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WATER CLOCK OVERVIEW Water clocks, along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical Gnomon and day-counting Tally Stick . 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. Some authors, however, write about water clocks appearing as early as 4000 BC . The Greek and Roman civilizations are credited for initially advancing the water clock design to include complex gearing, which was connected to fanciful Automata and improved accuracy. These advances were passed on through Byzantium and Islamic times, which eventually made their way on to Europe . Independently, China developed their own advanced water clocks, passing on their ideas to Korea and Japan . 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 17th century Europe. Egypt The oldest water clock of which there is physical evidence dates to ''c.'' 1400 BCE and was used in the Temple Of Amen-Re ., pp. 59–61 The oldest documentation of the water clock is the tomb inscription of the 16th century BCE Egyptian court official Amenemhet, which identifies him as its inventor.1 These simple water clocks, which were of the outflow type, 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 Month s 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. Babylon In Babylon, water clocks were of the outflow type and were cylindrical in shape. Use of the water clock as an aid to astronomical calculations dates back to the Old Babylonian Period (''c.'' 2000 BCE–''c.'' 1600 BCE).2 While there are no surviving water clocks from the Mesopotamian region, most evidence of their existence comes from writings on clay tablets. Two collections of tablets, for example, are the ''Enuma-Anu-Enlil'' (1600–1200 BCE) and the '' MUL.APIN '' (7th century BCE).3 In these tablets, water clocks are used in reference to payment of the night and day watches (guards). These clocks were unique, as they did not have an indicator such as hands (as are typically used today) or grooved notches (as were used in Egypt). Instead, these clocks measured time "by the weight of water flowing from" it. The volume was measured in capacity units called ''qa''. The weight, ''mana'' (the Greek unit for about one pound), is the weight of water in a water clock. It is important to note that during Babylonian times, time was measured with temporal hours. So, as seasons changed, so did the length of a day. "To define the length of a 'night watch' at the summer solstice, one had to pour two mana of water into a cylindrical clepsydra; its emptying indicated the end of the watch. One-sixth of a mana had to be added each succeeding half-month. At equinox, three mana had to be emptied in order to correspond to one watch, and four mana were emptied for each watch of the winter solstitial night." Greece and Rome In Greece , a water clock was known as a clepsydra (water thief). A commonly used water clock was the simple outflow clepsydra. This small earthenware vessel had a hole in its side near the base. In both Greek and Roman times, this type of clepsydra was used in courts for allocating periods of time to speakers. In important cases, when a person's life was at stake for example, it was filled. But, for more minor cases, it was only partially filled. If proceedings were interrupted for any reason, such as to examine documents, the hole in the clepsydra was stopped with wax until the speaker was able to resume his pleading. Between 270 BC and AD 500 , Greek ( Ctesibius , Hero Of Alexandria , Archimedes ) and Roman Horologists and Astronomer s 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. For example, some water clocks rang Bell s and Gong s, 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 Octagon al structure showed scholars and shoppers both Sundial s 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 Season s of the year and astrological dates and periods. India |
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