Ctesibius

, a mathematician of Alexandria, who flourished 135 years B.C. He was the inventor of the pump and other hydraulic instruments. He also invented a clepsydra , or water clock. This invention of measuring time by water was wonderful and ingenious. Water was made to drop upon wheels, which it turned. The wheels communicated their regular motion to a small wooden image, which, by a gradual rise, pointed with a stick to the proper hours and months, which were engraved on a column near the machine. This artful invention gave rise to many improvements; and the modern manner of measuring time with an hour-gla is an imitation of the clepsydra of Ctesibius. Vitruvius , On Architecture , bk. 9 , ch. 9 .――A cynic philosopher.――An historian, who flourished 254 years B.C., and died in his 104th year. Plutarch , Demosthenes .