when they re-ascend, and remain suspended above them, till the succeeding Evening. Here then a nocturnal Depression of the Atmosphere is obvious. But this Appearance will not prove that the Air does not descend below the Level of the Clouds: for, tho’ the Clouds descend with the Air; Vapour-Air, of which they are composed, becomes _transparent_ both by Dissolution, in a warmer Stratum, and Proximity to the Earth, as before mentioned. [Sidenote: Conclusion drawn from the above, applicable to Balloons.] 268. From the Variety of Winds experienced at different Heights, not only on _Teneriffe_, but in different Places; it is plain, that if Balloons can be made durable and Air-tight; they may be wasted between the Tropics by an East or West Current at Pleasure: and also throu’out the Globe; the Occasion being made, in some Respect, subservient to the Time.[79] CHAPTER L. CORROBORATING PROOFS OF A DEPRESSION. Sect. 268. Art. 1. The Author is well informed, that, during an Engagement at Sea;—in _ten_ Minutes after the Action has commenced;—tho’ it blew a _Gale_ before; (that is, tho’ it blew _violently_;) the Agitation of the Air, arising from the Explosion of the _great Guns_, and small Arms, woud counteract the Wind, and produce a dead Calm. 268. 2. Quere: does not the _new elastic_ Air, produced from the Nitre,[80] give an instantaneous Compression and Dilatation to the _incumbent_ atmospheric Air, round the Place of Action, while the _lighter floguisticated Air_ passes throu’ it, raising, and affecting to its highest Limit, the _whole_ Atmosphere. And does not the Effect of a sudden Calm, suppose the Wind to _descend from above_ with a Kind of _saltatory_ Motion, instantly counteracted by the _new elastic_ Air?—For if the Wind be supposed to blow sideways or horizontally, _to any considerable Height above_ the Water, woud not the fresh _lateral_ Air glide away, and prevent the Continuance of the Calm? 269. When a Squall happens, or only Rain falls; Air will _rush_ from all Sides, and from _above_, to supply the Vacancy of the fallen Cloud and Vapour. The Air immediately _above_ must fall: the lateral Air gravitating towards other Places. Hence _Cold_, and a bright Sky after Rain. 270. The Theory of Accumulation may account for the frequent _warm_ Rains in Winter, and during the Night. For the preceding diurnal Accumulation over the Sea, may _circulate_ during the Night, at a great Altitude, to restore the Equilibrium and Loss of _cold_ Land Air sent by a low or Ground-Wind to Sea, during the Day-Time: particularly, as the _Accumulation_ over the Sea, during Winter, is almost _continual_. 271. The _Wind_ would more frequently be perceived to _descend_ and _rebound upwards_, (Trials of which might be made by holding an Umbrella, extended at right Angles with its Axis, upright in the Hand;) if the same Opportunity offered, of opposing as great a Surface to it in a perpendicular, as is every Day done, in an horizontal Direction: for in walking, the whole Height of the Body, and half its Surface, is opposed horizontally to the Wind: but the Head only, which is covered, is opposed to the perpendicular Pressure. 272. As every Circumstance in the Order of Nature is so admirably contrived that each apparent Inconvenience rectifies itself; in _heavy_ Winds continuing to blow from a +cold+ Point; the Construction of the Atmosphere is such, that the _warm light_ Air from the opposite Points will necessarily rise up and flow over the cold Stratum, and by their Tendency to an Equilibrium, will produce an Air _less cold_, before the _same_ Wind is exhausted. 273. On the one Hand; it is probable, that, as cold Winds are heavy; the Eknèfiai Winds are covered with frequent Waves of the Apogay, or light warm Air rolling over them, frequently from the opposite Points. 274. On the other Hand, as the _Apogay_ Winds are naturally light and warm, it is _improbable_ that they shoud be _frequently_ covered with Waves of _cold heavy Air_, rolling over them from Eknèfiai Points. It may therefore be reasonably concluded, that the Eknèfiai Winds, when approaching or opposed to the Apogay, shoud be considered as _Ground Winds_, (i.e. Winds blowing next the Surface of the Earth, tho’ they be supposed at the same Time to descend) which receive the Apogay above them: and that the Apogay being warm light and +moist+, (which last will have the same Effect, as if they were more elastic;)[81] being also more turbulent, and endued with greater Velocity, press back the Eknèfiai from the Surface of the Earth, and upwards; and at the same Time flow above them. By which means the Eknèfiai partake of their Qualities;—become less _cold_, less _heavy_, and less _dry_.[82] CHAPTER LI. Section 275. If then this Reasoning be allowed; aërial Travellers will not be subject, when, at a considerable Height, even in Winter, to great Degrees of Cold, supposing that the Air does not actually freeze the Waters below; and the Apogay or Southerly Winds have continued for a few Days. On the Contrary; Aironauts may expect Cold, encreasing with their Ascent, even in Summer, tho’ _warm_ below; supposing the Eknèfiai or Northerly Winds to have continued but for a Day before the Ascent: they may possibly, indeed by soaring higher, rise into the regular Stratum of the warm Apogay floating above them. 276. From what has been said, there seems a Degree of Probability, that the Air for a Number of Miles, _above warm cultivated Plains_ shoud differ materially in its Temperature, from Air above Mountains, or _even on a Level_ with their Summits. That the former Air, in moderate Weather, shoud continue _warm and rarefied_: while the latter is _cool and condensed_. For the same Reason the Air over the Sea, on the Hours of Accumulation; i.e. during the Night, in Summer, and frequently in Winter, shoud be found _warm_ and _rarefied_: especially during a Continuance of the Apogay Winds. 277. It is likewise probable that the Atmosphere will be found +respirable+ at much greater Heights, than is at present imagined: during the Continuance of the Eknèfiai Winds; and also, on Account of the _defloguisticated_ Air,[83] which is _drier_ and _less elastic_ in Proportion to its Rarity.[84] 278. The Height of 10 Miles seems not too great to limit human Respiration, shoud any Attempt be made, to soar with a Balloon in a mild Atmosphere; and particularly between the Tropics.[85] But an Objection woud be found in the Size of a Balloon sufficiently capacious to contain nearly 6 Times the Bulk to which the Gass woud necessarily expand itself, at the Height of 10 Miles. [Sidenote: First Cause of Limitation, in the Ascent of Balloons.] [Sidenote: Second Cause of Limitation in the Ascent of Balloons.] 279. It seems most likely that the primary Cause that will affect the Ascent of Balloons is the Difficulty of encreasing the Dimension of the Balloon: the Second, is from the excessive Cold; if the Wind blows from any Points of the North. Supposing the Construction of the Atmosphere to be as represented by different Authors, (which, by the Way, is scarcely credible) ten Miles will perhaps be the utmost attainable Height. 280. There is a Circumstance relative to the Motion of the Air, which has not been sufficiently attended to: and bears some Analogy with that of a _Thorough Air_. This Circumstance may not improperly be called the _Reception_ and _Dispersion of Air_. In cold Climates, it is an Object of Dread: in warm ones, a most desirable Piece of Luxury. A gentle Undulation of the Air is perceived in Peru, and other hot Climates, by Persons sitting in _Arbours_ sheltered from the Sun. The surrounding Air is instantly _contracted_ by _Condensation_, during the Absence of the Sun’s Rays, and therefore occupies a _less Space_: _fresh Air_ is _received_, and as instantly _dispersed_ by Expansion towards those Parts, which are the warmest, i.e. where there is least Resistance: so that a gentle Breeze is constantly kept up, _probably_ by a Depression from _above_.[86] 281. Analagous to this, are those Winds which generally _rise early_ and die away at _Sunset_: the nocturnal Condensation of the Air being sufficient for the +reception+: as Air suffers some Compression without Tumult. To demonstrate the Changes owing also to remote and invisible Causes least suspected; Boyle somewhere speaks of an Instrument he made, which was so nicely contrived, that he coud tell, while sitting in his own Apartment, whenever any detached Cloud passed beneath the Sun’s Disk. The Principle on which it acted seems to have been that of a Reception and Dispersion of Air that took Place within _the_ +shadow+ proceeding from the Cloud. 282. An oblique Argument supporting the Doctrine of Depression, asserted to take Place, in fair Weather, is that _Wind_ drys up the Moisture from the Ground more than the _Sun_: and that March which is the _windiest_, is also the _most drying_, tho’ _not_ the _hottest_ Month. Bacon, in his Enquiry into Motions and Undulations of the Air, uses a Metaphor, which tho’ somewhat facetious, is strictly philosophical.[87] “_For when_ +winds+ _lead_ +the dance+, _it woud be agreeable to know the_ +figure+.”[88] And it is probable, that they really press the Earth with a saltatory progressive undulating Motion, _descending_ in elastic Steps of sudden Compression; and _rising_ with quick alternate ones, of Dilatation and Expansion. Dicker’s Balloon gave Proof of this. 283. Lastly: the +chill+ _of Air_ which always takes Place over +water+, and _moist_ Grounds, even in the +finest weather+, strongly favours the _Reception_ and _Dispersion_ of _it_, to the surrounding and more heated Lands: (which can only be supplied, as before mentioned, by Torrents of fresh Air _gradually descending_ from the etherial or middle Region of the Atmosphere;) and seems to produce the same Effect, viz. a constant Breeze, with that of the Arbor, Shade, or Shelter from the _Sun_: also with that of the _Shadow_ from the Cloud passing under his Disk, which affected a complete Thermometer and Hygrometer. 284. On a Change of Weather from Frost to Thaw, the Colour of the _upper Air_ +first+ alters from a _clear and deep_, to a _dull and faint_ Blue, or to a muddy Haze, not distinguishable into Clouds, but visible above them; a vivid Brightness still remaining, for many Hours, to about 500 Yards above the Surface of the Earth. Or, soft _warm_ Showers fall gently, without Wind, or any apparent Change in its Direction. All which seem to favour the Accumulation and Descent of _warm Air_, by Waves of the Apogay rolling over the Eknèfiai Winds. CHAPTER LII. [Sidenote: _Proper_ Days in the Month for the Ascent of Balloons.] Section 285. As the _safest Hour_ of the Day has been already pointed out, for the Ascent of those Aironauts, who propose to cross a Channel, or Arm of the Sea, in a Balloon _Air-tight_ or nearly so: it may not be useless to throw out a few Hints on the properest Days in _each Month_, for the Ascent of Balloons. 286. It will perhaps be found true, that the more frequent Winds are generated near the Surface of the Earth: but that _Storms_ are generated from above. Cold, Heat, Drought, and Moisture produce the more frequent and diurnal Winds: but the Conjunctions and Operations of the Moon and Planets contribute to the Production of Storms and other Inequalities of the Atmosphere: more especially the _Moon_: at the New and Full. These Attractions first affect the _superior Parts_ of the Atmosphere.[89] 287. “We are sure in the calmest Weather, to have some Breeze at Noon, and at full Tide.” Therefore, both are improper Times for Balloons to be at Sea: the Time of low Water and Midnight woud be best in those, if equal in other Respects. Changes of Weather as to Wind or Calm happen about the New and Full Moon.[90] 288. Varieties of Tide produced by the united or divided Forces of the Sun and Moon, occasion similar Changes in the Atmosphere nearly at the same Time. For Instance, at the Time of the New Moon or Conjunction, i.e. when the Earth, Moon, and Sun, are _nearly_ in a Line; the Moon being between them: also at the Time of the Full Moon; i.e. when the Moon, Earth, and Sun are _nearly_ in a Line; and the Earth between them, which is called the Opposition.[91] In the first Case, the Moon and Sun attract the Atmosphere of the Earth conjointly, or with united Force: in the second Case; the Earth being between them, they act in Opposition to each other, still nearly in the same Line. At these Times, the +spring+ _Tides_ are at the _highest_ i.e. once every Fortnight; and in the two interval Weeks are the +neap+ or _lowest_ Tides: for a like Reason. Because, in the latter Case, a Line supposed to be drawn from the Moon to the Earth, and another from the Earth to the Sun, woud form nearly a right Angle: or in other Words; because the Moon and Sun woud attract the Earth at right Angles to each other, or in a lateral Direction:—the Moon woud draw one Way and the Sun another:—their Forces woud be divided. Now it is a Fact, that the Ocean is raised considerably twice every twenty-five Hours, by the Attraction of the Moon, when she comes to the Meridian. So that the Surface of the Sea, instead of putting on the Form of a Sphere, or Globe, will be changed into an _oval_ Figure, whose longest Diameter being produced, woud pass throu’ the Moon. In like Manner a similar Elevation must take Place, as often as the Sun is in the Meridian; either above or below the Horizon. Moreover, this Elevation is _greatest_ on the New and Full Moon, because the Moon and Sun do then conspire in their Attractions: and _least_ in the Quarters: as they will then draw different Ways; the _Difference_ of their Actions only producing an Effect. Lastly, the Intumescence will be of a _middle_ Degree, at the Times between the Quarters, and New and Full Moon. 289. As in the Ocean, so in the Air above it; a Tide of Air must roll along the Atmosphere, throu’ the whole Extent of it; and rise upwards twice in about 24 Hours. And since the Height of the Atmosphere is computed by Halley at 45 Miles, and the Depth of the Ocean at an Average, but half a Mile; the Air will more easily and quickly obey the Attraction of the Moon and Sun, than the Tide of the Ocean: and, as it revolves in a Sphere which is about 100 Times larger than that of the Ocean, the Agitation and the Velocity of its Tide, will be something greater, in Proportion to its Elasticity, and inferior Density to the Water of the Ocean.[92] 290. The _Weight_ of the Air must now be considered. The Weight of the Atmosphere in England does not exceed 31½ Inches of Mercury in the Barometer: nor does the least Weight fall short of 28½: the greatest Difference in the Weights may be taken at 2 Inches: dividing 30 (nearly equal to the whole Weight) by 2, the Answer is 15. So that the under Parts of the Atmosphere being pressed upon by about a fifteenth Part less Weight at one Time, than at another; the _specific Gravity_ of the Air will sometimes be a fifteenth Part lighter. But the Height of the Atmosphere being estimated at 45 Miles, which is equipoised by about 30 Inches; when equipoised by a fifteenth Part less Weight; (that is, dividing 45 Miles by 15; which amounts to the same as if a fifteenth Part of the whole Height was taken away; the Answer is 3 Miles;) shews that the Atmosphere is 3 Miles higher at one Time than at another, over certain Places; indicated by the Barometer at those Places. Such an Accumulation of Air, arising only from Pressure or specific Gravity in one Part of the Atmosphere, and not in another; by its Tendency to an Equilibrium; and when to this Tendency is added its _elastic_ Force;—must be productive of +winds+, _descending Torrents_, Inundations of Air, or Storms, near the Surface of the Earth: and nearly such a Difference in the Barometer has been known to happen in a few Hours. Such Accumulation, however, is not properly _the Tide of Air_. 291. At the New and Full Moon, the united Attractions of the Moon and Sun raise the Spring Tides in the Ocean to the average Height of 10 Feet and a half.[93] And in the Moon’s Quarters, the Moon drawing one Way, while the Sun draws another, viz. at a right Angle, made by Lines from the Sun and Moon to the Earth’s Center; the average Height of the Neap Tides in the Ocean will be 6 Feet 7 Inches. The same Attraction which raises Water 10 Feet and a half, will raise Air, whose Density is 800 Times less, to almost one third of that to which the whole Pressure of the Atmosphere can raise Fluids:[94] Now it has been before seen, that the Pressure of the Atmosphere raised the Air 45 Miles: so that the Air is raised by the united Actions of the Moon and Sun, at the New and Full Moon, to one-third Part of 45; i.e. to 15 Miles. And for the same Reason, the Air is raised at the Moon’s Quarters to 10 Miles:[95] the Difference between which is 5 Miles. There is consequently a real _Tide of Air_ five Miles higher at each New and Full Moon, than at her Quarters: which Tide rolls with incredible Velocity along the Verge or highest Limit of the Atmosphere; and is generally productive of Wind below. 292. The Elasticity of the Air must likewise be brought into the Account, as contributing greatly to its Motion: the Spring of Air always increasing as the Pressure encreases. Considerable Changes must therefore ensue in the inferior Parts of the Atmosphere. For as the Effect of the Moon’s Attraction is to diminish the Weight of the Atmosphere (tho’ its Quantity be increased) by elevating the Column of Air in the Line of her Meridian; the Rarefaction of the Air is therefore encreased, first _at the Top_ of the Atmosphere; afterwards it gradually descends to the Bottom, or Surface of the Earth: so that the incumbent Weight being diminished, the Air beneath will be greatly _expanded_. At whatever Height therefore any _Quantity of Vapour_ or superior Cloud _rested_, while the Moon was in her Quarter; it woud _gradually descend_ at the Approach of the next New or Full: at which Times it woud remain suspended at a Height, where an Expansion took Place equivalent to the former Expansion, at the Moon’s Quarter: and, if the Height during the Moon’s Quarter was only equal to that of common Clouds; such Vapour woud, at the New and Full Moon, _descend_ in Mist, Rain, Snow, or Wind. 293. Little Reliance is to be placed, in these _Northern_ Climates, on the aggregate Weight (_or elastic Power_) of the Air, indicated by the Height of the Barometer, near the Times of the New and Full Moons: tho’, in general, it will _descend_ about those Times. [Sidenote: Proper Days for Ascent.] These Things being so; it woud be improvident to undertake an aërial Excursion, either three Days before, or three Days after the Day, either of the New, or Full Moon: the Ascent shoud be forborne every other Week; at least till the Art is a little more advanced. The two remaining alternate Weeks in each Month, viz. when the Moon is in the Quarters, and the Tide of Air flowing throu’ the Atmosphere, is checked, counterbalanced, and equalized, by the lateral Attractions of the Moon and Sun, acting at right Angles, i.e. on different Parts of the Air, pendent on the Earth’s Surface;—more settled and regular Weather may be naturally expected; and particularly freer from the Extremes of _Wind_ and _Cold_. Moreover, as the Almanack, and Ephèmeris[96] may be always consulted; the Day fixed on shoud not be _marked_ with Conjunctions of the Planets.[97] The Inequality of their united Attractions greatly deranges the Equilibrium of the upper Parts of the Atmosphere; producing sudden Squalls and Gusts of Wind: which, tho’ of short Continuance, perhaps a few Hours, are inauspicious to the successful Inflation and Ascent of a Balloon, during the Infancy of the Science. (See Section 211.) CHAPTER LIII. ON THE MEANS OF SUSTAINING A BALLOON ABOVE THE SURFACE OF THE WATER, BY A TEMPORARY LOSS OF BALLAST: AND OF RECOVERING THE BALLAST. Sect. 294. Art. 1. The two Inconveniencies arising from a _Discharge_ of Ballast, while the Balloon is under the _Pressure_ of a mediocèanal Column of Air, are, 1. First, lest the Balloon shoud rise too _high_; for by opening the Valve in order to descend; Gass escapes: which is an _actual Loss_: and the Balloon is rendered incapable of supporting its Burden at the same Height, as before. 2. The present Impossibility of resuming the Ballast, in order to _descend_, or _check the Elevation_, on approaching either Shore, or at any other Time. 294. 2. These Inconveniencies are to be remedied by the following Methods. If _Sand_ be the Ballast fixed on; put as much of it into a Bladder by Means of a Tin Funnel, as, when _less_ than _half_ blown, it will contain, without sinking below the Surface of +fresh+ _Water_. _Prepare_ the intended Weight of Ballast, in Bladders, after the same Manner. Also to +each+ Bladder _with Ballast_, tye another Bladder _without Ballast_, half blown. Tye fast each Set of Bladders, so prepared, with a _leathern_ Thong; the Ends of which may be left a few Inches to _spare_. The Grapple may remain in the Car. 294. 3. When the Balloon _begins_ to descend over Water; lower out the Cable, by Degrees. Tye a Pair of Bladders, one of which contains Ballast, very tight, round the End of the Cable. Then a second Pair, at such a Distance that the intermediate Part of the Cable, will _float_. Repeat this Process, till the proper Effect is obtained; or the whole Ballast is discharged. 294. 4. The Car and Balloon may be _hauled_ or wound _down_ to the Surface of the Water: and the Ballast resumed, as the Balloon approaches the Shore. 294. 5. If it be found necessary, the Ballast may be _discharged_ by cutting the +thongs+, _gradually_: or the +cable+, _at once_. 294. 6. If the Wind be _contrary_, and the Weather _moderate_; the Tide, or Stream may, by _Calculation_ and _Foresight_, be made to serve the Purpose of the Aironaut, in towing the Ballast which floats on its Surface: and thus checking, or gently drawing the Balloon after it. 294. 7. In such Cases, the Aironaut woud do well in applying his _propulsive_ Machinery. A GENERAL OBSERVATION. 294. 8. To prevent the car of the _Balloon_ from being drawn out of the Perpendicular, a Circumstance not infrequent; it is necessary to have some Contrivance, by which the Cable shall run throu’ a moveable Pulley, on a Swivel, in the Center above the Car; and that the Aironaut shall be able _instantly_, by a Screw, or otherways, to fasten the Pulley and Cable so tight, that the Stress shall remain on the Center above the Car, however _forcibly_ the Cable may be stretched. CHAPTER LIIII. ANOTHER METHOD OF SUSTAINING A BALLOON OVER WATER, WITHOUT LOSS OF GASS, OR OF BALLAST. Section 295. Let the Ballast consist of that Kind of Rope (wound on a Reel) that is either by Nature or Art, _specifically_ lighter than fresh Water: as a _hollow cylindrical_ Rope of Silk, in which Corks are thrust: the Silk to be dipped into elastic Varnish, to prevent the Absorption of Water into the Pores: or a common Rope well varnished; or covered over with a cylindric Case of varnished Silk, might answer the same Intention, if Corks or Bladders were tyed at proper Distances: in which Case, the Rope might, at the first Ascent of the Balloon, hang from the Center above the Car, at its full Extent, suppose a Mile or a Mile and half in Length, without the Encumbrance of a Reel. If Bladders are used; those that hang near the Car shoud not be more than _half blown_. By the above Expedient; as soon as the Balloon began to decline, from Evaporation of Gass, or Depression of the Atmosphere, and the lowest Part of the Rope touched the Water; the Balloon woud continue to levitate, in Proportion to the Quantity of Rope sustained on the Surface of the Water. The Aironaut woud move less _swift_ indeed, but more conveniently; as he woud not be obliged to rise _above_ the Wind: but be able to _lower_, and _raise_ himself at Pleasure: _first_, by pulling up a Part of the Rope into the Car; and having there _made it fast_; _Secondly_, by cutting away, as he saw Occasion, the loose End, and Folds of the Rope so drawn into the Car with him. CHAPTER LV. ON THE NECESSITY OF ASCERTAINING THE PROPER MODES OF DIRECTION, BY DIFFERENT AND FREQUENT EXPERIMENTS. [Sidenote: On the Necessity of frequent Experiments, in different Modes of Direction.] Section 296. The Necessity of making frequent Experiments, in order to prove how far the Balloon is capable of Direction, by different Combinations of the mechanical Powers, is so apparent; that no Balloon shoud rise a second Time, without the Application of Machinery to that End. Each Candidate for Fame, as Proprietor of a Balloon for _public Exhibition_, ought to vie in his Pretensions to a Superiority of Manouvres. Their respective Performances woud appear in the public Papers; and Decisions be made to the Advantage of the Art. For it is probable, that by such _Comparison_ chiefly;—the +comparison+ of _experimental Blunders_ and _Mistakes_, and not by an Union of Theory and Practice, cemented by liberal Patronage, the Balloon can arrive to any Degree of Perfection, in a Country, which is the Scene of _perpetual Contention_: where the Sum of Life seems devoted but to +party+; and where the _precious_ Time of the +great+ is sunk in Luxury, and their _exalted_ Talents lost in the _Labyrinth_ of Politics. [Sidenote: Precautions to secure a Landing.] 297. _To strive against the Stream_ is proverbially impossible: and it woud be literally so, to attempt by any Kind of Machinery to force the large Surface of a Balloon, with any Degree of Velocity, against _a Stream of_ +air+. (Section 201.) Ships, which have the Aid of an Element 800 Times _denser_ than the +air+, are obliged to wait _in Port_, till the Wind is favourable. But neither is this considered as an Argument against _maritime Navigation_: nor does the _Perfection_ of the Balloon require its Ascent in a Storm: tho’ the Preference due to the Balloon, on such Occasion, woud be decisive in its Favour: as the latter woud presently surmount the Wind, and _lie to_, in the _calm Air above_ it. Sect. 298. Art. 1. By Wings, or some propulsive Machinery, acting forcibly in a Direction required, and with Ease to the _Operator_; +two+ _useful Manouvres_ may be attempted, and will frequently be _found successful_. [Sidenote: _First Manouvre_: to secure the Landing in windy Weather.] 298. Art. 2. First, To +retard+ the Course of the Balloon during its Descent; in such a Manner, as to prevent the Wind from _damaging_ the _Machine_, or _snapping the Cable_: and thus to land with Safety, and at the _smallest Distance_ +beyond+ the Place assigned. [Sidenote: Preparatory Apparatus: and _Signal-Rope_.] 298. 3. A _silken_, or other _light_ Rope is to be provided: and to run throu’ a _snatch Block_ fastened to a +rudder+, or to the +car+, as in Crosbie’s Balloon.[98] Which Rope _alone_ woud lessen immediate and unforeseen Danger, by using the Balloon as a Sail, if it actually alighted on the Water. 298. Art. 4. The same Rope being _a Mile_, or _a Mile and Half_ in Length; the _Whole_, or a Part of it, might be suffered to run off the Wheel, and, falling on the Surface _below_, in _misty_ Weather, woud serve as a Signal to determine whether the Aironaut was over Land, or Water. Also by winding up his Wheel, he might, if the Weather was moderate, bring himself _down_ to the Grapple, which might be so contrived as to _run down_ the Rope, and remain at the Bottom, by Means of a Knot, or other Check. He might also _loose_ his Grapple, and _rise_ again: or when down; pull the Valve-Cord, and land. 298. 5. With a +second+ short Cable, snatch Block and Grapple, he woud be able to _moor_ the Balloon, from which, he might, by procuring the Country People to load the Car with fresh Ballast equal in Weight to himself;—get out, and even leave the Balloon in their Care. The Precaution of knowing whether he was over a fresh Water-Lake, (for he might hear the Sea) might be useful in misty and low cloudy Weather by Day, or during the Night; without expending Gass in the _exploratory_ Descent. 298. 6. To facilitate the landing, the _Signal-Rope_ may be used to the greatest Advantage, particularly in windy Weather; by _lowering out_ a Part, or the Whole, whether a Mile, or Mile and half, so that the Grapple may take Effect on the Ground, at the Distance of its Length _by Estimation_, _short_ of the Place where the Balloon is intended to land. As soon as the Grapple _holds_; it is in the Option of the Aironaut, to tye Parcels of his Ballast _loosely_ round the Cable, to run downwards along with it. (For _which Purpose_, Iron-Rings with _Spring-Swivels_, which _open_ by _Pressure_ of the Fingers, and _shut_ of themselves, might answer better than the _leathern Thongs_, as the former might be put, in _an Instant_, round the Cable, and woud run down _quicker_.) These Parcels of Ballast are to be sent down, in Succession, till the Balloon has acquired such Degrees of +false levity+, as will be sufficient to counteract that Tendency which the Wind will have to _depress_ the Car of the Balloon forcibly on the Surface, so long as it is connected with the Grapple _on the Ground_. 298. 7. When this Point is effected, the Balloon will remain suspended in the Air; and being acted upon by the Wind, will be pressed into a Direction approaching to an horizontal Line, in Proportion to the encreasing Power of the Wind. And here the Necessity of having the Cable fastened to a Center above the Car, in order to retain its Perpendicularity, is most evident. The Aironaut, in this Situation, may venture to wind up the Cable _gradually_, and descend, to the Grapple. 298. 8. Secondly: When the different Currents of Air, have been tried by Descent and Ascent of the Pioneer-Balloon,[99] and found to be _all_ unfavourable; the Aironaut is to _rise_ still higher, into a Calm, pursue his Course horizontally in the +blue serene+, by propulsive Machinery: estimating the Velocity, by the _evident Resistance_ of the half Mile white Flag described in Section 12, 13. and 12, 15. hanging at a proper Distance _below_, and of that which hangs loosely at the Side of the Car, to shew a Change in the Direction of the Wind, (then made by a Resistance of the Air): or he may judge o£ the Velocity and Direction, by the _Flight_ of a _Feather_, repeatedly let loose at certain Intervals of Time. CHAPTER LVI. NEW MODE OF ASCENT, TO DETERMINE THE INSTANT THE BALLOON IS ARRIVED AT ANY GIVEN HEIGHT: TO MEASURE THE HEIGHTS: AND TO ESTIMATE THE DENSITIES OF THE AIR AT THE GIVEN HEIGHTS. ALSO, A METHOD OF ASCENDING TO A FIXED BAROMETRIC HEIGHT: THERE TO REMAIN SUSPENDED IN EQUILIBRIO. Section 299. Previous to the Ascent, provide a Cord, which shall have sufficient Strength to support twice its own Weight, when so great a Quantity of it is _coiled_ together, as, if extended, woud measure half a Mile or a Mile. Weigh the whole _Coil_, or any Number of Yards, so as to obtain the whole Weight. Mark the whole Length of the Cord, with different _coloured_ Worsted, or otherways, at the Distance of every eight Yards: as a _sounding_ Line. Note the Marks in a Pocket-Book. These Things being done; give the Balloon, by +inflation+, a Power of Levity _at least_ equal to the known Weight of the Cord: which may be easily obtained by throwing into the Car, already _ballasted_ and prepared, a Weight equal to the Aironaut, together with that of the _Cord_. The Cord must also, previous to the Ascent, be rolled upon a Reel, (made fast in the Ground) whose Diameter shoud be +two+ Feet: each Turn of the Wheel may be called two Yards. A Barometer with an attached Thermometer fixed in the same Frame, also a second or detached Thermometer placed at the Distance of a Yard from the Frame, shoud remain upon the Ground during the Inflation. The same Apparatus of Barometer with attached and detached Thermometer, shoud be suspended in the Car. The Instant the Balloon ascends, an Observer below is to note in a Book the _Point_ at which the Quicksilver stands in each of the +three+ Tubes of the lower Apparatus, also the Time of Ascent: the Aironaut the same. The Rope is, previous to the Ascent, to be tyed to a Center above the Car: and as soon as the Balloon has elevated the Car 100 Yards; the Observations, as before, are to be set down below, and by the Aironaut: and repeated at the Height of each 100 Yards: a Drum to beat; during the Time each Observation _below_ is _noting_ down; and the Balloon not suffered to rise, till the Drum has ceased. By such repeated _Notice_, and _Silence_; the Aironaut will know the _exact Height_, at which the Balloon is checked in its Elevation: and the _exact Time_ during which its Elevation is impeded. This Process is to continue, till the Rope is raised to its full Length. At which Instant a double-barrel Gun is to be fired: the exact Time noted _below_: and the Time of hearing the Sound noted above. These Notes are to be compared at the Aironaut’s arrival on Earth. 300. For such _nice_ Experiments the Aironaut shoud ascend half an Hour before +sunrise+, or _Sunset_: and the Day chosen by the foregoing Rules. The Air must be +quite calm+: but it is not necessary that it shoud be free from Clouds or Mist. When the Rope is at its full Extent, the Operator _below_ is to shorten it, by winding down the Balloon, 100 Yards: the Signals _below_, being repeated, till the Balloon is arrived within 100 Yards of the Ground. [Sidenote: To estimate the Densities at different Heights.] 