Water clock

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A water clock or clepsydra is a device for measuring time by letting water regularly flow out of a container, usually through a tiny aperture. While never reaching the level of accuracy based on today's standards of timekeeping, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate pendulum clock in the 17th century.

1 Water Clock Overview
2 Resources
3 See also

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Water Clock Overview

According to researcher Jim Maciejewski, water clocks were among the earliest timekeepers created by mankind. While there is no consensus on where or when the first water clock was created, early water clocks have been shown to have existed in the Mesopotamian region (Sumer, Babylonia, Assyria), in India (Vedic people), and in China. The general timeframe is 1500 BC - 3000 BC, and perhaps even earlier. Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. In the earliest of time, the purpose for using a water clock was for astronomical and astrological reasons. These early water clocks were calibrated with a sundial. Through the centuries, water clocks were used for timing lawyer's speeches during a trial, labors of prostitutes, night watches of guards, sermons and masses in church, to name only a few.

One of the oldest archaelogical finds of a water clock was in the tomb of the Egyptian pharaoh Amenhotep I (1525 - 1504 BC). This outflow water clock was built in honor of Amenhotep I by Amenemhet, an 18th dynasty dignitary. Later named clepsydras ("water thieves") by the Greeks, who began using them by 325 BC, these were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. Other clepsydras were cylindrical or bowl-shaped containers designed to slowly fill with water entering at a constant rate. Markings on the inside surfaces measured the passage of "hours" as the water level reached them. These clocks were used to determine hours at night, but may have been used in daylight as well. Another version consisted of a metal bowl with a hole in the bottom; when placed in a container of water the bowl would fill and sink in a certain time. These were still in use in northern Africa in the 20th century.

More elaborate and impressive mechanized water clocks were developed between 270 BC and AD 500 by Greek (Ctesibius, Hero of Alexandria, Archimedes) and Roman horologists and astronomers. The added complexity was aimed at making the flow more constant by regulating the pressure, and at providing fancier displays of the passage of time. Some water clocks rang bells and gongs; others opened doors and windows to show little figures of people, or moved pointers, dials, and astrological models of the universe.

A Greek astronomer, Andronicus of Cyrrhus, supervised the construction of his Horologion, known today as the Tower of the Winds, in the Athens marketplace (or Agora) in the first half of the 1st century BC. This octagonal structure showed scholars and shoppers both sundials and mechanical hour indicators. It featured a 24-hour mechanized clepsydra and indicators for the eight winds from which the tower got its name, and it displayed the seasons of the year and astrological dates and periods. The Romans also developed mechanized clepsydras, though their complexity accomplished little improvement over simpler methods for determining the passage of time. Image:SuSongClock1.JPG Image:SuSongClock3.JPG Image:SuSongClock2.JPG Image:SuSongClock4.JPG Image:SuSongClock5.JPG

In eastern Asia, water clocks were very important in astronomy and astrology. Third century Chinese clepsydras drove various mechanisms that illustrated astronomical phenomena. One of the most elaborate clock towers was built by Su Sung (蘇頌) and his associates in 1088. Su Sung's mechanism incorporated a water-driven escapement invented about 725. The Su Sung clock tower, over 30 feet tall, possessed a bronze power-driven armillary sphere for observations, an automatically rotating celestial globe, and five front panels with doors that permitted the viewing of changing manikins which rang bells or gongs, and held tablets indicating the hour or other special times of the day. From the earliest of times, Chinese timekeeping devices were introduced to the Korean peninsula.

In Korea, timekeeping was both a royal duty and a royal prerogative from its Three Kingdom Period (c. 37 BC) onwards. By 1434 during the Choson Dynasty, Jang Young Sil, a chief engineer of Korea, constructed the Chagyongnu (self-striking water clock) for King Sejong. What made the Chagyongnu self-striking was the use of jack-work mechanisms, by which three wooden figures (jacks) struck objects to signal the time. The Chagyongnu was a fully automatic device that didn't require any human worker, known as "rooster men", to constantly replenish it. [1] By 554, the water clock spread from Korea to Japan. Water clocks were used and improved upon throughout Asia well into the 15th century.

Today, few water clocks exist. In 1979, Bernard Gitton began creating his Time-Flow Clocks, which are a modern-day approach to water clocks. His unique design can be found in a couple places in the United States and in over 30 locations throughout the world. Also, there are some other modern designs of water clocks, but overall the use of water flow to power a clock largely remains a lost art.

