166 A E R O S T 
the perfon who afcended to fupply the fire with fuel, and 
thus keep up the machine as long as he pleafed. The 
weight of the whole apparatus was upwards of i6oolbs. 
The experiment was performed on the j 5th of October, 
178-5. M. Pilatre having placed himfelf in the gallery, 
the machine was inflated, and permitted to afcend to the 
height of eighty-four feet, where he kept it afloat for 
about four minutes and a half; after which it defcended 
very gently : and fuch was its tendency to afcend, that it 
rebounded to a confiderable height after touching the 
ground. Two days after, he repeated the experiment 
with the fame fuccefs as before ; but, the wind being 
ftror.g, the machine did not fuftain itfelf fo well as for¬ 
merly. On repeating the experiment in calmer weather, 
he afcended to the height of 210 feet. Id is next afcent 
was 262 feet; and, in the defcent, a gulf of wind having 
blown the machine over fome large trees of an adjoining 
garden, M. Pilatre fuddenly extricated himfelf from fo 
dangerous a fituation, by throwing draw and chopped wool 
on the fire, which raifed him at once to a fuflicient height. 
On dcfcending again, he once more raifed himfelf to a 
proper height by throwing draw on the fire. Some time 
after, he afcended>in company with M. Gironcl de Vi- 
lette to the height of 330 feet; hovering over Paris at 
lead nine minutes in light of all the inhabitants, and the 
machine keeping all the while perfectly Iteady. 
Thefe experiments had (hewn, that the aerofiatic ma¬ 
chines might be raifed or lowered at the pleafure of the 
perfons who afcended: they had likewife difcovered, that 
the keeping them fall with the ropes was no advantage ; 
but, on the contrary, this was attended with inconvenience 
and hazard. On the 21ft of November!, 1783, therefore, 
M. Pilatre determined to undertake an aerial voyage in 
which the machine Ihould be fully fet at liberty. Every 
thing being got in readinefs, the balloon was filled in a 
few minutes; and M. Pilatre placed himfelf in the galle¬ 
ry, counterpoifed by the Marquis d’Arlandes, who occu¬ 
pied the other fide. It was intended to make fome preli¬ 
minary experiments on the afcending power of the ma¬ 
chine: but the violence of the wind prevented this from 
being done, and even damaged the balloon eflentially; fo 
that it would have been entirely deftroyed bad not timely 
aflillance been given. The extraordinary exertions of the 
workmen, however, repaired it again in two hours, and 
the adventurers fet out. They met with no inconvenience 
during their voyage, which lafted about twenty-five mi¬ 
nutes; during which time they had palled over a fpaceof 
above five miles. From the account given by the Mar¬ 
quis d’Arlandes, it appears, that they met with feveral 
different currents of air; the effedt of which was, to give 
a very fenfible fhock to the machine, and the direftion of 
the motion feemed to be from the upper part dow nwards. 
It appears alfo, that they were in fome danger of having 
the balloon burnt altogether; as the marquis obferved fe¬ 
veral round holes made by the fire in the low'er part of it, 
which alarmed him confiderably, and indeed not w ithout 
reafon. However, the progrefs of the fire was eafily flop¬ 
ped by the application of a wet fponge, and all appear¬ 
ance of danger ceaftd in a very fhort time. 
This voyage of M. Pilatre and the Marquis d’Arlandes 
may be faid to conclude the hiflory of thofe aerofiatic ma¬ 
chines which are elevated by means of fire; for, though 
many other attempts have been made upon the fame prin¬ 
ciple, mod of them have either proved unfuccefsful, or 
were of little confequence. They have therefore given 
place to the other kind, filled with inflammable air; 
which, by reafon of its fmaller fpecific gravity, is both 
more manageable, and capable of performing voyages of 
greater length, as it does not require to be fupplied with 
fuel like the others. This was invented a very fhort time 
after the difcovery had been made by M. Montgolfier. 