301. While one Observer _below_ is writing down the Observation to be made the Instant the Balloon has risen exactly 100 Yards; another Operator is to weigh, by Hand, with Spring Steel-Yards, the Force of Levity already acquired, which is to be noted down by a third Bystander. This Process is to be repeated at every 100 Yards. The Levity, it is true, will encrease as the Balloon rises, (probably in a geometric Progression;)[100] yet the Cord, by rising with the Balloon, will greatly check it: if, however, it prove insufficient for that Purpose, and, lest the Cord shoud be in Danger of breaking; the Bottom of the Balloon must be opened, or the upper Valve drawn. If the _Cord_, _Rope_, or _Balancer_, be sufficiently strong; there will be no Necessity for the Aironaut to throw out Ballast occasionally; nor for the Observations in the former Part of this Section: the _Densities_ will likewise be more easily determined, by the _Weights_; which shew the _Encrease_ of Levity and Expansion of the Balloon, at each of the _given_ Heights: Allowance being made for the Weight of the _Balance Rope_, _raised_ by the Balloon. [Sidenote: Method of ascending to a fixed _barometric_ Height: there to remain suspended _in Equilibrio_.] 302. The Aironaut, may, at any Height, marked by looking at the Barometer, when at 24 Inches for Example, or as soon as he finds his Balloon sufficiently expanded, pull up the Rope over a Pulley; or, wind it upon a Reel of two Feet Diameter, within the Car; and continue to do so; till he finds that the Barometer begins to _rise_, (which is a Sign that the Balloon _descends_), by the additional _Weight_ of the Balancer just brought into the Car: on which, by preconcerted Agreement, he may throw out a +white+ Flag, prepared to hang a Yard below the Car. On Sight of the Flag, the Person at the Reel _below_ is to cut the Rope: which Rope, or a Part of it, is to be drawn into the Car. The Balloon will rise no higher; but remain in _Equilibrio_ in the Air, at that Height. CHAPTER LVII. ON BALLOONS. THEIR DEFECTS AND FARTHER IMPROVEMENTS. Section 303. These Defects are best known from the History: a Detail of which is given to the World in an entertaining, elegant, and scientific Manner, by a celebrated Writer on other Subjects, _Mons. Faujas de Saint Fond_, in two Volumes, 12mo. for the two last Years, illustrated with Engravings by the best Masters. And he promises a Continuation, or annual Register of Experiments and Improvements. The Title of the Book is, “Description des Experiences de la Machine aërostatique, &c. &c.” 304. Mr. Cavallo has favoured the British Nation with a cursory tho’ clear Account of the same, in his “History of Airostation:” a Continuation of which it were to be wished he woud likewise publish annually. 305. It might contribute greatly to the Improvement of the Art; if Mr. Faujas woud give Engravings on a large Scale, of the different Machinery, already used or invented to direct the Balloon, with their Proportions: particularly the +moulinet+ of _Blanchard_: as well as that lately tried by Messrs. Auban and Vallet; whose Machinery is still _more distinguished_ and +effectual+. 306. The Titles and Sizes of all useful Books written on the Subject, also the Places where they are to be had, might likewise be inserted, at the End of each _annual_ Volume. 307. The principal Defects of the British Balloons are, in 1. The Construction. 2. Production of Gass. 3. Mode of Direction, and 4. Security of landing. First, Defects of the Construction are both in the Form, and Composition. The Form ought to be that of a +right+[101] _Cylinder_,[102] by which the _Capacity_ is doubled without encreasing the Resistance: ending above and below, each in a Hemisphere. A cylindrical Trunk, 2 Feet in Diameter, being added to convey the Gass _into_ the Balloon; and suffer it to escape, when too much expanded in the etherial Regions. It shoud also be furnished with a Valve, at the Bottom, of equal Diameter with the Trunk: keeping itself Air-tight; and opening outwards by a _given_ Resistance, (as that of ten Pounds Troy,) from the inside Gass. There must be an upper Valve as usual: occasionally to promote a _swift_ Descent. 308. The Form will likewise continue to be defective, till an interior Balloon for common Air is adopted, according to the Plan laid down by the ingenious Mons. Meunier, lately appointed by the French Academy of Sciences at Paris, one of the Commissioners for the Improvement of Airostation. The Use of which interior Balloon by Compression of the surrounding Gass in the external Balloon, prevents, it is said, the Loss of Ballast and of Gass: two very considerable Advantages. For the actual Sum total of Gass not being diminished; the Balloon will continue longer in the Air, before an Escape of Gass, throu’ the Pores of the Silk, makes it descend. There will, on the same Account, be less Occasion to take in _meer_ Ballast, for the Purpose of throwing it _overboard_, to prevent the Descent. Therefore an equal Weight of Articles necessary to remain in the Car, may be substituted in Place of the Ballast. 309. Art. 1. And, since it is next _to impossible_, the Atmosphere shoud continue for 24 Hours together, of the _same Density, Weight, and Temperature_; or, in short, without Motion;—the Aironaut will have a Power of seeking, at _different_ Heights, for that Current of Air, or _Wind_, which suits him best: or, in a very few Minutes, to rise above all Currents; become stationary, and _lie to_ in the +serene+, waiting for a _Wind_: which, as before mentioned, he may readily find, by lowering out a Mile of Twine, and his _white_ Flag: attending to it, with a small perspective Glass, or Magnifier. 309. 2. Another most _material_ Advantage is to be able, in a _high Wind_, to chuse the Spot on which he proposes to alight: or wait for a favourable Opportunity to descend. [Sidenote: To ascertain the Height of the Balloon by a Quadrant.] 310. To compute the Height and Distance of the Balloon, by Means of a _white_ Flag, or other _visible_ Object, suspended from the Car, at a certain Distance below it. Let the Observer take the Altitude of the Car with a Quadrant: and also the Altitude of the Object or Flag. Then by a Case in plain Trigonometry; if the Altitude of the Car be by the Quadrant 59° = HAC, the Altitude of the Object 55° = HAO, and the Length of the Line veered out be 200 Yards, or otherwise = CO. [Illustration] Then the Complement of HAO = AOH = 35°; and the Complement of the Angle HAC = ACH = 31°; and the Supplement of OAC + ACO = AOC = 145°. Then, CAO 4° : CO 200 :: AOC 145° : AC; and Radius : AC :: CAH 59° : CH 1409 Yards, the Height of the Balloon taken at the Time. Next, Radius : AC :: ACH 31° : AH 846 Yards, which is the horizontal Distance of the Place on the Earth from the Observer, over which the Balloon was then suspended. This Method finds the Height truer than the Barometer, and with fewer Circumstances of Confusion. And if the Balloon Art coud be perfected, so as to make them stationary at any Height; this Circumstance woud afford excellent Opportunities of proving the Heights by the Barometer: besides which, the Distance also has been obtained: a Point not before attempted.[103] CHAPTER LVIII. OF THE AIR-BOTTLE BALLOON. Section 311. Till the Particulars of Meunier’s Invention are made public,[104] an additional _Air-tight_ Balloon, or Air Bottle, at least 15 Feet in Diameter, of a _globular_ Form, appended below the Car, and furnished with a _Condenser_, to be worked by _pulling upwards_, or, as the Bellows of an Organ, by the alternate Motion of the Feet of the Aironaut, standing upright in the Car, may be used instead of the interior Balloon; to keep the _great Balloon_ at a _given_ Height: and consequently prevent the Aironaut _from rising too high_: to atchieve which Purpose, during the _first Ascent_; a Rope or Balancer may be used, a Mile and half long, fastened to the Car, and rising with the Balloon, (to _check_ its Power of _Ascent_,) till an Equilibrium is produced: at which Instant, on Sight of the _white_ Flag from the Car, the Balance-Rope is to be cut, by the Operator _below_. (Section 302.) If the Aironaut perceives by the Rise of the _Barometer_, that the Balloon descends; he may throw out a _little_ Ballast, (perhaps a Pound or two), and then wind up his Balancer, or suffer it to remain at any Length, at his Option. 312. By keeping the Balloon at a given Height _only_; no Gass is expended in preventing the necessary Tendency of Balloons to a perpetual Elevation: also, during the self Descent of the Balloon; by opening the Air-Bottle, the Aironaut will supersede the Necessity of throwing out Ballast, for a Re-ascent. 313. The Air-Bottle-Balloon shoud be covered by a strong _light_ Net, of a Dimension rather less than the Bottle, which will hinder it from bursting: the Resistence of the _condensed_ Air within, being then chiefly on the Net, and but little on the Bottle. The Net may be made of Silk and Cotton Thread; lest the Meshes, by the Pressure of the Knots, shoud eat into the Bottle. CHAPTER LIX. SUPERIORITY OF THE AIR-BOTTLE TO AN INTERIOR BALLOON. Section 314. The Air-Bottle can be attended with no Sort of Danger. For, if it burst; the only Effect is to raise the Balloon: which is made to descend, at Pleasure, by opening either the _lower_ or upper Valve. Whereas an interior Balloon condensed with common Air, presses against the surrounding exterior Gass: and the Gass, against the +inside+ of the _great Balloon_, when the latter is in an elevated and rarefied Atmosphere; which Atmosphere, in Proportion to its Height, makes _less_ Resistance to the _Outside_ of the great Balloon: and thereby encreases its Tendency to a Rupture. By the Application of the Air-Bottle, which will be to a Balloon, what an Air-Bladder, or _Swim_ is to a Fish; a concomitant Advantage is derivable. For the common Balloon and Air-Bottle, which may be called +a double balloon+, will, in their _present imperfect_ State, be able to remain a Day, or perhaps a Couple of Days in the Air: there being no Loss of Gass: unless by Evaporation, throu’ the Pores of the Silk. And this Advantage of _a double Balloon_ may be effected with little +expence+ (except that of a complete Net) to the different Proprietors, who may make alternate Voyages, with the Balloons _thus_ united: one being inflated with Gass; the other occasionally with three or more Atmospheres of common Air _condensed_. CHAPTER LX. HINTS FOR THE DIRECTION OF THE BALLOON. Sect. 315. Art. 1. In the London Chronicle, from the 20th to the 22d of August, 1785, is a Letter from Bury, containing an Account of Mr. Poole’s Balloon, with the following Circumstance, viz. “It was found necessary, before the Balloon was liberated, to cut away the Wings, intended to act as Sails, which had been constructed by an ingenious Piedmontese, patronized by +lord orford+, and which it was supposed, woud have contributed _to facilitate the Direction of the_ Balloon, but were found _greatly to retard the Celerity_ of its Motion.” Now if any Credit can be given to Newspaper Accounts, (that of the Beccles Balloon being an entire Fable,) it is to be lamented that the Wings were cut away for the Reason assigned: as it seems the only one that could properly be offered for applying them. 315. 2. Balloons already rise like a Rocket, and press forward almost with the Celerity of the Wind: it is therefore evident, that these Celerities must be _greatly retarded_, in order _to facilitate the Direction_: and consequently that the Wings bid fair to have answered the Intention of their ingenious Projector. And why precipitately cut them away, before the Balloon was left to the Pleasure of the Winds? since no regular or safe Manouvres ought to have been attempted, till that Time. There appears to have been much the same Reason for rejecting the Piedmontese Wings, that there was for condemning the use of a Parashute, to which a Dog being appended was killed in the Descent: because the Parashute was not let loose at a sufficient Height, nor was it properly distended. 315. 3. It seems, that as the Wings had _greatly_ +impeded+ the Balloon; a certain _Addition_ to them might have _nearly_ +stopped+ it in the Air. For the Balloon having once acquired an uniform Motion, by encreasing the Surface of the resisting Body, or Wings, the Balloon maybe retarded to a certain Point. But the Resistence encreasing woud raise the resisting[105] Body above its Power of Action, and therefore, in Fact, lessen it; by which Means the Balloon woud continue to be propelled in the Direction of the Wind, with a Force equal to that Diminution. Suppose, for Instance, that, instead of the half Mile Flag, which evidently checked the progressive Motion of the Balloon (Section 70) a larger square Surface, of varnished Silk, or a triangular Latteen Sail (like the Αρτεμων of Le Roi[106]) was substituted, and kept stretched, by a hollow Cane, or Yard.[107] 315. 4. Also, that by Means of a Fan or small Oar, acting as a Rudder, to be folded and taken back into the Car at Pleasure, the Balloon was compelled to move with a given Side foremost; that the Sail was let down below the Car, by strong silken Cords fastened to each Angle; and lastly, that leaden Weights, (each weighing an Ounce Averdupoise when widely perforated, and put throu’ the Ends of each Cord before it is fastened to the Car), be let down to each Angle; occasionally encreasing the Weights (or Sail) in Proportion to the Wind; which relative Weights (or Sail) will best be determined by repeated Experiments; will not such an Apparatus or Anemometer-Sail, acting as a Vis Inertiæ nearly at right Angles against the Force of the Wind, check the Balloon; till the encreasing Resistence raising the Sail upwards towards the Horizon diminishes its Power of Action? With this Sail therefore, which requires little Attention; and with the Assistance of Wings moved by Levers, pressed alternately downwards as the Bellows of an Organ, by the Feet of the Aironaut and mere Weight of his Body, standing upright near the Center of the Car; the Balloon may probably be, in some Respect, subject to Direction, and move obliquely against the Wind, or with Force in a Calm. The Balloon and Anemòmeter-Sail, like the Earth and Moon will turn on their common Center of Gravity. 315. 5. It is possible to erect a light hollow Mast throu’ the Car, and throu’ the Balloon, by Means of a cylindrical Tube of varnished Silk, extending from Top to Bottom, in order to sustain the Balloon in an upright Situation, and make it keep Pace with the Car, when the latter is propelled by the Wings. The Mast shoud be covered with soft Cotton, to lessen the Roughness of the Friction. It may also contain within it, another slenderer hollow Mast, after the Manner of a Cane Fish-Rod; either to be lowered out, and placed horizontally across or below the Car, to serve as a Guard for the Bottom of the Anemòmeter-Sail; or to be let down to any Depth occasionally: and other Sails connected, by the usual wooden Rings, and kept tight by Cords running throu’ Blocks fastened to any Part of _the equatorial Hoop_, as used at first, by the _gallant Admiral of the Air_ +blanchard+, and afterwards too precipitately rejected; since, in Case of a Rupture of Gass throu’ the upper Hemisphere of the Balloon; the equatorial Hoop preserves the Parashute complete: and for Want of which Hoop, young Arnold had certainly lost his Life, if the Water of the Thames had not broke his Fall. During the Descent of the Balloon, the Sails are to be taken in, and the lower Mast projected into its Socket. 315. 6. Different Trials may be repeatedly made: the Effects of which, whether evidently useful or _apparently otherwise_, being carefully recorded and regularly published _in Detail_, may afford Data for the Prosecution of further Discoveries, and lay the Foundation for a rational Superstructure of _airostatic Navigation_. [Sidenote: On the Manner in which the Wind, Anemòmeter, and propulsive Machinery will probably operate on the Balloon.] Sect. 316. Art. 1. By adding Weights, and encreasing the Surface of Anemòmeter-Sails; the Vis Inertiæ will become so powerful in the Direction of the resisting Medium of the Air; that the Wind in the opposite Direction will force the Balloon out of its Vertical, and incline it to the Horizon. The Car will be a Fulcrum Axis or Center of Motion: on an imaginary Point of which, as on a Pivot, the Balloon and Sails will turn opposite Ways, balancing each other in every Situation. 316. 2. The Balloon must therefore be brought back into the Vertical by a counter Exertion of the Wings: to which the Vis Inertiæ must always be made to bear a just Proportion. The Declination of the Balloon is the only Inconvenience foreseen to result from an Anemòmeter too large, or too heavily laden: and it is instantly remedied by slacking the Sail. One Thing still remains to be mentioned. 317. Balloons _durably_ Air-tight, and terminating in a _Hemisphere_ above, (Section 307); ought to have their Dimensions such, that there shoud be no Occasion for more than their upper Hemisphere to be inflated. Under which Form, they may with Ease and Safety be pitched as Tents on the Ground; by Cords fastened at equal Distances to the equatorial Hoop; and on Occasion by the Aironaut himself, while in the Car: who may be provided with Iron Ring Stakes barbed, and fastened or ready to be fastened to each Balloon-Cord: and, as soon as the Balloon is moored by the Anchor, Grapple, and snatch Block, (Section 298, 3) with a light Axe drive down the Stakes round the Car, and regulate them when he alights from it, on the Ground. CHAPTER LXI. HINT FOR A VANE-SAIL TO PREVENT THE BALLOON FROM TURNING ROUND, WHILE THE WIND CONTINUES STEADY. [Sidenote: Hint for a _Vane-Sail_.] Section 318. To the Block-Pulley in the equatorial Hoop, hoist a Sail, whose Shape is as follows. From the equatorial Hoop, let fall a Perpendicular: and from the lowest circular Point in the Circumference of the Balloon, draw a Tangent, or horizontal Line, till it meet the former: these Lines, together with that Part of the Circumference intercepted between them, in the Points where they touch the Circle, forms a Space, which is the Shape sought. The Sail may be kept steady by a hollow Cane or Bowsprit thrust out from the Car, and made fast with the usual Tackling. 319. Hint for an Umbrella-Pendulum or Valve-Swing, to project the Balloon in a Calm in the ethereal Regions, above the Station of Clouds; where the Resistence from the Air is much less than at the Surface of the Earth. [Sidenote: Hint for a _Valve-Swing_ to project the Balloon in a calm and elevated Atmosphere.] Let the Car of the Balloon be perforated so as to admit a light Gordon Mast, or Pole 18 or 20 Feet long, perpendicularly throu’ it. (315, 3.) At the Distance of five Feet from the upper End of the Pole, a light hollow cylindric Tube of Iron, one Foot long, as a Bolt, shoud be put throu’ it, at right Angles: so as to play smoothly in two Iron Bends, fixed in the Car; one Bend so far moveable, as to rise with a Hinge to admit the End of the Bolt; the other Part of the Bend to be perforated: throu’ which a hollow Staple is to be fastened, with a spring Cotterel chained: this Apparatus will prevent the Pole from turning round. Two light Frames of Wood, of a parallelogrammic Form, each twelve Feet by six, and covered with varnished Silk, are to be hooked, one on each of the opposite Sides of the Pole, from its lower End upwards; the Frames to be moveable in such a Manner, that on pressing the Pole one Way on the Axis or Bolt, the Frames shall lie close; but on recovering the Pressure, the Frames shall expand and open, so as to form an obtuse Angle with each other, or to lie almost in the same Plane, when the Recovery is made briskly, and with a Degree of Strength. A Handle of Wood, the same Size with the Bolt, may be fastened throu’ the Substance of the Pole near its upper End. The Operator is to stand in the Car, and work the Pole backwards and forwards, which will give a progressive Motion to the Balloon in a Calm. This Method may possibly prove more effectual than the Umbrella-Wheels, on an horizontal Axis, of Mons. Carra;[108] as the Umbrella-Pendulum is easily unrigged, removed, and brought into the Car, in Case of a Whirlwind; by Means of a _circular_ Rope fastened to the Axis or Bolt, one End being in the Car, and the other put throu’ the Aperture at the Bottom, and brought up from the Outside again into the Car. The Umbrella-Pendulum may be made to turn round horizontally on the Bolt; the Ends of the Bolt being fastened under a circular hinged Socket, or Groove, of Iron. CHAPTER LXII. DEFECTS, IN THE COMPOSITION FOR BALLOONS, REMEDIED. ALSO ON THE COCHUC-VARNISH. Section 320. Balloons are defective in the Composition for _the Varnish_; which, till lately, was incapable of rendering the Balloon completely and _durably_ Air-tight. 321. It was sometime ago reported at Paris, that Mr. Dutourny de Villiere had undertaken to construct a Balloon so truly _impèrmeable_, that he woud warrant the Duration of it, for _several Weeks_ in the Air. And it is _since_ known that this _Desideratum_ of the Art has been effected, in the Composition for the celebrated Balloon of Messrs. Auban and Vallet, +first+ made subject to Direction. 322. Mr. Berniard, a French Chymist, has made curious tho’ unsuccessful Experiments, in order to melt the cochuc or elastic Bottle; as may be seen in the 17th Volume of the “Journal de Physique.” Mr. Faujas and others made similar Trials. 323. The Writer, unacquainted with what had _then_ been done in this Matter, coud not help remarking the striking Properties of the _Cochuc_ in its present Form, to answer every Intention of the best Varnish, if its Price was lower;—viz. _compact_, _pliant_, _unadhesive_, and _unalterable by Weather_;—if it coud be dissolved, and afterwards made to recover its present +unadhesive+ Form: an Art in which the East and West-Indians are still _our Masters_. He has, however, after expensive Trials and Combinations, been able to reduce it into a _limpid Liquor_. As it may prove a useful Ingredient for _Air-tight_ Varnish; the Secret he now discovers to the World: and it is merely this. 324. “Take any Quantity of the Cochuc, as two Ounces Averdupois: cut it into small Bits, with a Pair of Scissars. Put a strong Iron-Ladle (such as Plumbers or Glaziers melt their _Lead_ in) over a common Pit-Coal or other Fire. The Fire must be gentle, glowing, and _without_ Smoke. When the Ladle is hot, much below a +red+ _Heat_; put a single Bit into the Ladle. If _black_ Smoke issues, it will presently _flame_, and disappear: or it will evaporate without Flame: the Ladle is _then_ too hot. When the Ladle is less hot, put in a second Bit, which will produce a +white+ _Smoke_. This +white+ _Smoke_ will continue during the Operation, and evaporate the Cochuc: therefore no Time is to be lost: but little Bits are to be put in, a few at a Time, till the whole are melted. It shoud be continually and gently stirred with an Iron or Brass Spoon. The Instant the Smoke changes from _white_ to +black+, take off the Ladle; or the whole will break out into a violent Flame, and be spoiled or lost. (Care must be taken that _no Water_ be added: a few Drops only of which, woud—on Account of its superior _specific Gravity_, for the Cochuc swims in Water—make it boil over furiously, with great Noise.) At this Period of the Process; two Pounds, or one Quart of the +best drying-oil+, (or even of _raw_ Linseed-Oil, which, together with a few Drops of Neat’s-Foot-Oil, must have stood a Month, or not so long, on a Lump of Quick-Lime, to make it more or less +drying+)—being poured off the Lime-Lees; is to be put into the melted Cochuc, and stirred till hot: and the whole poured into a glazed Vessel, throu’ a coarse Gauze, or fine Sieve. When settled and clear, which will be in a few Minutes; it is fit for Use, either hot or cold. The Silk shoud be stretched all Ways horizontally, by Pins or Tenter-Hooks, on Frames; which Frames, the greater they are in Length, the better: and the Varnish poured on +cold+, in _hot_ Weather; and +hot+, in _cold_ Weather. It is _perhaps_ best, always to lay it on, when _cold_. The Art of laying it on properly, consists in making +no intestine+ Motion in the Varnish, which woud create minute Bubbles. Therefore Brushes of every Kind are improper. Each Bubble breaks in drying, and forms a small Hole, throu’ which the _Air_ will _transpire_. CHAPTER LXIII. ON VARNISHES, CONTINUED. Section 325. To those, who are unacquainted with the Principles of Chemistry, or the Books which teach it; and yet are desirous to make Experiments, which may throw fresh Light on this curious and useful Art, when applied to Varnishes for Umbrellas or Balloons; the following detached Notes are recommended: which were communicated to the Author by _different_ Artists; each _eminent_ in his Profession. 326. To make copal Varnish. Procure some bluish Flemish alcaline Ashes, (an Ounce suppose): pound them _very fine_, and lay them before the Fire, till they become _hot_ and +dry+. Put them, while hot and dry, into Oil of Turpentine, (a Pint or Pound for Instance): or, into the same Quantity of Spirits of Wine. For by Means of the Alcaly,[109] all the Water invisibly contained in the Oil or Spirits will be absorbed, and leave the Oil or Spirits, +alcohol+, that is, quite pure, and highly rectified: which Process is called _alcalizing_ the Turpentine, or Spirits. Put the Turpentine or Spirits so alcalized, into a Copper Vessel, with half an Ounce of +yellow copal+ _finely_ pounded and sifted. Stir it, and the Copal will soon melt. N. B. If you alcalize the Spirit of Turpentine, when the Copal is dissolving, add a little Spirit of Wine: and if you alcalize the Spirit of Wine, when the Copal is dissolving, add a little Spirit of Turpentine. The +sediment+ of the Varnish will dry on the Silk, in a few Hours. The thicker the Varnish, the sooner it dries. [Sidenote: To make _thin_ Varnish.] 327. Article 1. To make an excellent +thin+ Varnish. To one Quart of _cold raw_ Linseed-Oil poured off from the Lees made by a Lump of _unslacked_ Lime on which the Oil has stood, ten or eight Days, at the least, in order to communicate a drying Quality: (or on _brown Umber_ burnt and pounded, which will have the like Effect:)—add half an Ounce of Litharge. Boil them for half an Hour. Then add half an Ounce of _the Copal Varnish_. 327. 2. While the Ingredients are on the Fire, in a Copper Vessel; put in one Ounce of Chio Turpentine, or common Rezin: and a few Drops of +neat’s-foot-oil+: and stir the whole with a Knife, or any clean Thing. When _cold_, it is ready for Use. 327. 3. The Neat’s-Foot-Oil prevents the Varnish from being sticky, or adhèsive: and may be put into the Linseed-Oil, at the same Time with the Lime, or burnt Umber. 327. 4. To make the above Varnish _transparent_, or _white_; use Mastic and Copal: to make it _brown_, use Seed or Shell-Lac, and _browner still_, use _pounded burnt_ Umber. 327. 5. _Rezin_, or _Chio Turpentine_ may be added, till the Varnish has obtained the desired _Thickness_. 327. 6. It must likewise be observed, that _Litharge_ rots the Silk: therefore Trials must be made without the Use of Litharge. 327. 7. The _longer_ the raw Linseed-Oil remains on the unslacked Lime, or Umber, the _sooner_ will the Oil dry, after it is used. If some Months; so much the better. Such Varnish will _set_, i.e. will not run, but keep its Place on the Silk, in four Hours. The Silk may then be turned, and varnished on the other Side. 328. +on gum mastic, sandarac, seed-lac, shell-lac, and copal.+ 328. 1. Gum _Mastic_ dissolves, _without pounding_, by adding a few Drops of Oil of Vitriol: so do Gum _Sandarac_, and Gum _Copal_, when finely pounded and sifted. 328. 2. Gum _Sandarac_, and Gum _Mastic_ are great Driers of themselves: and may be substituted for Litharge. 328. 3. The Mastic dissolved in the Oil of Vitriol, gives a _sweet_ Smell to the Varnish. 328. 4. Sandarac will soon grow _dusk_ in the Fire: it melts into a transparent Liquor. 328. 5. Sandarac, Seed-Lac, and Shell-Lac, must be finely pounded and sifted, before they are used. 329. The Author having examined different Kinds of varnished Silks, in different Places, does, from their Excellence, recommend those made by _Fawkner_, Umbrella-Maker, Alport-Street, Manchester; a Person wholly unknown to him, but from the Merit of the Work: which consists not only in the Varnish itself; but in the peculiar Method of _applying_ it, which the Author _is not at Liberty to make public_. _Fawkner_ can warrant his Silk _Air-tight_; _soft_ and _unadhesive_; durable, and _unalterable_ by that Excess of Heat and Cold, to which the Balloon is, at the same Time, subject; viz. _internally_, to the hot depredating and caustic Fumes, rising with the Gass: and _externally_, to the _Sun_, _Wet_, _Frost_, and _Drought_. CHAPTER LXIV. HINTS ON IMPROVEMENT OF THE MACHINERY. Section 330. In order to make Improvements of the Balloon still more rapid and general; the Society for the Encouragement of Arts, who have given no particular Encouragement, in Imitation of that at Lyons, to the much-wished-for Art of directing the Balloon;—might offer a Premium for different Inventions of a _propulsive Machinery_, the Models of which are to be made at the Expence of the Society, within a certain limited Sum: and, without condemning what cannot be known unless by repeated Trials,—give Encouragement for such Trials: the Models to remain with the Society for public Exhibition. 331. Also, Figures and Explanations of such Machinery as have been tried, viz. the Fly or Moulinet of Blanchard; and of those which have not succeeded for Want of Trial; might be sent by the Inventors, in order to perpetuate the Invention, either to the _Society of Arts_; or to the Editors of creditable Magazines, who woud be glad of such ingenious Acquisitions, as it woud be a Means of procuring Purchasers, and circulate the Knowledge of this _gigantic_ Infant Science. Improvement woud then go on apace, and in a Chain: each Labourer forging and finishing his respective Link. Whereas at present every one is obliged to find his own Materials, sink the Foundation, raise and finish the Building. And hence so little Work is done, worthy the Inspection of a skilful Architect. CHAPTER LXV. ON THE UTILITY OF BALLOONS: AN INTRODUCTORY CHAPTER. Sect. 332. Art. 1. It seems a favourite Question, among those who take a Pleasure in objecting to every Thing they neither do nor will understand, to ask, “Of what Use can these Balloons be made?” and without waiting for an Answer, to say—“they pick the Pockets of the Public, risque the Lives of the Incautious, encourage Mobbing and Sharpers, and terrify all the World.” These trite Reasonings are all very true, but little to the Purpose: the Effects above described being merely those arising from Novelty. If, says one in an inferior Station; “they coud convert Balloons into common Stage Waggons; Goods might be carried with the greater Expedition:” or, “into Stage Coaches,” says another: or, “into Mail Coaches” says Palmer; “it woud be certainly very clever, as I have the Patent:”—“or into comfortable Carriages to step in out of +the window+, at a Moment’s Notice; that woud be something,” cries a Nobleman: “it woud _save_ one a Couple of Sets of Horses, and woud eat Nothing: one might ride one’s own Balloon Matches, from one’s Window to Newmarket, and from Newmarket to +town+; dress for Court as we _do_, and make _Nothing_ of it.” Such are the different Ideas annexed by different Ranks of Men, to the Word +utility+ when applied to Balloons. 332. 2. For once let the feeble Voice of a French Philosopher be heard, the Abbée Bertholon: who may perhaps assert that all this is not impossible. A Series of Experiments only can determine: and let the following Remarks serve as an Introduction to his Opinions. 332. 3. It is certain that the Progress already made in the Improvement of Balloons, since their Invention only three Years ago, is far superior to the Acquirements in every other Art. The Antients knew, that excited Amber attracted Straws, and certain other light Substances: but medical Electricity, and a Preservative from Lightening, were notwithstanding reserved for the Moderns. They likewise attended to some striking Effects of the natural Loadstone: but were totally unacquainted with the artificial Magnet, and the amazing Powers conferrable by it in the Disorders of the Imagination: nor did they know the Polarity of its Needle, or Application of it in the Compass. They had not combined Nitre and Sulphur with Charcoal: much less had they changed the Mode of War into Science, by establishing Founderies for Cannon, and the Study of Tactics. Yet some Nations with a Knowledge of the Moderns, as the Chinese, have not improved, even in the Construction of their Vessels, according to the European Manner; continuing still in practical Ignorance. Nor have other Indians improved in Proportion to the Opportunities of Instruction in several Arts. Those of America, for Example, who continue to hunt, fish, and scalp: neglecting the Plough, and other Arts of Property and Peace. 332. 4. And thus it has been with the British Nation on the Subject of Airostation. Cavendish, Priestley, and others, had produced inflammable Air, weighed, and found it lighter than common Air: and all that had seen a bright Fire might conclude, if they reasoned at all, that hot Air was lighter than cold. Yet if Montgolfier had not made, +on a large scale+ the Application of hot Air, in a Bag open at the Bottom, and properly poised; Charles and Roberts woud probably not have thought of applying the Gass of Cavendish: and Mankind woud not _yet_ have soared into the etherial Regions. 332. 5. In this the French are still before the English, and will continue so to be, without a laudable and unlooked-for Emulation in the latter. That the former admire Liberty, Montesquieu’s “Spirit of Laws” may determine; but they are not _addicted_ to Politics. Their Nobility are endowed with a liberal and enterprizing Spirit. They join and patronize Men of Genius and Talents in the Cultivation of the Arts, and Improvement of every Kind of experimental Knowledge. Their Pleasure consists in a national Ambition to excel. They have Leisure, and are sober. Half that Time which Men of Fortune in France dedicate to Taste, Invention, and Refinement; Britons spend among the Beasts and Birds: the other half, at the Bottle, and in political Cabals. _Present Profit_ is almost the sole Motive for Excellence in Great-Britain: and Experiments[110] not made with that View, are seldom repeated; are overlooked and forgotten. CHAPTER LXVI. ON THE UTILITY OF BALLOONS. Section 333. The Balloon opens a new and unlimited Field for Philosophical Discoveries. 