Ctesibĭca Machĭna
An hydraulic engine named after its inventor,
Ctesibius (q.v.) of Alexandria. In the language of modern hydraulics it is a
double-action forcing pump. Vitruvius, in his description (x. 10 [7]), speaks of it as
designed to raise water, while Ctesibius's pupil, Hero (
Pneumat. p. 180),
describes, under the name of
σίφων, a machine identical in
principle, but of improved construction, and says that it was used as a fireengine (
εἰς τοὺς ἐμπρησμούς). Indeed, the same principle has been employed
in modern fire-engines. The remains of such a
σίφων were
discovered at Castrum Novum, near Cività Vecchia, in 1795, having probably served
to supply the public baths with water.
The following cut illustrates the construction of Ctesibius's invention as described by
Vitruvius.
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Ctesibica Machina. (Rich.)
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Two cylinders (
modioli), B B, are connected by pipes with a
receiver (
catinus), A, which is closed by a cowl (
paenula), D. In each cylinder a piston (
embolus masculus), C, is
worked by means of its rod (
regula). In the bottom of each cylinder, and
at the opening of each pipe into the receiver, is a movable lid or valve (
assis), which only opens upwards. The bottoms of the cylinders are inserted into a
reservoir, or connected with it by pipes. When one of the pistons is raised, a vacuum is
produced in the cylinder, and the atmospheric pressure forces a stream of
water past the raised valve into the cylinder. When this stream ceases, the valve falls; and
if the piston is forced down, the water is driven out of the cylinder into the pipe, and past
the valve into the receiver, and retained there by the closing of the valve. If the two
pistons are worked alternately, so that one descends as the other rises, a continuous stream
of water is forced out of the top of the
paenula.
