dissipate them through the surrounding medium. Besides, without this
atmospheric pressure, we should not even have any aeriform fluids,
strictly speaking, because the moment the force of attraction is
overcome by the repulsive power of the caloric, the particles would
separate themselves indefinitely, having nothing to give limits to their
expansion, unless their own gravity might collect them together, so as
to form an atmosphere.
Simple reflection upon the most common experiments is sufficient to
evince the truth of these positions. They are more particularly proved
by the following experiment, which I published in the Memoirs of the
French Academy for 1777, p. 426.
Having filled with sulphuric ether[5] a small narrow glass vessel, A,
(Plate VII. Fig. 17.), standing upon its stalk P, the vessel, which is
from twelve to fifteen lines diameter, is to be covered by a wet
bladder, tied round its neck with several turns of strong thread; for
greater security, fix a second bladder 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
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