334. The many curious and interesting Conjectures which Mons. de Luc (before the Invention of Balloons) throws out, in the Course of 4 large Volumes, on the Subject and Qualities of the Atmosphere; may now be determined by actual Trial. 335. The Abbée Bertholon wrote in 1784: and has particularly mentioned the following Points, as capable of ample Investigation, and. Discussion. Sect. 336. Art. 1. _The Temperature of the Air at different Heights._ Which will determine whether the Atmosphere be _practically Navigable_, at all Times and Places. 336. 2. _The dissolvent Power of the Air by Means of an Atmometer for Evaporation._ Probably the Height may be determined, to which Clouds commonly ascend in order to find the proper horizontal Level, in which Balloons can move with the greatest Ease, Safety, and Expedition. 336. 3. _Variations of the Barometer._ This will ascertain the exact Height, without Mensuration. 336. 4. _The_ +densities+ _at different Heights_. A principal Object in de Luc’s abstruse and scientific Researches: not only useful but necessary to determine the Laws of Refraction; without which, Astronomy, and consequently +navigation+, must remain defective. 336. 5. _The different Effects of Tastes and Odors, at different Heights_: _Experiments on Plants and Animals: also of_ +sound+.[111] These may produce new and salutary Effects on the human Body: and determine how far a Change from hot, putrid, and impure, to cool pure Air, impregnated with the invigorating aërial Acid, may contribute, without the Aid of Drugs, to the Recovery of the Sick, and Invalid: or promote Longevity. 336. 6. _The Direction and Velocity of the Wind._ The different Currents and their different Heights, the Limitation of each Stratum of Wind, together with their different Temperatures at the same Time, will point out the proper Paths for the Balloon to move in, at all Times, and _possibly_ without the Necessity of accurate Direction: the Mode of Ascent and Descent being _already_ known, and proper Instructions given for a secure Landing. 336. 7. _Electricity of the Air_, +meteors+. This may lead to the Birth Place of Lightening, and Methods how to avoid its Effects in the Air. Tho’ it be already known, that little Danger is to be apprehended, on Account of the mutual Repellency between the electric Fluid, inflammable Gass, and oiled Silk. The Irides, the Coronaes, Haloes, and other Phenomena of Colours: the Generation and Solution of which may be investigated on the Spot. 336. 8. _Geography may become a new Science._ 336. 9. _Use of the Balloon for Signals in the calm Air, above Molestation; above Winds still blowing below: to discover the Positions of an Army, or Navy._[112] 336. 10. _To throw principal Men into a Town: and convey others out of it._ 336. 11. With the Montgolfier Balloon, to try Experiments on Light, and Fire: to transport great Weights: raise them out of the Water: draw up Piles, raise Trees, Vessels, &c. 336. 12. The Parashute to secure a Man from too precipitate a Fall, is to be 5 Yards in Diameter, when extended: the Man,—weighing 140 Pounds, and the Parashute weighing 10 Pounds, with a Surface of 150 square Feet,—woud, in that Case, feel no greater Shock than if he had fallen from the Height of six Feet. 336. 13. _Compass and its Variations: also the different Branches in Astronomy._ His Hints on the Direction of the Machine are ingenious. 337. 1. Wheels furnished with Wings. 337. 2. Imitations of the Form and Motions of Fish.[113] 337. 3. Vessels to condense Air, as the Bladders of Fish. 337. 4. Wind-Guns, Wind-Fountains. 337. 5. Elopile and Vapour Steam. 337. 6. Contrary Currents at different Heights: Proof of. 337. 7. New Hints for Balloons to be raised by Steam. 337. 8. Mons. Gouan’s Invention to go +three hundred miles a day in a calm+. 338. The general Use to which Balloons seem capable of being applied, with the Assistance of propulsive Machinery, in the Calm which exists above the Level of a +contrary+ Wind; is that of a common Vehicle, not subject to the Inconvenience of Roads and Inns, between distant Places and Countries, for Passengers, properly accommodated in a Boat-shaped covered Car, furnished with Provisions, and occasional Siberian Cloathing: the Car to be surrounded with, and resting on Bladders, one _fourth blown_, and having each a few Drops of Water within, to keep them moist and elastic;—to prevent an _accidental_ Shock in alighting on Land; and from sinking, if on Water. Such a Conveyance (the Balloon being once made _Air-tight_, and furnished with an _Air-Bottle_ to ascend and descend _without Loss_ of Gass) is ready at all Seasons and Times: both Night and Day: for, as the Aironauts will enjoy continual Sunshine without a Cloud, from his Rising to his Setting: so, during the Night, the Light of the +stars+, always intercepted in its Passage to the Earth by Clouds or thick Vapours, will be greatly augmented, when above both: besides the probable Increase of Light _reflected_ from the upper Fields of white Clouds shone on continually by the different Planets and Constellations: all which will afford an Illumination equal, if not greater, than that of a cloudless frosty Night, when the Ground is covered with Snow. And such Light will be sufficient to read or write by: also to examine the _Barometer_,[114] in order to know the _Height_ and Level of the Balloon above the Surface of the Earth; and the +compass+ for Direction. If Aironauts propose to ascend by Night, and in the Moon’s Quarters; observing likewise the Precautions already given; it may be proper also to consult and take with them the Ephèmeris, in order to know the Time when the Moon rises, and also when she is at the highest, i.e. in the South, or has remained about half her Time above the Horizon. The plainest Points, on which not only the Success of an Excursion, but the Lives of Aironauts may depend, are too frequently neglected, as unimportant and trivial. CHAPTER LXVII. THE PROCESS OF INFLATION. [Sidenote: Process of Inflation on the Day of Ascent, viz. on Thursday the 8th Sept. 1785.] Sect. 339. Art. 1. Three cylindric wooden Vessels were sunk more than half their Depth into the Ground: two of them, each, 5 Feet Diameter, and 5 Feet high: the third, 8 Feet in Diameter, and 8 Feet high. An oblong Hole, 4 Inches by 3, was made in each Vessel: and each Hole was furnished with a solid wooden Plug (made tapering) 6 Inches in Length: throu’ these the Vitriol was poured. Besides which, there was an oblong Opening in each Vessel, large enough to admit a Workman, to distribute the Iron equally over the Bottom, and to pour in Buckets of Water: which Openings were well stopped, as soon as the Iron and Water were poured in. As the vitriolic Acid is _corrosive_, burning the Skin or Cloaths; the following Precautions were taken. An occasional moveable Tub was provided, 3 Feet high, and 3 wide: in the Center of whose Bottom was an oblong Aperture, equal to that in each of the Vessels: a corresponding Tin Tube, 6 Inches long, and narrowing to the Bottom, was nailed by its Border on the Inside of the occasional Tub; so as to go easily into any of the oblong Holes. A Bottle of Vitriol being brought in its Basket by two Men, and made to rest on the Top of one of the fermenting Vessels; a third Assistant held the occasional Tub in his Hands, with the Plug-Staff fastened in the Aperture of the Tin Tube; and the Instant a fourth Person opened the Hole in the fermenting Vessel; the Assistant placed the Tin Tube in the Hole, keeping the Plug tight, to prevent the Escape of Gass. The Bottle of Vitriol was then immediately poured into the occasional Tub: and the Bottle being removed, the Plug-Staff was taken out, and the Vitriol suffered to run into the fermenting Vessel: the Assistant watching for the Instant when the Vitriol was run out, in order to _force in_ the Plug-Staff again, and prevent the Escape of Gass: after which, the Tub was rinced with a few Quarts of Water, let also into the Vessel. The same Tub was then removed: the oblong Hole in the fermenting Vessel instantly covered; and, by driving down the solid wooden Plug, continued _Air-tight_; by Means of moist Clay, and a little Water, kept purposely on the Tops of each Vessel, to discover by the Bubbles, whether Gass escaped. [Sidenote: 20 Hundred Weight of Iron-Turnings.] In these Vessels, early on the Morning of the Inflation, were distributed 20 Hundred Weight, at 120lb. Averdupoise to the Hundred, consisting of cast Iron-Filings, and of a Mixture of Cannon-Borings. The Borings were bright and fresh when thrown into the Water: and any Bits of Wood that swam, were skimmed off. _Rusty_ Iron emits Gass, that is heavier than common Air, and therefore is improper. [Sidenote: 16 Bottles of Vitriol.] At the same Time, 16 Bottles of concentrated vitriolic Acid, or as it is improperly called Oil of Vitriol, were brought in their Packages near the Place, to be ready for Use: each Bottle at an Average containing 112 Pounds Averdupoise, of Vitriol: each full Bottle and Package together weighing from 136 to 148 Pounds. [Sidenote: 4 Pints of Water to a Pound Averdupoise of Acid.] 339. 2. To the Iron in each Vessel, was then poured a Quantity of Water, which was measured in the Proportion of about 4 to 1: i.e. 4 _Pints_ of Water to one _Pound_, of the vitriolic Acid. The Height of Water and Iron in each Vessel, being then gaged, was about 14 Inches. In a Line with the two smaller Vessels, and between them, was fixed another wooden Vessel or Cistern, filled with Water. [Sidenote: Improvements suggested.] (N. B. Fresh Water ought to have flowed continually into it, and to have run over the Top of the Cistern: for the same Quantity being once saturated, can no longer absorb the alcaline and fixed Air to be separated from the Gass before the latter enters the Balloon.) In the Cistern was fixed a Stage, consisting of 4 long Feet, (reaching to the Bottom of the Cistern,) nailed at their upper Ends to the Inside of an inverted Tub or Funnel, so placed over the Center of the Cistern, that 3 Inches of the lower Part of the Rim of the Funnel were under the Surface of the Cistern-Water: the Funnel was _cylindric_, 3 Feet across, and 2 Feet high. An Open was cut, 1 Foot Diameter, in the Bottom of the inverted Funnel: on the Circumference of which was nailed a Tin-Cylinder or common Conductor, 2 Feet high: and at a _certain_ Angle, as most convenient, was soldered a cylindric Arm, of equal Diameter, and 1 Foot long; having a Lip, Ring or Rim, on its outward circular Edge. Round this Rim was fastened a varnished Linen Tube, of equal Diameter with the Cylinder. At a small Distance, about a Yard from the Cistern, stood a slender Stillage, 3 Feet high; on which was supported a detached Tin-Cylinder or Connecter, 1 Foot long and 1 Foot Diameter, made with a Rim at each End: in the Center of whose lower Side was soldered, at right Angles, another Tin-Cylinder or Evacuatory, 6 Inches long and 6 wide: its Use is to let out any Water, that the Heat of the Mixture might cause to boil and rise up out of the fermenting Vessels: and thus be _evacuated_, without entering the Balloon: or, if condensed in the Balloon, might run out by the same Orifice. The opposite End of the varnished Linen Tube was fastened round one End of the detached Cylinder on the Stillage: and round the other, was tyed the Neck or Bottom-Opening of the Balloon. Each of the 2 smaller fermenting Vessels was furnished with a cylindric Tin-Tube; each Tube 4 Inches and a half Diameter, nailed on the Outside of a circular Opening in the Top or Head of each Vessel; communicating by additional rectangular Bends under the Funnel and Water in the Cistern: the great fermenting Vessel had 2 Tubes, each 4 Inches and a half Diameter; communicating with the Funnel. [Sidenote: Improvements suggested.] 340. The Process woud have been more complete, if the fermenting Vessels had been sunk till their Tops were even with the Ground: and plaistered round their Outsides with soft moist Clay, six Inches thick, to keep them Air-tight. Also, if the common Conductor had been only 1 Foot high: its horizontal or rectangular Arm only 6 Inches long: the Linen Trunk but 3 Feet, joining the Connecter on the Stillage 1 Foot high, to communicate with the Neck of the Balloon; which Neck shoud be 3 Yards in Length, and its circular Opening 1 Foot, at least in Diameter. CHAPTER LXVIII. [Sidenote: Inflation began about X. in the Morning.] Section 341. The Process of inflating the Balloon began about X. in the Morning, by pouring 4 Bottles of Vitriol, immediately one after the other, into the occasional Tub, properly placed over one of the smaller fermenting Vessels: the Tub being instantly rinced with a few Quarts of Water, which was suffered to fall into the same Vessel. The oblong Hole was left purposely open for a Minute, till the strong Smell of the Gass was perceived above the Orifice: i.e. till the Gass had pressed out all the common Air that remained floating over the Surface of the Mixture in the fermenting Vessel: which Smell being _plainly perceived_, the _solid_ Plug was immediately _driven_ down. And presently the Gass was known to press forward with an elastic Force throu’ the Tin Conductor, by the Motion it communicated to the Surface of the Water in the Cistern: thence upwards throu’ the common Conductor: at its Departure from both of which throu’ the Linen Trunk, and Neck into the Balloon, the Gass makes a guggling obtuse Sound by quick Intervals according to the Quantity of Gass protruded. And as the Intervals encreased, a Judgment was formed, that the Operation began to be less vigorous: and consequently that it became necessary, either to renew it by an Addition of more Vitriol and Water in the same Vessel, or to set the other small Vessel in Fermentation, the latter of which Mr. Lunardi preferred: this happened about half an Hour after the Vitriol was poured into the first Vessel. 342. After the second half Hour, eight Bottles were poured, by four at a Time, into the great Vessel. And at one o’Clock, the Balloon, without any farther Trouble was beautifully inflated. No Iron Rods were used to stir up the Borings or Filings at the Bottom of the Vessels: the Vitriol being found so heavy as to penetrate them as fast as the Iron, contiguous to the Vitriol, had parted with its Gass. At each of the two former Inflations, a similar Accident happened which may be imputed to the same Cause. 343. During the first Inflation, the solid oblong wooden Plug fell into one of the fermenting Vessels: the hot Vapour, forcibly issuing from the Orifice, was condensed in the Form of a _white_ Smoke; which being mistaken by the Company, a Cry was immediately heard of Fire, Fire: on which the Workmen retreated. Mr. Lunardi incautiously thrust his Arm into the Orifice to extract the Plug: at the same Time being much burnt, and failing in the Attempt; the Gass continued to escape, till a new Plug was prepared. 344. During the second Inflation, one of the Plugs being driven too forcibly; it was with Difficulty extricated, by the Strokes of a Hammer against the Sides of it, which tended at the same Time to displace the Boards forming the Top or Head of the Vessel: and, a little afterwards, occasioned it to burst, unexpectedly +inwards+,[115] rendering the Vessel useless for the Purpose of Inflation. _Observation._ Therefore instead of the solid oblong wooden Plug, a circular Hole, 4 Inches Diameter shoud be drilled in each Vessel: and a corresponding solid wooden Plug 8 Inches long, 5 Diameter at the upper Part, and tapering to near 3 at the Bottom, shoud be prepared by the Turner. In the upper Part of the Solid shoud be turned an inside Screw, to which an outside Screw of the circular Plug-Staff, made of Oak, Ash, or other heavy Wood, 4 Feet long, and 4 Inches Diameter, shoud be adapted: the Worm of the Screw to be 5 Inches long. A wooden Peg of Ash, about a Quarter of an Inch Diameter, may be put throu’ a Hole near the Top of the Staff, as a Handle. A Lever of such a Length and Weight will probably answer every Intention, as no sudden Blows will be required to _fasten or extract it_. The occasional Tub, Tube, Plug, and Staff, shoud be fashioned after this Model. 345. _The Price of the Iron and Vitriol for Inflation._ 2000lb. of Iron Filings or Borings[116] delivered on the Spot, at 6s. a Hundred, £. 6 0 0 16 Bottles of Vitriol, at an Average 38s. a Bottle 30 8 0 Concomitant Expences, 3 12 0 ——————— £. Total 40 0 0 _Observation 1._ A great Saving might be made by conducting the Process in a different Manner. The Author making two Journies to Manchester, purposely to observe the Process by Mr. Sadler; found that his Balloon was inflated in two Hours each Time; by Means only of the two smaller _identical_ fermenting Vessels which Mr. Lunardi afterwards purchased; but the Levity procured by the former, tho’ he also expended 16 Bottles, was by no Means so great as that gained with the Assistance of the great Vessel. It has likewise been remarked by the Author, who has made several Experiments to this End, that the Vessels always continued in Fermentation and Ebullition, with a _quick Pulsation_, for at least 24, and commonly during 48 Hours, after the Inflation was completed. And, that not more than the Depth of _half an Inch_ of Filings had been _calcined_ during the Operation: the rest being perfectly _bright_, and untouched by the Acid. _Observation. 2._ If therefore one Inch in Depth of Filings, be spread over the Bottom of each of the _smaller_ Vessels only; the proper Quantity of Water poured in; and _not more_ than two Bottles of Acid used at once, in each Vessel; also, as soon as the Fermentation begins to decline; other two Bottles, and a proportionable Supply of Water be added; if suffered to work double, triple, or quadruple the Time;—the Inflation will be as great, if not greater, for Instance, in six Hours with eight Bottles, and two small _Tubs_, as it woud in three Hours, with 16 Bottles, in the _same Vessels_. The small conducting Tin Tubes ought instead of four and a half, to be nine Inches Diameter: by which Means there will be no violent Pressure of Gass to endanger the Bursting of the Vessels: particularly if the Gass is not suffered to descend; but, on the contrary, according to Instructions already given, either to rise, or move, in an horizontal Direction, past the Evàcuatory, into the Balloon. 346. The Workmen may begin the Operation at twelve at Night, or at six in the Morning: and the Time previously fixed for the Exhibition, may be eight or ten Hours after the Operation has commenced. The Necessity of a Current of fresh Water, throu’ a Pipe of at least half Inch Bore, the larger the better, to supply the overflowing Cistern, cannot be too much _insisted_ on: as the Levity of the Gass almost wholly depends upon so trivial a Circumstance, as that of having a plentiful Supply of _cold fresh_ and _soft_ Water. 347. _Observation 3._ Supposing the Balloon +air-tight+, near half the Expence is thus saved in the Inflation. Besides the greater Probability of +calm+ Weather for the Inflation, if completed before X. in the Morning, more Time is given to remedy Accidents, and rectify Mistakes: the Warmth of the Air likewise encreases. But above all; if an upper Current carry the Balloon to Sea, the Aironaut may, (as before mentioned) drop into the Sea-Breeze, which will waft him safe back till IV. in the Afternoon, or even later. CHAPTER LXIX. MENSURATION OF HEIGHTS. [Sidenote: Rules for calculating Heights by Means of the Barometer and Thermometers.] Section 348. Rules for calculating the Height of Mountains, when applied to those elevated Stations in the Atmosphere _attainable_ only by Means of the Balloon, will henceforward become more useful, and be more frequently practised: as the Lives of Aironauts _may_ depend on a Knowledge of their _Height_ above the Earth; which, not being determinable by _Sight_, in _all Weathers_, or at all Times, must be referred to the _Barometer_ and _Thermometers_, they carry up with them. De Luc, Horseley, Maskelyne, Shuckburgh, and Roy, have each written +ably+ on the Subject, in the _Transactions_: tho’ few have either Leisure or Inclination to follow them. Sir George Shuckburgh has made successful Attempts to smooth the Way, by Examples and Tables, yet is still too concise for actual Learners, and the Generality of those who will have Spirit enough to go before the Calculators in exploring the Atmosphere; but cannot dedicate sufficient Leisure to overtake them in their Studies. Each may therefore assist the other. 349. Whoever is at the Trouble of comparing the Observations made by Shuckburgh, with the Directions here given, will find that the latter contains the _Essentials_ of the former, with this material Difference, that the Investigation moves here by Steps, which are all pointed out to the Learner; and not by Strides. Each Step is self evident: and, by carrying Conviction to the Mind, is just what the Mind itself woud make use of, in the Attainment of any _distant_ Truth. To do every Justice to Sir George, the Merit of whose Performance wants no Eulogium; his three Precepts are copied; tho’ rather as a Memorandum for those who understand the Methods; than as plain Directions for such as are yet to learn them. It will be found likewise, that the first, second, and fourth Tables are greatly enlarged: being calculated for those _extreme_ Temperatures, and Heights, which the Balloon _only_ can attempt to reach: and the fourth Table, for greater Dispatch in computing the Expansion of the Air. The Foundation and Construction of each Table, is also methodically traced and elucidated. CHAPTER LXX. METHODS TO ASCERTAIN THE TRUE HEIGHT. Section 350. Methods to be pursued on taking and comparing Heights, in order to ascertain the true Height of any Station in the Atmosphere, by the Barometer and Thermometers. For this Purpose it is necessary, 1st, to provide a Barometer, (whose Bulb or Cistern is _large_ enough to contain all the Quicksilver in the Tube;)—into the Frame of which, a Thermometer, on _Farenheit’s_ Scale, is to be fixed or _attached_. The Use of the _attached Thermometer_ is to point out the Temperature of the Barometer. 2d. A second or _detached Thermometer_ is also to be provided.[117] This is to be hung in the Shade at the Distance of a Yard (or two) from the other:—to shew the _general_ Temperature of the Air at the same Time and Place: and may be called the _Air Thermometer_. A proper Person, on the Ground, having a good Watch, with Pen Ink and Paper at Hand, is to attend the Instruments _below_ every ten Minutes, (or at any other _preconcerted_ Intervals of Time,) putting down, 1st. The Time of each Observation. 2d. The Point at which the Quicksilver stands in the Barometer. 3d. The Degree of Temperature of the _attached_ Thermometer. 4th, and lastly, the Degree of Temperature of the _detached_ or _Air_-Thermometer. This Employment is to be carefully attended to; during the Time, that _similar_ Observations, by _preconcerted_ Agreement, are making, with three other _similar_ Instruments, on the Top of the Mountain, or any elevated Station in the Atmosphere, by Means of the _Balloon_; and to be written with a _red Lead_ Pencil, in a Patent Asses Skin Pocket Book. [Sidenote: The Instruments to be compared on Return from the Mountain, or upper Station.] Each single Observation, made with one Set of Instruments _below_, is to be compared with each single corresponding Observation, made with the other Set _above_. And two Observations are said to _correspond_, when both are made _nearly_ at the _same_ Time, the one _below_, and the other _above_. 351. Take Shuckburgh’s first Example, (Ph. Tr. for 1777, 2d Part, Page 577.) viz. “Let the Point at which the Quicksilver stands in the Barometer, on the Ground, be 29 Inches 4 tenths: the attached Thermometer 50 Degrees of Temperature, and the Air Thermometer, or general Temperature of the Air 45°: at the same Time, that at the Top of the Mountain, or other elevated Station in the Atmosphere, the Barometer stands at 25 Inches 19 Tenths, the attached Thermometer at 46°, and the Air Thermometer at 39° and ½: required the upper Height in English Feet.” [Sidenote: Rules for the Work: and Practice of the first Example.] 352. The Work is divided into three Stages. The End proposed in this first Stage is to bring the colder Barometer, to the same _Expansion_ or _Temperature_ with the _other_. 353. 1st. Step. First, write down the Observation made on the Ground, or at the Bottom of the Mountain, thus: +Below.+ Barometer, 29 Inches 4 Tenths. attached Thermometer, 50 Degrees. Air Thermometer, 45°. 354. 2d. Step. Secondly, write down the Observation made at the Top of the Mountain, or upper Station in the Atmosphere, thus: +Above.+ Barometer, 25 Inches, .19 Tenths. attached Thermometer, 46°. Air Thermometer, 29½. 355. 3d Step. Subtract the _colder attached_ Thermometer, from the other attached Thermometer, thus: 46 colder from 50 warmer, and there remains 4° warmer, viz. the Number of Degrees of Temperature to which the _colder_ Barometer must be _expanded_, before it becomes equal in Temperature to the _warmer_ Barometer: each Barometer being always supposed _equal_ in Temperature with its _attached_ Thermometer. 356. 4th Step. Give the _colder_ Barometer the same _Temperature_ with the warmer: or, which amounts to the same, give the _colder_ Barometer that _Expansion_ which is communicated by the Addition of 4 Degrees of Temperature. Both Barometers will then have the same _Temperature_, or _Expansion_, viz. an Expansion equal to the warmer Barometer. This is to be done by referring to the first Table, for the Application of which there are separate Instructions: see the Explanation of the first Table.[118] CHAPTER LXXI. USE AND PRACTICE OF THE FIRST TABLE, IN THE FIRST EXAMPLE. _The_ +use+. Section 357. To find the Expansion of Quicksilver, and of the barometric Tube in which it is contained: or, in other Words, to find the Point to which the Quicksilver will rise in the Tube, (in Parts of an Inch) with a given additional Temperature, on Farenheit’s Scale. The Question in the first Example is, (Ph. Tr. for 1777, Page 578;) To find the Expansion that arises, _with_ the Addition of 4 Degrees of Heat, _on_ the _colder_ Barometer resting at Inches 25 .19 Tenths, in order to give it an Expansion equal to that of another Barometer, 4 Degrees warmer than the former: the Temperature of _each_ Barometer, being indicated by its respective _attached_ Thermometer. N. B. During the Application of the first Table, the Investigation moves forward two Steps only, viz. the 4th and 5th. _The 4th Step, applied in the first Example._ 358. The _Order_ to be observed in finding the Expansion of the Quicksilver, with 4 Degrees on Inches 25 .19 Tenths of the Barometer. 1st. Find the Expansion, With 4° on 25 Inches only. Then in order to obtain with 4° on .19, begin 2d. With 4° on 1 Inch above 25 Inches, i.e. on the 26th Inch. 3d. With 4° on .1, i.e. one Tenth of an Inch above 25 Inches: and lastly, 4th. With 4° on .19, Tenths above 25 Inches. _The_ +practice+. 359. 1st. In the _first_ Table, _with_ 4 Degrees on the left Hand vertical Column, and with 25 Inches, along the upper Range; at the Point of Meeting, is the Answer .0101[119] viz. the Expansion, or Rise of the Quicksilver standing at 25 Inches, and receiving an additional Heat of 4°: the Answer .0101 being the Expression for the ten thousand one hundredth Part of an Inch, (viz. in Height, by Expansion.) 360. Add this Number, .0101, Part of an Inch, or Rise by Expansion, to the Barometer resting at Inches 25, .19 Tenths, Units under Units, &c. thus: .0101. 361. 2d. Now, in order to obtain the Expansion _with_ 4 Degrees, _on_ .19 Tenths i.e. the nine hundred and tenth Part of an Inch of Quicksilver in the Tube (above 25 Inches,) it must be considered, where it ought to be found in the first Table. Tenths of 1 Inch, above 25 Inches, it must be observed, are at some intermediate Point between 25 and 26 Inches; that is, above 25, yet not so high as 26, or more than 25, yet less than 26. Therefore, to find the Expansion _with_ 4 Degrees, _on_ 1 Inch above 25, i.e. on the 26th Inch; look in the Table, first, _with_ 4 Degrees on 25 Inches: then _with_ 4 Degrees on 26 Inches. The respective Numbers are .0101 and .0105. And by taking the Expansion _with_ 4° on 25 Inches, from the Expansion, _with_ 4° _on_ 26 Inches, thus; Expansion { .0101 on 25 Inches, { .0105 on 26 Inches, ————— The Remainder .0004 is the Expansion with 4° on 1 Inch, above 25, i.e. on the 26th Inch. 362. 3d. To find the Expansion, with 4° on .1 above 25 Inches; add a Cypher and decimal Point to the former Answer, which then becomes .00004, viz. the Expansion, with 4° on one Tenth, above 25 Inches. 363. 4th. Lastly, to obtain the Expansion _with_ 4°, _on_ .19, above 25 Inches, say: If one Tenth of an Inch, above 25 Inches, gives this Expansion viz. .00004, what Expansion will nineteen Tenths above 25, give? answer .19 Tenths more; thus: If .1 : .00004 :: .19? .19 —————— 00036 0004 —————— .00076; then, in order to have as many decimal Places in the Product as are contained both in the Multiplicand and Multiplier, add a Cypher and Point to the left, and the Product becomes .0000076 which, being divided by .1, gives a Cypher less. viz. the Expansion with 4° on .19 above 25 Inches. THE FIRST TABLE: +shewing the expansion with HEAT on inches of the BAROMETER.+ +-------------------------------------------------------------------+ |+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ | | +-------+-------+-------+-------+-------+-------+-------+-------+ | | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | | +-------+-------+-------+-------+-------+-------+-------+-------+ | 1 |.00091 |.00102 |.00112 |.00122 |.00132 |.00142 |.00152 |.00162 | | 2 |.00182 |.00204 |.00224 |.00244 |.00264 |.00284 |.00304 |.00324 | | 3 |.00273 |.00306 |.00336 |.00366 |.00396 |.00426 |.00456 |.00486 | | 4 |.00364 |.00408 |.00448 |.00488 |.00528 |.00568 |.00608 |.00648 | | 5 |.00455 |.00510 |.00560 |.00610 |.00660 |.00710 |.00760 |.00810 | | 6 |.00546 |.00612 |.00672 |.00732 |.00792 |.00852 |.00912 |.00972 | | 7 |.00637 |.00714 |.00784 |.00854 |.00924 |.00994 |.01064 |.01134 | | 8 |.00728 |.00816 |.00896 |.00976 |.01056 |.01136 |.01216 |.01296 | | 9 |.00819 |.00918 |.01008 |.01098 |.01188 |.01278 |.01368 |.01458 | |10 |.00910 |.01020 |.01120 |.01220 |.01320 |.01420 |.01520 |.01620 | |11 |.01001 |.01122 |.01232 |.01342 |.01452 |.01562 |.01672 |.01782 | |12 |.01092 |.01224 |.01344 |.01464 |.01584 |.01704 |.01824 |.01944 | |13 |.01183 |.01326 |.01456 |.01586 |.01716 |.01846 |.01976 |.02106 | |14 |.01274 |.01428 |.01568 |.01708 |.01848 |.01988 |.02128 |.02268 | |15 |.01365 |.01530 |.01680 |.01830 |.01980 |.02130 |.02280 |.02430 | |16 |.01456 |.01632 |.01792 |.01952 |.02112 |.02272 |.02432 |.02592 | |17 |.01547 |.01734 |.01904 |.02074 |.02244 |.02414 |.02584 |.02754 | |18 |.01638 |.01836 |.02016 |.02196 |.02376 |.02556 |.02736 |.02916 | |19 |.01729 |.01938 |.02128 |.02318 |.02508 |.02698 |.02888 |.03078 | |20 |.01820 |.02040 |.02240 |.02440 |.02640 |.02840 |.03040 |.03240 | |21 |.01911 |.02142 |.02352 |.02562 |.02772 |.02982 |.03192 |.03402 | |22 |.02002 |.02244 |.02464 |.02684 |.02904 |.03124 |.03344 |.03564 | |23 |.02093 |.02346 |.02576 |.02806 |.03036 |.03266 |.03496 |.03726 | |24 |.02184 |.02448 |.02688 |.02928 |.03168 |.03408 |.03648 |.03888 | |25 |.02275 |.02550 |.02800 |.03050 |.03300 |.03550 |.03800 |.04050 | |26 |.02366 |.02652 |.02912 |.03172 |.03432 |.03692 |.03952 |.04212 | |27 |.02457 |.02754 |.03024 |.03294 |.03564 |.03834 |.04104 |.04374 | |28 |.02548 |.02856 |.03136 |.03416 |.03696 |.03976 |.04256 |.04536 | |29 |.02639 |.02958 |.03248 |.03538 |.03828 |.04118 |.04408 |.04698 | |30 |.02730 |.03060 |.03360 |.03660 |.03960 |.04260 |.04560 |.04860 | |31 |.02821 |.03162 |.03472 |.03782 |.04092 |.04402 |.04712 |.05022 | |32 |.02912 |.03264 |.03584 |.03904 |.04224 |.04544 |.04864 |.05184 | |33 |.03003 |.03366 |.03696 |.04026 |.04356 |.04686 |.05016 |.05346 | |34 |.03094 |.03468 |.03808 |.04148 |.04488 |.04828 |.05168 |.05508 | |35 |.03185 |.03570 |.03920 |.04270 |.04620 |.04970 |.05320 |.05670 | |36 |.03276 |.03672 |.04032 |.04392 |.04752 |.05112 |.05472 |.05832 | |37 |.03367 |.03774 |.04144 |.04514 |.04884 |.05254 |.05624 |.05994 | |38 |.03458 |.03876 |.04256 |.04636 |.05016 |.05396 |.05776 |.06156 | |39 |.03549 |.03978 |.04368 |.04758 |.05148 |.05538 |.05928 |.06318 | |40 |.03640 |.04080 |.04480 |.04880 |.05280 |.05680 |.06080 |.06480 | +---+-------+-------+-------+-------+-------+-------+-------+-------+ THE FIRST TABLE CONTINUED: +shewing the expansion with HEAT on inches of the BAROMETER.