AEROSTATION

47

air inclosed in any kind of covering be heated, and consequentlydilated to such a degree, as that the excess of the weight ot an- equalbulk of common air above the weight of the heated air, is greater thanthe weight of the covering'and its appendages this whole mass willascend in the atmosphere, till, by the cooling and condensation'of theincluded ah', or the diminished density of the surrounding air, it be-comes of the same specific gravity with the air in which it tloats; andwithout renewed lieu!, it will gradually descend. In like manneralso, if the covering be tilled with an elastic fluid, lighter than at-mospheric air, so that the excess of the weight of an equal bulk ofthe latter above that of the inclosed elastic fluid be greater thanthe weight of the covering and its appendages the whole mass willascend in the asmosphere, till it attains a height at winch the sur-rounding air is of the same specific gravity with itself- Inflam-mable air, or hydrogen gas, is a fluid of this kind. Mr. IlenryCavendish discovered that, if common air is -SOU times lighter thanwater, inflammable air is 7 times lip-liter than common air ; but itcommon air is 850 times lighter than water, then inflammable airis 10,8 times lighter than common air. Balloons have been con-structed both these ways, and are accordingly of two kinds, deno-minated live balloons, and air ballouns.

Mr. Cavendish suggested to l)r. Black, that perhaps a thin bagfdled with inflammable air might be buoyed up by the commonatmosphere. The same thought occurred afterwards to Mr. C'a-vallo l and he has the honour of being the first who made experi-ments on the subject, lie first tried bladders; but found themfoo heavy. lie then used Chinese paper; but that proved. per-meable to the air. His experiments, therefore, in 1782, proceed-ed no farther than blowing up soap bubbles with inflammable air,which ascended rapidly to the ceiling. _ About tins timethe two brothers Stephen and John Montgolfier, natives or An-nonav, constructed a balloon on the pvinc-iples of vaulred an.The experiment was made at Avignon with a tine silk bag; andby applying burning paper to an aperture at the bottom, the airwas rarilied, and the bag ascended to the height of 70 feet.—Various experiments were now tried upon a large scale, whichgreatly excited the public, curiosity.

On'the 5th of June 1783, they made an experiment at Anno-nay before a great concourse of people with a machine 35 feet indiameter, its cover was an immense bag of linen, lined with paper,containing upwards of 23,000 cubic feet, and raised a weight ofabout 500 pounds, including its own materials. Burning choppedstraw and wool under the aperture of the machine. , immediatelyoccasioned it to swell; and afterwards to ascend into the atmo-sphere. In ten minutes it had risen bOOO teet; and when its forcewas exhausted, it fell at the distance of 7068 feet from the place ithad left.

The philosophers of Paris , after the arrival of this news, soonperceived the propriety of repeating the experiment with inflam-mable air; and having by subscription raised money sufficient fordefraying, the expenoes, Messrs. Huberts were appointed toconstruct the machine ; and M. Charles, professor of experimentalphilosophy, to superintend the work. After surmounting manydifficulties in finding a substance light enough for the cover, andprocuring the gas requisite for tilling it, they at length construct-ed a globe ot silk called lutestring, varnished with dissolved elasticK u n>, to render it, impervious to the air. The diameter of this

aiioon was about 13 feet ; it had only one aperture, to which a* op cock was applied; the weight of the whole machine whenenrpty was 25 poun.ls, Qn the 23d of August 1783, they beganto fill the globe with inflammable air; but on account of thehindrances they met with, arising chiefly from inexperience, itwas not properly inflated till the. tddth, when the whole balloon andits contents ueie 3 j pounds lighter than an equal bulk of commonam At live o clock m the afternoon of the 27 th, the balloon wasdisengaged Irom its iastenings, m tl „. champ de Mars, and vo emajestically.before a great many thousand' spectators, and amidsta copious shower of rain. In less than two minutes time itascended to the height of about 3123 feet, and after remaining inthe atmosphere only | of an hour, fell in a field about 15 mile;from Paris . Us fall was owing to a rent occasioned by the ex-pansion of the imlrogen gas, .when the balloon had reached a lessdense; part of the atmosphere. In consequence of this brilliantexperiment, many balloons were made oh a small scale ; gold-bi-ateix skin .as used for the covering; and their size was from ffo 18 inches in diameter.

