XLI
raising the piston water enters the barrel, when the piston des
cends the valve in the bottom closes, whilst the other valve opens
and gives exit to the water. The height to which water may be
raised is not limited (in theory).
An application of this pump and of Hero's fountain we
see in the Fire-engine, 220; and in the Syringe, 219.
This pump (for watering a garden) is a combination of a
suctio-nand force-pump, the water enters through a leather-pipe
and for getting a continuous slow of it, it is forced at first into a
ball (Hero's fountain). Our frontispiece shows, that by means
of such leather-pipes fire-engines also can supply themselves
with water.
§ 94. 4) Pressure on bodies in air. Archimedes' principle
applied to gases. 213. That bodies lose part of their weight
in air may be verified by experiment. A scale-beam with a weight
at one side and a hollow copper sphere at the other side, which
in air counterbalance each other, is put under the receiver of