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Resources

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References

Clagett, Marshall. Ancient Egyptian Science, Volume II: Calendars, Clocks, and Astronomy. 1995. pp. 457-462. ISBN 0-87169-214-7
Hong, Sungook "Book Review: Korean Water-Clocks: "Chagyongnu," the Striking Clepsydra, and the History of Control and Instrumentation Engineering." Technology and Culture - Volume 39, Number 3, July 1998, pp. 553-555
K. Higgins, D. Miner, C.N. Smith, D.B. Sullivan (2004), A Walk Through Time (version 1.2.1). [Online] Available: http://physics.nist.gov/time [2005, December 8]. National Institute of Standards and Technology, Gaithersburg, MD.
Needham, J., Ling, W., and de Solla Price, D.J. "Heavenly Clockwork: The Great Astronomical Clocks of Medieval China." 2nd Edition. 1986. ISBN 0521322766.
Noble, J.V. and de Solla Price, D.J. "The Water Clock in the Tower of Winds.", Amer. J. Archaeol., 72 (1968), 345-55.
Selin, Helaine. "Time and Clocks in Korea."

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Barnett, Jo Ellen. Time's Pendulum: From Sundials to Atomic Clocks, the Fascinating History of Timekeeping and How Our Discoveries Changed the World. Plenum Press, NY, 1998. ISBN 0-15-600649-9
Bruton, Eric. The History of Clocks and Watches. 1979. ISBN 0-8478-0261-2
Cowan, Harrison J. Time and Its Measurement: From the Stone Age to the Nuclear Age. The World Publishing Company, Ohio 1958.
Gerhard Dohrn-van Rossum "History of the Hour: Clocks and Modern Temporal Orders. Translated by Thomas Dunlap. The University of Chicago Press, Chicago 1996.
K. Higgins, D. Miner, C.N. Smith, D.B. Sullivan (2004), A Walk Through Time (version 1.2.1). [Online] Available: http://physics.nist.gov/time [2005, December 8]. National Institute of Standards and Technology, Gaithersburg, MD.
Jespersen, James and Fitz-Randolph, Jane. "From Sundials to Atomic Clocks: Understanding Time and Frequency." Second Revised Edition, 1999. ISBN 0-486-40913-9
King, David A. “Towards a History from Antiquity to the Renaissance of Sundials and Other Instruments for Reckoning Time by the Sun and Stars.” Annals of Science, Taylor & Francis. V. 61, Num. 3. July 2004. pp. 375-388. DOI: 10.1080/00033790310001642795.
Landes, D. Revolution in Time. Harvard University Press (1983).
McNown, J.S. “When Time Flowed: The Story of the Clepsydra.” La Houille Blanche, 5, 1976, 347-353. ISSN 00186368
Milham, Willis I. Time & Timekeepers including The History, Construction, Care, and Accuracy of Clocks and Watches. The Macmillan Company, NY 1945.
Reese, Abraham. “Rees's Clocks, Watches, and Chronometers 1819-20.” Charles E. Tuttle Company, Inc. 1970.
E. G. Richards "Mapping Time: The Calendar and It's History." Oxford University Press, 1998.
Toulmin, S. & Goodhead, J. The Discovery of Time. University of Chicago Press, 1999.
Turner, Anthony J. The Time Museum, Volume I, Time Measuring Instruments; Part 3, Water-clocks, Sand-glasses, Fire-clocks (Time Museum Catalogue of Water-Clocks, Fire-Clocks, Sand-Gla)

Babylonian Water Clocks

Englund, R.K. "Administrative Timekeeping in Ancient Mesopotamia." Journal of the Economic and Social History of the Orient, V. XXXI, 31 (1988) 121-185.
Fermor, John, & Steele, John M. “The design of Babylonian waterclocks: Astronomical and experimental evidence.” Centaurus. International Journal of the History of Mathematics, Science, and Technology. Vol. 42 Issue 3, pp. 210-222. July 2000. Blackwell Publishing.
Michel-Nozières, C. “Second Millennium Babylonian Water Clocks: a physical study.” Centaurus, Vol. 42, Issue 3, pp. 180-209. July 2000.
Neugebauer, Otto. “Studies in Ancient Astronomy. VIII. The Water Clock in Babylonian Astronomy.” Isis, Vol. 37, No. 1/2, pp. 37-43. (May, 1947). JSTOR link. Reprinted in Neugebauer (1983), pp. 239-245 (*).
Price, Derek deSolla. Science Since Babylon. Yale University Press, New Haven 1976.
Teresi, Dick. "Lost Discoveries: The Ancient Roots of Modern Science - from the Babylonians to the Maya." Simon & Schuster, NY 2002.
van der Waerden, Bartel Leendert, “Babylonian Astronomy: III. The Earliest Astronomical Computations.” Journal of Near Eastern Studies, 10 (1951), 20-34 JSTOR link.

