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===Medieval Islamic world=== [[File:Al-jazari elephant clock.png|thumb|left|[[Al-Jazari]]'s [[Elephant clock|elephant water clock]] (1206).<ref>{{cite book | last = ibn al-Razzaz al-Jazari | author-link = al-Jazari | others = Translated and annotated by [[Donald Routledge Hill]] | title = The Book of Knowledge of Ingenious Mechanical Devices | year = 1974 | publisher = D. Reidel | location = Dordrecht | isbn = 969-8016-25-2}}</ref>]] In the [[Islamic Golden Age|medieval Islamic world]] (632-1280), the use of water clocks has its roots from Archimedes during the rise of [[Alexandria]] in [[Egypt]] and continues on through [[Byzantium]]. The water clocks by the Arabic engineer [[Al-Jazari]], however, are credited for going "well beyond anything" that had preceded them. In Al-Jazari's 1206 treatise, he describes one of his water clocks, the [[elephant clock]]. The clock recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks, the top tank was connected to the time indicating mechanisms and the bottom was connected to the [[Regulator (automatic control)|flow control regulator]]. Basically, at daybreak, the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.<ref>{{Harvnb|al-Hassan|Hill|1986|pp=57β59}}</ref> [[File:Clock of al Jazari before 1206.jpg|thumb|Water-powered automatic [[castle clock]] of [[Al-Jazari]], 12th century.]] The most sophisticated water-powered [[astronomical clock]] was [[Al-Jazari]]'s [[castle clock]], considered by some to be an early example of a programmable [[analog computer]], in 1206.<ref name="Ancient Discoveries">{{cite web|title=Ancient Discoveries, Episode 11: Ancient Robots |publisher=[[History (U.S. TV channel)|History Channel]] |url=https://www.youtube.com/watch?v=rxjbaQl0ad8 |access-date=2008-09-06 |url-status=dead |archive-url=https://web.archive.org/web/20140301151115/https://www.youtube.com/watch?v=rxjbaQl0ad8 |archive-date=March 1, 2014 }}</ref> It was a complex device that was about {{convert|11|ft|m}} high, and had multiple functions alongside timekeeping. It included a display of the [[zodiac]] and the solar and lunar orbits, and a pointer in the shape of the crescent moon which traveled across the top of a gateway, moved by a hidden cart and causing automatic doors to open, each revealing a mannequin, every hour.<ref>Howard R. Turner (1997), ''Science in Medieval Islam: An Illustrated Introduction'', p. 184. [[University of Texas Press]], {{ISBN|0-292-78149-0}}.</ref><ref name=Hill2>[[Donald Routledge Hill|Routledge Hill, Donald]], "Mechanical Engineering in the Medieval Near East", ''Scientific American'', May 1991, pp. 64β69. ([[cf.]] [[Donald Routledge Hill]], [http://home.swipnet.se/islam/articles/HistoryofSciences.htm Mechanical Engineering] {{Webarchive|url=https://web.archive.org/web/20071225091836/http://home.swipnet.se/islam/articles/HistoryofSciences.htm |date=2007-12-25 }})</ref> It was possible to re-program the length of day and night in order to account for the changing lengths of day and night throughout the year, and it also featured five musician automata who automatically play music when moved by levers operated by a hidden camshaft attached to a water wheel.<ref name="Ancient Discoveries"/> Other components of the castle clock included a main reservoir with a float, a [[float chamber]] and flow regulator, plate and valve trough, two pulleys, crescent disc displaying the zodiac, and two falcon [[Automaton|automata]] dropping balls into vases.<ref>{{cite web|url=http://www.google.com.my/search?hl=en&q=two+falcon+automata+dropping+balls+into+vases&um=1&ie=UTF-8&tbo=u&tbs=bks:1&source=og&sa=N&tab=wp|title=two falcon automata dropping balls into vases β Google Search|website=www.google.com.my}}</ref>{{Unreliable source?|sure=y|reason=This is just a link to a google search for the preceding phrase"|date=March 2017}} The first water clocks to employ complex segmental and [[epicyclic gearing]] was invented earlier by the [[Arab]] engineer [[Ibn Khalaf al-Muradi]] in [[Al-Andalus|Islamic Iberia]] c. 1000. His water clocks were driven by [[water wheel]]s, as was also the case for several Chinese water clocks in the 11th century.<ref name=Hassan/> Comparable water clocks were built in [[Damascus]] and [[Fes, Morocco|Fez]]. The latter ([[Dar al-Magana]]) remains until today and its mechanism has been reconstructed. The first European clock to employ these complex gears was the astronomical clock created by [[Giovanni Dondi dell'Orologio|Giovanni de Dondi]] in c. 1365. Like the Chinese, Arab engineers at the time also developed an [[escapement]] mechanism which they employed in some of their water clocks. The escapement mechanism was in the form of a constant-head system, while heavy floats were used as weights.<ref name=Hassan>[[Ahmad Y Hassan|Hassan, Ahmad Y]], [http://www.history-science-technology.com/Articles/articles%2071.htm Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic Engineering], ''History of Science and Technology in Islam''</ref>
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