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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.

Ctesibica Machina. (Rich.)

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.

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