CTESI´BICA MA´CHINA
CTESI´BICA MA´CHINA a hydraulic engine
named after its inventor, Ctesibius of Alexandria,
quiet
vim spiritus naturalis pneumaticasque res invenit (
Vitr. 9.9 (8), § 2). In the language of
modern hydraulics it is a doubleactioned forcing pump. Vitruvius in his
description (10.10 (7)), speaks of it as designed to raise water, while
Ctesibius' 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
fire-engine (
εἰς τοὺς ἐμπρησμούς).
Indeed the same principle is employed in our modern fire-engines. The
remains of such a
σίφων were discovered at
Castrum Novum, near Cività Vecchia, in 1795 (Schneider on Vitruv.
l.c.), having probably served to supply the
public baths with water.
The following cut illustrates the construction of Ctesibius' invention as
described by Vitruvius. 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
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Ctesibica Machina. (Rich.)
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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.
If we turn to the accompanying illustrations from the pump found at Castrum
Novum and to Hero's description, we find the cylinders (
πυξίδες) A A, with their valves (
ἀσσάρια) FF, the pistons (
ἐμβολεῖς), as B, the piston--rods (
κανόνια), as C, identical with those described above; but in
place of the pipes a horizontal tube D with
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Ctesibica Machina. (Rich.)
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valves F F is used, and in place of the
catinus a vertical tube (
σωλὴν
ὄρθιος) E. It is clear, however, that these improvements in
construction do not affect the principle of the machine or the mode of its
working. (Plin.
Ep.
[p. 1.571]10.42, 2; Isid.
Or. 20.6, 9;
Dig. 33,
7,
12.18.)
[
J.H.F]