+ +-------------------------------------------------------------------+ |+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ | | +-------+-------+-------+-------+-------+-------+-------+-------+ | | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | | +-------+-------+-------+-------+-------+-------+-------+-------+ | 1 |.00172 |.00182 |.00192 |.00203 |.00213 |.00223 |.00233 |.00243 | | 2 |.00344 |.00364 |.00384 |.00406 |.00426 |.00446 |.00466 |.00486 | | 3 |.00516 |.00546 |.00576 |.00609 |.00639 |.00669 |.00699 |.00729 | | 4 |.00688 |.00728 |.00768 |.00812 |.00852 |.00892 |.00932 |.00972 | | 5 |.00860 |.00910 |.00960 |.01015 |.01065 |.01115 |.01165 |.01215 | | 6 |.01032 |.01092 |.01152 |.01218 |.01278 |.01338 |.01398 |.01458 | | 7 |.01204 |.01274 |.01344 |.01421 |.01491 |.01561 |.01631 |.01701 | | 8 |.01376 |.01456 |.01536 |.01624 |.01704 |.01784 |.01864 |.01944 | | 9 |.01548 |.01638 |.01728 |.01827 |.01917 |.02007 |.02097 |.02187 | |10 |.01720 |.01820 |.01920 |.02030 |.02130 |.02230 |.02330 |.02430 | |11 |.01892 |.02002 |.02112 |.02233 |.02343 |.02453 |.02563 |.02673 | |12 |.02064 |.02184 |.02304 |.02436 |.02556 |.02676 |.02796 |.02916 | |13 |.02236 |.02366 |.02496 |.02639 |.02769 |.02899 |.03029 |.03159 | |14 |.02408 |.02548 |.02688 |.02842 |.02982 |.03122 |.03262 |.03402 | |15 |.02580 |.02730 |.02880 |.03045 |.03195 |.03345 |.03495 |.03645 | |16 |.02752 |.02912 |.03072 |.03248 |.03408 |.03568 |.03728 |.03888 | |17 |.02924 |.03094 |.03264 |.03451 |.03621 |.03791 |.03961 |.04131 | |18 |.03096 |.03276 |.03456 |.03654 |.03834 |.04014 |.04194 |.04374 | |19 |.03268 |.03458 |.03648 |.03857 |.04047 |.04237 |.04427 |.04617 | |20 |.03440 |.03640 |.03840 |.04060 |.04260 |.04460 |.04660 |.04860 | |21 |.03612 |.03822 |.04032 |.04263 |.04473 |.04683 |.04893 |.05103 | |22 |.03784 |.04004 |.04224 |.04466 |.04686 |.04906 |.05126 |.05346 | |23 |.03956 |.04186 |.04416 |.04669 |.04899 |.05129 |.05359 |.05589 | |24 |.04128 |.04368 |.04608 |.04872 |.05112 |.05352 |.05592 |.05832 | |25 |.04300 |.04550 |.04800 |.05075 |.05325 |.05575 |.05825 |.06075 | |26 |.04472 |.04732 |.04992 |.05278 |.05538 |.05798 |.06058 |.06318 | |27 |.04644 |.04914 |.05184 |.05481 |.05751 |.06021 |.06291 |.06561 | |28 |.04816 |.05096 |.05376 |.05684 |.05964 |.06244 |.06524 |.06804 | |29 |.04988 |.05278 |.05568 |.05887 |.06177 |.06467 |.06757 |.07047 | |30 |.05160 |.05460 |.05760 |.06090 |.06390 |.06690 |.06990 |.07290 | |31 |.05332 |.05642 |.05952 |.06293 |.06603 |.06913 |.07223 |.07533 | |32 |.05504 |.05824 |.06144 |.06496 |.06816 |.07139 |.07456 |.07776 | |33 |.05676 |.06006 |.06336 |.06699 |.07029 |.07359 |.07689 |.08019 | |34 |.05848 |.06188 |.06528 |.06902 |.07242 |.07582 |.07922 |.08262 | |35 |.06020 |.06350 |.06720 |.07105 |.07455 |.07805 |.08155 |.08505 | |36 |.06192 |.06534 |.06912 |.07308 |.07668 |.08028 |.08388 |.08748 | |37 |.06364 |.06716 |.07104 |.07511 |.07881 |.08251 |.08621 |.08991 | |38 |.06536 |.06892 |.07296 |.07714 |.08094 |.08474 |.08854 |.09234 | |39 |.06708 |.07078 |.07488 |.07917 |.08307 |.08697 |.09087 |.09477 | |40 |.06880 |.07260 |.07680 |.08120 |.08520 |.08920 |.09320 |.09720 | +---+-------+-------+-------+-------+-------+-------+-------+-------+ THE FIRST TABLE CONCLUDED: +shewing the expansion with HEAT on inches of the BAROMETER.+ +-------------------------------------------------------------------+ |+degrees of the THERMOMETER, from 1 to 40, on farenheit’s scale.+ | | +-------+-------+-------+-------+-------+-------+-------+-------+ | | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | | +-------+-------+-------+-------+-------+-------+-------+-------+ | 1 |.00253 |.00263 |.00274 |.00284 |.00294 |.00304 |.00314 |.00324 | | 2 |.00506 |.00526 |.00548 |.00568 |.00588 |.00608 |.00628 |.00648 | | 3 |.00759 |.00789 |.00822 |.00852 |.00882 |.00912 |.00942 |.00972 | | 4 |.01012 |.01052 |.01096 |.01136 |.01176 |.01216 |.01256 |.01296 | | 5 |.01265 |.01315 |.01370 |.01420 |.01470 |.01520 |.01570 |.01620 | | 6 |.01518 |.01578 |.01644 |.01704 |.01764 |.01824 |.01884 |.01944 | | 7 |.01771 |.01841 |.01918 |.01988 |.02058 |.02128 |.02198 |.02268 | | 8 |.02024 |.02104 |.02192 |.02272 |.02352 |.02432 |.02512 |.0259? | | 9 |.02277 |.02367 |.02466 |.02556 |.02646 |.02736 |.02826 |.02916 | |10 |.02530 |.02630 |.02740 |.02840 |.02940 |.03040 |.03140 |.03240 | |11 |.02783 |.02893 |.03014 |.03124 |.03234 |.03344 |.03454 |.03564 | |12 |.03036 |.03156 |.03288 |.03408 |.03528 |.03648 |.03768 |.03888 | |13 |.03289 |.03419 |.03562 |.03692 |.03822 |.03952 |.04082 |.04212 | |14 |.03542 |.03682 |.03836 |.03976 |.04116 |.04256 |.04396 |.04536 | |15 |.03795 |.03945 |.04110 |.04260 |.04410 |.04560 |.04710 |.04860 | |16 |.04048 |.04208 |.04384 |.04544 |.04704 |.04864 |.05024 |.05184 | |17 |.04301 |.04471 |.04658 |.04828 |.04998 |.05168 |.05338 |.05508 | |18 |.04554 |.04734 |.04932 |.05112 |.05292 |.05472 |.05652 |.05832 | |19 |.04807 |.04997 |.05206 |.05396 |.05586 |.05776 |.05966 |.06156 | |20 |.05060 |.05260 |.05480 |.05680 |.05880 |.06080 |.06280 |.06480 | |21 |.05313 |.05523 |.05754 |.05964 |.06174 |.06384 |.06594 |.06804 | |22 |.05566 |.05786 |.06028 |.06248 |.06468 |.06688 |.06908 |.07128 | |23 |.05819 |.06049 |.06302 |.06532 |.06762 |.06992 |.07222 |.07452 | |24 |.06072 |.06312 |.06576 |.06816 |.07056 |.07296 |.07536 |.07776 | |25 |.06325 |.06575 |.06850 |.07100 |.07350 |.07600 |.07850 |.08100 | |26 |.06578 |.06838 |.07124 |.07384 |.07644 |.07904 |.08164 |.08424 | |27 |.06831 |.07101 |.07398 |.07668 |.07938 |.08208 |.08478 |.08748 | |28 |.07084 |.07364 |.07672 |.07952 |.08232 |.08512 |.0879 |.09072 | |29 |.07337 |.07627 |.07946 |.08236 |.08526 |.08816 |.09106 |.09396 | |30 |.07590 |.07890 |.08220 |.08520 |.08820 |.09120 |.09420 |.09720 | |31 |.07843 |.08153 |.08494 |.08804 |.09114 |.09424 |.09734 |.10044 | |32 |.08096 |.08416 |.08768 |.09088 |.09408 |.09728 |.10048 |.10368 | |33 |.08349 |.08679 |.09042 |.09372 |.09702 |.10032 |.10362 |.10692 | |34 |.08602 |.08942 |.09316 |.09656 |.09996 |.10336 |.10676 |.11016 | |35 |.08855 |.09205 |.09590 |.09940 |.10290 |.10640 |.10990 |.11340 | |36 |.09108 |.09468 |.09864 |.10224 |.10584 |.10944 |.11314 |.11664 | |37 |.09361 |.09731 |.10138 |.10508 |.10878 |.11248 |.11618 |.11988 | |38 |.09614 |.09994 |.10412 |.10792 |.11172 |.11552 |.11932 |.12312 | |39 |.09867 |.10257 |.10686 |.11076 |.11466 |.11866 |.12246 |.12636 | |40 |.10120 |.10520 |.10960 |.11360 |.11760 |.12160 |.12560 |.12960 | +---+-------+-------+-------+--------+-------+-------+------+-------+ _The 5th Step, applied in the first Example._ 364. Add this, to the former Expansion, thus: Inches 25.19 Tenths with 4° on 25 .0101 Expansion with 4° on .19 .0000076 Expansion —————————————— The Answer is 25.2|001076, viz. the Point at which the Quicksilver woud stand, in the coldest Barometer, when equally _expanded_, i.e. of the same Temperature with the warmer. Reject all but the first Decimal as too minute: this is seen by a Line drawn between the first and second Decimal. Practice will shew how far to proceed, without computing the decimal Parts of an Inch, to more than 4 Places; but it is always more exact, to follow minutely the above Rules. CHAPTER LXXII. Section 365. Having therefore understood the Foundation, Construction, and Use of the first Table; in the present Case, having also added the decimal Parts of an Inch just found, for the Expansion,—to the Inches and Tenths, expressing the colder Barometer; which will then have the _same Expansion_, or _Temperature_ with the warmer, thus; Inches. 25.19 _colder_ Barometer: .0101 Expansion _on_ the same, in Parts of an Inch with 4° of Temperature, (rejecting all but the first Decimal as too ———————— minute,) 25.2|001 added; this Sum will express the Point at which the Quicksilver in the colder Barometer woud stand, when equally expanded, i.e. in the same Temperature, with the warmer. 366. 6th Step. Place both Barometers, now of _equal_ Temperature with the warmer, together, first, the _upper_ Barometer; and under it the _lower_, thus: Inches 25. 2 Tenths. 29. 4 END OF THE FIRST STAGE. * * * * * 367. The Ends proposed in the _second Stage_ of the Work, (the colder Barometer being _now_ brought to the same Expansion or Temperature with the warmer,) are two: First, to find, (by the Application of the second Table) the Heights, in Feet and Tenths, in the Atmosphere, corresponding to the Points at which the Quicksilver stands in both Barometers, which have now the same Temperature, viz. that of the warmer equal to 50°: on a Supposition that they were both exposed to the Temperature of 31°.24, on Farenheit’s Scale, which is about the Standard or freezing Point, for which sole Purpose the 2d Table is calculated. N. B. The _Second Stage_ includes two Steps only, viz. the 7th and 8th. 368. 7th Step. The Barometers being placed in one View, as before directed, thus: Upper Barometer, Inches 25 .2 Tenths. Lower Barometer, Inches 29 .4; find, with the Temperature of 31°.24, the corresponding Heights in the Atmosphere. This is to be done by referring to the 2d Table, for the Application of which there are separate Instructions: See the Explanation of the second Table.[120] CHAPTER LXXIII. USE AND PRACTICE OF THE SECOND TABLE IN THE FIRST EXAMPLE. _The_ +use+. Section 369. To find the Heights, in Feet and Tenths, in the Atmosphere, corresponding to the Points at which the Quicksilver stands in both Barometers, which have _now_ the _same Temperature_, viz. that of the _warmer_ Barometer, on a Supposition that they were both exposed to the Standard-Temperature of 31°.24, on Farenheit’s Scale. _The_ +practice+. _The 7th Step applied in the first Example._ 370. Look at the first Column, in the _second_ Table, for 25.2, and the Answer is 6225.0 in the second Column; and for 29.4, and the Answer is 2208.2. The Answers are the Heights, in Feet and Tenths, in the Atmosphere, at which the Quicksilver stands in both Barometers, with the Temperature of 31°.24: corresponding to their respective Points, for which _sole_ Purpose this Table is calculated. 371. 8th Step. Having placed the Barometers and their corresponding Heights in the Atmosphere, shewn by the second Table, at one View: subtract the lesser from the whole Height, and there will remain, +secondly+; (see Section 367) the greater Height, viz. the Height corresponding to the Barometer in the elevated Station, above the Height corresponding to the Barometer, on the Ground, (both being at the Temperature of 31°.24) thus: Feet. Inches 25.2 correspond to 6225.0 Inches 29.4 correspond to 2208.2; subtract: —————— and the Remainder is 4016.8 viz. a Number in Feet and Tenths corresponding to the Height of the upper above the lower Barometer, both being in the Temperature of 31°.34. (See Page 295.) THE SECOND TABLE. The 1st Column shews the Quicksilver in the barometric Tube standing at each Inch from 1 to 10, and at each Tenth from 10 to 32 Inches. The 2d Column shews the Height of the barometric Tube, above the _imaginary Level at 32 Inches_,—_with_ the Temperature of 31.24;—in Feet and Tenths, answering to Inches and Tenths of the Barometer in the first Column. The 3d Column shews the Height in Feet and Tenths, answering to a Tenth of an Inch on the Barometer, being the +difference+ between each two adjoining Heights in the 2d Column. +-----+---------+-----------+ |Inch.| Feet. |Difference.| | | | | | 1 | 90309.0 | | | | | 18061.8 | | 2 | 72247.2 | | | | | 10565.4 | | 3 | 61681.8 | | | | | 7496.4 | | 4 | 54185.4 | | | | | 5814.6 | | 5 | 48370.8 | | | | | 4750.9 | | 6 | 43619.9 | | | | | 4016.8 | | 7 | 39603.1 | | | | | 3479.5 | | 8 | 36123.6 | | | | | 3069.2 | | 9 | 33054.4 | | | | | 2745.4 | |10.0 | 30309.0 | | | | | 259.6 | | .1 | 30049.4 | | | | | 256.4 | | .2 | 29793.0 | | | | | 254.3 | | .3 | 29538.7 | | | | | 251.8 | | .4 | 29286.9 | | | | | 249.3 | | .5 | 29037.6 | | | | | 247.0 | | .6 | 28790.6 | | | | | 244.7 | | .7 | 28545.9 | | | | | 242.4 | | .8 | 28303.5 | | | | | 240.2 | | .9 | 28063.3 | | | | | 237.9 | |11.0 | 27825.4 | | | | | 235.8 | | .1 | 27589.6 | | | | | 233.7 | | .2 | 27355.9 | | | | | 231.6 | | .3 | 27124.3 | | | | | 229.6 | | .4 | 26894.7 | | | | | 227.6 | | .5 | 26667.1 | | | | | 225.6 | | .6 | 26441.5 | | | | | 223.7 | | .7 | 26217.8 | | | | | 221.7 | | .8 | 25996.1 | | | | | 220.0 | | .9 | 25776.1 | | | | | 218.0 | |12.0 | 25558.1 | | | | | 216.3 | |12.1 | 25341.8 | | | | | 214.4 | | .2 | 25127.4 | | | | | 212.7 | | .3 | 24914.7 | | | | | 211.0 | | .4 | 24703.7 | | | | | 209.3 | | .5 | 24494.4 | | | | | 207.7 | | .6 | 24286.7 | | | | | 206.0 | | .7 | 24080.7 | | | | | 204.3 | | .8 | 23876.4 | | | | | 202.8 | | .9 | 23673.6 | | | | | 201.2 | |13.0 | 23472.4 | | | | | 199.7 | | .1 | 23272.7 | | | | | 198.2 | | .2 | 23074.5 | | | | | 196.6 | | .3 | 22877.9 | | | | | 195.2 | | .4 | 22682.7 | | | | | 193.7 | | .5 | 22489.0 | | | | | 192.4 | | .6 | 22296.6 | | | | | 191.0 | | .7 | 22105.6 | | | | | 189.4 | | .8 | 21916.2 | | | | | 188.1 | | .9 | 21728.1 | | | | | 186.8 | |14.0 | 21541.3 | | | | | 185.5 | | .1 | 21355.8 | | | | | 184.1 | | .2 | 21171.7 | | | | | 182.9 | | .3 | 20988.8 | | | | | 181.6 | | .4 | 20807.2 | | | | | 180.3 | | .5 | 20626.9 | | | | | 179.0 | | .6 | 20447.9 | | | | | 178.0 | | .7 | 20269.9 | | | | | 176.7 | | .8 | 20093.2 | | | | | 175.4 | | .9 | 19917.8 | | | | | 174.3 | |15.0 | 19743.5 | | | | | 173.1 | |15.1 | 19570.4 | | | | | 172.0 | | .2 | 19398.4 | | | | | 170.9 | | .3 | 19227.5 | | | | | 169.8 | | .4 | 19057.7 | | | | | 168.6 | | .5 | 18889.1 | | | | | 167.6 | | .6 | 18721.5 | | | | | 166.5 | | .7 | 18555.0 | | | | | 165.4 | | .8 | 18389.6 | | | | | 164.1 | | .9 | 18225.5 | | | | | 163.7 | |16.0 | 18061.8 | | | | | 162.4 | | .1 | 17899.4 | | | | | 161.3 | | .2 | 17738.1 | | | | | 160.4 | | .3 | 17577.7 | | | | | 159.3 | | .4 | 17418.4 | | | | | 158.4 | | .5 | 17260.0 | | | | | 157.5 | | .6 | 17102.5 | | | | | 156.5 | | .7 | 16946.0 | | | | | 155.6 | | .8 | 16790.4 | | | | | 154.6 | | .9 | 16635.8 | | | | | 153.7 | |17.0 | 16482.1 | | | | | 152.9 | | .1 | 16329.2 | | | | | 151.9 | | .2 | 16177.3 | | | | | 151.1 | | .3 | 16026.2 | | | | | 150.2 | | .4 | 15876.0 | | | | | 149.3 | | .5 | 15726.7 | | | | | 148.5 | | .6 | 15578.2 | | | | | 147.6 | | .7 | 15430.6 | | | | | 146.8 | | .8 | 15283.8 | | | | | 146.0 | | .9 | 15137.8 | | | | | 145.2 | |18.0 | 14992.6 | | | | | 144.3 | |18.1 | 14848.3 | | | | | 143.6 | | .2 | 14704.7 | | | | | 142.8 | | .3 | 14561.9 | | | | | 142.0 | | .4 | 14419.9 | | | | | 141.2 | | .5 | 14278.7 | | | | | 140.5 | | .6 | 14138.2 | | | | | 139.7 | | .7 | 13998.5 | | | | | 139.0 | | .8 | 13859.5 | | | | | 138.2 | | .9 | 13721.3 | | | | | 137.5 | |19.0 | 13583.8 | | | | | 136.8 | | .1 | 13447.0 | | | | | 136.1 | | .2 | 13310.9 | | | | | 135.3 | | .3 | 13175.6 | | | | | 134.5 | | .4 | 13041.1 | | | | | 134.2 | | .5 | 12906.9 | | | | | 133.3 | | .6 | 12773.6 | | | | | 132.6 | | .7 | 12641.0 | | | | | 131.9 | | .8 | 12509.1 | | | | | 131.3 | | .9 | 12377.8 | | | | | 130.6 | |20.0 | 12247.2 | | | | | 130.0 | | .1 | 12117.2 | | | | | 129.3 | | .2 | 11987.9 | | | | | 128.7 | | .3 | 11859.2 | | | | | 128.0 | | .4 | 11731.2 | | | | | 127.4 | | .5 | 11603.8 | | | | | 126.8 | | .6 | 11477.0 | | | | | 126.2 | | .7 | 11350.8 | | | | | 125.6 | | .8 | 11225.2 | | | | | 125.0 | | .9 | 11100.2 | | | | | 124.4 | |21.0 | 10975.8 | | | | | 123.7 | | .1 | 10852.1 | | | | | 123.3 | | .2 | 10728.8 | | | | | 122.6 | | .3 | 10606.2 | | | | | 122.0 | | .4 | 10484.2 | | | | | 121.5 | | .5 | 10362.7 | | | | | 120.9 | | .6 | 10241.8 | | | | | 120.4 | | .7 | 10121.4 | | | | | 119.8 | | .8 | 10001.6 | | | | | 119.2 | | .9 | 9882.4 | | | | | 118.8 | |22.0 | 9763.6 | | | | | 118.1 | |22.1 | 9645.5 | | | | | 117.7 | | .2 | 9527.8 | | | | | 117.1 | | .3 | 9410.7 | | | | | 116.6 | | .4 | 9294.1 | | | | | 116.0 | | .5 | 9178.1 | | | | | 115.6 | | .6 | 9062.5 | | | | | 115.1 | | .7 | 8947.4 | | | | | 114.5 | | .8 | 8832.9 | | | | | 114.0 | | .9 | 8718.9 | | | | | 113.6 | |23.0 | 8605.3 | | | | | 113.0 | | .1 | 8492.3 | | | | | 112.6 | | .2 | 8379.7 | | | | | 112.1 | | .3 | 8267.6 | | | | | 111.6 | | .4 | 8156.0 | | | | | 111.1 | | .5 | 8044.9 | | | | | 110.6 | | .6 | 7934.3 | | | | | 110.2 | | .7 | 7824.1 | | | | | 109.7 | | .8 | 7714.4 | | | | | 109.3 | | .9 | 7605.1 | | | | | 108.8 | |24.0 | 7496.3 | | | | | 108.3 | | .1 | 7388.0 | | | | | 107.9 | | .2 | 7280.1 | | | | | 107.5 | | .3 | 7172.6 | | | | | 107.0 | | .4 | 7065.6 | | | | | 106.6 | | .5 | 6959.0 | | | | | 106.1 | | .6 | 6852.9 | | | | | 105.7 | | .7 | 6747.2 | | | | | 105.3 | | .8 | 6641.9 | | | | | 104.9 | | .9 | 6537.0 | | | | | 104.4 | |25.0 | 6432.6 | | | | | 104.0 | | .1 | 6328.6 | | | | | 103.6 | | .2 | 6225.0 | | | | | 103.2 | | .3 | 6121.8 | | | | | 102.8 | | .4 | 6019.0 | | | | | 102.4 | | .5 | 5916.6 | | | | | 102.0 | | .6 | 5814.6 | | | | | 101.6 | | .7 | 5713.0 | | | | | 101.2 | | .8 | 5611.8 | | | | | 100.8 | | .9 | 5511.0 | | | | | 100.6 | |26.0 | 5410.4 | | | | | 99.8 | | .1 | 5310.6 | | | | | 99.7 | | .2 | 5210.9 | | | | | 99.3 | | .3 | 5111.6 | | | | | 98.8 | | .4 | 5012.8 | | | | | 98.6 | | .5 | 4914.2 | | | | | 98.1 | | .6 | 4816.1 | | | | | 97.8 | | .7 | 4718.3 | | | | | 97.4 | | .8 | 4620.9 | | | | | 97.0 | | .9 | 4523.9 | | | | | 96.7 | |27.0 | 4427.2 | | | | | 96.4 | | .1 | 4330.8 | | | | | 95.9 | | .2 | 4234.9 | | | | | 95.7 | | .3 | 4139.2 | | | | | 95.2 | | .4 | 4044.0 | | | | | 95.0 | | .5 | 3949.0 | | | | | 94.5 | | .6 | 3854.5 | | | | | 94.3 | | .7 | 3760.2 | | | | | 93.9 | | .8 | 3666.3 | | | | | 93.6 | | .9 | 3572.7 | | | | | 93.2 | |28.0 | 3479.5 | | | | | 92.9 | | .1 | 3386.6 | | | | | 92.6 | | .2 | 3294.0 | | | | | 92.2 | | .3 | 3201.8 | | | | | 91.9 | | .4 | 3109.9 | | | | | 91.6 | | .5 | 3018.3 | | | | | 91.3 | | .6 | 2927.0 | | | | | 90.9 | | .7 | 2836.1 | | | | | 90.7 | | .8 | 2745.4 | | | | | 90.3 | | .9 | 2655.1 | | | | | 90.0 | |29.0 | 2565.1 | | | | | 89.7 | | .1 | 2475.4 | | | | | 89.4 | | .2 | 2386.0 | | | | | 89.1 | | .3 | 2296.9 | | | | | 88.7 | | .4 | 2208.2 | | | | | 88.5 | | .5 | 2119.7 | | | | | 88.2 | | .6 | 2031.5 | | | | | 87.9 | | .7 | 1943.6 | | | | | 87.6 | | .8 | 1856.0 | | | | | 87.3 | | .9 | 1768.7 | | | | | 87.0 | |30.0 | 1681.7 | | | | | 86.7 | | .1 | 1595.0 | | | | | 86.4 | | .2 | 1508.6 | | | | | 86.2 | | .3 | 1422.4 | | | | | 85.8 | | .4 | 1236.6 | | | | | 85.6 | | .5 | 1251.0 | | | | | 85.3 | | .6 | 1165.7 | | | | | 85.0 | | .7 | 1080.7 | | | | | 84.7 | | .8 | 996.0 | | | | | 84.5 | | .9 | 911.5 | | | | | 84.2 | |31.0 | 827.3 | | | | | 83.9 | | .1 | 743.4 | | | | | 83.7 | | .2 | 659.7 | | | | | 83.4 | | .3 | 576.3 | | | | | 83.1 | | .4 | 493.2 | | | | | 82.8 | |31.5 | 410.4 | | | | | 82.6 | | .6 | 327.8 | | | | | 82.4 | | .7 | 245.4 | | | | | 82.0 | | .8 | 163.4 | | | | | 81.8 | | .9 | 81.6 | | | | | 81.6 | |32.0 | 00.0 | | +-----+---------+-----------+ 372. _Now_ apply the third Table, or Table for Tenths, _if necessary_; including two more Steps, viz. the 9th and 10th: which, being useless, in the first Example, are, for the present, omitted. 373. An Explanation of the third Table, or Table for Tenths, is, however, for the Sake of _Order_, _here_ subjoined.[122] (See Page 298.) THE THIRD TABLE, OR TABLE FOR TENTHS: Serving to compleat the 2d Table, on Expansion of the Barometer, with the Temperature of 31°.24. 1. The upper horizontal Figures shew the Number of Parts into which the Tenth of an Inch has been divided. 2. The Figures in the left vertical Column express the Height in +feet+, (above the imaginary Level, at 32 Inches of the Barometer,) or Expansion corresponding to a single Tenth of an Inch of Quicksilver. 3. The +feet+ in the Place of Meeting are called +tenths+: thus, 90 Feet are 9 Tenths of 100 Feet. +-------+-----------------------------------------------------+ |_Feet._| _Parts into which the Tenth of an Inch is divided._ | | | ⅒ | ²⁄₁₀ | ³⁄₁₀| ⁴⁄₁₀ | ⁵⁄₁₀ | ⁶⁄₁₀ | ⁷⁄₁₀ | ⁸⁄₁₀ | ⁹⁄₁₀ | +-------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 81 | 8 | 16 | 24 | 32 | 40 | 49 | 57 | 65 | 73 | | 82 | 8 | 16 | 25 | 33 | 41 | 49 | 57 | 66 | 74 | | 83 | 8 | 17 | 25 | 33 | 41 | 50 | 58 | 66 | 75 | | 84 | 8 | 17 | 25 | 34 | 42 | 50 | 59 | 67 | 76 | | 85 | 8 | 17 | 25 | 34 | 42 | 51 | 59 | 68 | 76 | | 86 | 9 | 17 | 26 | 34 | 43 | 52 | 60 | 69 | 77 | | 87 | 9 | 17 | 26 | 35 | 43 | 52 | 61 | 70 | 78 | | 88 | 9 | 18 | 26 | 35 | 44 | 53 | 62 | 70 | 79 | | 89 | 9 | 18 | 27 | 36 | 44 | 53 | 62 | 71 | 80 | | 90 | 9 | 18 | 27 | 36 | 45 | 54 | 63 | 72 | 81 | | 91 | 9 | 18 | 27 | 36 | 45 | 55 | 64 | 73 | 82 | | 92 | 9 | 18 | 28 | 37 | 46 | 55 | 64 | 74 | 83 | | 93 | 9 | 19 | 28 | 37 | 46 | 56 | 65 | 74 | 84 | | 94 | 9 | 19 | 28 | 38 | 47 | 56 | 66 | 75 | 85 | | 95 | 9 | 19 | 28 | 38 | 47 | 57 | 66 | 76 | 85 | | 96 | 10 | 19 | 29 | 38 | 48 | 58 | 67 | 77 | 86 | | 97 | 10 | 19 | 29 | 39 | 48 | 58 | 68 | 78 | 87 | | 98 | 10 | 20 | 29 | 39 | 49 | 59 | 69 | 78 | 88 | | 99 | 10 | 20 | 30 | 40 | 49 | 59 | 69 | 79 | 89 | | 100 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | | 101 | 10 | 20 | 30 | 40 | 50 | 61 | 71 | 81 | 91 | | 102 | 10 | 20 | 31 | 41 | 51 | 61 | 71 | 82 | 92 | | 103 | 10 | 21 | 31 | 41 | 51 | 62 | 72 | 82 | 93 | | 104 | 10 | 21 | 31 | 42 | 52 | 62 | 73 | 83 | 94 | | 105 | 10 | 21 | 31 | 42 | 52 | 63 | 73 | 84 | 94 | | 106 | 11 | 21 | 32 | 42 | 53 | 64 | 74 | 85 | 95 | | 107 | 11 | 21 | 32 | 43 | 53 | 64 | 75 | 86 | 96 | | 108 | 11 | 22 | 32 | 43 | 54 | 65 | 76 | 86 | 97 | | 109 | 11 | 22 | 33 | 44 | 54 | 65 | 76 | 87 | 98 | | 110 | 11 | 22 | 33 | 44 | 55 | 66 | 77 | 88 | 99 | | 111 | 11 | 22 | 33 | 44 | 55 | 67 | 78 | 89 | 100 | | 112 | 11 | 22 | 34 | 45 | 56 | 67 | 78 | 90 | 101 | | 113 | 11 | 23 | 34 | 45 | 56 | 68 | 79 | 90 | 102 | | 114 | 11 | 23 | 34 | 46 | 57 | 68 | 80 | 91 | 103 | | 115 | 11 | 23 | 34 | 46 | 57 | 69 | 80 | 92 | 103 | | 116 | 12 | 23 | 35 | 46 | 58 | 70 | 81 | 93 | 104 | | 117 | 12 | 23 | 35 | 47 | 58 | 70 | 82 | 94 | 105 | | 118 | 12 | 24 | 35 | 47 | 59 | 71 | 83 | 94 | 106 | | 119 | 12 | 24 | 36 | 48 | 59 | 71 | 83 | 95 | 107 | | 120 | 12 | 24 | 36 | 48 | 60 | 72 | 84 | 96 | 108 | | 121 | 12 | 24 | 36 | 48 | 60 | 73 | 85 | 97 | 109 | | 122 | 12 | 24 | 37 | 49 | 61 | 73 | 85 | 98 | 110 | | 123 | 12 | 25 | 37 | 49 | 61 | 74 | 86 | 98 | 111 | | 124 | 12 | 25 | 37 | 50 | 62 | 74 | 87 | 99 | 112 | | 125 | 12 | 25 | 37 | 50 | 62 | 75 | 87 | 100 | 112 | | 126 | 13 | 25 | 38 | 50 | 63 | 76 | 88 | 101 | 113 | | 127 | 13 | 25 | 38 | 51 | 63 | 76 | 89 | 102 | 114 | | 128 | 13 | 26 | 38 | 51 | 64 | 77 | 90 | 102 | 113 | | 129 | 13 | 26 | 39 | 52 | 64 | 77 | 90 | 103 | 116 | | 130 | 13 | 26 | 39 | 52 | 65 | 78 | 91 | 104 | 117 | +-------+-----+-----+-----+-----+-----+-----+-----+-----+-----+ END OF THE SECOND STAGE. 374. The Ends proposed in the third and last Stage of the Work, are, first, to add the _general_ Temperatures of the Air, or detached Air-Thermometers, at each Place of Observation _above_ and _below_, into one Sum. Secondly, to divide that Sum: each Moiety of which is called the _mean Temperature_ of the Air. Thirdly, to apply that Moiety to each Barometer, (both of which have been already brought to the Standard-Temperature of 31°. 24;) in order to prove whether the Moiety (or Quantity of Heat assigned to each Barometer by the _general_ Temperature of the Air) _exceeded_, _fell short of_, or equalled the Standard-Temperature of the Barometers, by the 2d Table. And fourthly, from the Moiety or mean Temperature of the Air, to find the true Height of the upper Barometer: which Temperature resolves itself into three Cases. 375. 1st. If the Moiety or mean Temperature of the Air is greater than the Standard Temperature, viz. that to which the Barometers are now brought; find the Expansion of Air corresponding to such _Excess_ of Temperature by the fourth Table, which Height by Expansion, being added to the Height already found in the 2d Table, shews the true Height, viz. of the upper Barometer. N. B. The 3d and last Stage includes two Steps only, viz, 11th and 12th. 376. 11th Step. The detached Air-Thermometer _above_ was — — 39½ Degrees. The detached Air-Thermometer _below_ was — — 45 1st. Add them, for the whole Heat. — — — 2)84½ Degrees. 2d. For _mean Temperature_ of the Air-Thermometers, or a _Moiety_ of the Heat, divide by 2. — 42¼ 3d. Deduct the Standard-Temperature of — — — 31¼ from either Moiety, and the Remainder ——— — — — 11 is the 11 Degrees of Heat, more than the Standard[123] for each Barometer. For 42°¼, and 42°¼, equal to 84°½, was the whole Height of the Air at both Places of Observation in the upper and lower Stations; of which whole Height the detached or Air-Thermometer _above_ received 39°½, and the detached or Air-Thermometer _below_, received 45°. 377. 12th Step. Find the Height corresponding to the Expansion of Air, with Excess of Heat or Temperature above the Standard-Temperature of the Barometers: and add it (as in the first Example) to the Height of the upper Barometer, corresponding to the Standard-Temperature already found in the _second_ Table, and the Sum is the _true_ Height of the upper Barometer. This is to be done by referring to the 4th Table, shewing Expansion of Air with Heat; for the Application of which there are separate Instructions: see the Explanation of the 4th Table.[124] 378. The Expansion of Air, in the first Example, is found by the 4th Table to be Feet 107.3 Tenths _higher_ than the 4016.8, viz. the Remainder from the 2d Table (Section 371); which Numbers added give 4124.1 Feet: viz. the true Height of the upper Station required. CHAPTER LXXIIII. USE AND PRACTICE OF THE FOURTH TABLE, IN THE FIRST EXAMPLE. _The_ +use+. Section 379. To shew in Feet, and Tenths, what is the Expansion of Air on each thousand Feet, from 1000 to 9000 Feet, _with_ each Degree of Temperature from 1 to 100 Degrees, on Farenheit’s Scale. _The_ +practice+. _The 12th Step applied in the first Example._ 380. For the Expansion of Air with 11 Degrees of Heat on 4016.8 Feet, look in the fourth Table, _with_ 11 in the left Hand vertical Column of Temperature, and (first) _on_ 4000 Feet, along the upper Line: the Place of Meeting gives the Expansion of the Air, _with_ 11 Degrees _on_ 4000 Feet: viz. 106.92.[126] Next; look _with_ 11 Degrees, and (as there is a Cypher only in the Place of Hundreds) _on_ 10, (viz. of the 16 Feet) call the 10, a 1000; the Place of Meeting, or Answer is 26.73: Thirdly; _with_ 11, _on_ 6, (viz. of the 16,) calling it 6000; the Answer is 160.38: Fourthly; _with_ 11, _on_ 8, (viz. the .8,) and the Answer is 213.84. 381. Having added the respective Expansions together, thus; _with_ 11°, _on_ 4016.8 Feet. Tenths. } 4000 = 106.92 106.92 } 10 = 26.73 .2673 _with_ 11° } 6 = 160.38 .16038 _on_ } .8 = 213.84 .021384 } —————————— } Expansion 107.369064; (See Page 306.) THE FOURTH TABLE, +shewing the expansion with HEAT, from 1 to 100 degrees, on each THOUSAND FEET in the atmosphere, from 1000 to 9000 feet.+ +-----------------------------------------------------------------------+ |+degrees of the THERMOMETER, from 1 to 50, on farenheit’s scale.+ | | +------+------+------+------+-------+-------+-------+-------+-------+ | | 1000 | 2000 | 3000 | 4000 | 5000 | 6000 | 7000 | 8000 | 9000 | | +------+------+------+------+-------+-------+-------+-------+-------+ | 1| 2.43| 4.86| 7.29| 9.72| 12.15| 14.58| 17.01| 19.44| 21.87| | 2| 4.86| 9.72| 14.58| 19.44| 24.30| 29.16| 34.02| 38.88| 43.74| | 3| 7.29| 14.58| 21.87| 29.16| 36.45| 43.74| 51.03| 58.32| 65.61| | 4| 9.72| 19.44| 29.16| 38.88| 48.60| 58.32| 68.04| 77.76| 87.48| | 5| 12.15| 24.30| 36.45| 48.60| 60.75| 72.90| 85.05| 97.20| 109.35| | 6| 14.58| 29.16| 43.74| 58.32| 72.90| 87.49| 102.06| 116.64| 131.22| | 7| 17.01| 34.02| 51.03| 68.04| 85.05| 102.06| 119.07| 136.08| 153.09| | 8| 19.44| 38.88| 58.32| 77.76| 97.20| 116.64| 136.08| 155.52| 174.96| | 9| 21.87| 43.74| 65.61| 87.48| 109.35| 131.22| 153.09| 174.96| 196.83| | 10| 24.30| 48.60| 72.90| 97.20| 121.50| 145.80| 170.10| 194.40| 218.70| | 11| 26.73| 53.46| 80.19|106.92| 133.65| 160.38| 187.11| 213.84| 240.57| | 12| 29.16| 58.32| 87.48|116.64| 145.80| 174.96| 204.12| 233.28| 262.44| | 13| 31.59| 63.18| 94.77|126.36| 157.95| 189.54| 221.13| 252.72| 284.31| | 14| 34.02| 68.04|102.06|136.08| 170.10| 204.12| 238.14| 272.16| 306.18| | 15| 36.45| 72.90|109.35|145.80| 182.25| 218.70| 255.15| 291.60| 328.05| | 16| 38.88| 77.76|116.64|155.52| 194.40| 233.28| 272.16| 311.04| 349.92| | 17| 41.31| 82.62|123.93|165.24| 206.55| 247.86| 289.17| 330.48| 371.79| | 18| 43.74| 87.48|131.22|174.96| 218.70| 262.44| 306.18| 349.92| 393.66| | 19| 46.17| 92.34|138.51|184.68| 230.85| 277.02| 323.19| 369.36| 415.53| | 20| 48.60| 97.20|145.80|194.40| 243.00| 291.60| 340.20| 388.80| 437.40| | 21| 51.03|102.06|153.09|204.12| 255.15| 306.18| 357.21| 408.24| 459.27| | 22| 53.46|106.92|160.38|213.84| 267.30| 320.76| 374.22| 427.68| 481.14| | 23| 55.89|111.78|167.67|223.56| 279.45| 335.34| 391.23| 447.12| 503.01| | 24| 58.32|116.64|174.96|233.28| 291.60| 349.92| 408.24| 466.56| 524.88| | 25| 60.75|121.50|182.25|243.00| 303.75| 364.50| 425.25| 486.00| 546.75| | 26| 63.18|126.36|189.54|252.72| 315.90| 379.08| 442.26| 505.44| 568.62| | 27| 65.61|131.22|196.83|262.44| 328.05| 393.66| 459.27| 524.88| 590.49| | 28| 68.04|136.08|204.12|272.16| 340.20| 408.24| 476.28| 544.32| 612.36| | 29| 70.47|140.94|211.41|281.88| 352.35| 422.82| 493.29| 563.76| 634.23| | 30| 72.90|145.80|218.70|291.60| 364.50| 437.40| 510.30| 583.20| 656.10| | 31| 75.33|150.66|225.99|301.32| 376.65| 451.98| 527.31| 602.64| 677.97| | 32| 77.76|155.52|233.28|311.04| 388.80| 466.56| 544.32| 622.08| 699.84| | 33| 80.19|160.38|240.57|320.76| 400.95| 481.14| 561.33| 641.52| 721.71| | 34| 82.62|165.24|247.86|330.48| 413.10| 495.72| 578.34| 660.96| 743.58| | 35| 85.05|170.10|255.15|340.20| 425.25| 510.30| 595.35| 680.40| 765.45| | 36| 87.48|174.96|262.44|349.92| 437.40| 524.88| 612.36| 699.84| 787.32| | 37| 89.91|179.82|269.73|359.64| 449.55| 539.46| 629.37| 719.28| 809.19| | 38| 92.34|184.68|277.02|369.36| 461.70| 554.04| 646.38| 738.72| 831.06| | 39| 94.77|189.54|284.31|379.08| 473.85| 568.62| 663.39| 758.16| 852.93| | 40| 97.20|194.40|291.60|388.80| 486.00| 583.20| 680.40| 777.60| 874.80| | 41| 99.63|199.26|298.89|398.52| 498.15| 597.78| 697.41| 797.04| 896.67| | 42|102.06|204.12|306.18|408.24| 510.30| 612.36| 714.42| 816.48| 918.54| | 43|104.49|208.98|313.47|417.96| 522.45| 626.94| 731.43| 835.92| 940.41| | 44|106.92|213.84|320.76|427.68| 534.60| 641.52| 748.44| 855.36| 962.28| | 45|109.35|218.70|328.05|437.40| 546.75| 656.10| 765.45| 874.80| 984.15| | 46|111.78|223.56|335.34|447.12| 558.90| 670.68| 782.46| 894.24|1006.02| | 47|114.21|228.42|342.63|456.84| 571.05| 685.26| 799.47| 913.68|1027.89| | 48|116.64|233.28|349.92|466.56| 583.20| 699.84| 816.48| 933.12|1049.76| | 49|119.07|238.14|357.21|476.28| 595.35| 714.42| 833.49| 952.56|1071.63| | 50|121.50|243.00|364.50|486.00| 607.50| 729.00| 850.5 | 972.00|1093.5 | | 51|123.93|247.86|371.79|495.72| 619.65| 743.58| 867.51| 991.44|1115.37| | 52|126.36|252.72|379.08|505.44| 631.80| 758.16| 884.52|1010.88|1137.24| | 53|128.79|257.58|386.37|515.16| 643.95| 772.74| 901.53|1030.32|1159.11| | 54|131.22|262.44|393.66|524.88| 656.10| 787.32| 918.54|1049.76|1180.98| | 55|133.65|267.30|400.95|534.60| 668.25| 801.90| 935.55|1069.20|1202.85| | 56|136.08|272.16|408.24|544.32| 680.40| 816.48| 952.56|1088.64|1224.72| | 57|138.51|277.02|415.53|554.04| 692.55| 831.06| 969.57|1108.08|1246.59| | 58|140.94|281.88|422.82|563.76| 704.70| 845.64| 986.58|1127.52|1268.46| | 59|143.37|286.74|430.11|573.48| 716.85| 860.22|1003.59|1146.96|1290.33| | 60|145.80|291.60|437.40|583.20| 729.00| 874.80|1020.60|1166.40|1312.20| | 61|148.23|296.46|444.69|592.92| 741.15| 889.38|1037.61|1185.84|1334.07| | 62|150.66|301.32|451.98|602.64| 743.30| 903.96|1054.62|1205.28|1355.94| | 63|153.09|306.18|459.27|612.36| 755.45| 918.54|1071.63|1224.72|1377.81| | 64|155.52|311.04|466.56|622.08| 767.60| 933.12|1088.64|1244.16|1399.68| | 65|157.95|315.90|473.85|631.80| 779.75| 947.70|1105.65|1263.60|1421.55| | 66|160.38|320.76|481.14|641.52| 791.90| 962.28|1122.66|1283.04|1443.42| | 67|162.81|325.62|488.43|651.24| 814.05| 976.86|1139.67|1302.48|1465.29| | 68|165.24|330.48|495.72|660.96| 826.20| 991.44|1156.68|1321.92|1487.16| | 69|167.67|335.34|503.01|670.68| 838.35|1006.02|1173.69|1341.36|1509.03| | 70|170.10|340.20|510.30|680.40| 850.50|1020.60|1190.70|1360.80|1530.90| | 71|172.53|345.06|517.59|690.12| 862.65|1035.18|1207.71|1380.24|1552.77| | 72|174.96|349.92|524.88|699.84| 874.80|1049.76|1224.72|1399.68|1574.64| | 73|177.39|354.78|532.17|709.56| 886.95|1064.34|1241.73|1419.12|1596.51| | 74|179.82|359.64|539.46|719.28| 899.10|1078.92|1258.74|1438.56|1618.38| | 75|182.25|364.50|546.75|729.00| 911.25|1093.50|1275.75|1458.00|1640.25| | 76|184.68|369.36|554.04|738.72| 923.40|1108.08|1292.76|1477.44|1662.12| | 77|187.11|374.22|561.33|748.44| 935.55|1122.66|1309.77|1496.88|1683.99| | 78|189.54|379.08|568.62|758.16| 947.70|1137.24|1326.78|1516.32|1705.86| | 79|191.97|383.94|575.91|767.88| 959.85|1151.82|1343.79|1535.76|1727.73| | 80|194.40|388.80|583.20|777.60| 972.00|1166.40|1360.80|1555.20|1749.60| | 81|196.83|393.66|590.49|787.32| 984.15|1180.98|1377.81|1574.64|1771.47| | 82|199.26|398.52|597.78|797.04| 996.30|1195.56|1394.82|1594.08|1793.34| | 83|201.69|403.38|605.07|806.76|1008.45|1210.14|1411.83|1613.52|1815.21| | 84|204.12|408.24|612.36|816.48|1020.60|1224.72|1428.84|1632.96|1837.08| | 85|206.55|413.10|619.65|826.20|1032.75|1239.30|1445.85|1652.40|1858.95| | 86|208.98|417.96|626.94|835.92|1044.90|1253.88|1462.86|1671.84|1880.82| | 87|211.41|422.82|634.23|845.64|1057.05|1268.46|1479.87|1691.28|1902.69| | 88|213.84|427.68|641.52|855.36|1069.20|1283.04|1496.88|1710.72|1924.56| | 89|216.27|432.54|648.81|865.08|1081.35|1297.62|1513.89|1730.16|1946.43| | 90|218.70|437.40|656.10|874.80|1093.50|1312.20|1530.90|1749.60|1968.30| | 91|221.13|442.26|663.39|884.52|1105.65|1326.78|1547.91|1769.04|1990.17| | 92|223.56|447.12|670.68|894.24|1117.80|1341.36|1564.92|1788.48|2012.04| | 93|225.99|451.98|677.97|903.96|1129.95|1355.94|1581.93|1807.92|2033.91| | 94|228.42|456.84|685.26|913.68|1142.10|1370.52|1598.94|1827.36|2055.78| | 95|230.85|461.70|692.55|923.40|1154.25|1385.10|1615.95|1846.80|2077.65| | 96|233.28|466.56|699.84|933.12|1166.40|1399.68|1632.96|1866.24|2099.52| | 97|235.71|471.42|707.13|942.84|1178.55|1414.26|1649.97|1885.68|2121.39| | 98|238.14|476.28|714.42|952.56|1190.70|1428.84|1666.98|1905.12|2143.26| | 99|240.57|481.14|721.71|962.28|1212.85|1443.42|1683.99|1924.56|2165.13| |100|243.00|486.00|729.00|972.00|1215.00|1458.00|1701.00|1944.00|2187.00| +---+------+------+------+------+-------+-------+-------+-------+-------+ 382. The decimal Points in the Answer must be changed, thus: 1. For the Place of _Thousands_ in the Question, (viz. 4000,) the Answer must remain, viz. 106.92, as in the Table, which is calculated for the Place of _Thousands_. 