Chinese Water Clocks

Needham, J., Ling, W., and de Solla Price, D.J. "Heavenly Clockwork: The Great Astronomical Clocks of Medieval China." 2nd Edition. 1986. ISBN 0521322766.
Quan, He Jun. “Research on scale and precision of the water clock in ancient China.” History of Oriental Astronomy, pp. 57-61. (Proceedings of the International Astronomical Union Colloquium No. 91 held in New Delhi, November 13-16, 1985). Edited by G. Swarup, A. K. Bag and K. S. Shukla. Cambridge University Press, Cambridge, 1987. ISBN 0-521-34659-2.
Walsh, Jennifer Robin. “Ancient Chinese Astronomical Technologies.” American Physical Society, Northwest Section. May, 2004. Meeting, 21-22 May, 2004. Pullman, WA.

Egyptian Water Clocks

Clagett, Marshall. Ancient Egyptian Science, Volume II: Calendars, Clocks, and Astronomy. 1995. pp. 457-462. ISBN 0-87169-214-7
Fermor, John, “Timing the Sun in Egypt and Mesopotamia.” Vistas in Astronomy, 41 (1997), 157-167. Elsevier Science. DOI: 10.1016/S0083-6656(96)00069-4.
Neugebauer, Otto & Parker, Richard A. “Egyptian Astronomical Texts: Iii. Decans, Planets, Constellations, and Zodiacs.”
Pogo, Alexander. “Egyptian water clocks”, Isis, vol. 25, pp. 403-425, 1936. Reprinted in Philosophers and Machines, O. Mayr, editor, Science History Publications, 1976. ISSN 00211753

Greek and Alexandrian Water Clocks

Hill, D.R. (ed. & trans.) (1976). Archimedes “On the Construction of Water-Clocks,” Turner & Devereux, Paris.
Noble, J.V. & de Solla Price, D. J. “The Water clock in the Tower of the Winds.” American Journal of Archaeology, 72, 1968, 345-355.
Woodcroft, Bennet (translator). "The Pneumatics of Hero of Alexandria." London, Taylor Walton and Maberly, 1851.
Vitruvius, P., The Ten Books on Architecture. (M.H. Morgan, translator) New York: Dover Publications, Inc., 1960.

Indian Water Clocks

Achar, N. “On the Vedic origin of the ancient mathematical astronomy of India.” Journal of Studies on Ancient India, vol 1, 95-108, 1998.
Fleet, J. F., “The ancient Indian water clock.” Journal of the Royal Asiatic Society, 213-230, 1915.
Kak, Subhash. "Babylonian and Indian Astronomy: Early Connections." February 17, 2003.
Pingree, D. “The Mesopotamian origin of early Indian mathematical astronomy.” Journal of the History of Astronomy, vol. 4, 1-12, 1973.
Pingree, D. “The recovery of early Greek astronomy from India.” Journal for the History of Astronomy, vol 7, 109-123, 1976.

Islamic Water Clocks

Hill, Donald Routledge (ed. & trans.) (1976). Archimedes “On the Construction of Water-Clocks,” Turner & Devereux, Paris.
Hill, Donald Routledge & Hasan, Ahmad Yusuf. “Islamic technology: an illustrated history.” New York: Cambridge University Press/Paris: Unesco, 1986. GALVIN
Hill, Donald Routledge. “Studies in Medieval Islamic Technology: From Philo to Al-Jazari - from Alexandria to Diyar Bakr.” (Collected Studies Series, 555)
King, D. Mikat. “Astronomical Timekeeping.” The Encyclopaedia of Islam. 7, Brill, (1990) Reprinted as Chapter V in King, D. “Astronomy in the Service of Islam Variorum.” (1993)

Korean Water Clocks

Hong, Sungook "Book Review: Korean Water-Clocks: "Chagyongnu," the Striking Clepsydra, and the History of Control and Instrumentation Engineering." Technology and Culture - Volume 39, Number 3, July 1998, pp. 553-555
Needham, Joseph, Major, John S., & Gwei-Djen, Lu. “Hall of Heavenly Records: Korean Astronomical Instruments and Clocks, 1380-1780.” Cambridge [Cambridgeshire] ; New York : Cambridge University Press, 1986. ISBN 0521303680
Selin, Helaine. "Time and Clocks in Korea."

