338 
fite fide is deftined to conduét the air 
which frft prefents itfelf, through a refer- 
voir filled with a cauftic lixivium, and 
to convey it into the balloon. The cy- 
imders are partly filled with coarfe iron 
Hlings, which the exceflive heat of the 
furnace, Kept up ‘with pit-coal during 
the whole time of the operation, reduces 
to a ftate of excandefcence. At this ftage 
of the procefs, the valve of one of the 
tubes of each cylinder is opened, and a 
fmall quantity of boiling water is gently 
poured into the heated cylinder. Ag 
doon as the vapour of the water’ touches 
the heated iron, the two fubftances which 
compoie the water are feparated : the one 
{the oxygen) attaches itfelf to the iron, 
which it calcines, and which, after the 
operation, is found partly cryftallited, 
after the manner of volcanic productions : 
the other of the component fubfances of 
the water (the hydrogen) combines with 
@ quantity of the igneous fubffance 
termed calorique, and becomes inflam- 
mable air (hydrogen gas), which conti- 
gues Ina permanent ftate of elaftic fluidity, 
and weighs feven or eight times lefs than 
the atmofpheric air, * 
As the water contains a fall portion of 
the fubffance of carbone ( carbonique) which 
would render the air in the balloon heavy, 
the air, as it firft ruthes out of the cylin- 
ders is made to pafs through a refervoir 
ef water imprecnated with a cauftic al- 
ahi. This fuid attraéts to itfelf all the 
earbonique, and nothing rifes into the bal- 
leon but very pure inflammable air, 
During the operation, it has fometimes 
happened that the cylinders, heated to 
exeandefcence, melted. To guard againgt 
this accident, the projecting end of the 
cylinder is furnifhed with a pyrometer, 
and a fcale, which, by means of an iron 
rod, indicates the decrees of rarefaGtion 
of the air. A particular point on the 
feale announces the moment when the cy- 
Iinders are heated in the degree neareft to 
ulion: when fuch js the cafe, the fire is 
mimediately diminifhed. The Operation 
of filline a bailoon of thirty feet diameter 
employs one third of a day. 
‘The exercifing balloon at Meudon is of 
2 {pherical form, and thirty-two feet in 
diameter. Its upper half is covered with 
a linen cafe to keep off the rain from the 
balloon and its netting. This netting, 
woven with ftrong cords, embraces the 
upper part of the balloon, and is deftined 
to fupport the car tor the reception of 
the acronauts. The balloon, kept con- 
fiantly full and ready for afcent, and ex- 
pofed in the open air in all weathers, 
bed Fg, 
Soy 
lait 
French Aéroftatic Inftitute. 
[Nov. 
preferves its buoyant ftation in the atmof 
phere, being faftened on the ereat terrace 
of the lodge. When the weather is i 
vourable, the aéronautic exercifes are be- 
gun. The balloon is fet free from its 
taftenings, and elevated to a certain 
height ; when the car is made faft to the 
.cords which hang down from the net: 
the whole of this is done in five minutes, 
A colonel then mounts the car with one 
ot the pupils, and the balloon rifes to 
the height, generally, of from a hundred © 
and fixty to two hundred and forty yards. 
The pupils feparate into divifions, for the 
purpofe ot helding the balloon im the air, 
fuffering it to mount, and crawing it 
down, by means of three principal ropes 
faftened to the ret, and ramified with {e- 
_veral others: in thefe manceuvres they 
employ the aid of a capftern. When the 
balloon-has heen newly filled, has yet 
{uffered no evaporation, and fill retains 
all its force, it requires the ftrength of 
twenty perfons to hold it; and in that 
ftate it will bear eight hundred weight, 
After a {pace of two months; though 
much evaporated, it is ftili capable of 
bearing two perfons with their inftru- 
ments, and even a confiderable ballaft, 
at the fame height in the air: but then 
ten perions are fuffcient to hold it, 
The car is conftructed of a light lattice 
work of wood, lined with prepared lea- 
ther, and hangs about fixteen feet beneath 
the balloon: it affords convenient room 
for two perfons feated oppofite each other, 
with the necefiz ry inftruments formaking 
obfervations: ; 
The balloon afcends as often in the day 
as is requifite for the fucceffion of ob. 
fervations which are to be made; but 
thefe afcents take place only in calm and 
ferene weather. Whenever any unfore- 
feen accident occurs, the aérial machine, ' 
is hauled down. in five _minutes, In: 
firong gufts of wind which fuddenly arife, 
the aeronauts are always expofed to fome 
danger: the hallo rv, held by the ropes, 
cannot rife freely ; and its vibrations and 
fluétuation refemble thofe of a paper kite 
which has not yet reached a certain de- 
eree of altitude. This {pectacle, never- 
thelefs, is more terrific to the {pectator 
than to the aéronaut, who, feated in his 
car which its own weight preferves in a 
perpendicular pofition under the balloon, 
is but dlightly affetted by its defultory 
motion, No inftance of any unfortunate 
accident has yet occurred at Meudon. 
All fear, all idea of danger, vanifheg 
on examining the folidity of the whole 
apparatus, the precautionary meafures 
adopted 
