WATER CLOCK

The water clock, or Clepsydra, has been reliably dated to 1600 BC in Egypt. It functioned by water dripping through a hole in the base of a container, which lowered the water level past markings on the container sides. These markings were spaced to indicate fixed periods of time. Many variations were based on this design. Ctesibius of Alexandria made a clepsydra in which a figure floating on the water surface pointed to the time scale. In another type, dripping water turned a wheel that was connected to pointers on a dial face similar to a modern clock. Before the third century BC the clepsydra was used by the Greeks to indicate intervals of time, especially in law court; later it functioned as a clock. Clepsydras were later used in Rome, the Arab world, and China.