Water clock
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A water clock, or clepsydra, is a timepiece by which time is measured by the regulated flow of liquid into or out from a vessel, and where the amount of liquid can then be measured.
Water clock calculations by Nabû-apla-iddina.
A display of two outflow water clocks from the Ancient Agora Museum in Athens. The top is an original from the late 5th century BC. The bottom is a reconstruction of a clay original.
Eschinardi's water clock (Reproduced from Francesco Eschinardi, Appendix Ad Exodium de Tympano)
The water-powered mechanism of Su Song's astronomical clock tower, featuring a clepsydra tank, waterwheel, escapement mechanism, and chain drive to power an armillary sphere and 113 striking clock jacks to sound the hours and to display informative plaques
Hourglass
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An hourglass is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated flow of a substance from the upper bulb to the
Water clock
…History of timekeeping devices Hourglass al-Hassan, Ahmad Y.; Hill, Donald R. (1986). Islamic Technology: An Illustrated History. Cambridge University Press. ISBN 0-521-26333-6. OCLC 13332728…
German half-hour sand glass, first quarter of the 16th century, bronze-gilt and silver-gilt, height: 8.3 cm, diameter: 8.4 cm, Metropolitan of Art (New York City)
Antique sandglasses
Sarcophagus dated c. 350, representing the wedding of Peleus and Thetis (with magnification of an hourglass held by Morpheus)
Temperance bearing an hourglass; detail Lorenzetti's Allegory of Good Government, 1338