- G. J. Toomer
Inventor (fl. 270 bce), was the son of a barber in *Alexandria (1), and employed by *Ptolemy (1) II. He was the first to make devices employing ‘*pneumatics’, i.e. the action of air under pressure. His work on the subject is lost, but descriptions of some of his inventions are preserved by *Philon (2), *Vitruvius, and *Heron. These include the pump with plunger and valve (Vitr. 10. 7; Heron, Pneumatics 1. 28), the water-organ (Vitr. 10. 8), the first accurate water-clock (Vitr. 9. 8. 4 ff.; see clocks) and a war-catapult (Philon, Belopoeica43). No great theoretician, Ctesibius was a mechanical genius, some of whose inventions were of permanent value. It is probable that many of the basic ideas in the works of Philon and Heron on mechanical devices derive from him.