2. For the Place of _Hundreds_, in the Question, (viz. which in the present Case was a Cypher;) if there had been a Figure or Figures in the Place of hundreds; then the decimal Point in the Answer must have been removed over _one_ Figure or Place to the left. 3. For the Place of _Tens_, in the Question, (viz. 10 Feet,) the decimal Point in the Answer, must be removed over _two_ Figures, or Places, to the left. 4. For the Place of _Units_, in the Question, (viz. 6) the decimal Point in the Answer, must be removed over _three_ Figures, or Places, to the left. 5. For the Place of a _Decimal_, in the Question, (viz. .8) the decimal Point, in the Answer, must be removed over _four_ Figures, or Places to the left, by adding a Cypher: and for the Place of each further Decimal in the Question;—_one_ Place more in the Answer, by the further occasional Addition of a Cypher, thus: _on_ Feet 4000, the Ans. 106.92 is still 106.92 10 26.73 becomes .2673 6 160.38 .16038 .8 213.84 .021384 —————————— 107.369064 383. Which Sum, by rejecting all but the first Decimal, in the Answer, is Feet 107.3 Tenths equal to the Expansion of Air, _with_ 11° of Heat, _on_ 4016.8 Feet, the Height of the upper Barometer, with the Temperature of 31°.24, according to the 2d Table. END OF THE LAST STAGE. * * * * * [Sidenote: +Rule+ copied.] 384. The +rule+ underneath, consisting of 3 Precepts _only_, is laid down by Sir George Shuckburgh, in the Transactions for 1777, Page 574, in order to ascertain the Height of Mountains, &c. (See Section 349).[127] [Sidenote: 1st. Step, in Section 353.] 385. Recapitulation for each Step of the Work, in the first Example; referring to the Sections. [Sidenote: 2d. Step, in Section 354.] Below. Barometer, Inches 29, .4 Tenths. Attached Thermometer, 50 Degrees, Air-Thermometer 45°. [Sidenote: 3d. Step, in Section 355.] Above. Barometer, Inches 25, .19 Tenths. Attached Thermometer 46°, Air Thermometer, 29°½. From 50° subtract 46 —— and there remains 4 Degrees of Temperature to be added to the colder Barometer. [Sidenote: _4th Step, in Section 356._] By Means of the first Table, find the Expansion of the _colder_ Barometer, with Degrees of Heat, viz. 4° on Inches 25, .19, _gradually_, thus: [Sidenote: 5th Step, in Section 364.] with 4° on 25. = .0101 with 4° on .19 = .0000076 ———————————————— 25.2| [Sidenote: 6th Step, in Section 366.] Upper Barometer, Inches 25, .2 Tenths. Lower Barometer, 29, .4 _End of the first Stage._ [Sidenote: _7th Step, in Section 368._] By Means of the 2d Table, find the corresponding Heights in the Air, at 31°. 24. [Sidenote: 8th Step, in Section 371.] 25, .2 Answer 6225.0 29, .4 2208.0 —————— The Remainder is 4016.8 Height in Feet, &c. [Sidenote: _9th and 10th Steps, in Section 373._] The 3d Table, or Table for _Heights_ in the Atmosphere corresponding to the _Tenth_ of an Inch _on_ the Barometer, including the 9th and 10th Steps, is useless in this first Example. _End of the Second Stage._ [Sidenote: 11th Step, in Section 376.] Detached Air-Thermometer, _above_, 29½ Ditto _below_, 45° ——— Whole Heat 2)84½ Half Heat or mean Temperature 43¼ Deduct Standard 31¼ ——— Moiety above Standard 11° [Sidenote: _12th step, in Section 377._] By Means of the 4th Table, find the Expansion of Air, with 11° on 4106.8 Feet viz. 107.3 which added to the same Height gives 4124.1 for the true Height, in English Feet, of the _Mountain_, or _upper Station_, sought. _End of the last Stage._ CHAPTER LXXV. PRACTICE OF THE SECOND EXAMPLE: _With a distinct View of the Work. (Ph. Tr. for 1777, Page 579.)_ Section 386. The Point at which the Quicksilver stood in the Tube of the Barometer on the Mountain, or in the Car of the Balloon, being Inches 24.178 Tenths; its _attached_ Thermometer, Degrees 57.2 Tenths, and its Air-Thermometer 56°; while the Barometer on the Ground stood at Inches 28, .1318 Tenths; its _attached_ Thermometer, Degrees 61, .8 Tenths, and its Air-Thermometer 63°, .9; what is the Height of the _upper_ Station? [Sidenote: 1st. Step.] 387. 1st. Step. Set down the Observation on the Ground, thus: +Below+, Barometer, Inches 28, .1318 Tenths, _Attached_ Thermometer, Degrees 61, .8 Tenths. _Air_-Thermometer, 63°, .9. [Sidenote: 2d. Step.] 388. 2d. Step. Set down the Observation, on the Mountain, or _in the Car_, thus: +Above+, Barometer, Inches 24, .178 Tenths. _Attached_ Thermometer, Degrees 57, .2 Tenths. _Air_-Thermom. 56°. [Sidenote: 3d. Step.] 389. 3d. Step. From the _warmer attached_ Thermometer, subtract the colder, thus: 61°, .8 57, .2 ——————— 4, .6 390. 4th. Step. Give the _colder_ Barometer the same Expansion, viz. 4°, .6 with the warmer, by the _first_ Table. CHAPTER LXXVI. PRACTICE OF THE FIRST TABLE IN THE SECOND EXAMPLE. _4th Step applied in the 2d Example._ [Sidenote: _4th Step applied._] Section 391. The _Order_ to be observed in finding the Expansion _with_ 4°.6, i.e. with 4 Degrees, .6 Tenths of Heat, on 24.178, i.e. 24 Inches, .178 Tenths of the coldest Barometer. Find the Expansion required, thus: _Case the 1st._ 1st. Part. _With_ 4° _on_ 24 Inches. 2d. Part. _With_ 4° _on_ .178 Tenths of an Inch above 24 Inches. _Case the 2d._ 1st. Part. _With_ .6 Tenths of a Degree, _on_ 24 Inches. 2d. Part. _With_ .6 Tenths of a Degree, _on_ .178 Tenths above 24 Inches. +specifically+, _thus_: 1st. Part of _Case the 1st._ To find the Expansion, _With_ 4° _on_ 24 Inches. 2d. Part of _Case the 1st._ _With_ 4°, _on_ .178 Tenths of an Inch above 24 Inches; begin thus: _With_ 4°, _on_ 24 Inches: then, _With_ 4°, _on_ 25: then, _With_ 4°, _on_ 1 Inch above 24, i.e. _on_ the 25th Inch: then, _With_ 4°, _on_ .1 Tenth above 24: then, _With_ 4°, _on_ .178 Tenths above 24. 1st Part of _Case the 2d._ To find the Expansion, _With_ .6 above 4° _on_ 24; begin thus: _With_ 4° _on_ 24 Inches: then, _With_ 5° _on_ 24: then, _With_ 1° above 4°, _on_ 24, i.e. the 5th°: then, _With_ .1 Tenth above 4°, _on_ 24: then _With_ .6 Tenths above 4°, _on_ 24. 2d Part of _Case the 2d._ To find the Expansion, _With_ .6 Tenths above 4° of Heat _on_ .178 Tenths above 24 Inches: to be done thus: _The_ +expansion+ _with 4°, on .178 Tenths above 24 Inches, being once found; divide_ +it+ _by 4: and the Quotient is the Expansion with 1° above 4°, on .178 Tenths of an Inch above 24 Inches_. _Then for the Expansion with .1 Tenth above 4°, on .178 Tenths above 24 Inches; add a Cypher and decimal Point to the left of the same Quotient._ _Then for the Expansion with .6; multiply that Sum into .6, and add a Cypher and decimal Point._ _The Answer is the_ +part+ _of an Inch, to which .6 Tenths of a Degree above 4° of Heat, on .178 Tenths of an Inch above 24 Inches, raises the Barometer_. _It is true, the_ +part+ _is so minute as to be rejected: yet the Mode of Proceeding, in order to investigate the Expansion with Precision, is proper to be retained_. 392. +practice+ of the first Part of _Case the 1st._ For the Expansion _with_ 4°, _on_ 24 Inches; look, in the first Table, (Sect. 363) and in the left vertical Column, _with_ 4 Degrees of the Thermometer; and along the upper horizontal Line, _on_ 24 Inches of Quicksilver in the Tube of the Barometer: the Point of Meeting gives the Expansion .0097;[128] which, preparatory to Addition, is to be placed under the 24, .178 thus, .0097 +practice+ of the 2d Part of _Case the first_. 393. In order to obtain the Expansion, _with_ 4°, of Heat _on_ .178 Tenths of an Inch above 24 Inches of the Barometer; let it be considered where it ought to be found in the Table: for, Tenths of 1 Inch above 24 Inches, are at some intermediate Point between 24 and 25; that is, above 24, yet not so high as 25: or more than 24, yet less than 25. Look therefore in the Table, _with_ 4 Degrees of Heat, _on_ 24 Inches; then _with_ 4° _on_ 25 Inches: and the respective Numbers are .0097 and .0101. And by taking the Expansion _with_ 4° _on_ 24 Inches, from 4° on 25; the Remainder will be the Expansion with 4° on 1 Inch above 24 Inches, viz. on the 25th Inch, thus: } 25 = .0101 from; _With_ 4° _on_ } } 24 = .0097 subtract: ————— .0004: This therefore is the Expansion _with_ 4°, _on_ 1 Inch above 24 Inches. Then _with_ 4°, _on_ .1 Tenth of an Inch above 24 Inches. The Answer is the same as the former, viz. .0004, with the Addition of a Cypher and decimal Point to the left, thus; .0004 becomes .00004, viz. the Expansion _with_ 4°, _on_ .1 Tenth of an Inch above 24 Inches. Then for the Expansion _with_ 4°, _on_ .178 Tenths, say, If the Expansion _with_ 4°, _on_ .1 Tenth above 24 Inches gives .00004 Part of an Inch, what will the Expansion _with_ 4°, _on_ .178 give? Thus; .1 : .00004 :: .178? Multiply the two last Terms, thus: .00004 .178 —————— 00032 00028 00004 ——————— 0000712: and, as in Multiplication of Decimals, the Product must have as many decimal Places, as are in the Factors; a Cypher must be added to the left Hand, thus: .00000712: but having divided that Product by the first Term .1, viz. a Decimal, the Answer is a Cypher less; viz. .0000712. This Answer is the Expansion _with_ 4°, _on_ .178 Tenths of an Inch above 24 Inches: prepare it for _Addition_, as the former, 24.178 .0097 .0000712 +practice+ of the first Part of _Case the 2d._ 394. For the Expansion of .6 Tenths of a Degree of Heat, (more than the 4 Degrees) on 24 Inches of the _coldest_ Barometer; it shoud be considered where such Tenths can lie in the Table. Now .6 Tenths of 1 Degree, (more than the 4°) are at some intermediate Point of the Thermometer between 1 and 2 Degrees: above 1; yet not so high as 2: or more than 1; yet less than 2. Therefore .6 Tenths of 1 Degree above 4 Degrees, are somewhere between the 4th and 5th Degree: above 4; yet not so high as 5: or more than 4; yet less than 5. Look in the Table (Section 363); first _with_ 4 Degrees of Heat, _on_ 24 Inches, and then _with_ 5 Degrees of Heat _on_ 24 Inches; and the respective Numbers are .0097 and .0121: and by taking the Expansion _with_ 4 Degrees _on_ 24 Inches, from the Expansion _with_ 5 Degrees _on_ the same 24 Inches; the Remainder will be the Expansion _with_ 1 Degree above 4° _on_ 24 Inches: viz. _with_ {5° = .0121} _on_ 24 Inches, as in whole {4° = .0097} Numbers. ————— Remainder, .0024 This therefore is the Expansion _with_ 1 Degree of Heat, above 4, viz. _with_ the 5th Degree, _on_ 24 Inches of the Barometer. Then say, if 1 Degree of the Thermometer (above 4, viz. the 5th Degree) gives by Expansion, a certain additional Height, or Part of an Inch, viz. .0024, _on_ 24 Inches of the Barometer; what Height will 6 Degrees give? Answer 6 Times _more_. Multiply the 2d and 3d Terms, and divide by the first, thus; 1 : .0024 :: 6? 6 ————— .0144 is the Expansion, or Height, in Parts of an Inch, for 6 Degrees. And farther, to proportion for the Decimal; say as .1 Tenth of a Degree gives a certain Tenth of the former .0024, in additional Height, viz. .00024; what Height will .6 Tenths give? Answer, .00144. Prepare this _Height_ for Addition to the Numbers already found. +practice+ of the 2d Part of _Case the 2d._ 395. To find the Expansion of .6 above 4° on .178 above 24 Inches. The Expansion _with_ 4° _on_ .178 is already found to be .0000712: divide it by 4, and the Answer is .0000178, viz. the Expansion _with_ 1° _on_ .178 above 24 Inches: And, for the Expansion with .1 Tenth; the Answer, with the Addition of a Cypher and decimal Point to the left, becomes .00000178. Lastly, for the Expansion with .6, say, If .1 : .00000178 :: .6? Multiply the 2d and 3d Terms, and divide by first: .00000178 .6 —————————— .000001068. The Answer is a Decimal less, viz. .00001068; i.e. the Decimal of an Inch, to which .6 Tenths of a Degree above 4 Degrees of Heat, on .178 Tenths of an Inch above 24 Inches, raises the Barometer: which, after all, is so inconsiderable, that it may be fairly rejected. Yet the Rules by which these Deductions are made, may be useful in other Cases. Prepare for Addition, as before. The Decimals, in the Answers, may be omitted, when they exceed four Places. [Sidenote: 5th Step.] 396. 5th Step. To proceed with the second Example. Place the different Expansions now found, above each other, Units, Tens, &c. under Units, Tens, &c. preparatory to Addition, thus; For the Expansion _with_ 4°, .6 _on_ 24, .178: 1st. _with_ 4°, _on_ 24, .0097 2d. _with_ .6 _on_ 24, .00144 3d. _with_ 4°, _on_ .178 .0000712 4th. _with_ .6 _on_ .178 .00001068 ————————— The Expansions with 4°,.6 added = .01122188 To the Sum add the Height of the _colder_ Barometer 24.178 ——————————— 24.1892| The Answer is Height of the _colder_ Barometer, now equal in Temperature to the _warmer_: (rejecting all but the four first Decimals.) [Sidenote: 6th Step.] 397. 6th Step. Place the Barometers _now_ of the same Temperature, i.e. _equal_ to the warmer, in one View, thus: 1st. the _upper_ Barometer, 24.1892 2d. the _lower_ Barometer, 28.1328 END OF THE FIRST STAGE. _The 7th Step applied in the second Example._ [Sidenote: _7th Step._] 398. Find the Height, in Feet, in the 2d Column of the 2d Table, corresponding to Inches and Tenths of the _upper_ barometric Tube, in the 1st. Column of the same Table, thus: (Sect. 371.) The Barometer standing at 24.1892; it must be considered where, in the 2d Column of the 2d Table, a Height corresponding to _such_ Inches and Tenths can lie: and the Answer is, somewhere _above_ 24 Inches .1 Tenth, but not so high as 24 Inches .2 Tenths: 24 Inches .1892 Tenths, being _more_ than 24 Inches .1 Tenth, but _less_ than 24 Inches .2 Tenths. First then, look in the 1st Column for Inches 24, .1 Tenth; and the corresponding Height in Feet is 7388.0: but the Height for 24, .2, in the 2d Column, beneath the former Number, is _only_ 7280.1. [Sidenote: 8th Step.] 399. 8th Step. Subtract the latter from the former and the Remainder is 107.9, the same as in the 3d Column: viz. the Height, in Feet and Tenths, corresponding to one Tenth only, namely, the ist Tenth above Inches 24, .1 Tenth: with the Temperature of 31.24 of Farenheit, for which sole Purpose the 2d Table is calculated. A new Question _then_ arises, viz. what are the Heights in Feet and Tenths, corresponding to the remaining Tenths or Decimals of an Inch above Inches 24, .1 Tenth, viz. .08 .009 .0002? which is to be resolved, by Application of the 3d Table, or Table for _Tenths_, which see, (Section 373.) [Sidenote: _9th Step._] 400. _9th Step applied in the 2d. Example._ First for the _upper_ Barometer. Look in the Table for Tenths, in the left vertical Column with 107, (rejecting the .9, as too minute;) and along the horizontal Line at the top, with 8: and find the Answer _gradually_, thus: 1st. With 107, and 8, (as a whole Number,) answering to .08: which, in the Place of Meeting, gives 86 Feet. 2d. With 107, and 9, (as a whole Number,) answering to .009: which, in the Place of Meeting, gives 97. 3d. With 107, and 2, (as a whole Number,) answering to 0002: which, in the Place of Meeting, gives 21. Place them in View, and add, and bring them back again into Decimals, thus: With 107 and 8, answering to .08 giving 86. Feet and 9, to .009 9.7 and 2, to .0002 .21 ————— 95.9|1 (Next: with the 9, _if required_; which was before rejected:) but there being no .9 Tenths in the left Vertical, call it 90, and allow for it in each Answer by moving the decimal Point two Places to the left, thus: with 90, and 8, answering to .08 giving 72 = .72 and 9, to .009 81 = .081 and 2, to .0002 18 = .0018 ———— To .8|00|28 Add the former Sum 95.9| ————— Total = 96.7) Which 95.9 is the _Height_ in Feet and Tenths corresponding to .0892 Decimals of an Inch above Inches 24 .1 Tenth: and 24 .1 gave Feet 7388.0 in _Height_; therefore an additional _Height_, of so many Tenths of an Inch of Quicksilver in the Tube of the Barometer, must give in Feet, a _less_ Height of the Barometer elevated above the _imaginary_ Level indicated at 32 Inches. [Sidenote: _10th. Step._] 401. 10th. Step. Subtract the _Height_ in Feet, corresponding to the _Expansion_ on .0892 Tenths of an Inch, (_less_ than Inches 24.2 Tenths, of the _upper_ barometric Tube,) from the _Height_, in Feet, corresponding to _the Expansion on_ Inches 24.1 Tenth of the same barometric Tube, continuing at the Standard Heat,[129] viz. 7388.0 95.9 —————— The Remainder 7292.1 gives the real, viz. the _less_ Height of the _upper_ Barometer, at 24.1892 with the Standard Temperature. Repeat the same Process, viz. the 9th. and 10th. Steps, for the _lower_ Barometer, thus: For the lower Barometer in the 2d. Example. First, Find the Height, in _Feet_, of the lower Barometer, standing at Inches 28.1318 Tenths, in the 2d. Column of the 2d. Table, corresponding to Inches and Tenths of the Quicksilver in the barometric Tube, in the first Column of the same Table, thus: The lower Barometer standing at 28.1318; it must be considered, where in the 2d. Column of the 2d. Table, a Height corresponding to such Inches and Tenths can lye: and the Answer is, somewhere above 28 Inches, .1 Tenth, but not so high as 28 Inches .2 Tenths: 28.1318 Tenths being more than 28 Inches .1 Tenth, yet less than 28 Inches .2 Tenths. First, then, look, in the first Column for 28.1, and the corresponding Height, in Feet, is 3386.6: but the Height for 28.2, is only 3294.0: —————— subtracting the less from the greater; the Remainder is 92.6, the same as in the 3d. Column, viz. the Height, in Feet and Tenths, corresponding to _one Tenth only_ above 28.1. Having therefore found that Feet 92.6 Tenths, are the Height, corresponding to one Tenth only above Inches 28.1 Tenth, of the lower Barometer, with the Temperature of freezing; for which _sole_ Purpose, the 2d Table is calculated;—a new Question arises, viz. what are the Heights, in Feet and Tenths, corresponding to the remaining Decimals above 28.1, viz. .03 .001 .0008; to be resolved by Application of the third Table, or Table for Tenths, which see, (in Section 373.) Look in the 3d. Table, with 92, (omitting the .6 as too minute) and with 3 answering to .03, which gives 28 = Feet 28. 1 to .001, 9 = .9 8 to .0008, 74 = .74 —————— 29.6|4 Which 29.6 is the _Height_ in Feet and Tenths corresponding to .0318 Tenths above Inches 28.1 Tenth: and Inches 28.1 Tenth gave Feet 3386.6 Tenths in Height: therefore an additional Height of so many Tenths or Decimals of an Inch of Quicksilver in the Tube of the Barometer, must give in Feet, a _less_ Height of the _lower_ Barometer, elevated above the _imaginary_ Level indicated by the Quicksilver resting in the Tube at 32 Inches.[130] 402. Therefore subtract the _Height_, in Feet, corresponding to the _Expansion on_ .0318 Tenths of an Inch (_less_ than Inches 28.2 Tenths of the _lower_ barometric Tube,) from the Height, in Feet, corresponding to the _Expansion on_ 28.1 Tenth of the same Barometer, viz. 3386.6 29.6 —————— and the Remainder - 3357.0, gives the _real_ Height in Feet of the lower Barometer, at 28.1318 when above the _imaginary_ Level, and with the Temperature of _freezing_ by the second Table. 403. Then, by taking the Number of Feet and Tenths _above_ the imaginary Level, (indicated by the Quicksilver, in both Tubes, resting at 32 Inches) answering to the _Expansion on_ Inches and Tenths of the _lower_ Tube, from the Number of Feet, &c. by the former Process, answering to that of the _upper_ Tube; viz. _upper_ 7292.1 _lower_ 3357.0 —————— the remaining Feet 3935.1 Tenth is the _Height_, by which the _Station_ of the _upper_ Barometer exceeds the _Station_ of the _lower_; both being at the Temperature of 31°.24 on Farenheit’s Scale. See Section 371. END OF THE SECOND STAGE * * * * * [Sidenote: 11th Step.] Section 404. 11th Step. (See the Practice in the 1st Example, Sect. 376.) _Air_-Thermom. +above+ was 56°. _Air_-Thermom. +below+ was 63.9 ————— Whole Heat 119.9(0 adding a Cypher) Half Heat 59.95 Standard-Heat 31.24 which deduct; and there —————— remains each Moiety, 28.71 above the Standard-Heat. [Sidenote: _12th Step._] 405. 12th Step. (See the Practice in the first Example, Section 377.) By the fourth Table, find the Expansion of Air, _with_ 28.71, (more than the Standard-Temperature) _on_ Feet 3935, .1 Tenth, gradually, thus: 406. _First_ _with_ 28° _on_ Feet 3000 = 204.1[131] 900 as 9000 = 612.3 30 3000 = 204.1 5 5000 = 340.1 .1 1000 = 68.0 Note: 1st. The decimal Point in the Answer corresponding to the Place of _Thousands_, in the Question, is to remain, as taken from the Table calculated for thousand Feet, thus: 204.1. 2d. For _Hundreds_ in the Question, remove the decimal Point _one Place_ in the Answer, thus: 612.3 becomes 61.23: 3d. For _Tens_, _two_ Places, thus: 204.1 becomes 2.041: 4th. For _Units_, _three_ Places, thus: 340.1 becomes .3401: 5th. And for each _Decimal_, a Place more, by adding Cyphers to the left, if wanted, thus: 68.0 becomes .00680. 407. Place the plain and decimated Answers, in one View, and add the latter together, thus: 204.1 = the same 204.1 612.3 = becomes 61.23 204.1 = 2.041 340.1 = .3401 68.0 = .00680 ————————— viz. Expansion of Air _with_} 267.7|179 28° _on_ 3935.1 } 408. _Second_, _with_ .71° _on_ Feet 3000 = 517.5 900 as 9000 = 1552.7 30 3000 = 517.5 5 5000 = 862.6 .1 1000 = 172.5 In order to decimate these Answers, it must be observed that the Expansion was not _with_ 71 Degrees, but with .71 _Tenths_ of a Degree of Heat; therefore the decimal Point corresponding to 3000 Feet in the Question, must in the Answer be removed _two_ Places to the left, thus: 517.5 becomes 5.175: for the 100, three Places: for 1.5527 the 10, _four_ Places: and so .05175 on. .008626 .0001725 —————————— 6.7|882485 The Expansion with .71 being found, viz. Feet 6.7 Tenths; add it to the Expansion on 28 Feet already found, viz. 267.7 ————— 274.4 Answer. Which _Height_ in Feet and Tenths, corresponding to the _Expansion_ of Air with 28°.71 Tenths of a Degree of Heat more than the Standard 31°.24, being added to the _Height_ in Feet and Tenths, corresponding to the _Expansion on Inches_ of the Quicksilver in the _upper_ Barometer, with the Standard-Heat, already found, viz. 3935.1 gives the _real Height_ of the _Mountain_, 274.4 —————— or _upper Station_, sought. 4209.5 END OF THE THIRD STAGE. * * * * * _The second Example_ briefly _stated: referring to the Sections._ [Sidenote: Section, 391.] 409. Below: Barometer 28.1318. Attached Thermometer 61°.8; Air ditto 63.9. Above: Barom. 24.178. Attached Thermometer 57°.2; Air ditto 56°. Degrees of Heat, viz. 4°.6 to be added to the _colder_ Barometer at Inches 24.178 Tenths, by the first Table, viz. .0112 Parts of an Inch of the Quicksilver in the Barometer, raised by 4°.6 of Heat. ——————— The Sum 24.1892 is the +point+, in Inches and Tenths of an Inch, at which the upper Barometer _now_ rests, being of _equal_ Heat with the lower. _End of the first Stage._ [Sidenote: Section, 399.] By the 2d. Table, find the _Height_, in Feet and Tenths, corresponding to the _said_ +point+ when at the Standard-Heat; gradually, thus: the _Height_ corresponding to Feet 24.1 is 7388.0: then with the Difference 107.9, (rejecting the .9). [Sidenote: Section, 400.] Find the Height by the 3d. Table corresponding to .08 86.0 } .009 9.7 } = Feet 95.9 Tenths. .0002 .2 } Which Height subtract from 7388.0 95.9 —————— And there remains, in Feet, 7292.1 The Height corresponding to Inches 24.1892 Tenths of the _upper_ Barometer, with the Standard Temperature of 31.24; for which sole Purpose the 2d. Table is calculated. Repeat the last Process with the _lower_ Barometer, resting at 28.1318, gradually, thus: [Sidenote: Section, 401.] By the 2d. Table, find the _Height_ corresponding to 28.1, which is 3386.61; then with the Difference 92.6 (rejecting the .6) find the corresponding _Height_, by the 3d. Table for the remaining Tenths or Decimals of an Inch, above 28.1, viz. .03 28.0 } .001 .9 } = Feet 29.6 Tenths. .0008 .7 } [Sidenote: Section 402.] Which _Height_ subtract from 3386.6 29.6 —————— And there remains, 3357.0 viz. the _Height_ in Feet corresponding to Inches 28.1318 Tenths of the lower Barometer, with the Standard Temperature of 31.24, for which sole Purpose the 2d. Table is calculated. [Sidenote: Section 403.] Subtract the _Height_ in Feet, corresponding to Inches of Quicksilver in the upper Barometer, viz. 7292.1 from ditto in _lower_ Barometer, viz. 3357.0 and there remains the _Height_ in Feet —————— of the upper Barometer at the Standard-Temperature viz. 3935.1 of 31.24. _End of the second Stage._ [Sidenote: Section, 404.] On which Number of Feet, viz. 3935.1, by the 4th Table, find the _Height_, with 28°.71 of Heat: _With_ 28°. _on_ Feet 3935.1 = 267.7 and _With_ .71 _on_ the same = 6.7 ————— Sum 274.4: which Height, more than the Standard-Heat, being _added_ to 3935.1 the Height, with the Standard, —————— gives the true Height, viz. 4209.5. _End of the third Stage._ CHAPTER LXXVII. PRACTICE OF THE THIRD EXAMPLE, REFERRING TO THE SECTIONS.[132] Section 410. _Below_: Barom. Inches 30, .0168: Attached Therm. 60°.6; Air-ditto, 60°.2: _Above_: Barom. - - Inches 29, .5218: Attached Therm. 56°.6; Air-ditto, 57°. Subtract the _colder_ ————— from the _warmer_, and there remains 4° of Heat to be added to the _colder_ Barometer; to give it an _equal_ Temperature: which is to be done by _the 1st Table_, thus: [Sidenote: Section, 356.] To find the Expansion _with_ 4° of Heat, _on_ the _colder_ Barometer; (which, as before, is the _upper_ Barometer) standing at Inches 29, .5218 Tenths. _First_, _with_ 4° _on_ 29 Inches = .0117: _2d_, _with_ 4° _on_ .5218 Tenths _above_ 29 Inches: In order to obtain which, begin _with_ 4° _on_ 29 = .0117 then _with_ 4° _on_ 30 = .0121 Subtract for the Expansion _with_ ————— 4° _on_ 1 Inch above 29, and there remains .0004. [Sidenote: Section 362.] Then for the Expansion _with_ 4° _on_ .1 Tenth of an Inch above 29 Inches; add a Cypher and decimal Point, viz. .00004: [Sidenote: Section 363.] Then for the Expansion on .5128, multiply the two last Terms, and divide ————— the Product by the first Term .1: the Answer is .0002|0872 Add the Expansion _with_ 4° _on_ 29 Inches, just found, .0117 to the Inches of the _colder_ Barometer, viz. 29.5218 ——————— Answer; Inches 29.5337 Tenths of the _colder_ Barometer, are _now_ expanded equally with the _warmer_: (rejecting the Decimals as in Section 395.) Place the Barometers, thus: _Upper_ Barometer, 29.5337 _Lower_ Barometer, 30.0168 _End of the first Stage._ [Sidenote: Section 371.] 411. _By the 2d Table_, and in the 2d Column, find the _Height_ of each Barometer, _with_ the _Standard-Heat_, in Feet and Tenths, corresponding to the Inches and +nearest+ Tenth _above_ and _below_ the Point required: and First of the _upper_, at 29.5337: The Inches and _nearest Tenth_ is above Feet. 29.5, corresp. to 2119.7 } Difference and below 29.6, cor. to 2031.5 } between .5 and .6 —————— } above 29 Inches. 88|.2 } [Sidenote: Section 373.] 412. _By the 3d Table_, _with_ the _Difference_ 88 Feet, find the _Expansion_ on the remaining Decimals, above 29.5, viz. on .0337, thus: on 03 = 26 decimated 26. 003 = 26 2.6 0007 = 62 .62 ————— Feet 29.22 From the _Height_ corresponding to 29.5 viz. Feet 2119.7 Tenths, subtract the 29.22, i.e. Height cor. to .0338 and there ————————— ——————— remains 2090.4|8, the _Height_ cor. to 29.5338 with Expansion of the Standard-Heat. 413. Repeat the 4 last Steps for the _lower_ Barometer, at 30.0168. 1st. The Inches and _nearest_ Tenth is _above_ 30. corresp. to Feet 1681.7 } Difference of and _below_ 30.1 cor. 1595.0 } .1 above 30 —————— } Inches. 86|.7 2d. Then with 86 Feet, find the _Expansion_ on the remaining Decimals, above 30, viz. .0168, thus: on 01 = 9 9. 006 = 52 5.2 0008 = 69 .69 ————— Feet 14.89 414. (3d.) From the _Height_ corresponding to 30 Inches, viz. Feet 1681.7 Tenths, subtract the Height 14.89 corresp. to .0168, ——————— and there remains 1666.8|1, the Height corresp. to 30.0168, with _Expansion_ of the Standard-Heat. 4th. From the _upper_ Height, at 2090.48 Subtract the _lower_ Height, at 1666.81 ——————— And there remains the Height 423.67 in Feet and Tenths of the upper Barometer, with the Standard Temperature. _End of the second Stage._ [Sidenote: Section 374.] 415. Detached Therm. _above_ 57° Detached ditto, _below_ 60.2 ——————— _Whole_ Heat 117.2 _Half_ Heat 58.6(0 adding a Cypher) _Standard_ Heat 31.24 —————— which being deducted, leaves 27°.36, viz. Degrees of Heat more than the _Standard_, for each Barometer. [Sidenote: Section 380.] 416. By the 4th Table, find the Expansion of Air, with 27°.36, on Feet 423.67 Tenths. [Sidenote: Section 406.] _First_, _with_ 27°, _on_ 423.67, thus: viz. _on_ 400 as 4000 = 262.4 decimated 26.24 20 as 2000 = 131.2 1.312 3 as 3000 = 196.8 .1968 .6 as 6000 = 393.6 .03936 .07 as 7000 = 459.2 .004592 ————————— Expansion = 27.692752 [Sidenote: Section 407.] _Second_, _with_ .36 _on_ the _same_, thus: on 400 as 4000 = 349.9 decimated .3499 20 as 2000 = 174.9 .01749 3 as 3000 = 262.4 .002624 .6 as 6000 = 524.8 .0005248 .07 as 7000 = 612.3 .00006123 ————————— Expansion = .37050003 Add the former 27.692752 ——————————— Height in Feet 28.06325203 417. Which Height for Expansion of Air, _with more than_ the Standard Heat, being +added+[133] to the Height, for Expansion of the Barometer, _with_ the Standard-Heat, gives the true Height of the upper Barometer, at the given Heat. For _Expansion_ of _Air_ above Standard Heat, Height in Feet 28.0 For _Expansion_ of _Barometer_, with Standard: Height in Feet 423.6 ————— 418. True Height of the _upper_ Barometer 451.6 _Lower_ Barometer 1 Foot above the Water 1.0 Height of the Top of the Cross above the Gallery 50.0 ————— Height of the Top of the Cross above the Tyber 502.6 Height of the same, measured the same Day geometrically, was Feet 502.9 _End of the last Stage._ CHAPTER LXXVIII. PRACTICE OF THE FOURTH EXAMPLE,[134] FOR MEASURING SMALL HEIGHTS. [Sidenote: By this Example, _small_ Heights are easily measured.] Section 419. Attached Therm. _below_, 71°.0 Attached Therm. _above_, 70 .5 ————— Subtract, and there remains .5 Tenths of a Degree of Heat to be added to the _colder_ Barometer (which in the present Case is the _upper_, but might possibly have been otherwise) by the 1st Table. _First_, _with_ 0°.5 _on_ 29 Inches. To obtain which, begin _with_ 1°.0 _on_ 29 Inches = .002: _with_ 0°.1 above 1°, _on_ 29 = .0002: then _with_ 0°.5 above 1°, _on_ 29 = .001. Prepare it for Addition to the _colder_ Barometer. colder Barometer 29.985 Expansion _with_ .5 above 1°, _on_ 29 .001 —————— 29.986 _Secondly_, _with_ .5 Tenths above 1°, _on_ .985 Tenths above 29 Inches. To obtain which, (having already found the Height from Expansion _with_ .5 above 1°, _on_ 29 Inches, to be .001;) since the Expansion on .985 Tenths above 29 Inches, is somewhere above 29, yet below 30 Inches; find the Expansion _with_ .5 above 1°, _on_ 30 Inches, thus: first, _with_ 1°, _on_ 30 = .003 2d. _with_ 0°.1 above 1°, _on_ 30 = .0003 3d. _with_ 0°.5 above 1°, _on_ 30 = .0015 Subtract the Expansion _with_ .5 Tenths above 1°, _on_ 29 Inches, from the Expansion _with_ .5 Tenths above 1°, _on_ 30 Inches: viz. _on_ 30 = .0015 _on_ 29 = .001 ————— The Answer is .0005, the Height from Expansion, _with_ .5 Tenths above 1°, _on_ 1 Inch above 29, i.e. on the 30th Inch: Then, if 1 Inch above 29 gives .0005; .1 gives .00005: and 985 ——————— multiplied 00025 as whole 00040 Numbers, 00045 ———————— give .0004|925 add the former Number 29.986 and, for the three remaining Decimals, _may_ be substituted 1 Decimal in the fourth Place 1 ——————— colder Barometer of equal Heat } 29.9865 with the _warmer_ } 420. _When the Quicksilver in each Barometer indicates the same Number of Inches_, differing _but_ one _or_ two Tenths _at the most; (which will frequently be the Case, in levelling flat Countries, or measuring small Heights;—instead of the usual Method, (to find the Height of each Barometer_ separately, _with the Standard-Heat, by the_ 2d Column _of the 2d Table, as in Section 411;)—it will be more convenient,_ 1st. _To subtract the lower Barometer from the upper. Then,_ 2dly. _By the_ 3d Column _of the same Table, find the_ +difference+, (_viz. of_ one _or_ two Tenths _at the most_) below _the Inches and_ nearest Tenth _of the_ lower _Barometer_. _And_ lastly, _with that_ +difference+, _find by the_ 3d Table, _the Height at the Standard-Heat, corresponding to the remaining Decimals_ above _the_ upper _Barometer_. 421.(_1st._) From the lower Barom. viz. 30.082 Subtract the upper 29.9865 ——————— Remaining Decimals _above_ the upper .0955 _2d._ Find, by the 2d Table, the Height corresponding to the Inches, and _nearest_ Tenth _above_ and _below_ the Point at which the Quicksilver rests in the lower Barometer. The Inches and _nearest_ Tenth is _above_ 30 Inches, correspond. to Feet 1681.7 and _below_ 30.1, corresponding to 1595.0 —————— 86.7 which is the +difference+ of .1 _below_ 30.1. _Lastly._ Find, by the 3d Table, _with_ the +difference+, viz. 86 Feet, _on_ the remaining Decimals, for the Height, in Feet, corresponding to the Standard-Heat. viz. .09 77 = 77. Feet. .005 43 = 4.3 .0005 43 = .43 ————— Answer, Height in Feet 81.73 corresponding to .0955 above Inches 29.9865 Tenths of an Inch, of Quicksilver in the upper Barometer thus brought to the Standard-Heat. 422. Prepare for Expansion of Air from Excess above Standard-Heat, on the same Number of Feet: Detached Thermom. _above_ 76°. Detached Thermom. _below_ 68.0 ———— Whole Heat 144.0 Half Heat 72.0(0 adding a Cypher) Standard-Heat 31.24 ————— which deduct, and there remains 40.76: with which, by the 4th Table, find the Expansion of Air on Feet 81.73: _First, with_ 40°, _on_ 81.73, thus: _on_ 80. as 8000 – 777.6 = 7.776 1. as 1000 – 97.2 = .0972 .7 as 7000 – 680.4 = .06804 .03 as 3000 – 291.6 = .002916 ———————— 7.944156 _Second_, _with_ .76 _on_ 81.73, thus: _on_ 80. as 8000 – 1477.4 = .14774 1. as 1000 – 184.6 = .001846 .7 as 7000 – 1292.7 = .0012927 .03 as 3000 – 554.0 = .0000554 ———————— Expansion .1509341 add the former Expansion 7.944156 ————————— Sum of the Expansions, viz. } Height in Feet } 8.0950901 from Excess of Heat above Standard, _with_ 40°.76 _on_ 81.73, +added+ to the Height at the Standard-Heat, } in Feet } 81.73 gives, in Feet and Tenths, the true —————— Height of the Tarpeian Rock 89.8|2. CHAPTER LXXIX. A CALCULATION TO ASCERTAIN THE HEIGHT OF THE BALLOON ON THE DAY OF ASCENT: ONE BAROMETER AND ONE THERMOMETER ONLY, BEING TAKEN UP INTO THE CAR. Section 423. The Question is stated from Section 36: and the Mode of Operation taken from the _Recapitulation_ of the second Example, Section 409. Observation before the Ascent: Below: Barometer 29.8; attached Thermometer 0; detached Thermometer 65°. Above: Barometer 23¼ = 23²⁵⁄₁₀₀ or 23.25;[135] attached Thermom. 