A E R 



made of fuch matctals as llint every fquare foot of it weighs 

 two ounces, ami thai the « i^l'.l iucvoatcs in the proper 



tiim of the incrcalc of t!ic fi- 



II i\\h talc the diameter 



of tlie parachute, wliich w il dciotnd at the 'late of ten 

 feet per fccoud, mull be upwards of 78 feet 5 but if the 

 parachute be concave on tlie lower fide, its power will be 

 r.\t'iT •.^■•! Mtrr, and its diaintter nay be lefs. In order to 

 t . : 1 I I : iwer of a flat circular paracluite, or the re- 

 liilaiiet ii i...^ii witli fru.n air of a mean dcnfity, when de- 

 .fcendi:i(» with a given velocity, fay as the nun'.ber isoo is to 

 tiie fqiiarc of the velocity jn feet, fo is the fquare of the 

 diameter in feet to a fourth number, wlilch will be the re- 

 fillance in poundi. And if it be required to know, with 

 what velocity a paracluite will delcend with a given weight, 

 fay a> the given diameter is to the fquare root of the weight, 

 fo is the nun.ber zSj to a fourth, wliich will be tU? veio- 

 citv in air of a mean denfity. Thus, if the diair.cter of a 

 b;dloon be 50, and its weight, together with that of a n.an, 

 be 530 pounds, the fquare root of which is 23 very nearly ; 

 then 50: 23 :: 28', : 13 ; and therefore tlie man and pa- 

 ■' raeliutc will dcfcend wltii the velocity of 13 feet per feeond, 

 which, as it is equal to that acquired by leaping freely 

 from a lieight of two feet two inches, may be vei7 fafely 

 fullained. 



Aerostation, ///rj 0,/i The advantages of an art, fo 

 lately difcovercd, have not yet been fufiiciently afcertained ; 

 but we may reafonably expett, eonfidenng the progrefs it 

 has ma<le in fo (hoit a fpace of time, that many benefits 

 mav refnlt from the farther prolecution of it. To fay the 

 leail. It is unphilofophical to difcourage future trials and 

 improvements, becaufe the ufes jf this art do not immedi- 

 ately appear. With regard to philofophical obfervations, 

 derived from aeroilation, it is acknowledged that very few 

 have yet been made. The novelty of the dilcovery, and of the 

 profpeCl, fays Mr. Cavallo, has generally dillrafted the at- 

 tention ; and befides, moft of the aerial voyages have been 

 liiade by perfons who had pecuniary profit alone in view, 

 or who were lUmulated to afcend in the atmofphere for the 

 fake of the profpeft, or by the vanity of adding their 

 names to the lift of aerial adventurers. Aerial navigation, 

 confidered as a mode of travelling between diftant places, 

 independently of its furnifliing means of conveyance to 

 places othcrwife inacctffible, is attended with many advan- 

 ^tages and conveniences. The aeronaut has much lefs 

 trouble with this machine than a failor with a (hip in the 

 moft favourable circumftances. "With a moderate wind, 

 aerial navigators have often gone at the rate of forty or fifty 

 miles an hour, and very commonly at the rate of thirty 

 miles witliout any agitation, or even feeling the wind, and 

 without the danger of lofing time by being often becalmed. 

 Aeroftatic machines may ferve the purpofc of efcapii:;r 

 from (hips that cannot fafely land, from befieged places, 

 and from other circumftances of danger. A fmaJl balloon 

 fix or feveji feet in diameter, fays an anonymous author in 

 his propofal of various means for faving the crews of veflels 

 ftiipwrecked near the coall, would anfwer this purpofe, by 

 canying to the fliore a ftring capable of drawing a cord, 

 with which feveral ropes might be afterwards conveyed to 

 the veffcl. They alfo expedite the communication of im- 

 portant events by llgnals, and ferve for exploring, from a 

 great elevation, adjacent coafts or regions, fleets and annies. 

