Ctesibĭus in Harpers Dictionary of Classical Antiquities（Κτησίβιος). A native of Ascra and contemporary of Archimedes, who flourished during the reigns of Ptolemy II. and Ptolemy III., or between B.C. 260 and 240. He was the son of a barber, and for some time exercised at Alexandria the calling of his parent. His mechanical genius, however, soon caused him to emerge from obscurity, and he became known as the inventor of several very ingenious contrivances for raising water, etc. The invention of clepsydrae, or water clocks, is also ascribed to him. (Cf. Vitruvius, ix. 9.) He wrote a book on hydraulic machines, which is now lost. See Clepsydra; Ctesibica Machina; Horologium.
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