0; detached Thermom. 65°. There being no attached Thermometers; the _first_ Table is useless: the Barometer below is therefore supposed to be of the same Temperature as when above; the detached Thermometer remaining at the same Degree, viz. 65°. State the Barometer, thus: when _below_, at 29.8 when _above_, at 23.25. _End of the first Stage._ 424. Find the Height (at the Standard-Heat) corresponding to the Inches and _nearest_ Tenth above and below 23.25: i.e. above 23.2, and below 23.3: by the 2d Table. Now 23.2 corresponds to 8379.7: and the Difference of .1 above, i.e. to 23.3, is in Feet = 112|.1: by the 3d Column of the same Table. With this Difference, consult the 3d Table: i.e. with 112, (omitting the .1 as too minute) on the remaining Decimals above 23.2, viz. on 05, as on 5, or ⁵⁄₁₀; and the Answer is 56 Feet: which Number being subtracted from 8379.7, the Remainder 8323.7, is the Height in Feet of the Barometer in the Car, at the Standard-Heat. Repeat the last Process for the Barometer on the Ground. Now 29.8, by the 2d Table, corresponds to 1856.0; and there being no Parts or Decimals more minute than a Tenth, viz. .8, there is no Occasion for the 3d Table. Subtract the Barometer in the Car, from the same when on the Ground; and, by the 2d Table, upper Barom. 23.25, corresp. to 8323.7, and the lower Barom. 29.8, to 1856.0: the Remainder is the Height in Feet —————— of the Barometer in the Car viz. 6467.7, with the Standard-Heat. _End of the second Stage._ 425. Detached Therm. above, at 65° Detached Therm. when below, at 65 ——— Whole Heat 130 Half Heat 65.(00 adding Cyphers) Standard-Heat 31.24 ————— which deduct, and there remains 33.76 Degrees more than the Standard-Heat, for each Barometer. Then for the Expansion of Air, with such Heat more than the Standard, consult the 4th Table: viz. _with_ 33°.76 _on_ Inches 6467.7, the Height of the Barometer in the Car with the Standard-Heat, thus: 426. _First_, _with_ 33°, _on_ 6467.7 _on_ 6000 as 6000 = 481.1, decimated 481.1 400 as 4000 = 320.7 32.07 60 as 6000 = 481.1 4.811 7 as 7000 = 561.3 .5613 .07 as 7000 = 561.3 .05613 ————————— Expansion = 518.59843 427. _Second_, _with_ .76 _on_ 6467.7: _on_, as before, 6000 = 1108. decim. 11.08 4000 = 738.7 .7387 6000 = 1108. .1108 7000 = 1292.7 .012927 7000 = 1292.7 .0012927 —————————— Expansion = 11.9437197 Add the former 518.59843 ———————————— Total Expansion = 530.5|542197 viz. Height _by Expansion_ in Feet, with more than the Standard-Heat, add to Height in Feet at the Standard-Heat 6467.7 —————— 428. The true Height, in Feet and Tenths, of the Barometer in the Car 6998.2 Feet in a Yard 3) —————— Yards in a Mile 1760) 2332.2 Feet. 1760 (1 Mile. —————— Yards in a Quarter of a Mile 440 ) 572 (1 Qr. 440 ——— 32 Yards. The Height of the Balloon 1 Mile, 1 Quarter, 32 Yards, and 2 Feet. _End of the last Stage, and of the Mensuration of Heights._ N. B. A _thermometric_ sliding Rule, for the Expansion of Quicksilver, and of Air, may possibly, from the foregoing Tables, be so contrived and adapted to the Barometer, as to tell the Height by Inspection, while in the Car of the Balloon. CHAPTER LXXX. HINTS, ON THE CHEAPEST METHOD OF INFLATING BALLOONS, WITH DESCRIPTIONS OF DIFFERENT MODELS FOR A GASS-STEAM-ENGINE. Section 429. The _Expence_ attending the Inflation of Balloons is a solid Objection to their frequent Use. A Check is thereby given to every Improvement that might otherwise be expected from a Repetition of Experiments. It is, in short, the chief Difficulty under which the +aironautic art+ at present labours. This Difficulty, however, if once overcome, (and of which there is little Doubt) will probably bring those extraordinary Machines, into general Estimation. What _now_ costs fifty Pounds, may _then_ be done for five: abating the Expence of the preparatory Engine. Mons. Lavoisier, by the Application of Steam to Iron Filings enclosed in a Copper Retort, has generated inflammable Air, or light Gass:[136] and Dr. Priestley, by converting a Gun-Barrel into a Steam-Engine, has produced a Gass 13 Times lighter than common Air;[137] whereas by the present expensive Method, with Metal and Acid, the Gass for Inflation is seldom more than six Times lighter. What has hitherto been atchieved on a small Scale, is here meant to be extended. As no Particulars are made public, or at least, have yet come to the Author’s Knowledge, relative to the Construction of such a Gass-Steam-Engine, as may, with Safety and Effect, be applied to the Inflation of Balloons; the following Descriptions of different Models may deserve some Notice:—may possibly excite the Attention of the ingenious; and put them on contriving _easier_ Means to obtain the _same_ End. I. 430. Let there be an Iron _Hot-hearth_, one Yard square, and two Inches thick. Let it be _set_ on a Common Brick Stove, built as near the Ground as possible, (or even below it) in the open Air. Its Chimney to consist of malleable Iron, flat at the Top, and strong enough to support a Tea-Kettle or Boiler to produce Steam: and extending at least one Yard from the End of the Hearth horizontally, before it turns up. It may rise three or four Yards high, slanting farther from the Hearth: the Form a hollow Cylinder: with a Turn-Cap at the Top, two Feet long, set on at right Angles; for the Management of the Smoke. Supposing then the Fire-Place to face the West; the Chimney may project Eastward. The North Side is to be appropriated to the Iron-Borings or Turnings; and on the South Side is to be deposited the Dross or Calx. A Muffle or Mould of malleable Iron is to be screwed and luted over the hot Hearth. The four Sides of the Muffle next the Hearth are to have horizontal Lips or Rims projecting half an Inch: and Screws are to be driven, throu’ Holes drilled at proper Distances, into the Hearth. The Sides are to rise upright a Couple of Inches: closing, as they rise, in the Form of a hollow Cylinder, one Foot in Diameter, and perhaps a Yard above the Hearth: which is now converted into a _Gass-Steam-Engine_. It is proposed to strew over the _Hot-hearth_ a thin Layer of Borings, one Tenth of an Inch thick; to which Layer when _red_ hot, the boiling Steam is to be applied. The extricated Gass is to be conveyed from the Top of the Cylinder, by Means of an extended Trunk of Tin, and varnished Linen, into a Tub of cold Water kept _continually_ flowing over, into which a few Lumps of quick Lime are thrown: and from thence the Gass is to rise into the Balloon. 431. The Iron, whether Filings or Turnings, proper for Inflation, must be _bright_; wholly free from Chips, Bits of Wood, and all heterogeneous Particles: but particularly RUST, and GREASE: _less_ than a cubic Inch of the latter, woud spoil a Ton of the brightest, and otherwise the best prepared Materials. (Section 339.) A Day or two _only_, before a Balloon is inflated; the proper Quantity of bright Iron shoud be heated +red hot+ in _Charcoal_, and suffered to go cold. For Want of this simple Preparation of the Iron, the Gass has proved defective in Point of _LEVITY_: altho’ the Balloon appeared fully inflated. This Misfortune happened at Birmingham, and other Places. 432. The _Desideratum_ is, _quickly_ to apply, and _remove_ the Borings, keeping the Machine _nearly_ Air-tight. For, it is now well known, that the Gass will _explode_, if one-third Part of common Air be introduced: or, if less; it may _unite_ with the _Gass_, and detract from _its_ Levity. 433. The following _Particulars_ may likewise be considered as an Improvement. II. 1. To lay a Plate of Iron, Brass, or Copper, over the Hearth; which, if made of _cast_ Iron, will be apt to crack, in Contact with the Steam; and will also unite with and concrete the Iron Turnings or Gun-Borings into a solid Mass, that woud be separated with Difficulty. 2. To make the Dross-Pit in the Form of a hollow Wedge, narrow at the Top: screwing and luting it to the South Side of the Hearth. It shoud hold the Dross arising from a Ton of Borings; which will be sufficient for the Inflation of a Balloon, to carry one Person. 3. On the North Side is to be erected a Platform of Brick, a Yard square, _floored_ with a Plate of Iron: the inside Surface to be even with the Bottom of the Hearth. 4. The Ton of Borings is to be placed on the _Floor_, and covered with another Muffle, secured and luted to the Side of the Hearth: having a Communication of two Inches high, and one Yard wide, with the Bottom of the Hearth: as the Dross-Pit has. 5. A Brass or Copper Rake is to remain within the two Muffles: to press forward the Borings, spread them over the Hearth; stir them frequently;—by turning the Instrument, scrape them into the Dross-Pit; and apply fresh from the _Deposit_. 6. To perform these manual Operations within the Machine kept Air-tight; it will be necessary, at the exterior End of the Muffle, to fasten a strong leathern Case, made very wide and pliant, and two Yards long: into which the End of the Rake-Handle is to be inserted. III. 434. _The Mode of Operation._ The Borings being spread on the Hearth, and _red_ hot; the Steam Pipe is to be opened, and _instantly_ shut. The Gass being _suddenly_ extricated; the Pipe is to be opened, and shut again as before: the Borings pushed into the Dross-Pit, and a fresh Supply spread. This Process to be renewed, till the Inflation is completed. If it be thought necessary to prevent the Steam from communicating with the whole Depôt of Borings, and so evolve too much Gass; a little Brass Door with Hinges of the same, might be made to hang from the Top of the Communication between the two Muffles: which Door opening inwards, and hanging vertically, woud by the Pressure of the Gass, stop up the Open: and yet, if made strong, _not_ prevent the Operations of the Rake, at proper Times. IIII. 435. The Machine woud be less complex, with one large Muffle, somewhat longer North and South than the Hearth; furnished with leathern Case and Rake. Put in the Borings at one End: keep the Steam-Pipe always open; with a _Hand_ at the Rake; pushing away the Dross, and pressing forwards fresh Borings. V. 436. Further: it has since occurred, that a Machine in the Form of a +gun-barrel+, _extended in all its Dimensions_, will probably answer _every_ Intention. And of this Kind are the hollow cylindrical Tubes, of _different_ Lengths, and about a Foot in Diameter,[138] which are _cast_, for the Conveyance of Steam, from the Boiler of a Steam-Engine. Such a one, (previously lined with a Cylinder of Copper, or malleable Iron, to prevent the Adhesion of the Borings, when reduced to a Calx by the Admission of Steam;) might be placed horizontally over a Stove, (with or without a Chimney) and surrounded with _red_ hot Coals. The Ton of Borings might be deposited at one End of the Tube; and, by Means of the Air-tight flexible leathern Case, be pressed with a Rake, _gradually_ into the Fire, and _beyond_ it when calcined. Care must be taken to make the _Apparatus_ nearly Air-tight. The Steam shoud pass into the Tube, from _below_: and the Gass be conducted towards the Balloon throu’ another Iron Cylinder, nearly equal in Diameter and at right Angles with the first; lying also in an horizontal Direction; along the Ground. The Tubes might be _forged_ or _cast_, so as to form but one rectangular Piece. The further End of the second Tube shoud communicate with a _third_, made of Tin, and bent downwards about a Foot; thence at right Angles, for six Inches: then to rise up, also at right Angles, the Length of six Inches more. The Tin Tube is to descend into a Cistern of cold Water, made to flow over continually, by a fresh Supply; and into which, a few Lumps of Quicklime shoud be thrown. The Gass, which will press upwards throu’ the Water, is to be received into an inverted Funnel, and thence (as in Section 339, Art. 2.) conveyed to the Balloon. VI. 437. The following Alterations woud supersede the Use of the Rake, and _leathern_ Cases: the latter of which, by any accidental Crack or Flaw in the Leather, might admit a sufficient Quantity of common Air to produce an Explosion. The cylindric Form of the Copper, or malleable Iron (to be used as a Lining for the Tube) is to be changed, into that of a half Cylinder, or inverted Muffle: and to be perforated with small Holes. This Muffle is to be _nearly_ filled with a Ton of Iron Borings: (the Ends to be made up, to prevent the Borings from falling out into the Tube;) the Muffle itself is to be supported by a Cradle[139] of the same Form, made of +strong+ Copper Wire,[140] like the _open_ _Iron-Wire_-Fenders: and the whole is to be thrust into the Tube. The Length of the Muffle depends on the Quantity of Borings that are intended to be used. The Ends of the Tube shoud not be made so strong as the Tube itself: that, if an Explosion happens, they _may_ give way first, and prevent a Rupture of the Tube: not that any Danger is to be apprehended, that such an Event will take Place, so long as the Steam-Pipe is attended to, by a proper Person: the above Caution being only given, to prevent a Possibility of Rupture. Each End shoud be cast, or forged with a hollow Handle; and shoud screw into the Tube. The Length of the Tube shoud be such, that the Person who attends the Steam-Pipe, shoud feel no Inconvenience from the Heat of the Fire. Nine Feet woud therefore be a proper Length: the conducting Tube the same. Within six Inches from each End of the Tube which holds the Borings, a Hole, half an Inch in Diameter shoud be drilled across the Middle of the Tube, in an horizontal Direction. Into these, an Iron Axis is to be fitted, (so as to take out _occasionally_) and pass throu’ the Tube: each End of the Axis is to project outwards a Couple of Inches, and to be made _square_, for the Socket of a strong Iron Winch or Handle. Each Axis to be furnished with a strong Chain, of equal Length with the Tube; one End of which Chain is to be riveted, or otherwise fixed, to the Middle of the Axis; and the other, to be fastened _occasionally_ to one Extremity of the Cradle and Muffle: the second Axis and Chain in like Manner, to the other Extremity. The Muffle is to be placed in the Cradle: both are then to be thrust into the Tube, and fastened to the Chain at the farther Axis: in which Position the Muffle may be filled with Borings, and gradually drawn into the Tube; till the same End has reached the Center of the Fire. The nearer End is then to be hooked by the nearer Chain, already wrapped round the nearer Axis: and the light Iron Caps to be screwed on each End of the Tube. 438. The Boiler for Steam may be fixed on any Part of the Tube near the Fire, and near the opposite Axis; so that one Person may attend both the Steam-Pipe, and Axis. The Steam to be conveyed throu’ a small Orifice made in the Bottom of the Tube, between the same Axis and the Fire. 439. As soon as the Materials, above the Center of the Fire, are supposed to be _red_ hot, the Steam-Pipe is to be opened for a Moment and +shut again+. The extricated Gass will be instantly +heard+, rushing throu’ the Vessel of _cold_ Water; and as instantly +seen+ to swell the varnished Linen-Trunk as it passes into the Balloon. The Steam-Pipe is to be regulated by these infallible Signals: and the Process continued, till that Quantity of Borings, that was in the Center of the Fire, and consequently _red_ hot, is supposed to be calcined. At which Time, the Handles are to be applied to the Axis, and the Cradle and Muffle drawn 5 or 6 Inches forward into the Fire. When drawn too far; Recourse must be had to the second Axis. 440. If great Expedition is required, two or three Conductors from the same Tube may be used: and, at the Distance of six or seven Feet from the Fire, _Tin-Conductors_ may be added; taking Care that they are _made_, _applied_, and _continued Air-tight_. THE END. An _alphabetical_ +index of the contents+: Referring to the +sections+ and +notes+, but _not_ to the _Pages_. A. Section. Absorption of Water by Air, _Experiment to prove_ the, 247 Accumulation of Air, _mediocèanal_, 259, 260 Aërial Scenes _described_, 39, 47, 51, 56 Air gives +form+ to _Things_, 53 - _gentle_, its Effect on the _Surface_ of the Balloon, 201 - _calm_, its _Effect_ on the _Surface_ of the Balloon, 202 - _pure_, cool, defloguisticated, perpetually descending, 252 - _descending Torrents_ of, on Etna and Teneriffe, 265 - _Reception and Dispersion of_, what, 280 Air Bottle Balloon, _its Use_, 311 - - - _preferred_ to an _interior_ Balloon, 314 Aironaut _Employments_ of the, in the Balloon, 29 - - _Attitude_ of the, in the Balloon, 32, 33 - - _lost over a Country_ well-known when _below_, 177 - - to _try_ different Heights, to find a _favorable Wind_, 309 - - to _wait_, in the _Calm above_ the Clouds, for a _Wind_, 309 Airostat, a small one _first_ liberated, 8 Altitude _apparent_, from the Balloon when _stationary_, 49 - - _barometric_, 49, _b_. Anchor and Cable, 13 Apogay Winds, what, 241 Apparent Height _proportioned_ to the _barometric_ Height, 49 Appearance of a Plain _below_, the Size of a moderate Carpet, what, 179, 189 Appearance of a Plain _below_, the Size of a Handkerchief, what, 181, 187 Appearances at _different_ Altitudes, _from the Balloon_, 213 Articles, _Weight_ and _Number_ of, 26 Ascent, to _check_ and _promote_, 14 - - _Preparations_ for, 22 - - of the Balloon at 40 Minutes past I. o’clock, 28 - - with _twenty Pounds_ of _Levity_, 28 - - of Balloons, Causes to _limit_ the, 279 - - _proper Times_ for, 285 - - _new_ Mode of, to _determine_ the _Height_, 299 Atmosphere _gross_, when seen throu’, _from below_, 55 - - Depression of the, 232 - - State of, _favorable_ to the _Direction_ of Balloons, 268 - - Conjectures concerning the _Warmth_ of the _superior_, 275 - - probably _respirable_ at _great Altitudes_, 277 - - _Height_ of, 290 - - _Weight_ of, in _England_, 290 Attention to the Balloon _necessary_, 35 Aurora Borealis, Conjectures concerning _Appearance_ of, 274 B. Ballast of what it consisted, 27 - - when to be _first_ thrown out, 21 - - in Hand, ready to throw out, 91 - - thrown down, 67, 95 - - thrown over _nearly_ 32 Pounds, 103 - - poured down at once 20 Pounds, 183 Balloon going to Sea, 75, 87, 90 - - in a quiescent Bed of Air, 75 - - of rowing it to any Point, in a Calm, 75 - - drawn aside out of the Perpendicular, 103 - - shrunk to its former Shape, 123 - - alternately rising and falling, 125, 138 - - in the Air five Hours and a Quarter, 207 - - sustained above Water, how, 294, 295 - - best Form of, 307 - - Double, what, 314 Balloons their Defects, and further Improvements, 303 - - Air-tight Varnish for, 320, 325 Barometer, and Thermometer, when stationary, 36 - - Fluctuation of the Quicksilver in the, 37 - - Mensuration of Heights by the, 350 Beautiful preferred to the Sublime, in Prospects, 42 - - Appearance, 43 Bladders necessary, 26 - - began to _crackle_, 116 Bottles of Air thrown down, Caution, 74, 77, 84 Breath not affected, nor visible, during the Excursion, 126 Breeze Sea-, 88, 92, 257 C. Cable, and Anchor or _Grapple_, 13 - - to be fastened to a _Center above_ the Car, 297 Calculations of the _Distance_ seen from the Balloon, 52, _a_. - - of the Height of _Mountains_, 171, _a_. Calm _above_, and Wind _below_, at the same Time, 168 Canal artificial, Duke of Bridgewater’s, Appearance of, 166 Cannon first discharged at IX. o’clock, 7 - - the second Time, at XII., 11 - - the third Time, at 40 Minutes and a half past I., 64 - - the last Time, at 10 Minutes and a half past II., 62 Car and Hoops, their _Dimensions_, 35 Caution to keep the Circle clear during the Inflation, 23 - - against the _Dropping_ of Water _out of_ the Balloon, 31 - - on Landing, 98 - - _not_ to open the upper Valve, 122 Charts Balloon, first suggested, 168 Chilliness _first_ perceived, 92; again, 109 - - _felt_ near moist Places, 283 Circularity of Prospect, 79, 221 Circumstance, _each_ to be recorded, 4 Circumstances _apparently superfluous_, mentioned and repeated, why, 5 Clouds, an upper Tier _seen_ to move in a safe Direction, 7, 46 - - Perspective of the, 51 - - _appearing_ in rapid Motion, 163 - - View of the, taken from above them, 130, 171 - - Colouring of the, 172 - - _highest visible_, 213 Cochuc-Varnish, 320 Cold, its Effects on the Balloon, 94 Colour of the Rivers, _red_, 44 - - of the City of Chester, _blue_, 45 - - of Thunder-Clouds, 54 - - of upper Clouds, 57, 172, Colours, _primary_, of Objects beneath, 129 Columns of Air, depressing, observed by the Ancients, 239 Compass, the properest Kind of, 38, _a_. Conclusions, useful, 159 Conjunction of the Planets _preceding_ a Hurricane, 211 Contemplation of the Prospect, 113 Course of the Balloon traced, to shew the Manner in which it was affected in passing over Water, 78 Curls and Streams of Air, Smoke and Vapour, 250, _b_. Currents of Air, horizontal, 20 - - from _above_, to be guarded against, 21 Currents _under_, of Air, 87 - - of Air, blowing _to and from_ great Towns, 250 - - of Air, _contrary_, at different Heights, at the same Time, 267 - - the Balloon rising throu’ _different_, 106 D. Defects in the Composition for Balloons, _remedied_, 320 Depressing Torrents of Air, 254 Depression of the Atmosphere, 232 - - over _moist_ Places in _fair_ Weather, 243 - - of the Atmosphere proved from History, 253 - - _nocturnal_, of the Atmosphere, 267 - - corroborating Proofs of a, 268 Depth below, conveys no Idea of Distance, 157 Depths, Mensuration of, with Barometers, &c. 348, 368, _a_, _a_. Descent of the Balloon, to _retard_ the, 15 - - Signs of the, 17, 159, 181 - - at _first rapid_, with a rushing Noise, 96, 97 - - Proof of _gentle_, 100 - - Change in _visible_ Objects, during the, 182 - - of Balloons over Water, _enquired_ into, 229, 230 - - - - - - Means to prevent, 294, 295 Description of the Ascent, 47 Diameter of the Prospects _above_ and _below_, 52, 79 Diminution of Objects, _excessive_, when seen from the Balloon, 223 - - - - Laws respecting the, 224 Direction of the Balloon, Hints for the. 315 Distance seen from the Balloon, Calculations of the. 52, _a_. - - of the Balloon from _Chester_, at the Report of the 4th Cannon, 64 - - Idea of, from _Experience_, 158 - - what is the _greatest_, to be seen from the Summits of the _highest_ Mountains, 171, _a_. - - at which an Object can be distinguished by a _good_ Eye, 175, _a_. - - of the Balloon-_Course_, 191 - - at which, the Balloon was seen, 227 - - and Height of a Balloon, found by a Quadrant, 310 Dove turned out of the Car, 61 E. Earth removed from _Sight_, 170 Echo none _above_, 39 Eknèfiai Winds, what, 241 - - a dry Wind, 267 Electricity of the Air, 65 Elliptic Solid, the Form of the Balloon an, 160 Employments of the Aironaut, 32 Engines _Steam_, Models of, for Inflation, described, 429 Equatorial Hoop, its Use, 161, 315 Evaporation of _Steam_, 249 Expansion of the Balloon, by what Manouvre, 132 Experiment to prove whether the _superior_ Atmosphere be _hazy_, tho’ the Sun continue _shining_, 47, _a_. Experiments necessary, in order to improve the Modes of _Direction_, 296 Examples in the Mensuration of _Heights_ with Barometers. See Table. Example 1st, Practice of the, 351 - - - Recapitulation of the, 385 - - 2d, Practice of the, 386 - - - Recapitulation of the, 409 - - 3d, Practice of the, 410 - - 4th, Practice of the, to determine _small_ Heights, 419 - - 5th, Practice of the, to determine the Height of the Balloon, 423 F. Fish _Dìodon-Globe_, a _Model_ for Balloons, 377 Flag _white_, hung out a Quarter of a Mile in Length, 4 - - hung out half a Mile, in all, 66 - thrown _down_ at a Mile high, 59 - Descent of the, 60 - _white_, its Effect on the Balloon, 70 - - Progress of the Balloon marked by the. 91 - - _impeding_ the Balloon, 103 - - the remaining one unfolded, 105 - - shewed a Change in the _Direction_ of the _Wind_, 105 Flights with the Balloon, for three Hours longer, 193 Flying-Coach, 149 Foot Roman, the _Measure_ of a, 49, _b_. Form of the Balloon at its _greatest_ Altitude, 14 - - - the _same_ at each Descent, 159 G. Gass not offensive during the _Voyage_, why, 34 - procured by Means of _Acid_, 338 Gass procured by Means of _Steam_, 429 Geography Balloon, _first_ suggested, 167 Globe-Fish, a _Model_ for Balloons, 377 Grapple or Anchor, 13 Gums Copal, Sandarac, Mastic, &c., 326 H. Heat of the _Sun_, _greatest_, while in the Car, 59 Height _apparent_, proportioned to the _barometric_ Height, 49 - - of the Balloon, when _stationary_, at the _first_ Ascent, viz. 2332 Yards, 52, _a_. - - in the Balloon, conveys no Apprehension of falling, 156 - - of _principal_ Mountains, noted, 171 - - of a Mountain, seen at a _Distance_, calculated, 171, _a_, _a_. - - to which Balloons will _probably_ ascend, 278 - - fixed, Method of ascending to any, 299 - - of the Balloon, to ascertain by a _Quadrant_, 310 - - _preparatory_ Instruments to observe the, 350 - - of the Balloon measured, 425 Heights to measure, Densities to estimate, 299 - - of the Atmosphere, while they encrease in an _arithmetical_ Progression, the Densities are said to encrease in _geometrical_ Progression: the Meaning of such Terms, 301, _a_. Hemisphere _upper only_, of a Balloon to be inflated, 315 Hoop equatorial, its Use, 161, 315 Horizontal Motion, Signs of, _deceitful_, 18 Hours proper for the Ascent of _Balloons over Water_, 254, 255, 261 Hygrometer _Horse-Hair_, the _best_ Kind, 217 I. Illustration of the Scenery, 72 Improvement during the Process of Inflation, 24 Improvements how to be made in the propulsive Machinery, 319, 330 - - in the Process of Inflation by Acid, suggested, 339 - - suggested in the Process by Steam, 429 Incorrectness of Maps, 81 Inflation began at X. o’clock, with a small Balloon, 8 - - Degree of, to be limited, 278, 317 - - Process of, 339 - - by Means of Acid, Expence saved in the, 347 - - by Means of Steam, Expence saved in the, 429 Inflation by Means of Steam, Model and Mode of, 429 - - by Steam, preferred to the Process by Acid, 429 Information derived from the Shape of the Balloon, 159, 160 Inventory of the Voyage, 12 Iris 1st, round the Shadow of the Balloon, 56 - 2d, 73 - 3d, 136 Iron _bright_ and _fresh_, proper for inflation, 431 L. Landing, Manouvres during the, 98 - - first, near _Frodsham_ in _Cheshire_, 100 - - second, near _Warrington_ in _Lancashire_, 188 - - Precautions to secure a safe, 297 - - in _windy_ Weather, Precautions to secure a safe, 298 - - _improved_ Mode of, 317 Latitudes variable, _light Airs_ playing in Eddies, common in the, 241 Level of the _lowest_ Stratum of Clouds in _fair_ Weather, 93 - all Inequalities of Surface reduced to the _same_, 111 Light of a _red_ Colour, Conjectures concerning the, 222 M. Machinery _propulsive_, to be used in the _Calm_, _above Winds_, 319 Magnitude of Objects, Laws respecting the, 224 Manouvres seen at a _great_ Distance, 140 Map consulted, 174 Mast, a light _hollow_, 315 Meanders of the River _encreased_ to the _View_, 81 Mensuration of Heights and _Depths_ by Barometers, 348 Methods to ascertain the _true_ Height, 350 Method, the cheapest to inflate by Steam instead of Acid, 429 Mistakes to be noticed, to prevent Repetition, 2 Motion encreased, progressive not perceived, 165 Motion of Air, called _Reception and Dispersion of Air_, what, 280 Mountains, Names and Heights of principal, 171, _a_. - - their Use, 265 Mouth of the Balloon, _closed_, 102 N. Neck of the Balloon, how to place it, 31 - - _first_ tyed, 125 - - risen near _eight_ Feet upwards, 119 - - an _Attempt_ to reach it, 121 - - held _Air-tight_ in the _Hand_, 125 Notes made during the Voyage, 36 O. Objects diminishing as the Balloon arises, Description of, 109 Objects, all _terrestrial_, disappearing, 163 Order preserved during the Inflation, 23 P. Parashute or Umbrella, 15 - the Balloon formed a vast, 184 Perspective new, 39, 229 Place where the Balloon alighted, 100, 187 Points, the plainest generally most essential, frequently overlooked, 4, 338 Preparations for Ascent, 22 Prospects _most beautiful_, at what Height, 93 - below noted, 128 Pulley or Reel, 13 R. Rain _warm_ in Winter, accounted for from the Theory of Accumulation, 270 Reception and Dispersion of Air, 280 Reel or Pulley, its Defects remedied, 41, _a._ Respiration easy during the Excursion, 114 Resistence of the Air, as the _Square_ of the Velocity of the falling Body, 15, _a._ Rising, Signs of, 16, 30 Rivers, _no Appearance of_ Water in the, 110 Rule, general for measuring Heights, copied, 384 Rusty Iron, _improper_ for Inflation, 398 S. Sail, three seen in the _Liverpool_ Channel, 108 - _triangular_ Latteen, _purposely to retard_ the Balloon, 315 - Anemòmeter, what, 315 - Weights to be added to the, 316 - Vane-, what, 318 Scenes aërial, described. See Sublime. Sea-Breeze discovered, 88 - - its Duration, 256 - - its Extent, 257 Sensation of _rising_ described, 30 Sensations accompanying the Balloon, 141, 154 Shadow of the Balloon _traced_ on the Clouds, 56, 73, 136 Shadows, their Length, _at Noon_, calculated, 84 - - - - - _at half past III._ calculated, 100 - - encreased, seemed to raise the Objects, 127 Shape of the Balloon _altered_, 118 Sign of Descent, 181 Signs to be observed in the Management of Balloons, 14, 15, 17, 20 Situation novel, peculiar to the Balloon, 221 Sound of the Gass throu’ the upper Valve, 134 - in the Air, an _uncommon_, 162 Sounds immediately under the Balloon, their Effects, 175, _a._ Spirits raised by the Purity of the Air, 155 Spunges of Air, 247 Squalls of Wind, the Day preceding the Ascent, 6 Stationary, the Balloon, 36, 122 Steam, Mode of Inflation by Means of, 429 Storms of _Collection_ and _Dispersion_, 232, 263 Sublime and beautiful Scenes, 3, 39, 47, 48, 49, 51, 71, 84, 112 Sun, when hottest, 59 Sympathy of the Spectators, 46 T. Table the 1st. See Mensuration. - - for Expansion with Heat, from 1 to 40 Degrees, on Inches of the Barometer, from 9 to 32 Inches, 363 - the 2nd, shewing the Variations of the Barometer, at each Inch and Tenth of the Quicksilver, from 1 to 32 Inches, the Air being at the freezing Point, 371 - the 3d, for easy Calculations, from the 2d Table, 373 - the 4th, shewing the Expansion with Heat, from 1 to 100 Degrees, on any Number of Feet in the Air, 381 Tastes not altered, on Account of the Height, 65 Thermometer warmer _above_ than _below_, 126 Thermometers compared, 12, _c._ Thunder-Clouds described, 52 - - under the Balloon, 172 Tide of Air in the Atmosphere, 291 Tides highest, 288, 289 Time, noted, 7, 8, 11, 22, 28, 36, 62, 63, 68, 73, 77, 85, 100, 101, 124, 162, 174, 186, 203, 206 - of Ascent, 28 Time, in which the Excursion was performed, viz. two Hours and a Quarter, 191 - Noon, a dangerous one, for Balloons to pass an Arm of the Sea, 256 - the best, pointed out, 256 - Noon and full Tide, improper: Midnight and low Water, proper Hours for Ascent, over Water, 287 Torrents of Air mediocèanal, depressing, 257, 258, 259 - - - - - accumulating, 260 Transparency circular, of Vapour, 222 Twine cut, lest it should prove a Conductor of Electricity between the Balloon and Earth, 103 U. Useful Conclusions, 159 Utility of Balloons, 332, 333 Utility _general_, of Balloons, 338 V. Valve upper, emits the _lightest_ Gass, 124 - _first_ tried, 133 - -Swing, or Umbrella-Pendulum, as _propulsive_ Machinery, communicates a _progressive_ Motion to the Balloon, 319 Vane-Sail, 318 Vapour, Observation of the _reddish_, 33 - _white_, _beautiful_ Effects of, 71 - - began to be accumulated at a _certain_ Height, 80 Vapours, their _Transparency_, 222 Varnishes, 320, 325 Velocity of the Balloon, 192 Vessels, the _four_ and the River Wever _disappeared_, 110 View _circular_, from the Balloon at its _greatest_ Elevation, 55 - of the Balloon over _Helsbye-Crag_,77 - of the Clouds, _from_ above _them_, 171 - _from_ the Balloon of the Country between Chester and Rixton-Moss, 192 Vis Inertiæ, 70, 316 W. Warmth of the superior Atmosphere, 275 - of the Air above Plains and cultivated Countries, 276 - of the Air over the _Sea_, at certain Times and Seasons, 276 - descending from _above_, 284 Water poured down, to observe the Effects of Air upon it, 74 - Balloon influenced on its Approach to, 76, 78 - Balloon above the Influence of, 131 - the Descent of Balloons over, 229 - the Causes of their Descent over, 230 - Absorption of, by Air, 247 - a curious Phenomenon seen on its Surface, 249, 250, _b._ - Means to prevent the Descent of Balloons over, and within its Influence, 294, 295 Waves of Air, 21 - of the Sea, the Dashing of, heard; the Sea being invisible, 80 Weather, about the Time of the Excursion, 211 Weighing during the Inflation avoided, how, 24 Weight of Provisions and Articles, 24 - of the Balloon, and its Apparatus, 25 Wind heard below, 86 Winds, the Eknèfiai and Apogay, what, 241 - the Directions in which they blow, 253, _a._ - the Eknèfiai productive of Cold, 253, _a._ - _Land_- and _Sea_-, 253, _a._ - contrary, at different Heights, their Use to waft Balloons to a given Point, 268 Wings, their Use, first to retard, second to direct, 315 Winter-Dress, preparatory, 26, 338 - -Prospect from the Balloon, 169 FOOTNOTES: [1] Ποιησον δ᾽ Αιθρην, δος δ᾽ Οφθαλμοῖσιν ιδεσθαι· Ἐν δε Φαει και ολεσσον, επει νυ τοι ευαδεν οὑτως. Homer’s Iliad, Book 17, Line 646. [2] Phil. Trans. Vol. LXVII, for 1777, Part II, Page 513, containing Sir G. Shuckburgh’s Rules for the Mensuration of Heights with the Barometer. Also Vol. LXVIII, for 1778, Part II, Page 681: [3] And Page 688. [4] It were to be wished that the Divisions of the Thermometer by Farenheit were become general throughout Europe, in preference to those by Reaumur yet retained _abroad_; which Divisions of Reaumur are not sufficiently minute to mark the least sensible Change in the Temperature, are subject to frequent Mistakes, and the Inconvenience of adding in the Notation, the Words _above_ or _below_ the Cypher, zero, or Point of Congelation: besides their being in Conversation not easily compared with those of Farenheit; each Degree of the latter having to that of the former nearly the Proportion of 18 to 11: since Farenheit from the freezing Point upwards to boiling Water has 212−32=180°, and Reaumur to the same Height, 110° Divisions: Mr. Saussure says as 4 to 9; in which there is an evident Oversight: see his curious and philosophic Investigation of the Atmosphere in “Essais fur L’Hygrometrie.” 