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CLEPSYDRA (from Gr. rc1,Eirrerr, to s...

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Originally appearing in Volume V06, Page 496 of the 1911 Encyclopedia Britannica.
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CLEPSYDRA (from Gr. rc1,Eirrerr, to steal, and See also:Mop, See also:water) , the chronometer of the Greeks and See also:Romans, which measured See also:time by the flow of water. In its simplest See also:form it was a See also:short-necked earthenware globe of known capacity, pierced at the bottom with several small holes, through which the water escaped or " See also:stole away," The See also:instrument was employed to set a limit to the speeches in courts of See also:justice, hence the phrases aquam dare, to give the See also:advocate speaking time, and aquam perdere, to See also:waste time. Smaller clepsydrae of See also:glass were very See also:early used in See also:place of the See also:sun-See also:dial, to See also:mark the See also:hours. But as the length of the See also:hour varied according to the See also:season of the See also:year, various arrangements, of which we have no clear See also:account, were necessary to obviate this and other defects. For instance, the flow of water varied with the temperature and pressure of the See also:air, and secondly, the See also:rate of flow became less as the See also:vessel emptied itself. The latter defect was remedied by keeping the level of the water in the clepsydra See also:uniform, the See also:volume of that discharged being noted. See also:Plato is said to have invented a complicated clepsydra to indicate the hours of the See also:night as well as of the See also:day. In the clepsydra or See also:hydraulic See also:clock of Ctesibius of See also:Alexandria, made about 135 B.C., the See also:movement of water-wheels caused the See also:gradual rise of a little figure, which pointed out the hours with a little stick on an See also:index attached to the See also:machine. The clepsydra is said to have been known to the Egyptians. There was one in the See also:Tower of the Winds at See also:Athens; and the See also:turret on the See also:south See also:side of the tower is supposed to have contained the cistern which supplied the water. See See also:Marquardt, Das Privatleben der Romer, i. (2nd ed., 1886), p 992; G.

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Bilfinger, See also:Die Zeitmesser der antiken Volker (1886), and Die antiken Stundenangaben (1888).

End of Article: CLEPSYDRA (from Gr. rc1,Eirrerr, to steal, and Mop, water)

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