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Ancient device for measuring time by the gradual flow of water. One form, used by North American Indians and some African peoples, consisted of a small boat or floating vessel that shipped water through a hole until it sank. In another form, water escaped through a hole in a vessel marked with graduated lines; specimens from Egypt date from the 14th century BC. The Romans invented a clepsydra consisting of a cylinder into which water dripped from a reservoir; a float provided readings against a scale on the cylinder wall. Galileo used a mercury clepsydra to time his experimental falling bodies. See alsoclock.
Variants of WATER CLOCK
water clock or clepsydra
This entry comes from Encyclopædia Britannica Concise. For the full entry on water clock, visit Britannica.com.