adder over the first. The vessel should
be filled in such a manner with the ether, as not to leave the smallest
portion of air between the liquor and the bladder. It is now to be
placed under the recipient BCD of an air-pump, of which the upper part B
ought to be fitted with a leathern lid, through which passes a wire EF,
having its point F very sharp; and in the same receiver there ought to
be placed the barometer GH. The whole being thus disposed, let the
recipient be exhausted, and then, by pushing down the wire EF, we make a
hole in the bladder. Immediately the ether begins to boil with great
violence, and is changed into an elastic aeriform fluid, which fills the
receiver. If the quantity of ether be sufficient to leave a few drops in
the phial after the evaporation is finished, the elastic fluid produced
will sustain the mercury in the barometer attached to the air-pump, at
eight or ten inches in winter, and from twenty to twenty-five in
summer[6]. To render this experiment more complete, we may introduce a
small thermometer into the phial A, containing the ether, which will
descend considerably during the evaporation.

The only effect produced in this experiment is, the taking away the
weight of the atmosphere, which, in its ordinary state, presses on the
surface of the ether; and the effects resulting from this removal
evidently prove, that, in the ordinary temperature of the earth, ether
would always exist in an aeriform state, but for the pressure of the
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 col