This gentleman had indeed defigned to keep his method 
in fome degree a fec-ret from the world; but, as it could 
not be concealed, that a bag filled with any kind of fluid 
lighter than the common atmofphere would rile in it, in- 
A T I O N. 
flammable air was naturally thought of as a proper fucce- 
daneum for the rarefied air of M. Montgolfier. The firft 
experiment was made by two brothers, Meflrs. Roberts, 
and M. Charles, a profeffor of experimental philofopls-y. 
The bag which contained the gas was compofed of lute- 
firing, varnilhed overw'itha folution of theelaftic gum called 
caoutchouc and that with which they made their firft elfay 
was only about thirteen Englilh feet in diameter. Many 
difficulties occurred in filling it with the inflammable air, 
chiefly owing to their ignorance of the proper apparatus ; 
infomuch, that, after a whole day’s labour from nine in the 
morning, they had got the balloon only one third part full. 
Next morning they were furprifed to find that it had fully 
inflated of itfelf during the night: but, upon inquiry, it 
was found, that they had inadvertently left open a flop- 
cock connected with the balloon, by which the common 
air, gaining accefs, had mixed itfelf with the inflammable 
air ; forming a compound full lighter titan the common at- 
rnofphere, but not fufficiently light to anfwer the purpo- 
fes of aeroflation. Thus they were obliged to renew their 
operation ; and, by fix o’clock in the evening of the next 
day, they found the machine confiderably lighter than the 
common air; and, in an hour after, it made a confidera¬ 
ble effort to afcend. The public exhibition, however, 
had been announced only for the third day after; fo that 
the balloon was allowed to remain in an inflated flate for 
a whole day ; during which they found it had loll a power 
of afcent equal to about three pounds, being one-feventh 
part of the whole. When it was at lad fet at liberty, af¬ 
ter having been well filled with inflammable air, it was 
thirty-five pounds lighter than an equal bulk of common 
air. It remained in the atmofphere only three quarters 
of an hour, during which it had traverfed fifteen miles. 
Its hidden defcent was fuppofed to have been owing to a 
rupture which had taken place when it afcended into the 
higher regions of the atmofphere. 
The fuccefs of this experiment, and the aerial voyage 
made by Meflrs. Rozier and Arlandes, naturally fuggeft- 
ed the idea of undertaking fomething of the fame kind 
with a balloon filled with inflammable air. The machine 
ufed on this occafion was formed of gores of IIlk, covered 
over with a varnifh made of caoutchouc , of a fpherical fi¬ 
gure, and meafuring twenty-feven feet and a half in dia¬ 
meter. A net was fpread over the upper hemifphere, and 
w as faftened to an hoop which paffed round the middle of 
the balloon. To this a fort of car, or rather boat, was 
fufpended by ropes, in fuch a manner as to hang a few feet 
below the lower part of the balloon ; and, in order to pre¬ 
vent the burfling of the machine, a valve was placed in 
it; by opening of which fome of the inflammable air 
might be occaiionally let out. A long lilken pipe com¬ 
municated with the balloon, by means of which it was 
filled. The boat was made of balket-work, covered with 
painted linen, and beautifully ornamented ; being eight 
feet long, four broad, and three and a half deep ; its 
weight 130 pounds. At this time, however, as at the for¬ 
mer, they met with great difficulties in filling the machine 
with inflammable air, owing to their ignorance of the moll 
proper apparatus. But at laft, all obftacles being remo¬ 
ved, the two adventurers took their feats at three quar¬ 
ters after one in the afternoon of the firft of December,' 
1783. Perfons (killed in the mathematics were conveni¬ 
ently ftationed with proper inftruments to calculate the 
height, velocity, See. cf the balloon. The weight of the 
whole apparatus, including that of the two adventurers, 
was found to be 604£ pounds, and the power of afcent 
when they fet out was twenty pounds; fo that the whole 
difference betwixt the weight of this balloon and an equal 
bulk of common air was 624 pounds. But tire weight of 
common atmofphere difplaced by the inflammable gas was 
calculated to be 771 pounds, fo that there remains 147 for 
the weight of. the latter; and this calculation makes it 
only five times and a quarter lighter than common air. 
At the time the balloon left the ground, the ther¬ 
mometer flood at 9 0 of Fahrenheit’s fcale, and the quick- 
3 ftlver 
