nd place it on the
plate of the pump. When the air is exhausted, turn the cock, take the
tube off the plate, and plunge it into a basin of mercury or water.
Then the cock being again turned, the fluid, by the pressure of the
air, will play upon the tube in the form of a beautiful fountain.

_The Exploded Bladder._

Take a glass pipe open at both ends, to one of which tie fast a wet
bladder, and let it dry. Then place it on the plate of the pump. While
the air presses the bladder equally on both sides, it will lie even
and straight; but as soon as the air is exhausted, it will press
inwards, and be quite concave on the upper side. In proportion as the
air is exhausted, the bladder will become more stretched; it will soon
yield to the incumbent pressure, and burst with a loud explosion. To
make this experiment more easy, one part of the bladder should be
scraped with a knife, and some of its external fibres taken off.

_The Cemented Bladder._

Tie the neck of the bladder to a stop-cock, which is to be screwed to
the plate of the pump, and the air exhausted from the bladder; then
turn the stop-cock, to prevent the re-entrance of the air, and unscrew
the whole from the pump. The bladder will be transformed into two flat
skins, so closely applied together, that the strongest man cannot
raise them half an inch from each other; for an ordinary-sized
bladder, of six inches across the widest part, will have one side
pressed upon the other with a force equal to 396 pounds' weight.

_Cork heavier than Lead._

Let a large piece of cork be pendent from one end of a balance beam,
and a small piece of lead from the other; the lead should rather
preponderate. If this apparatus be placed under a receiver on the
pump, you will find that when the air is exhausted, the lead, which
seemed the heaviest body, will ascend, and the cork outweigh the lead.
Restore the air, and the effect will cease. This phenomenon is only on
account of the difference of the size in the two objects. The lead,
which owes its heaviness to the operation of the air, yields to a
lighter because a larger substance when deprived of its assistance.

_The animated Bacchus._

Construct a figure of Bacchus, seated on a cask; let his belly be
formed by a bladder, and let a tube proceed from his mouth to the
cask. Fill this tube with coloured water or wine, then place the whole
under the receiver. Exhaust the air, and the liquor will be thrown up
into his m