Mesopotamian Water Clocks

Brown, David R., Fermor, John, & Walker, Christopher B.F., “The Water Clock in Mesopotamia.” Archiv für Orientforschung, 46/47 (1999/2000)
Chadwick, R. “The Origins of Astronomy and Astrology in Mesopotamia.” Archaeoastronomy. BULL. CTR ARCH. V. 7:1-4, P. 89, 1984. KNUDSEN Bibliographic Code: 1984BuCAr...7...89C
Fermor, John, “Timing the Sun in Egypt and Mesopotamia.” Vistas in Astronomy, 41 (1997), 157-167. Elsevier Science. DOI: 10.1016/S0083-6656(96)00069-4.
Walker, Christopher and Britton, John. “Astronomy and Astrology in Mesopotamia.” BMP, 1996 (especially pp. 42-67)

Present-day Water Clocks

Gitton, Bernard. “Time, like an everflowing stream.” Trans. Mlle. Annie Chadeyron. Ed. Anthony Randall. Horological Journal 131.12 (June 1989): 18-20.
Taylor, Robert. "Taiwan's Biggest Cuckoo Clock?: Recreating an Astronomical Timepiece". Sinorama Magazine. 3-15-2006
Xuan, Gao. "Principle Research and Reconstruction Experiment of the Astronomical Clock Tower in Ancient China." Proceeding of the 11th World Congress in Mechanism and machine Science. August 18-21, 2003. Tianjin, China.

Other Topics on Water Clocks and Related Material

Bedini, S.A. "The Compartmented Cylindrical Clepsydra." Technology and Culture 3(2):115-141. 1962. ISSN 0040165X
Goodenow, J., Orr, R., & Ross, D. "Mathematical Models of Water Clocks." Rochester Institute of Technology
Hill, Donald Routledge. “A History of Engineering in Classical and Medieval Times.” La Salle, Ill.: Open Court Pub., 1984. GALVIN. [Croom Helm, 1984.?]
Hill, Donald Routledge. "The Toledo Water-Clocks of c.1075." History of Technology, vol.16, 1994, pp.62-71
Landels, John G. "Water-Clocks and Time Measurement in Classical Antiquity." Endeavour 3(1):32-37. 1979. ISSN 01609327
Lepschy, Antonio M. "Feedback Control in Ancient Water and Mechanical Clocks." IEEE Transactions on Education, Vol. 35, No. 1, February, 1992.
Mills, A.A. “Newton’s Water Clocks and the Fluid Mechanics of Clepsydrae.” Notes and Records of the Royal Society of London. 37(1):35-61. 1982. ISSN 00355914
Neugebauer, Otto. The Exact Sciences in Antiquity. Dover Publications, NY 1969.
Sarma, S.R., “Setting up the Water Clock for Telling the Time of Marriage.” in Studies in the History of the Exact Sciences in Honour of David Pingree, éd. Ch. Burnett, J.P. Hogendijk, K. Plofker, M. Yano, Leiden-Boston, 2004, pp. 302-330.
Snell, Daniel. “Life in the Ancient Near East, 3100-332 B.C.E.” ISBN 0300076665.

Non-English Resources

Bilfinger, Gustav, Die babylonische Doppelstunde: Eine chronologische Untersuchung (Wildt, Suttgart, 1888).
Borchardt, Ludwig. 1920. “Die Altägyptische Zeitmessung.” (Old Egyptian time measurement). Berlin/Leipzig.
Ginzel, Friedrich Karl, “Die Wassermessungen der Babylonier und das Sexagesimalsystem”, Klio: Beiträge zur alten Geschichte, 16 (1920), 234-241.
Høyrup, J., “A Note on Waterclocks and the Authority of Texts.” Archiv für Orientforschung, 44/45 (1997/98), 192-194 (*).
Planchon, "L'Heure Par Les Clepsydres." La Nature. pp.55-59.
Thureau-Dangin, François, “La clepsydre chez les Babyloniens [Notes assyriologiques LXIX]”, Revue d’assyriologie et d’archéologie orientale, 29 (1932), 133-136.
Thureau-Dangin, François, “Clepsydre babylonienne et clepsydre égyptienne”, Revue d’assyriologie et d’archéologie orientale, 30 (1933), 51-52.
Thureau-Dangin, François, “Le clepsydre babylonienne”, Revue d’assyriologie et d’archéologie orientale, 34 (1937), 144.

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