Soon after this, Mr. Montgolfier, invited by the Academy .ofSciences to repeat his experiments at their expence, constructed alarge balloon of an elliptical form. Thu machine was inflated bythe combustion of 50 pounds of straw, and 12 pounds of wool,in about nine minutes, when its force of asren-qqp became sogreat, that it raised eight men who held it somCfcet from theground. This machine was so much damagedIivjJie raju, thatit was found necessary to prepare another for exhibition before theking and royal family on the IfKh. And such expedition wasused, that this vast balloon, near til) feet in height and 43 in dia-meter, was made, painted within and without, and finely decorat-ed, in 1)15 hours. Along w ith it was sent a wicker cage, containinga sheep, a cock, and a duck, which were the first animals eversent on such a voyage. The full success of the experiment was,however, prevented by a violent gust of wind, which tore the ma-chine in two places near the top before it ascended. Still it rose1441) feet; and after remaining in the air about eight minutes, fellto the ground at the distance of 111,200 feet from the place of itssetting out. The animals were not in the least hurt,

In consequence of this experiment M. Pilatre de Rozier, witha philosophical intrepidity offered himself as the first adventurer inthis aerial navigation. For this purpose Mr. Montgolfier con-structed a new machine of an oval form, about 74 feel high, and4S in diameter. A wicker gallery about three feet broad, with aballustrqde three feel high was attached to the aperture, from themiddle of which an iron grate w : as suspended by' chains, and socontrived that a person from the gallery might supply the tire onthe grate with fuel, and regulate the dilatation of the* inclosed airof tlie machine at pleasure. The weight of the aerostat was up-wards of ItiOO pounds. On the 15th of October, .the fire ■ beinglighted, and the machine inflated, M. P. de RozieFpIaced himselfin the gallery, and to the astonishment of a multitude of specta-tors, ascended 84 feet from the ground and there kept the macl/meafloat during 4m. 25s. by repeatedly throwing straw and wool uponthe tire; the machine "then descended gradually to the ground;and the intrepid adventurer assured the spectators that he had.notexperienced the lead inconvenience in this aerial excursion. M.P. de Rozier ascended again on the ,17th and 19 th, after comingdown to the earth the machine rebounded considerably,..and toavoid danger lie caused it to re-ascend by the addition of fuel,thus evincing, that the balloon may be made to rise or fall at thepleasure of the aeronaut, by a proper regulation of the lire: whenit was down M. Giraudc embarked, and ascended with M. Ko-zier. They hovered about nine minutes over Paris at'an eleva-tion of 330 feet. In a subsequent trial the Marquis of Avlandestook a like voyage along with the tirst adventurer. In these ex-periments the balloon was secured by means of ropes, but soonafter the same machine was made use of without being confined.On the 21st of November, M. P. dc Rozier and the Marquis d’Ar-landes took their respective posts in the gallery, the machine, en-tirely at liberty,' ascended calmly and majestically in the atufo-spliere. The aeronauts having readied the height of about 280teet, waved their hats to the astonished multitude : but they soonrose too high to be distinguished, and are thought to have soaredto an elevation of above 3900 feet. They were at tirst driven bya north-west wind horizontally over the river Seine and overParis , taking care to clear the steeples and high buildings by in-creasing the tire; ami in rising met with a current of air, whichcarried them southward. Having passed the Boulevard, and de-sisting from supplying the tire with fuel, they descended verygently in a field beyond the New Boulevard, about 9000 yardsdistant from the palace, having been in the air about 25 minutes.The weight of the whole apparatus, including that of the two tra-vellers, was between 1(500 and 1700 pounds. Count Zambeccari,an ingenious Italian, was the'first who publicly sent up a balloonin this country; it was L0 feet in diameter, and weighed 11 pounds..-Having introduced a sufficient quantity of inflammable air, it waslaunched from the Artillery-Ground on the 25lh of November,.atone o’clock in the afternoon, and was taken up at half past threeat Petworth, distant from London 48 miles ; hence jt travellednearly 20 miles per hour. Us fall was occasioned by a rent in.thecover. M. Charles and Ml Roberts abbve mentioned were thetirst who ascended in an air balloon. The machine used on .this,occasion was formed of gores of silk, covered with a varnUh ofcaoutchouc, of a spherical figure, nearly 27 feet and a half in dia-meter. A net was spread over the upper hemisphere, and fastened

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