Water clock

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A water clock or clepsydra is any timekeeper operated by means of a regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where it is measured.

Contents 1 Water clock overview 2 Resources 2.1 References 2.2 Further reading 3 External links 4 See also

[edit] Water clock overview

Water clocks are possibly the oldest time-measuring instruments, with the only exceptions being the gnomon and day-counting tally sticks. Given their great antiquity, where and when they first existed are not known and perhaps unknowable. The simplest form of water clocks, the bowl-shaped outflow type, are known to have existed in Babylon and in Egypt around the 16th century B.C. Other regions of the world, including India and China, also have early evidence of water clocks but the earliest dates are less certain. It is possible that the earliest water clocks existed as early as 3000 BC, given the advancement of civilizations during that time.

Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. It is important to point out that the need for the common person to 'know what time it is' largely did not exist until the Industrial Revolution, when it became important to keep track of hours worked. In the earliest of time, however, 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. 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.

In February 1885, one of the oldest detailed descriptions of an outflow water clock was found in the tomb of an 18th dynasty (16th century B.C.) dignitary named Amenemhet located near the top of the hill of Sheikh Abd el-Gurnah in Western Thebes. However, the oldest surviving archaeological evidence of a water clock on record is from the temple of Karnak in Upper Egypt, dating from King Amenhotep III (1415 - 1380 B.C). These simple water clocks were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. There were twelve separate columns with consistently spaced markings on the inside to measure the passage of "hours" as the water level reached them. The columns were for each of the twelve months to allow for the variations of the seasonal hours. These clocks were used to determine hours at night, but may have been used in daylight as well.

In Greece, a water clock was known as a clepsydra (water thief). Between 270 BC and AD 500, Greek (Ctesibius, Hero of Alexandria, Archimedes) and Roman horologists and astronomers were developing more elaborate mechanized water clocks. 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, while others opened doors and windows to show figurines of people, or moved pointers, and dials. Some even displayed 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.

In eastern Asia, water clocks were very important in the study of astronomy and astrology. The 3rd century Chinese clepsydras drove various mechanisms that illustrated astronomical phenomena. One of the most elaborate clock towers was built by Su Song (蘇頌) and his associates in 1088, during the Chinese Song Dynasty. Su Song's mechanism incorporated a water-driven escapement invented about 725 (during the Tang Dynasty). 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. In 1434 during the Choson (or Joseon) Dynasty, Chang Yongsil (or Jang Young Sil), Palace Guard and later Chief Court Engineer, constructed the Chagyongnu (self-striking water clock or striking clepsydra) for King Sejong. What made the Chagyongnu self-striking (or automatic) was the use of jack-work mechanisms, by which three wooden figures (jacks) struck objects to signal the time. This innovation no longer required the reliance of human workers, known as "rooster men", to constantly replenish it. 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 glasstube design can be found in a couple places in the United States, including the Children's Museum in Indianapolis, Indiana, and in over 30 locations throughout the world, including the Shopping Iguatemi in São Paulo, Brasil. Also, there are some other modern designs of water clocks, including the Royal Gorge water clock in Colorado and the Woodgrove Mall in Nanaimo, British Columbia. Today overall, the use of water flow to power a clock is a rarely practiced art, where its purpose has become more for show and novelty than for functional accuracy.

[edit] Resources

[edit] 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 0-521-32276-6.
• 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."

[edit] Further reading

Overview of water clocks and other time instruments

• 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 0018-6368
• 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, Stephen & Goodhead, J. The Discovery of Time. University of Chicago Press, 1999. ISBN 0-226-80842-4
• 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.
• Høyrup, J., “A Note on Waterclocks and the Authority of Texts.” Archiv für Orientforschung, 44/45 (1997/98), 192-194 (*).
• 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

• Lorch, Richard P. "Al-Khazini's Balance-clock and the Chinese Steelyard Clepsydra." Archives Internationales d'Histoire des Sciences, June 1981, 31: 183-189.
• Needham, J., Ling, W., and de Solla Price, D.J. "Heavenly Clockwork: The Great Astronomical Clocks of Medieval China." 2nd Edition. 1986. ISBN 0-521-32276-6.
• 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 0021-1753
• Slowley, R.W., "Ancient Clepsydrae", Ancient Egypt, 1924, pages 43-50.
• Slowley, R.W., "Primitive methods of measuring time", JEA 17, 1931, pages 174-176.

