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§ 90. 3) Apparatus founed on these properties of air
1. The air pump (208)
Applications of this instrument, besides what is stated al
ready, are: crushing force of the atmosphere, 209; the wine
tester does not flow, 210; mineral waters, beer and wine lose
their taste, 209; the fall of bodies in vacuo, 211; the foun
tains in vacuo (a flask containing water and air is put under
the receiver of an air-pump, the neck of the flask is closed and a
tube, dipping in the water, passes through the cork; after the
air is rarefied water issues from the tube).
§ 91. 2. The condensing pump or an apparatus for
compressing air. It consists of a cylinder in which a solid piston
(without valve) moves up and down, the cylinder is connected
with a receiver below, and besides that is provided with a valve,
which permits the entrance of fresh air. The piston descends
and air is compelled to enter the receiver, the receiver having
been shut the piston ascends and fresh air enters and so on.
An application of this pump we see in the air-gun. 216. 217.
A compression of air takes place also in bellows, and in our
chest, whilst breathing, sucking, smoking, and drinking. 195.
§ 92. 3. Hero's fountain see: 218, and the fountain in
vacuo under 1. (Hero of Alexandria 210 B. C.)
§ 93. 4. Water-pumps.
a) The section- or lift-pump. 193. (The piston per
forated and provided with a valve).
b) The force-pump, by means of which water is raised, not
in consequence of the atmospheric pressure but of the pressure
of the piston. Hence there is no valve in the piston and no
lifting pipe, but the barrel itself with a valve in the bottom
(opening upward) is dipped in the liquid. The water is forced
out through a long tube with a valve placed in its orifice. In
