atmosphere, and that the passing of the ether from the liquid to the
aeriform state is accompanied by a considerable lessening of heat;
because, during the evaporation, a part of the caloric, which was before
in a free state, or at least in equilibrio in the surrounding bodies,
combines with the ether, and causes it to assume the aeriform state.
The same experiment succeeds with all evaporable fluids, such as
alkohol, water, and even mercury; with this difference, that the
atmosphere formed in the receiver by alkohol only supports the attached
barometer about one inch in winter, and about four or five inches in
summer; that formed by water, in the same situation, raises the mercury
only a few lines, and that by quicksilver but a few fractions of a line.
There is therefore less fluid evaporated from alkohol than from ether,
less from water than from alkohol, and still less from mercury than from
either; consequently there is less caloric employed, and less cold
produced, which quadrates exactly with the results of these experiments.
Another species of experiment proves very evidently that the aeriform
state is a modification of bodies dependent on the degree of
temperature, and on the pressure which these bodies undergo. In a Memoir
read by Mr de la Place and me to the Academy in 1777, which has not been
printed, we have shown, that, when ether is subjected to a pressure
equal to twenty-eight inches of the barometer, or about the medium
pressure of the atmosphere, it boils at the temperature of about 32
(104 ), or 33 (106.25 ), of the thermometer. Mr de Luc, who has made
similar experiments with spirit of wine, finds it boils at 67
(182.75 ). And all the world knows that water boils at 80 (212 ). Now,
boiling being only the evaporation of a liquid, or the moment of its
passing from the fluid to the aeriform state, it is evident that, if we
keep ether continually at the temperature of 33 (106.25 ), and under
the common pressure of the atmosphere, we shall have it always in an
elastic aeriform state; and that the same thing will happen with alkohol
when above 67 (182.75 ), and with water when above 80 (212 ); all
which are perfectly conformable to the following experiment[7].
I filled a large vessel ABCD (Plate VII. Fig. 16.) with water, at 35
(110.75 ), or 36 (113 ); I suppose the vessel transparent, that we may
see what takes place in the experiment; and we can easily hold the hands
in water at that temperature without inconvenience. Into it I plunged
some narrow necked bottles F, G, which were filled with the water, after
35