1803. ] 
The apparatus invented by Gay Lus- 
sac is extremely simple; it consists of 
-two,balloons, with a double tubulure and 
equal incapacity; to one of the tubulures 
was adapted a spigot, and to the other a 
very sensible spirit of wine thermometer. 
These balloons having been freed from 
all humidity, by means of dried muriate 
of jime, the air was exhausted, and one 
of the balloons filled up with the gas, 
which was to be ezamined; he then 
opened the communicatioa between the 
two balloons, on which a portion of the 
gas inclosed in the first rashed into the 
second, until an equilibrium was esta- 
blished, when M. Gay Lussac accurately 
remarked the change of temperature in- 
dicated by the two thermometers. 
In the first experiment, which had for 
its object atmospheric air, he was asto- 
nished to observe the thermometer in the 
empty balloon evidently ascend in pro- 
portion as the air entered it. 
This appeared in perfect contradiction 
to another well! known fact, which is, that 
a mass of air inclosed in the body of 
a pump, absorbs caloric in proportion as 
the air is dilated by the raising up of the 
piston, 
Are we then prepared to affirm, that 
the vacuum was not sufficiently accurate 
im the second balloon, and that the air 
which remained in it was compressed by 
the rushing in of the new air, and by that 
means was forced to yield up a portion of 
itscaloric? MM. Gay Lussac combats this 
explanation, both by reasoning a priori, 
and direct experiment. 
If spirit of wine ascends in the second 
thermometer, it descends very nearly in 
the same quantity m the first. Now if 
after having produced a vacuum in the 
two balloons, we establish the communi- 
eation between them, the gas equally 
distributed will be reduced to one-half of 
its original density, when one of the ther- 
mometers will be observed to ascend, 
and the other te descend, in quantities 
still equal, between them, though less in 
proportion to the dimimution of the den- 
sity; and if by a similar operation the 
density be reduced to one-half of what it 
was inthis second trial, and consequently 
to one-eighth of its original density, the 
variation will be equal, aud contrary in 
the two thermometers, as they still fol- 
low the proportion of the new density. 
From similar experiments, conducted 
with the greatest possible attention to ac- 
curacy, with hydrogen, oxygen, and car- 
‘bonic acid gas, the same results were ob- 
ed; or, in other words, the quantities 
Proceedings of Learned Socteties. 
Y51 
of caloric absorbed in the frst balloon, 
and disengaged in the second, were uni- 
formly found to be equal to each other, 
and in proportion to the density. 
In order to make an accurate compa- 
rison between these different experi- 
ments, It was necessary that the time 
consumed in the efilux of the gas should 
be the same in all the different gases, 
and M. Gay Lussac succeeded in regu- 
lating this part of the process by an ap- 
paratus equally simple and ingenious, 
which diminished the oriiice of the ‘com- 
municating tube in proportion to the 
square of the densities, by which means 
the time of the efflux is eleven seconds 
for all the different gases. 
By this work, worthy the attention of 
naturalists, and which it is proposed 
still farther to verify and extend by 
observations, M. Gay Lussac has suc- 
ceeded in deducing the following conse- 
quences, which he proposes with all that 
‘caution that characterizes the trae philo- 
sopher. 
1. When an empty space becomes 
filled with gas, the caloric which is dis- 
engaged, does not proceed from the 
small portion of air which may have re- 
mained in it. 
2. If a communication be established - 
between two equals, the one empty and 
the other full of gas, the variations of 
temperature, positive in the one, and ne= 
gative in che other, are equal in quan- 
tity, but not in intensity. 
3. In the same gas these variations are 
in proportion te the change of density 
which it experiences. 
4. The variations perceivable in dif 
ferent gases are greater in proportion as 
their specific gravity is less, 
5. The capacities of the same gas for 
caloric diminishes, im the’same bulk, with 
the density. 
6. The capacities of gas for caloric, m 
given bulks, are greater as their specific 
gravities are less; this last result will be 
evident to those who are acquainted with 
the experiments, by which Gay Lussac 
formerly proved that all gaseous bodies 
are equally influenced by the same eleva~ 
tions of temperature. 
M, Cotte, a corresponding membezs of 
the Institute, compared, during the three 
warmest days of the memorable summers 
of 1202, 1805, and 1806, the range of 
several spirit of wine and mercurial ther- 
mometers, at differené exposures. 
wo of these thermometers, the one 
filled with mercury, and the other with 
spirit of wine, were placed in the shade 
towards 