4to. A Neuchatel, 1783. Frequent Mention being made of the Thermometer graduated according to Farenheit’s Scale, in different Parts of the following Account; it may not be amiss to shew the corresponding Points according to Reaumur, taken from “Thermometre universel de Comparaison, extrait du Journal de Physique de M. L’Abbé Rozier.” Farenheit, Reaumur. 54 13 & 4-9ths above the Cypher. 55 14 ditto, nearly. 57 15 2-9ths ditto, nearly. 59 16 4-9ths ditto, nearly. 60 17 1-9th ditto. 65 20 1-9th ditto, nearly. [5] The Strength of the Rope, or Cable, if its Length does not exceed 10 or 12 Yards, ought to be such as to support a weight, greater than the Weight of the Balloon and it’s Appendages, for the Resistance made by the Grapple against the Balloon acted on by the Wind is immediate: The Rope ought therefore to be made of Indian-Gut, as most elastic, or Silk, as lightest. But if the Rope be half a Mile, or a Mile long; the Resistance is gradual: the Balloon descending for some Minutes; and having an open Space to move in through the Air: the Rope or Cable acting as a Radius, and the Levity of the Balloon and Opposition of the circumambient Air preventing it from falling with any Violence. The shorter Cable may be used at the Height of 10 Yards; in aid of the longer, to prevent it from rising; or to moor it, by winding the Reel, and hauling down the Balloon close to the Ground. [6] The Resistance being as the Square of the Velocity; therefore if the Velocity be increased 3 Times, the Resistance will be as 3×3=9, i.e. will be increased 9 Times. [7] Pounds Averdupois. Weight of the Aironaut 160 Provisions and Articles calculated at 20 Sand-Ballast prepared in Bags 44 Levity for Ascent 10 ——— _Sum total_, 234 [8] Ancient Warriors among the Arabs, Spaniards, Romans, Gauls, and Germans, being frequently obliged to pass deep Rivers, never undertook a Campaign without them. For the above Anecdote, and many curious Experiments on Air, see Sam. Reyheri, _Dissertatio de Aëre_, tertium edita. Kiliæ. 1673. [9] Equal Time with a Regulator corrected by an Observation. [10] Being a Dial-Compass, the Dipping of the Needle was frequently checked by the Glass at the Top. A Mariner’s Compass is the best. [11] [Sidenote: The Defect of the Reel remedied] The Loop shoud have been furnished with a +Swivel+: or the Lath or Reel shoud have been a Kind of Pulley, a Foot in Diameter, and two Inches wide. The Hook of which having also a Swivel might have been held in the Hand: and thus the Twine woud have run off in a short Time with the greatest Readiness; the Swivel conforming to the circular Motion of the Balloon. [12] +Slate+ (according to Cronstedt) is the +Whetstone+ _of fine Particles_, composed of Glimmer, Quartz; and, in some Species, of a martial argillaceous Earth, See “Essay on Mineralogy” by Mendes Da Costa, Sect. 264. [13] [Sidenote: Method of discovering Haze round the Sun, in bright Weather.] _To know whether the Air is hazy, tho’ the Sun continues shining._ The Method taken for that Purpose was by placing the Hand so as to cover his Disk or Body, and then observe the Glory blazing round him; which may, in general, be seen to issue in great Abundance, in Rays of a _golden Colour_: occasioned by a Haziness or Vapour which pervades the _lower_ Regions of the Air, most frequently in the hottest and calmest Weather, and in the hottest Climates. The Accumulation of these Vapours, before they are formed into Clouds, are often so great as to intercept the Sun’s Rays, or dye them the Colour of Blood: an Appearance frequent in Virginia, and also throughout the torrid Zone. In the _Campania_ of Rome, for Instance, the Italians have a peculiar Name for such Kind of Weather, when the Sun is neither _visible nor invisible_: Il Sole si vede, e’ non si vede. By Degrees the Hand is to be removed so as just to have a Glance of the Sun’s Limb. And it frequently happens that the Air is exceedingly hazy; tho’ not a Cloud appears above the Horizon. [14] Esse in +Imaginibus+ quâpropter _Causa_ videtur _Cernendi_, neque posse +sine his+ Res ulla videri. Lucretius de Rerum Natura. L. 4. V. 238. [15] Notwithstanding what has been said; +this+, to the great and to the sordid Vulgar, woud still appear a solitary, helpless, and deplorable Situation. But such are not captivated with the golden Lines of +Epictetus+, (Chap. 13. Line 3. see Mrs. Carter’s Translation.) “ΠΑΝΤΑ ΘΕΩΝ μεστα και ΔΑΙΜΟΝΩΝ·—Βλεπων τον ΗΛΙΟΝ και Σεληνην, και Ἀστρα, και ΓΗΣ απολαυων και ΘΑΛΑΣΣΗΣ, ἐρημος εστιν ου μαλλον ἠ και ἀβοηθητος·” Nor are they +practically+ influenced by the better Words of a much finer Writer: “The Earth is full,” &c. &c. And “If I take the Wings of the Morning,” &c. &c. [16] There being, at first, no Clouds, as usual, to occupy the Place of the lowest Stratum. [17] It has been said that the _apparent_ Height from the Balloon to the Ground was 7 Miles, viz. 4 to the Summit of the Clouds, and 3 below: and the _barometric_ Height was about a Mile and half, viz. 2332 Yards, _a Calculation of which will be given_. If then we divide that Height or Distance into 2 such Parts, that the greater shall be to the less as 4 to 3; we obtain the Length of each Part; i.e. the barometric Height from the Balloon to the Summit of the Clouds, and thence to the Earth; which is done thus: Suppose the whole Distance to be any Line, as A. B. to be divided in C. Then, as 7 is the whole Line, and 4 the greater Part; say, as the whole 7 is to the greater Part 4, so is the whole Distance to a fourth Term proportional, which will be equal to the greater Distance sought: Whole Distance in Yards. Greater Distance in Yards. Thus 7, : 4 :: 2332 : 1332⁴⁄₇ Ans. 4 ————— 7 ) 9328 2332 the whole. 1332⁴⁄₇ 1332⁴⁄₇ being the greater Distance found; take the greater from the whole, and then will remain the lesser Distance wanted, viz. 999³⁄₇: the 1332⁴⁄₇ = the greater Distance, and 999³⁄₇ = the lesser Distance: and adding the Fractions ⁴⁄₇ ³⁄₇ = 1 to the 999; we have 1332 Yards for the greater Distance, or Height of the Balloon above the Summit of the superior Clouds: and 1000 Yards for the less Distance, or Height from the Earth to the Summit of the superior Clouds. Note. _The Line A. B. here selected is the_ famous Measure _of (half) a_ +mathematical+ _Rhinland and Roman_ +Foot+, _according to Snellius_. (_See_ Geographia Generalis _of Varenius, published by_ Newton. _Lib. 1. Cap. 2. De variis Mensuris._) [18] PROBLEM. To find the circular Boundary of the _celestial_ Prospect over the Tops of the superior Clouds, from the Balloon at the Height of near a Mile and half above the Surface of the Earth, viz. 2332 Yards. The Height from the Earth to the upper Surface or Floor of Clouds being 1000 Yards; and the Height above the Floor to the Balloon being 1332 Yards. _On the Curvature of the Earth and Clouds, and Elevation of the Eye above their circular Horizon._ Rule. To the Earth’s Diameter, equal to 7940 geographical Miles, add _the Height_ of the Eye above its Surface: multiply the Sum by that Height: then the square Root of the Product gives the Distance at which an Object on the Surface of the Earth can be seen by an Eye so elevated. Note the Diameter of the Earth, in Feet, is 41798117, according to Newton. (See Practical Navigator, by J. Moore, 7th Ed. Page 251.) FIRST. Double 1000 Yards, the Height from the Earth to the Clouds for an Addition to the Diameter of the Earth, whose Surface is now considered, as extended to the concentric Floor of Cloud. 1000 1000 ———— 2000 SECOND. 13932702(⅓) Diameter of the Earth in Yards. 2000 Addition to the Diameter. ———————— 13934702 Sum, to which add 1332 the Height of the Eye or of the ———————— Balloon above the Floor of Cloud. 13936034 Sum, which multiply into 1332 the Height of the Eye above the ———————— Floor. 27872068 41808102 41808102 13936034 Extract the ——————————— Square . . . . . 1760) Yards in a Mile. Root 18562797288 (136245 (77 Miles. 1 12320 —— ——————— 23) 85 13045 69 12320 ——— ——————— 266) 1662 Yards 440) 725 (1 Quarter of a Mile. 1596 440 ———— ——— 2722) 6679 285 Yards. 5444 ————— Ans. 77 Miles, 1 Qu. 285 Yards. 27244) 123572 108976 —————— 272485) 1459688 1362425 ——————— 97263 [Sidenote: Circular Boundary of the _terrestrial_ Prospect from the Balloon on a _clear_ Day.] PROBLEM. To find the circular Boundary of the _terrestrial_ Prospect, on a clear Day, from the Balloon at the Height of near a Mile and half, viz. 2332 Yards: the Earth’s Diameter being equal to 13932705⅔ Yards, add 2332 the Height of the Eye or ———————— Balloon. 13935037 the Sum, multiply into 2332 the Height of the Eye, &c. ———————— 27870074 41805111 41805111 27870074 ——————————— Extract the . . . . . 1760) Yards in a Mile. square Root 32496506284 (180267 (102, 1 1760 say 102½ Miles, Ans. —— ———— 28) 224 4267 224 3520 ——— ———— 3602) 9650 747 Yards, Remainder. 7204 ———— 36046) 244662 216276 —————— 360527) 2838684 2523689 ——————— 314995 Remainder. [19] See his “Minute Philosopher.” [20] Ullòa in his voyage to South-America relates, that in passing over the +Deserts+, Írides are frequently seen by Travellers round _their own Heads_ as the Center of the _Iris_; and visible only to themselves. But what Analogy the _Balloon Iris_ bears to them, Time and future Experiments may discover. See his “Voyage to South America, Vol. 1. Pa. 442.” [21] As Sound travels 1142 Feet in a Second, it must have moved in 30 Seconds ———— Feet in a Yard 3 )34260 = Feet Yards in a Mile 1760 )11420( 6 Miles 10560 ————— Yards in a Quarter of a Mile 440)860( 1 Quarter 440 ————— Answer 6 Miles, 1 Quarter, and 420 Yards. [22] Equal to 2085 Yards; or 1 Mile, 325 Yards. [23] Long’s Astronomy. Pages 227, 229. [24] Also called the _Horsham Stone_, from a Place so named, in Surrey, where great Quantities are found. [25] PROBLEM. To find the _Length_ of the _Shadow_ from a Person of _middle_ Stature, (five Feet and a half High) viz. at XII o’Clock, on the 8th Day of September, 1785, at Chester, whose North Latitude is 53° 12′; (and 3° 11′ West Longitude from London.) FIRST, To find the Sun’s Altitude at XII. From 90°. 00′ Subtract The Latitude 53. 12 ——————— The Remain. 36. 48 is the Complement of Latitude, to which add (from the Tables) Sun’s N. Decl. 5. 29 ——————— The Remain. 42. 17 is the Sun’s Altitude (viz. at XII.) SECOND, For the Shadow say, As the Sine of the Sun’s Altitude 42° 17′ To the Person’s Height, viz. 66 Inches, So is the Co-Sine of the Sun’s Altitude, To the Length of the Shadow. For the Sine of the Sun’s Altitude 42° 17′ in the Table of artificial Sines, is the Logarithm 9.82788, which, subtracted from the arithmetic Complement, viz. 9.99999 (supposing the last Figure a 10) becomes, .17212 Then for the Person’s Height, viz. 66 Inches: in the Table of Logarithms is the corresponding Number, 1.81254 And for the Co-Sine (had by subtracting the Altitude 42.17 from 90.00) viz. 47.43: among the artificial Sines is the Logarithm, 9.86913 ———————— The above Sums added, are 11.86079 which logarithmic Number (deducting the _Initial_ 1 as useless) viz. 1.86079, in the Table of Logarithms, corresponds to 72.57, equal to 72 Inches, for the Length of the Shadow at XII. Reducing then the Numbers 66 and 72, to the lowest Denomination, thus 6)⁶⁶⁄₇₂ = ¹¹⁄₁₂ the Proportion which the _Length_ of the _Shadow_ bears to the _Height_ of the _Object_ is thereby obtained: that is [26] If the _Length_ of the Shadow be divided into 12 Parts, the Height of the Object would be 11 of those Parts. See Moore’s Practical Navigator. See Page 98 [34]. PROBLEM. An +easy+ Way to find the Proportion which the _Length_ of the Shadow bears to the _Height_ of an Object is, +AT ANY TIME WHEN THE SUN SHINES+, to fix a Plummet Line and +frame+ _upright_ in the Ground; measure the _Length_ of its _Shadow_, and compare _it_ with the _Height_ of the +frame+. [27] Equal to 3 Quarters of a Mile and 121 Yards. [28] i.e. When the Barometer _below_ is at 30 Inches, and Thermometer _below_ at 60° viz. about 1000 Yards high in _fine_ Weather, and 500 in _changeable_. [29] Being 1083 Yards, i.e. half a Mile, and 203 Yards. [30] It was High Water at Chester and Frodsham-Bridge, at 38 Minutes past I. [31] Articles parted with, to check the _first_ Descent at Bellair, near Frodsham: and to ascend the _second_ Time. To check the _first_ Descent. Pounds. Ounces. Ballast, at twice: 24 0 To clear Trees and Hedges, and _re-ascend_: Barometer and Frame, 0 12½ Basket with Tunning Dish and Bottles (except the Flask with Brandy and Water) 4 10 Half Mile of Twine on the Reel 1 0 Speaking Trumpet 0 8½ Woollen Gloves 0 1 ——————— 31 0 24 0 ——————— Remains for Re-ascent 7 0 [32] The Sun’s Azimuth from the North Point _Westward_, being 118.26′: its Supplement to 180° is 61°.34′ South westerly: i.e. South West by West, half West _nearly_. [33] The _Length_ of the Shadows being more than _double_ the Height of the +Objects+: see [34]. [34] To find the Length of the Shadow at half past III. (See Section 84, Note _a_.) {Lat. of Chester, 53° 12′} Given {Sun’s Dec. 5 29 } To find Sun’s Alt. {Hour III, 30M. 52 30 } This is the Case of an oblique spheric Triangle, wherein are two Sides and one Angle between them given, to find the Sun’s Azimuth, and the Sun’s Co-Alt. Side 84. 31 } Sum of Sides 121. 19 Side 36. 48 } Diff. of Sides 47. 43 (3½ Hour) Angle contained 52. 30 Half ditto 26. 15 } 63. 45 Half Sum of Sides 60. 39 } Co. 29. 22 Half Difference ditto 23. 51 } 66. 9 THE FIRST PREPARATIVE PROPORTION. As Sine of ½ Sum of Sides 60. 39 0.05966 Co-Ar. To Sine of ½ Difference of Sides 23. 51 9.60675 So Co-Tangent ½ contained Angle 63. 45 10.30703 —————— ———————— To T. of ½ Diff. of the other two Angles 43. 15 9.97344 SECOND PREPARATIVE PROPORTION. As Co-Sine ½ Sum of Sides 29. 21 0.30968 Co-Ar. To Co-Sine ½ Diff. 66. 9 9.96123 So Co-Tangent ½ contained Angle 63. 45 10.30703 ———————— To T. ½ Sum of other Angles 75. 11 10.57794 Half Diff. before found 43. 15 —————— Sum, is greater Angle 118. 26 = Sun’s Azim. Diff. is lesser Angle 31. 56 = S’s right Asc. Then by first Axiom in Trigonometry, to know the Sun’s Altitude say, As Sine Sun’s right Asc. 31. 56 0.27659 To Sine Co-Lat. 36. 48 9.77744 So Sine of the contained Angle 52. 30 9.89947 ——————— To Co-Sine of the Sun’s Alt. 63. 57 9.95350 from 90. —————— Sun’s Alt. 26. 3 Having Sun’s Alt. to find the Shadow, As Sine Sun’s Alt. 26. 3 0.35738 Co-Ar. To Person’s Height, 66 _Inches_, 1.81954 So Co-Sine of the Sun’s Alt. 63. 57 9.95350 ———— To Length of Shadow, 135 _Inches_, 2.13042 Then 6(⁶⁶⁄₁₃₅ = ¹¹⁄₂₂ - | - ³⁄₆ or ½, i.e. as 22 to 45: supposing the Length of the Shadow divided into 45 Parts; the _Height_ of the Object woud be 22 of those Parts; or not quite _half_ the _Length_ of the Shadow, at half past III. See Section 84, Note [26]. [35] See “Priestley on Electricity.” [36] Εὔροια. [37] [Sidenote: An Account of the _Breath_ being visible at Sea, when the Thermometer was at 61.] The Breath is said to become _visible_ at Sea or Land at any Temperature of the Thermometer not _exceeding_ 60°: tho’, in Latitude 41°, and Westward of the Azores Islands, being in Sight of the Peak of +st. george+, (which probably equals, if not exceeds, the Height of Teneriffe) the Observer has seen his _own Breath_, and _that_ of the Sailors on Deck, when the Thermometer in the _Shade_ was at 61: the Air (in January) being _then remarkably_ damp. [38] This Assertion may seem to contradict what was said in Section 44: When—“every Thing, that coud be seen at all, was seen +distinct+:” but it only proves that the Balloon had attained a greater Altitude during the Re-ascent, and that the +shadows+ were _much lengthened_, as the Evening advanced. [39] Angelica Kauffman. [40] It consists of a Frame, made by placing two strong Posts, moveable at Pleasure, each nine or ten Feet high, upright in the Ground, at the Distance of two Yards: the Posts being well secured by broad Pedestals, to keep them firm: a strong horizontal Iron Axis goes throu’ the Top of the Posts; and throu’ the Centers of four Arms or Levers at their Junction. Between the four corresponding Ends of each two Arms, (which Arms are also strengthened by Beams from one to the other), are fixed four Seats or Boxes, well secured, each holding three or four Persons, and moving on Iron Pivots, near the Top of the Boxes, so as always to preserve the _vertical_ Equilibrium. [41] [Sidenote: Recommended to _Invalids_.] Why not recommend the Use of that Machine to Invalids? who woud find Refreshment in the +open+ Air: as its Rotation communicates a gentle Motion to the System,[42] without the least Fatigue; _rather_ encreasing the _Animal_ Spirits. [42] Particularly the Stomach and Diaphragm. See “Berdoe’s Enquiry.” [43] Talis Aër qualis Spiritus. See “_Health’s Improvement_,” by Dr. Moffet, Chapter 3, Of Air, Page 79. [44] Or Solid of _least_ +resistance+, see Chambers’s Dictionary, with the Supplement. [45] It will be found, that, on comparing the _two_ Calculations in Section 52, Note (_a_), _corrected_; the circular _Distance_ from the Eye, above the Clouds, was 102 Miles, 1 Quarter, 320 Yards: while _that_ above the Earth, seen from the same elevated Situation, (supposing the Day to have been +clear+ for such a View,) was 102 Miles, 1 Quarter, 307 Yards: whose Difference is only 13 Yards: that is, the _Distance_ above the Clouds to the _nebulous_ Horizon, was _rather_ more extensive, than _that_ above the Earth to the _terrestrial_ Horizon. It may not, to some Readers, be deemed either unentertaining, or foreign to the Subject; if the Distance of the _Prospect_ from the Balloon at its greatest _barometric_ Altitude, viz. 2332 Yards, or a Mile and Half within 33 Yards, be compared with the Distance which may be seen from the _Summit_ of the principal Mountains in different Parts of the Globe. 1. Cotopàzy, a Mountain in the Province of Quito, in America, and under the equinoctial Line, is _said_ by Ullòa (Vol. 1. Page 422) to be 3126 Toizes or Fathom, i.e. 6252 Yards, or 3 Miles and a Half and 92 Yards in Height. 2. White Mountain, called by the French Mount Blanc, near Geneva, is considered by Sir G. Shuckburgh (Phil. Trans. Vol. 67, Part 2d, Page 598, for the Year 1777) as the highest Land in Europe, Asia, or Africa (known to Europeans) and calculated by him at 5220 Yards, or 3 Miles within 60 Yards above the Level of the Mediterranean Sea. Mons. Bourit just returned from his last Tour, see his “Description de Glacieres” in 1773, makes the White Mountain but 5102 Yards in Height, (which is 30 Yards lower than Teneriffe) including the 410 Yards for the Level of the Lake of Geneva above the Mediterranean. 3. The Peak of Teneriffe in the Canary Islands, which, _in approaching towards it_, Authors agree, may be seen at the Distance of 120 Miles at Sea, if the Weather is clear; (Modern History, Vol. 14th, Page 451;) and, in _returning from it_, is discoverable at the Distance of 150 Miles, according to Glas’s History of the Canaries (Page 234);—has been estimated by Dr. Heberden in Madeira (Guide to the Lakes, Page 187) at 5132 Yards, or 3 Miles within 148 Yards. Glas remarks farther, that in sailing from Teneriffe, the Peak, at the Distance of 150 Miles is very little darker than the _azure_ Sky, on Account of the great Quantity of Vapour intercepted between the Eye and the Mountain: and _not_ because it ceased to be an Object too small for the Sight; or was in Fact, below the Horizon, and only raised by Refraction of the Vapour. With Respect to the Peak of St. George, situated in the Island called _Pico_, one of the Azòres; the Writer of this Account asserts, from the Mouth of an able and experienced Officer in his +Majesty’s+ _Navy_, who, during the last War, cruized some Weeks off those Islands; that the latter has frequently observed the Peak, at the Distance of 120 Miles, and coud then distinguish a _third_ Part of its Height _down_ the Mountain. Section 126, Note (_a_), see also [46] below. 4. Etna is 3877 Yards above the Mediterranean: (according to Brydone’s Tour throu’ Sicily and Malta, Vol. 1. Page 211) or 2 Miles and 357 Yards. 5. Blue Ridge, the highest Mountain in the Island of Jamaica, is, according to Dr. Clark, who measured it in November last, 3080 Yards, or 1 Mile and three Quarters, above the Level of the Ocean. The +distance+ to be +seen+ is considered as terminating the Radius of a Circle, whose Center is the +eye+ of the Observer, on _each_ Mountain. _Height of the Mountains._ +distance+ _to be_ +seen+ _from them in Miles_. _Cotopàzy_ 3 Miles and a Half and } 92 Yards, (for the Process, } 167½ and 405 see Section 52, Note (_a_)). } Yards. _White Mountain_ 3 Miles within } 153¼ and 13 60 Yards. } Yards. _Peak of Teneriffe_ 3 Miles within } 152 within 72 148 Yards. } Yards. _Mount Etna_ 2 Miles and 357 } 132 and 127 Yards. } Yards. _Blue Ridge_ 1 Mile and 3 Quarters. } 117¾ and 30 } Yards. _Balloon_ 1 Mile and half within } 102¼ and 307 33 Yards. } Yards. As it is well known that Objects of the _greatest_ Magnitude appear but as +blue air+ at even a _less_ Distance than 100 Miles; to which add the Difficulty of Journies, and Ascent to the Summit of these astonishing Mounds of Earth; and all this for the Sake, not of a complete +down prospect+, subject to _a perpetual Variety_, but merely an _imperfect Side-View_: the +pleasure+ and +ease+ of attaining still _more_ stupendous Heights at _any_ Place and Time, by Means of the +balloon+, are strikingly in Favor of that Invention. And, notwithstanding the confessed Merit of Dr. Black’s Project with the _Farciminàlis_ of a Calf, and Mr. Cavallo’s Soap Bubbles with inflammable Air; (see his History of Aerostation, Page 34;) if the Emperor had been alive who offered a Reward for the Invention of a _NEW PLEASURE_; the _first_ Prize had been due to the Brothers Montgolfier, and a _second_ to the Brothers Roberts. [46] As therefore it may be supposed that the Peak of St. George, in _receding_ from it, woud _vanish_ at the Distance of 150 Miles; its Height may _easily_ be ascertained geometrically thus: [Illustration] See the Figure annexed. Let M be the Summit of the Mountain: and let the Line M T drawn to the Circumference of the Circle at T, be the _evanescent_ Distance of the Mountain in the Horizon, viz. 150 Miles. Join T C, viz. a Line drawn from the _Tangent_ to the Center of the Circle, which Line will therefore represent the Semidiameter of the _Earth_, viz. 3958 Miles, according to Newton. Draw a Line from C to M, which will pass throu’ some Point of the Circumference as H, the Base of the Mountain. Then, in the Triangle M T C, as the Angle at T is a right Angle (Euclid’s Elements, Book 3, Proposition 18;) and the Sides M T, and T C, containing the right Angle, are _known_; the _third_ Side C M is readily found: (being a Corollary to the 47th Prop. 1st Book Euclid:) viz. having the two Sides of a right Angle Triangle given to find the _third_. Therefore RULE. Multiply the Sides containing the right Angle, each into itself: viz. 150 and 3958: add the Products into one Sum: from which extract the _square Root_; _equal_ to the Length in Miles, of the _third_ Side required. From the _third_ Side, subtract that Part, viz. C H, which is equal to the Semidiameter T C already found: and the Remainder H M is the _Height of the Mountain_. Thus: 150 Miles. 3958 Miles in the Semidiameter of 150 3958 the Earth. ——— ———— 7500 31664 15 19790 ————— 35622 22500 11874 Square of the ———————— greatest visible 15665764 Square of the Semidiameter Distance. add 22500 of the Earth. ———————— Extract the sq. Root, 15688264 ( 3960.84 Square Root. 9 3958 subtract. —— ———— 69) 668 Rem. 2.84 Answer in Miles. 621 ——— 786) 478.2 471 6 ————— 79208) 6664.00 continued to 2 Decimals. 6336 64 ——————— 792164) 32736.00 ditto. 31686 56 ———————— 104944 To find the .84 Part of a Mile; multiply 1760 Yards in a Mile, Decimal Parts of a Mile to be reduced .84 into Yards. ———— 7040 14080 —————— 1760)1478.40(0 Subtract 1478 ———— 282 Answer: the Height of the Mountain is 2 Miles 282 Yards. [47] Rays flowing from the Sun seem to be +red orange+ or +yellow+, according to the Quantity of Vapours floating in the Atmosphere, which absorbs the most refrangible ones: and the fewer the Vapours the more does the Sun’s Light approach to a perfect and intense +white+, according to the Doctrine of Newton: which seems to receive Confirmation from the Purity of the Solar Light, when seen _above Clouds_ and _Vapours_, in the Balloon: where the Sun shines not so much with a _golden_ as with a _sparkling_ +silver+ Light. [48] +Sounds immediately under+ the Balloon, seemed, as if originated _near_ the Ear, and _louder_ than they would have been heard, at the Distance of some Yards _only_, when on a Level with themselves: augmenting rather than decreasing, during the _Ascent_ of the Balloon, till it arrived to a Height indicated by the Barometer at 27 Inches. Presently afterwards, the Balloon still rising; the Sounds _died away_: much sooner indeed than was expected. The like was observed in _descending_ from a State of perfect Tranquillity and Silence: _Sounds_ from _below_, when about the same Height, _suddenly rushing_ on the Ear. It must be considered that by _this_ Time, the +shadows+ were much encreased; tho’ at half past II, they were _more_ than double in Length to the Height of each Object. The Trees woud therefore spread a +shade+ _across_ the Road. The +tops+ of the _Houses_ likewise, being Part of them in the Shade; and either _thatched_ with Straw, or covered with Slates of a _dusky_ Hue; woud prevent their _throwing off_ any _striking_ Colour. Possibly the _Encrease_ of Shade _alone_, might give the Face of the Country _below_, a _dark-green_ Cast. It is certain that the Height of the Balloon must have been very great, to prevent the Sight of public and _Turnpike-Roads_, _above_ which it _frequently_ passed, and which had been +plainly+ seen _before_ the _Re-ascent_. For suppose the Road but 5 Yards wide, which is less than the Truth; if it be allowed that an Object may be distinguished by a _sharp_-sighted Person, when its _Distance_ from the Eye does not _exceed_ 5156 Times the Diameter of the Object; i.e. when the Object does not subtend a _less_ Angle at the Eye than _30 Seconds_ of a Circle, (Smith’s Optics, Article 97) which is the _smallest_ visible Point, and equal to the 8000th Part of an Inch on the _Retina_;—by multiplying 5 Yards, viz. the Diameter of the public Road, into 5156 (or, in round Numbers, into 5000) Times its Distance from the Eye in the Balloon; the Product is 25000 Yards: which Product being divided by 1760, the Number of Yards in a Mile, amounts to 14 Miles, and 360 Yards. Supposing farther, that a _common_ Eye can _only_ see an Object at _half_ that Distance; the Height woud _then_ be 7 Miles. The _Improbability_, therefore, (on Account of the _Warmth_ of the Air at that Height, viz. 60°;) of having _soared_ to so great an Altitude, seems to point out, that the +shadows+ must have contributed a _principal_ Share, in preventing a Sight of the public and _Turnpike_ Roads. [49] The +magnitude+ of an Object _decreases_, as the +squares+ of its Distance from the Eye _increase_. At whatever Distance, for Example, the Eye can see any Object clearly; as at the Distance of a Foot, or a Yard, if the Object be removed to _twice_ that Distance; it will appear 4 Times smaller than it did before: 2 multiplied into 2, equals 4, which is the Square of 2: in the same Manner, if the Object be removed to thrice the Distance from the Eye, it will appear 9 Times as small, as at the first Distance: for 3 into 3 gives 9, the Square of 3: and so of any farther Distance. [50] See “Berkeley’s New Theory of Vision, Section 67.” [51] Dr. Smith having Recourse to _intervening Objects_; the Writer cannot assent to the Validity of his Argument, illustrated by a well-known Figure, to solve the Appearance of the _horizontal Moon_. See “Priestley’s History of Light and Colours, Page 712.” [52] Phil. Trans. for 1785, Part 1, Page 287. [53] Cavallo’s Treatise on Air, Page 576. Vitriolic Acid Air, Alkaline Air, and other elastic Fluids, are instantly +absorbed+ by _Water_; (Page 673.) Inflammable Air, and fixed Air, are likewise +absorbed+ by +water+. (Page 434). [54] Nam fit, ut interdum tanquam demissâ Columnâ In Mare de Cœlo descendat.—Lucr. L. 6. V. 425. _Una_ Eurus Notusque ruunt, creberque Procellis Africus. Also Omnia Ventorum _concurrere_ Prælia vidi. +Virgil.+ [55] Franklin’s Account of Whirlwinds and Waterspouts, in his Miscellaneous Tracts. Lowthorp’s Abridgement of Phil. Trans. Vol. 2. Page 103. Varenius Geogr. Gen. C. 21, Pag. 265. A clear Account of the Effects of a +depression+ is to be met with in “the History of Jamaica, in 3 vols. vol. 3. Page 800, on _Trade and Land Winds_.” [56] Mons. Maupertius has found, that the extreme Cold at Tornea, in the northern Regions beyond the Artic Circle, came directly from _above_: see “La Figure de la Terre,” Page 59. Il semble que le vent souffle—de tous Côtés à la Fois; et il lance la _Neige_ avec une telle Impetuosité, qu’en un Moment tous les Chemins font perdus. “It seems that the Wind blows from all Points of the Compass at once,” &c. [57] The Doctrine of smokey Chimnies distinctly treated of under the Article +smoke+, in the Encyclopædia Britannica, may receive some Improvement, from Circumstances which ascertain the sudden Descent, Elevation, and quick Depression of _Columns_ or rather _Torrents_ of Air, viz. by widening the Tubes, and covering their Tops. [58] It is thought more _candid_, and will to _many_ be more _satisfactory_; to make occasional References to different Authors who have treated distinctly on a Subject, and leave the Reader to draw his own Conclusions by applying to their _express_ Words;—than, either to insert abundant Quotations; or _weave_ their Thoughts into the _Texture_ of the Work: which must encrease its Bulk, without producing any Thing either new or instructive. [59] Once, particularly, in the Month of January, at Lausanne: Farenheit’s Thermometer at 7 only: the Country covered with Snow; and a North Wind beating +violently+ on the Lake, which continued liquid without Ice: owing, perhaps, in _Part_, to subterranean Heat, and Exhalations. [60] The Depression and Reverberation of the Wind near Rivers, and its Descent from Mountains, _a Point to be discussed_, may furnish a Hint and Reason, why Rain falls more in one Place, than in another not far distant: and why in the same Place it falls in different Quantities, at different Heights, irregularly. [61] Cavallo’s Treatise on Air, Page 446.—— [62] 442.—— [63] 441.—— [64] 442. [65] It is _light_ in Consequence of its _Warmth_, when compared with the _cooler condensed Air_ above it. [66] In the same Manner that Curls and Streams of Air _descended_ into the Bason over the rising _Steam_, and interrupted the Regularity of _its_ Elevation; in the _larger_ Towns, during Winter (_the Weather being moderate_) the Pressure of Air on all Sides, from without, produces a constant Breeze towards the Center of the Town: as may be discovered, not only by the Smoke in its Deviation from the Perpendicular, as it issues from the Chimneys; but by all who are inclined to make the Trial; for, on leaving the Town, they will _meet_ the Breeze. In calm Weather, during Summer, the contrary Event happens: but more particularly in _hot_ Climates. For the Country being hotter than the Town; a _Depression_ of the Atmosphere takes Place, and scatters the Smoke on all Sides round the Town. The Cities in Italy, and other hot Climates, on Account of the Buildings, and _desirable_ Narrowness of the Streets, form _one_ contiguous _Shelter_, _Arbor_, or grand _Parasol_: For which Reason, the Nobility leave the Country, and reside in the Towns during Summer: there finding a Coolness and Refreshment unknown on the _scorching_ Plains. A _Reception_ and _Dispersion_ of Air takes Place; _as will presently be mentioned_. The same ocular Proof and Process in the Evaporation of Steam, accounts at once, for a curious Phenomenon constantly observable on all Waters; viz. _a narrow_ +smooth+ _irregular Surface of considerable Length, nearly in the Direction of the Wind, yet unaffected by it_: all which is probably nothing more than _rising_ Volumes of _elastic invisible_ Steam; _resisting_ the _two_ nearest _descending Waves_ of +air+; and preventing them from approaching the _Surface_ of Water, over which the Steam is compressed; and _there_ producing a _temporary_ +calm+. [67] Phil. Trans. for 1777, Page 470. Thibet in Lat. 31, _cold_ with Snow and Frost. See Ullòa’s Voyage to South-America, Book 6, Chapter 7; where he describes the snowy Mountains, under the Equator. As the Weather, near the Equinoctial, is more regular, its Changes closely following those of the Moon; and also the Winds and Hurricanes more violent; the Truth of the foregoing Theory will receive the strongest Confirmation by tracing the Effects of +depressing torrents of air+, in the Island of Jamaica, extracted from the Author already mentioned. “The cool Vapour _rushes_ from the Mountains towards the hot dry Air, which hovers over the Savannahs or Vallies. The Rain falls heaviest in the Mountains. Vol. 3, Page 600. The _Land-Wind_ after Rain, proceeds from that Quarter whence the Rain has fallen _heaviest_; and seems to _rush_ from above. In Spain and North-America, the Wind _rushes down_. Page 601. When the _Land_ is _most_ heated, the Sea-Breeze blows almost _all_ Night. Page 602. The Barometer subsides from 1 Inch to 1½ _at_ the full Moon, or just _after_ it. Wind blows from the Mountains all round the Island: and still a Sea-Breeze over the Mountains: to the Low-Lands, none, 604. (In Jamaica likewise the Wind blows off the Island _every way_ at once, so that no Ship can any where come in by Night, or go out but early in the Morning, before the Sea-Breeze sets in. See Abr. Phil. Tr. Vol. 3, P. 548.) _Mountain Air rushes down in a continual Current to every Part of the Coast, the Stream descending incessantly throu’ the Night: while heavy cold Air descends to the Mountain Tops_, 604. With a _West_ Wind below there is an _East Scud above_, 605. _Mountains_ +cloudy+, _low Lands_ +sunny+. 