European water clocks

• Drover, C.B. "A Medieval Monastic Water Clock", Antiquarian Horology, Vol. I, No. 5 (1954), 54-58.
• Hill, Donald Routledge. "A History of Engineering in Classical and Medieval Times." La Salle, Ill., Open Court Pub. 1996. ISBN 0-415-15291-7
• Hill, D.R. "The Toledo Water-Clocks of c.1075." History of Technology, vol.16, 1994, pp.62-71
• Scattergood, John. "Writing the clock: the reconstruction of time in the late Middle Ages." European Review, Issue 4 (Oct, 2003), 11: 453-474 Cambridge University Press (School of English, Trinity College, Dublin 2, Ireland. jscatter@tcd.ie)

Greek and Alexandrian water clocks

• Hill, D.R. (ed. & trans.) (1976). Archimedes “On the Construction of Water-Clocks,” Turner & Devereux, Paris.
• Lepschy, Antonio M. "Feedback Control in Ancient Water and Mechanical Clocks." IEEE Transactions on Education, Vol. 35, No. 1, February, 1992.
• 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)

Japanese water clocks

• Kiyoyasu, Maruyma. "Hoken shakai to gijutsu - wadokei ni shuyaku sareta hoken gijutsu." Kagakushi kenkyu, Sept. 1954, 31:16-22.

Korean water clocks

• Hahn, Young-Ho and Nam, Moon-Hyon. "Reconstruction of the Armillary Spheres of Mid-Chosun: The Armillary Clocks of Yi Minchol." Hanguk Kwahaksa Hakhoeji (Journal of the Korean History of Science Society)19.1 (1997): 3-19. (in Korean)
• Hahn, Young-Ho, et al. "Astronomical Clocks of Chosun Dynasty: King Sejong's Heumgyonggaknu. Kisulgwa Yoksa (Journal of the Korean Society for the History of Technology and Industry) 1.1 (2000): 99-140. (in Korean).
• 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
• Nam, Moon-Hyon. “Chagyongnu: The Automatic Striking Water clock.” Korea Journal, 30.7 (1990): 9-21.
• Nam, Moon-Hyon. Korean Water Clocks: Jagyongnu, The Striking Clepsydra and The History of Control and Instrumentation Engineering. Seoul: Konkuk University Press, 1995. (in Korean)
• Nam, Moon-Hyon. On the BORUGAKGI of Kim Don -- Principles and Structures of JAYEONGNU. Hanguksa Yeongu (Studies on Korean History),101 (1998): 75-114 (in Korean)
• Nam, Moon-Hyon. Jang Yeong-Shil and Jagyeongnu - Reconstruction of Time Measuring History of Choseon Period. Seoul National University Press, 2002. (in Korean)
• Nam, Moon-Hyon and Jeon San-Woon. “Timekeeping Systems of Early Choson Dynasty.” Proceedings of First International Conference on Oriental Astronomy, From Guo Shoujing to King Sejong, Seoul, October 6-11, 1993, Seoul, Yonsei University Press, 1997. 305-324.
• 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 0-521-30368-0
• Hyeonjong Shillock (Veritable Records of King Hyeonjong), 1669
• Jungjong Shillok (Veritable Records of King Jungjong), 1536.
• Sejong Shillock (Veritable Records of King Sejong), Chapter. 65, A.D. 1434 and Chapter. 80, A.D. 1438.

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 0040-165X
• Goodenow, J., Orr, R., & Ross, D. "Mathematical Models of Water Clocks." Rochester Institute of Technology
• Landels, John G. "Water-Clocks and Time Measurement in Classical Antiquity." Endeavour 3(1):32-37. 1979. ISSN 0160-9327
• 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 0035-9149
• 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 0-300-07666-5.

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.
• Daressy, G., "Deux clepsydres antiques", BIE, serie 5, 9, 1915, pages 5-16
• Ginzel, Friedrich Karl, “Die Wassermessungen der Babylonier und das Sexagesimalsystem”, Klio: Beiträge zur alten Geschichte, 16 (1920), 234-241.
• 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.

[edit] External links

• http://www.marcdatabase.com/~lemur/dm-gitton.html#iw-time-flow-clocks
• http://www.perseus.tufts.edu/GreekScience/Students/Jesse/CLOCK1A.html
• http://physics.nist.gov/GenInt/Time/time.html
• http://www.ubr.com/clocks/pub/clep/clep.html
• http://www.childrensmuseum.org/themuseum/waterclock.htm
• http://www.landmarkclocks.com/page14.html

[edit] See also

• Hourglass
• Armillary Sphere
• Astrolabe
• Gnomon