 To the latter of thefe porpofes they have been actually ap- 

 plied by the French, in the courfe of the laft war ; and to 

 tlie elevation of a balloon, and the information obtained in 

 coiifequence of thus reconnoitering the army of the enemy, 

 they aicribe the fignal viclory obtained in the battle of 

 Jleurusin 1794. The balloon employed on this occafion, 



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was called the Entrtpr:nant, and it was under the dirci£tion 

 of M. Coutd, the captain of the aemnauts at Meudon, ac- 

 companied by an adjutant and a general. He afcended 

 twice in the fame day, to the height of 220 fathoms, for 

 the purpofe of obferving the pofition and manoeuvres of the 

 eiiemv. He continued each time four hours in the air, and 

 correiponded with General Jourdan, who commamkd the 

 French army, by means of pre-cojicerted fignals. I'he en- 

 teipiife was difcovered by the enemy , and a batteiy opone4 

 its fire againlt the afcending aeronauts ; but they foon 

 gained an elevation which was beyond the reach of their 

 fire. This balloon was prepared iu>der the direflion of thp 

 j'krOjQatk Institute, for the ufe of the army of t!:e north; 

 as were alfo another called Cehjh, for the anny of the 

 Sambre and Meufe ; and the Heraile and Intref'uU, for the 

 army of the Rhine and iVIofelle. Another, thirty feet in 

 circumference, and weighing 160 pounds, was deftined for 

 the army of Italy. A new machine, invented by M. Conte, 

 the director of the Aeroftatic Inititute, was defigned to aid 

 the aeronauts in communicating intelligence, and was de- 

 nominated the Acrojlat'ic Telegraph. Balloons may like- 

 wile ferve to explore the ftate of the atmofphere at differ- 

 ent heights, and to furnifti obfervations, which fhall illnftrate 

 a variety of phenomena, depending on the denfity, tempera- 

 ture, and other qualities of the an\ From one experiment 

 that has been already made we learn, that the air of a 

 high region, prefei-ved and examined by means of nitrous 

 air, was found to be purer than the air below. The appli- 

 cation of thefe machines to eleftrical experiments, is a very- 

 obvious ufe of which they are capable. The firft perfon 

 who employed them in this way feems to have been fhe 

 Abbe Bertholon, at Montpellier. He raifed feveral air 

 balloons, furniihed with long and (lender wires, having 

 their lower ends fattened to a glafs ftick, or other infulating 

 fubftance ; and thereby obtained fronn the wires eleftric 

 fluid fufHcient to iliew the attraftion, repulfion, and even 

 the fparks of eleClricity. The exiltence of a continual elec- 

 tricity, of the pofitive kind, in a clear atmofphere, known 

 indeed before, has been farther afcertained by ilrings faf- 

 teiied to balloons floating in the atniolphere. Some have 

 apprehended danger from the electricity of the atmofphere ; 

 and have thought that a ftroke of lightning, or the fmallell 

 eleftrical fpark, happening near a balloon, might fet fire to 

 the inflammable air, and deftroy both the machine and the 

 adventurers. Mr. Cavallo has fnggefted (everal confidera* 

 tions for dimir.Khing apprehenfions of this kind. Balloons 

 have been already railed in every feafon of the year, and 

 even when thunder has been heard, without injury. ]n 

 cafe of, danger, the aeronauts may either defcend to the 

 earth, or afcend above the region of the clouds and thunder 

 ftorms. Befides, as balloons are formed of materials that 

 are not conductors of electricity, they are not likely to re- 

 ceive ilrokes, efpecially as by being encompaffed with air 

 they ftand infulated. Moreover, inflammable air by itfelf, or 

 unmixed with a certain quantity of common air, will ijot 

 burn ; fo that if an electric fpark fhou'd happen to pafs 

 through the balloon, it would not fet fii-e to the inflammable 

 air, unlefs a hole was made in the covering. 



For a variety of other important and ufeful particulars 

 relating to the fubjeft of aeroilation, we mu(l refer to Mr. 

 Cavallo's curious and comprehenfive work, entitled, the 

 Hiftor)- and Practice of Aeroftation, 8vo. 1785; which 

 will afford the reader ample inforraation concerning the 

 principles of this art, and the hiftory of its progrefs, the 

 method of conftrufting and managing balloons, the na- 

 ture and preparation of the materials of which they are 

 formed, the obfervations and ufes to which tliey are 

 2 adapted. 