606. In +all+ _the River-Courses of Jamaica, there is a sensible Current of Air. Rain never comes without some Wind: and the Showers almost invariably follow the very Meanders of the larger Rivers_, 608. Rain always cools: the Thermometer falling, after a Shower, from 6 to 8 Degrees, 610. (And Iron rusts least in rainy Weather: [the Air being then +driest+,] descending from the _upper_ Regions. Abr. Ph. Tr. V. 3, P. 546.)” It is said also that “in Jamaica the Clouds gather, and _shape_ according to the Mountains: so that _old Seamen_ will tell you each _Island_ towards Evening, by the _Shape_ of the Cloud _over_ it.” The Sea-Breeze, being counterpoised by _Descent_ of the _etherial Air_, produces a +calm+. The same Author likewise says, that “the Clouds begin to gather about 2 or 3 o’Clock in the Afternoon _at the Mountains_, and do not _embody_ first in the Air, and after settle there, but _settle_ first and _embody_ there: the rest of the Sky being clear till _Sun-set_. So that they do not pass _near_ the Earth in a _Body_, and only _stop_ where they meet with Parts of the Earth elevated _above the rest_; but +precipitate+ _from a very great Height_, and in Particles of an _exceeding rarified Nature_; _so as not to obscure the Air or Sky at all_: that great Variety of beautiful Colours in the Canopy of Heaven being raised to a much greater Distance [he means Height] in Jamaica than it is here.” Abr. Ph. Tr. V. 3, P. 557. (Prognostics of Weather, at certain Periods of the Moon, are mentioned by Captain Langford. Lowthorp’s Abr. Phil. Trans. Vol. 2, Page 105.) [68] The Depression of a _Torrent_ of Air in the Form of an hyperbolic Solid, _contracting_ as it _descends_ to the Earth, in Proportion as its _Density_ encreases; may furnish a Hint towards the Solution of a Difficulty how to account for the Augmentation of vesiculous Vapours into large solid Drops, frequent during _Summer_-Showers. [69] Mons. Saussure’s valuable “Essais sur L’Hygrometrie,” throw new Light on the Doctrine of Rarefaction and Condensation not unfavourable to the Hypothesis here advanced. Page 260. [70] Ice, when exposed to marine acid Air, is dissolved by it, as fast as if it touched a red hot Iron. See Cavallo’s Treatise on Air, Page 727. Also Priestley’s Experiments and Observations, Vol. 1, Page 148. [71] “The +water+ remains +transparent+ or colourless, tho’ saturated with marine acid Air, and by a very gentle Degree of Heat, the Gass may be again expelled from it, as it is expelled from Spirit of Salt.” This Observation is applicable to the Transparency of Vapours, in the Air, tho’ mixed with the marine Acid exhaled from the Sea: for when the acid or Sea Air is mixed with Alkaline or Land Air, they instantly _combine_; lose their Elasticity, and form a _white_ visible Substance or _Cloud_. Cavallo, Page 728. Priestley’s Exp. and Obs. Vol. 2, Page 293. [72] On the Descent of Air in _Thunder-Gusts_, see “Chalmer’s Account of the Weather in South-Carolina, Vol. 1, Page 1, to 39.” [73] “Historia Ventorum, Pag. 54, Art. 34.” [74] Book V. Chapter 2d. [75] Vol. 1. Page 184. [76] Page 195. [77] History of the Canary Isles, Page 252. [78] As the superior Clouds, during the Balloon Excursion, did not much exceed the Height of 1000 Yards; supposing then the Clouds at an equal Height above the Sea, near Teneriffe; one ought to conclude, either, that the Peak was not so high as Glas represents it; or, that the Level of the Clouds was less than half the Height of the Mountain. [79] See “Royal Astronomer, by R. Heath, Page 321, on _Trade Winds and Monsoons_.” [80] One Pound of Nitre only, producing by mere Heat, 6 cubic Feet of Air. “Cavallo, Page 332, and 811, Experiments on Gun-Powder.” [81] “See Recherches surles Modifications de l’Atmosphere. No. 715.” Ph. Trans. Part 2, for 1777. Col. Roy’s Experiments, Sect. 2d, Page 689, 744, 753, 764. [82] The different Phenomena of the _Aurora Borealis_ may be owing to the Ascent and Motion of the Apogay, in the _middle_ Region, over the Stratum of Eknèfiai or _Ground_-Winds. The Effects of _Tides in the Air yet to be_ mentioned, must not, however, be wholly excluded. The Aurora Borealis is seen in _Spring_, _Autumn_, and _Winter_: sometimes _culminating_, sometimes moving in _Streams_ and _Waves_ in the _superior_ Regions of the Atmosphere: when culminating; as if rising out of Clouds in the North. This Appearance may be owing to warm moist Air perpetually generating between the Tropics, and rolling over the cold _dry_ Stratum of Eknèfiai Winds, which cut off its Communication with the Earth: till accumulating over the Poles, it enlightens the Atmosphere, converting a six _Month’s Night_ into Day; and returns to the Surface silently: or in Lightning, whenever it is communicated to the Earth, throu’ _Vapour descending_ by its own specific Gravity; or along with _depressing_ Torrents of Air, known to be accompanied by frequent +flashes+. When the Vapour is _condensed_ in its Descent, by passing throu’ a Stratum of the Eknèfiai Winds; it becomes _overcharged_ with the electric Matter, _surrounding_ and _adhering_ to it; and deposits the Overplus in Lightning, on its Approach to _other_ Clouds, or to the _Earth_. It is visible in the Form of a Vapour, when the Vapour to which it adheres, becomes overcharged with electric Matter, by Descent into a _cool_ Eknèfiai Stratum below: there forming a luminous and transparent Atmosphere: the Particles of Light and Vapour being repelled to great Distances from each other at so _rare_ a Height. It culminates above the Vapour, because less heavy than the circumambient Air: and may be subject to the Attraction of other Planets. The Aurora Borealis is also seen to issue in Streams and Waves of Light, with inexpressible Velocity, on its Return to the South, in a lower Stratum, as it _passes throu’_ Interstices, between the Vesicles of warm Vapour, raised and dispersed by the turbulent Apogay Winds, in the middle Region. During Summer, the middle Region becomes blended with the lower, throu’ Defect of Cold: and the electric Matter is supposed to be communicated to the Earth, silently, and continually; but by Lightning, when a lower and colder Atmosphere condenses and overcharges the Vapour, and cuts off the Communication. It cannot be seen but in escaping from Vesicle to Vesicle: nor, during Summer, after Sunset, on Account of the Twilight. [83] Air is not unfit for Respiration, by having lost its _vital_ Principle, but because it has imbibed _Floguiston_, which cannot _easily_ be separated from it, but by Agitation in Water. Cavallo, on Air, Pages 479, 670. [84] For if Moisture be one Cause, which keeps the Particles of Air at greater Distances from each other; this Cause decreases at _great_ Altitudes. If also the _Elasticity_ decreases in Proportion, not only to the Height, but the Driness; its Particles must, on both Accounts, approach each other, at great Altitudes: tho’, from the Altitude only; they woud separate according to the Rule, viz. that the Rarity of the Air is proportionable to the Relaxation of the Force compressing it. So that at the Height of 8 or 10 Miles, a Quantity of Air taken from the Surface of the Earth, woud occupy 6 Times its former Space: supposing the Air both below and above to be of the _same Kind_, as well as of the _same mean_ Temperature of 55, on the Thermometer. See “Martin’s Philosophical Grammar, Page 178.” [85] Chalmer describing a Whirlwind, which is a _Storm_ of +collection+ and _Ascent_ of +hot+ Air, &c. by Rarefaction, says, “as the Wind ceased, presently after the Whirlwind passed, the +branches+ and Leaves of various Sorts of Trees, which had been carried into the Air, continued to +fall+ for +half an hour+; and, in their Descent, appeared like Flocks of Birds of different Sizes.” This Circumstance proves that Columns of +hot+ Air must have been raised in a Body, in Succession, to so considerable a Height, that _Branches_ of Trees carried up by them, took _half an Hour_ in falling. [86] It may be from this Principle, that in the East, Liquids are kept _cool_ by being hung in the Shade, in the _open_ Air, suspended in _wet Cloths_: there being a continual Breeze and Succession of +cool dry+ _Spunges_ (as it were) of Air, in Contact with the _wetted_ Cloths, whose Moisture will thus be more quickly evaporated. [87] Historia Ventorum, Pag. 48, Art. 33. [88] “Cum enim (Venti) Choreas ducant, Ordinem Saltationis nosse jucundum fuerit. Art. 18.” [89] On the Action of the Sun and Moon over Animal Bodies, by Dr. Mead, Miscell. Cur. Vol. 1. P. 372, 373. [90] For these Observations see Gassendus’s Natural Philosophy. De Chales’s Navigator. And Astro-Meteoro-Logica, per J. Goad. [91] See Maclaurin’s Newton, Page 376. [92] Air at a Medium is 800 Times _rarer_ than Water: so that if 800 Times the Quantity of Air _naturally_ contained in a Vessel whose Dimensions are those of a cubic Foot, were pressed into it by a Syringe or _Condenser_, the Air woud differ nothing from Water in Density. [93] See Wilson on Climate, Chap. 15. Pages 46, 54. [94] 55. [95] By reducing 10 Feet 6 Inches, and 6 Feet 7 Inches, into Inches, and dividing by common Divisors, as 3 and 2; it is found that 10 Feet 6 Inches, will be to 6 Feet 7 Inches, as 3 to 2 nearly: that is, as 15 Miles to 10 Miles. [96] White’s Ephèmeris, Page 38, for the Speculum Phenomenorum, or Mirror of the Heavens. [97] See the Book which gives an Account of Walker’s Eidouranion. The _intelligent_ Reader will easily distinguish the Effects, attributed to the Planets, viz. their mutual Attractions, owing to natural Causes only;—from the futile Ravings of judicial Astrology. [98] See London Chronicle, 26th July, 1785. [99] To find the Direction of an upper Current, without the Inconvenience of rising above the Level which the Aironaut has fixed on. This the Abbé Bertholon has hinted at, by Means of a smaller Balloon. The Dimensions of which, must however be so large; that, allowing for the Evaporation of Gass, it will _just_ rise with the Weight of a Quantity of Cord, a Mile and half, for Instance, in Length: and have sufficient Room left within, to admit of the Expansion of Gass without Rupture. The Pioneer-Balloon may be taken up, _empty_, and filled with Gass necessarily escaping from +the mouth+ of the _great Balloon_, when stationary: and may be sent up with a Cord, fastened to the Center above the Car of the _great Balloon_, to reconnoitre the _superior_ Currents: or it may be only filled _in Part_; and made to _descend_, and _discover_ the _lower_ Currents. See “Des Avantages de Ballons, &c. Page 72.” [100] As the _Heights_ of the Atmosphere encrease in an _arithmetical_ Progression; the Densities are said to encrease in a _geometrical_ Progression: which is a mathematical and pedantic Mode of Expression. For _arithmetical_ Progression _here_ means no more than the Height of 1, 2, 3, 4, 5, 6, &c. &c. Yards, Fathoms, Roods, or any other equal Interval. If then at the Height of one Yard, the Balloon has acquired (suppose) the Levity of 1 Pound; then, if this Levity encreases in geometrical Progression; (as twice 1 is 2,) it will, at the Height of 2 Yards, have encreased to 2 Pounds: and, as twice 2 is 4;) it will, at the Height of 3 Yards, have encreased to 4 Pounds: and, as (as twice 4 is 8;) it will, at the Height of 4 Yards, have encreased to 8 Pounds: and, (as twice 8 is 16;) it will, at the Height of 5 Yards, have encreased to 16: and, (as twice 16 is 32;) the Levity will, at the Height of 6 Yards, have encreased to 32 Pounds; and so on, _doubling_ the preceding Number; at the Height of each Yard, Fathom, Rood, Mile, &c. &c. [101] _Whiston’s_ Tacquet’s Euclid, Book XI. Definition of a _right_ Cylinder, Art. 3, Page 166. [102] Archimedes’s Theorems. Proposition 33, 34; at the End of _Whiston’s_ Euclid, Page 42. [103] Inferred in the Chester Chronicle, Sept. 30, 1785. [104] The Writer not having yet been able to procure it from the London Booksellers. [105] See Chambers’s Dictionary under the Article +resistence+. [106] See his “Navires des Anciens.” [107] See “Gordon’s Principles of Naval Architecture.” Also the Balzaes and Guaraes, in Ullòa’s Voyage to America, Book 4, Chapter 9, Vol. 1, Page 183. [108] Mons. Carra proposed to ascend with two Balloons. One, a seventh Part less than the other, is to be connected by a Rope, throu’ a Pulley fixed in the equatorial Hoop of the great Balloon, to a Reel in the Center of the Car: in descending, the Reel is to be unwound: the great Balloon and Car will therefore descend, while the small Balloon remains in the Air. The Scheme is certainly practicable. See the Cut in the London Magazine for June, 1784. [109] See “Lewis’s Commerce of the Arts.” [110] See Priestley’s numerous Experiments: and that Library of _curious Investigation_, the Philosophical Transactions. [111] And _Magnitude_ of distant Objects. Bacon says that Objects are more _visible_ in an East Wind, and Sounds more _audible_ in a West Wind; being heard at a _greater_ Distance. “Historia Ventorum, P. 37, Art. 31.” [112] See Le Roi’s Uses of the airostatic Globe _at Sea_, in his “Navires des Anciens, Page 225.” [113] The _natural Figure_ of the _Dìodon-Globe-Fish_, a coloured Print of which is given in “Martyn’s new and elegant Dictionary of natural History:” where it is described as follows: “The Form of the Body is usually oblong: but when the Creature is alarmed, it possesses the Power of _inflating_ its Belly to a globular Shape of great Size;”—seems to furnish a Hint for the proper Figure of a Balloon, when the Art is more improved. The Balloon, as far as it is meant to resemble the upper Part of the Fish, is to be made stiff, with Pasteboard or _Papier-mâchè_ varnished; for, being strong, and in a permanent Form, it is more capable of continuing Air-tight: the lower Parts being _flaccid_, will be inflated, as the Balloon rises, and deflated during the Descent. Rowers, and propulsive Machinery, are to be fixed within the Fish, in Place of the Fins: and Goods of +greater+ Weight placed in a covered Car below: the Air-Bottle-Balloon being fixed between both. [114] And by _Kunckel’s_ or _Canton’s_ Phosphorus, See “Priestley’s History of +light+. Pages 585, 370.” [115] This was owing to the cool Air rushing in to supply the Tendency to a Vacuum by the Expansion of hot Steam, with the extricated Gass. The Accident proves that no Danger is to be dreaded from +expansion+ of the Gass. [116] From _Bersham-Forge_ near _Wrexham_, where there is always a sufficient Quantity. [117] The _detached_ Thermometer might be protected from the _Sun_, by being swung a few Inches _below_ the Car of the Balloon by means of an _Opening_ made purposely throu’ the Center of the Car. [118] _Foundation of the first Table._ (Ph. Tr. for 1777, Part 2d, Page 567.)—It was found by Experiment that the Decimal .000262 was the Expansion _on_ 30 Inches of Quicksilver, _with_ each Degree of Temperature from freezing to boiling Water: also, the Decimal .000042 was the Expansion _on_ 30 Inches of the Glass Tube (containing the Quicksilver), _with_ each Degree of ——————— Temperature: therefore by Addition, .000304 or by taking only 4 Decimals, .0003 is the Expansion _on_ 30 Inches of Quicksilver, and the Glass Tube containing it, _with_ each Degree of Temperature. _Construction of the first Table._ Thus any vertical Number, shewing the Expansion, may be readily _formed_, by _doubling_, _first_, the Number immediately under each Inch for the Expansion below it: and _afterwards_, by adding the Number immediately under each Inch, to the Expansion last found. Note: The vertical Columns, below each Inch of Quicksilver shew the Expansion _on_ that Inch, _with_ corresponding Degrees of Temperature indicated by the Thermometer in the Column to the left Hand. Example: to find the Expansion _on_ 30 Inches of Quicksilver _with_ 1 Degree of Temperature: the Answer in the Table is .003: i.e. such Expansion raises the Quicksilver the 3000th Part of an Inch. [119] There is seldom Occasion to take more than the four first Decimals out of the Table, the Remainder being of _little value_. [120] _The Foundation of the second Table._ This Table is calculated from Briggs’s Logarithms: each Number, in the second Column, being nothing more than the Logarithm—corresponding to the Point, (in the _first_ Column,) at which the Quicksilver stands in the barometric Tube,—subtracted from the Logarithm of 32 Inches multiplied by 6. _Construction of the second Table._ This Table consists of three _vertical_ Columns only: tho’ _here tripled_, for the greater Convenience of Inspection. The first or left Hand Column shews, in Inches and Tenths (from ten Inches) the Gradations of the Quicksilver in the barometric Tube, beginning as low as one Inch above the Surface in the Cistern, and proceeding throu’ all the intermediate Points, to the unusual Extent of 32 Inches:[121] supposing likewise that the Tube is elevated in the Atmosphere, so that the contained Quicksilver, when exposed to the Temperature of 31°.24 of Farenheit, rests at each Point in the Table. The second vertical Column gives the different Heights in Feet and Tenths, to which the barometric Tube must be raised above its Level at 32 Inches, in order that the contained Quicksilver, if exposed to the Temperature of 31°.24 of Farenheit, may stand at each Point indicated in the first Column. The third vertical Column, gives, likewise in Feet and Tenths, the +difference+ between each two adjoining Heights in the second Column, corresponding to a single Tenth (of Quicksilver): which single Tenth is the Difference between each two adjoining Tenths of an Inch in the first Column. For Example: Suppose the Quicksilver in the barometric Tube, in the first Column, stands at Inches 16.1 answering to 19570.4 } Height in Feet And again at 16.2 answering to 19398.4 } in the Atmosphere. ——————— _Difference_ of .1 in Feet: remaining = 172.0 which sixteen Inches two Tenths, is a single Tenth more than sixteen Inches one Tenth, and will therefore answer to a _less_ Height in the Atmosphere by that single Tenth; considering that the lower the Quicksilver falls in the Tube, the higher must the Barometer itself be raised in the Atmosphere, in order that the Quicksilver may rest at the lower Points of the Tube. If therefore a _less_ Height in the Atmosphere be required which shall answer to one Tenth more than 16 Inches two Tenths; subtract the Height answering to 16.2 from the Height answering to 16.1, i.e. subtract the _less_ Height from the _greater_, and the Remainder gives that _less_ Height in the third Column, answering to the Height of one Tenth more than 16 Inches 2 Tenths, of the Barometer. [121] _The Barometer, (to which the Scale of Heights is applied, in the 2d Column of the 2d Table) is supposed to be sunk within the Surface of the Earth, till the Quicksilver rests at 32 Inches, as appears from the last Article in the table, viz. 32 Inches, 0.00 Feet. 32 Inches is therefore the Foundation of the Table, and corresponds, according to Shuckburgh, to 1647 Feet, under the Surface of the Sea, at low Water._ This Depth _then being_ the imaginary Level _pointed out by the Quicksilver, at the_ unusual _Extent of 32 Inches_; _each_ interior _Inch and Tenth of Quicksilver will correspond to a_ superior _Elevation of the Instrument, in Feet and Tenths above that Level, and will include the Mensuration of the deepest Mines._ _For the_ mean _Pressure of the Barometer, at low Water, from 132 Observations in Italy and England, is 30.04 Inches: the Temperature of the Barometer being at 55°, i.e. Temperate, and that of the Air at 62°._ [122] _Foundation of the Table for Tenths._ The Height, in _Feet_, corresponding to the Expansion on the Tenth of an inch of Quicksilver with the Temperature of 31°.24 (as in the 3d Column of the 2d Table) are reduced by this Table into a ten Times less Number of Feet; and the Tenth of an Inch (of Quicksilver) is also again divided into _ten_ more Parts: in order to shew, in a ten Times less Number of _such_ Feet, the Expansion corresponding to any of those Parts into which the _Tenth_ of an Inch (of Quicksilver) has been divided. _Construction and Use of the Table for Tenths._ 1. The Figures in the left vertical Column shew the Height in _Feet_, (from 81 to 130) corresponding to a single Tenth of an Inch of Quicksilver, viz. to the higher of two adjoining Tenths, as in the 3d Column of the 2d Table. 2. The Figures, along the upper horizontal Line, shew the Number of Parts into which the Tenth of an Inch has been divided. 3. The Figures, at the Point of Meeting, express, in a ten Times less Number, of _the Feet_ in the left vertical Column, the Expansion corresponding to any of those Parts, into which the Tenth of an Inch (of Quicksilver) has been divided. Thus: 90 is a _Number of Feet_ called 9 Tenths of 100: but the _Tenths_ are _Feet_, and not Tenths of a Foot. [123] The Standard Temperature was 31°.24, which not being exactly 1 Quarter, another Decimal is added, (for Ease in Computation,) by which 31.24 becomes 31.25, i.e. by dividing one Degree of Heat into 100 Parts, and taking 25 of those Parts, or dividing the 100 by 25, the Answer is 4, i.e. ¼ of the whole 100: or (31)¼. [124] _The Foundation of the fourth Table._ (Ph. Tr. for 1777, Part 2d, Pages 564, and 566,)—From the _Mean_ of a Series of Experiments with a Manòmeter, or Instrument to measure the _Rarity_ and Density of the Atmosphere, depending on the Action of _Heat_ and Cold, it was found, that when the _Portion of a Tube_ containing Air (at the Temperature of freezing by Farenheit, and Pressure of 30½ Inches[125] by a common Barometer) was divided into 1000 Parts; the Volume of _Air_ within it, encreased _nearly_ in a certain Proportion, as each Degree of Temperature encreased; viz. at a Mean, 2.43, or simply (by rejecting the 2d Decimal as too minute) 2.4: that is, a 1000 Parts of Air became by Expansion with one Degree of the Thermometer, equal to 1002.43: i.e. the Portion of Air occupying 1000 Parts, did, with the Addition of one Degree of Heat, occupy 1002.43 Parts: that is (by rejecting the 2d Decimal 3 as too minute) occupied two Parts and 4 Tenths more than the thousand. _Construction of the fourth Table._ Supposing therefore that the Portion of the Tube containing Air, was one Foot in Length of Height, divided also into a thousand Parts; one Degree of Heat would encrease or expand it two Parts and four Tenths more than the thousand Parts into which the Foot was divided. CAUTION. _The fourth Table properly consists of only nine horizontal Columns of thousands, in Breadth; which Columns are extended in Length to one hundred Lines, corresponding to 100 Degrees of Heat._ _The Table is here divided, in order that it may conform to the Size of the Pages: by which Means the Formation of each vertical Number by the following Rule, (which renders the Table_ self-evident_) might without this Caution, have been attended with some Difficulty._ The vertical Columns _below_ the Figures expressing each thousand, shew the Expansion of Air _on_ each respective thousand, _with_ the corresponding Degrees of Temperature indicated by the Thermometer in the vertical Column to the left Hand. Example the first: to find the Expansion of Air _on_ one thousand Feet, _with_ one Degree of Temperature; the Answer in the Table is 2.4, or 2.43: i.e. 2 Feet and 4 Tenths of a Foot, rejecting the 2d Decimal as too minute. Example the second: to find the Expansion _on_ 8 thousand Feet, _with_ 99 Degrees of Heat: the Answer is 1924.56: and so of the Rest. Thus _any_ of the _vertical Numbers_ shewing the Expansion, may be readily _formed_, by _doubling_, _first_, the Number immediately under each thousand in the horizontal Line, for the nine first thousands, (of which the Breadth of the Table properly consists, exclusive of the thermometric Column) for the Expansion below it: and, _afterwards_, for each Expansion immediately below the former, by adding, to the Expansion _last_ found, the Number immediately under its respective thousand. First Example: to find the vertical Number for the Expansion under the first thousand, viz. 1000, _with_ 2 Degrees of Heat: the Number under 1000 is 2.43: double this: and the Answer is 4.86. Second Example: suppose the Expansion _last_ found be that _on_ one thousand Feet _with_ 24 Degrees of Heat; viz. 58.32: and the Expansion _on_ the same thousand, _with_ one Degree of Heat more, viz. on 25 Degrees, be required; add the Expansion _on_ one thousand Feet, _with_ 24 Degrees, viz. 58.32 to the Expansion _on_ the same 1000, _with_ 1 Degree, viz. 2.43 ————— and the Answer is, by Addition, 60.75 Third Example: supposing the Expansion _last_ found to be the Expansion _on_ 9000 Feet _with_ 99 Degrees of Heat, which in the Table is 2165.1. It is required to find the Expansion _on_ the same 9000 Feet, with 100 Degrees of Heat; add to the Expansion last found, viz. 2165.13, the Expansion on the same 9000 Feet, viz. 21.87 with one Degree of Heat, and ——————— 2187.00 is the Answer by Addition. _Any vertical Number shewing the Expansion may_ likewise _be_ found, first, _by multiplying the first Figure, or Number, of the_ given _thousand Feet (in the horizontal Line,) into the Answer or Expansion on the_ first _thousand Feet, with one Degree of Heat: for Example_; To find the Expansion on 9000 Feet with one Degree of Heat. _The Expansion on 1000 Feet, with 1 Degree of Heat (from whence, all the other Expansions are derived) being 2.43; multiply that Number by 9, the first Figure of the given thousand Feet, and the Answer or Expansion with 1 Degree of Heat, is 21.87: hence all the Answers or Expansions_, immediately _under the horizontal Line of thousands, are_ formed. _Then 2dly, any other vertical Number or Expansion may be_ formed _by multiplying the Expansion_ immediately _under the_ given _thousand Feet in the horizontal Line, into the_ given _Number of Degrees: for Example_; To find the Expansion on 9000 Feet, with 50 Degrees. _The Expansion with one Degree on 9000, is 21.87: therefore the Expansion with 50°, is 50 Times more, viz. 1093.50, and so of the Rest._ _These different Methods serve to prove the Answers, and to elucidate the Table._ [125] _These Experiments were made with the Manòmeter when the Atmosphere was half an Inch heavier than in the Experiments to prove the Expansion of Quicksilver, the Barometer_ then _standing at 30 Inches only._ [126] There is _seldom_ Occasion to take more than the first Decimal out of the Table. [127] “RULE. “_Precept the 1st. With the Difference of the two Thermometers that give the Heat of the Barometer (and which for Distinction sake, are called the attached Thermometers) enter Table I, with the Degrees of Heat in the Column on the left Hand, and with the Height of the Barometer in Inches, in the horizontal Line at the Top; in the common Point of Meeting of the two Lines will be found the Correction for the Expansion of the Quicksilver by Heat, expressed in decimal Parts of an English Inch; which added to the coldest Barometer, or subtracted from the hottest, will give the Height of the two Barometers, such as would have obtained, had both Instruments been exposed to the same Temperature._ “_Precept the 2d. With these corrected Heights of the Barometers enter Table II, and take out respectively the Numbers corresponding to the nearest Tenth of an Inch; and if the Barometers, corrected as in the first Precept, are found to stand at an even Tenth, without any further Fraction, the Difference of these two tabular Numbers (found by subtracting the less from the greater) will give the approximate Height in English Feet. But if, as will commonly happen, the correct Height of the Barometers should not be at an even Tenth, write out the Difference for one entire Tenth, found in the Column adjoining, intitled_ Differences; _and with this Number enter Table III, of proportional Parts in the first vertical Column to the left Hand, or in the 11th Column; and, with the next Decimal, following the Tenths of an Inch in the Height of the Barometer (viz. the hundredths) enter the horizontal Line at the Top, the Point of meeting will give a certain Number of Feet, which write down by itself; do the same by the next decimal Figure in the Height of the_ _Barometer (viz. the thousandths of an Inch,) with this Difference, striking off the last Cypher to the right Hand for a Fraction; add together the two Numbers thus found in the Table of proportional Parts, and their Sum subduct from the tabular Numbers, just found in Table II; the Differences of the tabular Numbers, so diminished, will give the approximate Height in English Feet._ “_Precept the 3d. Add together the Degrees of the two detached or Air Thermometers, and divide their Sum by 2, the Quotient will be an intermediate Heat, and must be taken for the mean Temperature of the vertical Column of Air intercepted between the two Places of Observation: if this Temperature should be 31°¼ on the Thermometer, then will the approximate Height before found be the true Height; but if not, take its Difference from 31°¼, and with this Difference seek the Correction in Table IV, for the Expansion of Air, with the Number of Degrees in the vertical Column on the left Hand, and the approximate Height to the nearest thousand Feet in the horizontal Line at the Top; for the hundred Feet strike off one Cypher to the right Hand; for the Tens strike off two; for the Units three: the Sum of these several Numbers added to the approximate Height, if the Temperature be greater than 31°¼, subtracted if less, will give the correct Height in English Feet. An Example or two will make this quite plain._” [128] There is no Occasion to take more than four Decimals out of the Table. [129] See Section 368, Note (_a_). [130] Section 368, Note (_a_) on Note (_a_). [131] Taking one Decimal _only_ out of the Table. [132] +The question+: In the upper Gallery of the Dome of St. Peter’s Church at Rome, and 50 Feet below the Top of the Cross, the Barometer, from a Mean of several Observations, stood at Inches 29.5218 Tenths: the attached Thermometer being at Degrees 56.6 Tenths; and the Air-Thermometer at 57 Degrees: at the same Time that another, placed on the Banks of the River Tyber, one Foot above the Surface of the Water, stood at 30.0168, the attached Thermometer at 60°.6, and the Air-Thermometer at 60°.2: what, was the Height of the Building above the Level of the River? [133] See Section 375. 2dly. If the Moiety, _Half-Heat_, or mean Temperature of the Air, _is equal_ to the Standard-Temperature, to which the two Barometers are brought, by the 2d Table; the fourth Table, for _Expansion of Air_, is needless: the Height already found, in the 2d Table, being the _true_ Height of the _upper Station_. 3dly. If the Moiety, _Half-Heat_, or mean Temperature of the Air, is _less than_ the Standard-Temperature of 31°.24; subtract the mean Temperature from 31.24; and with the Remainder find the Expansion, as usual, by the 4th Table: subtract the Sum, (which is a corresponding Height in Feet and Tenths) from the Height in Feet and Tenths of the _upper_ Barometer, at the _Standard-Temperature_, in the 2d Table: and the Remainder will be the _true_ Height of the _Mountain_ or _upper Station_. Section 384, Note _a_. [134] +The question+: Near the Convent of St. Clare, in a Street called _La Strada dei Specchi_, at Rome, the _lower_ Barometer stood at 30.082, its attached Thermometer 71 Degrees, and detached ditto at 68 Degrees: on the Tarpeian Rock, or West-End of the famous Hill called The Capitol, the _upper_ Barometer was at 29.985, its attached Thermometer 70°.5, and detached ditto 76°: what was the Height of the Eminence? [135] Sadler’s _Practical Arithmetic_, Page 293. [136] The Writer has not hitherto been so fortunate as to meet with the original Memoir, containing the Particulars of this curious Experiment by Mons. Lavoisier. [137] Dr. Priestley’s Experiments and Observations relating to Air and Water. Ph. Tr. for 1785, Vol. 75, Part 1, Page 279. [138] The Diameter may be enlarged. [139] By Means of the Cradle, _both_ are more easily moved: the Muffle is prevented from adhering to the Tube; and Steam is admitted to the Borings. [140] Copper sustaining a _red_ Heat, better than Iron; the latter of which, _calcines_ with Steam, or, in cooling. Transcriber’s Notes: • Text enclosed by underscores is in italics (_italics_). • Text enclosed by pluses is in small caps (+small caps+). • Obvious typographical errors have been silently corrected. • Archaic language and spelling is left as-is, except “AERIAL” was printed with dots above the ‘A’ and ‘E’, this was assumed to be a typesetter's limitation and replaced with “AËRIAL", to match the lower case usage. • Errata have been applied, as much as I understood them. • Numbers for sections 259–261 are repeated. *** END OF THE PROJECT GUTENBERG EBOOK AIROPAIDIA *** Updated editions will replace the previous one—the old editions will be renamed. 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