GREEK WATER CLOCKS

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This is the newest post in category SUNDIALS AND CLOCKS.

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Ctesibius built a complex water clock. A tank was kept full by wasting excess water down a spillway. The constant pressure at the bottom filled a bucket with water. The bucket would tip, dumping its contents into a lower tank and.rotating an axle 60 degrees. A statue of a naked soldier floated on the water in the lower tank, his spear pointing to lines on a wide cylinder. Once a day, the water level in the lower tank tripped a syphon, emptying the lower tank.
The rotating axle connected to a train of gears that rotated the wide cylinder once every 360 days. The curved lines on the wide cylinder marked sunrise as zero hour, noon as 6 and sunset as 12 and the next sunrise as 24. Rotation of the cylinder gave the correct time of sunrise and sunset for each day of the year

Another Greek clock design turned a hand like that on the face of modern non-digital clocks.
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VARIOUS CLOCKS

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Al-Jazari borrowed from another Muslim the idea of attaching a thin rope between a large candle and a counterweight. As the candle burned away, the counterweight caused a small statue of a man to rise, causing his sword to point to the hour. Al-Jazari invented a push-and-twist “bayonet fitting“ to hold the candle.
Later Alexandria Greek designs of water clocks wasted less water, using float valves to keep the upper tank full. Greeks and Muslims knew that temperature greatly affected the speed of water clocks.
Al-Jazari built a mercury clock in which a pulley rope was wrapped around a small barrel half-filled with mercury. The barrel contained compartments connected to each other by small holes.
The ancient Hindu water clocks used a bowl with a hole design that took 4 hours to sink, causing a gong to be hit, Later Hindu designs automatically reset the bowl.
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AL-JAZARI’S PSEUDO-ARCHIMEDES CLOCK

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This castle clock in al-Jazari’s 1206 book was invented by a Greek who wrote under the pseudonym of Archimedes. One existed in the Greek Christian city of Gaza prior to the year 529. Many centuries later, al-Jazari made a small improvement in the mechanism for adjusting the speed to make the days longer in the summer.
A float valve kept Tank#2 exactly full from water in tank #1. Tank#2 delivered water at a constant rate to tank#3. Once an hour, when tank#3 tipped over, one or 2 balls at the top of the clock would be released to power opening of display doors, and the released water struck musical instruments and blew a flute or horn.
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AL-JAZARI’S ELEPHANT CLOCK

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In the year 1050, the Hindu prince Bhoja wrote about a type of water clock used in India. It had an elephant shape with a rotating statue of a scribe with a pen in his hand pointing at the time. Once every half hour, the bowl sank from water entering a hole in its bottom, and the scribe statue would return to its starting position.
I assume the bowl was automatically reset, perhaps by the same weight of a falling ball method as the elephant clock written about by al-Jazari 156 years later in what is now Turkey. The 24 elephant clock hours were of equal length.
Both the Hindus and al-Jazari made other shapes of water.clocks that made various noises.
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SUNDIALS

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Synopsis:
In the 14th century the astronomer ibn al-Shatir in Damascus tilted the face of his sundial to be inclined at an angle of 56.5 degrees (90 degrees minus his latitude).
This made the face of the sundial parallel to the plane of the equator, so the sundial told time the same way as a sundial at the North Pole. It divided the day into 24 hours of equal length.
A problem was that prayer time in Islam is instead based on sundial hours that are 1/12 of the time from sunrise to sunset.
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