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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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Al-Jazari’s sinking bowl water clocks were similar to the elephant clocks built centuries earlier by Hindus in India. The Hindu day was divided into 6 divisions each 240 minutes long, and each of these was divided into 5 or 10 divisions of 24 minutes or 48 minutes each.
The earliest Hindu clocks used a floating bowl with a hole in its bottom, requiring a student or servant to reset the bowl every 4 hours.
In the year 1050, several centuries prior to al-Jazari, the Hindu prince Bhoja wrote about 2 types of water clocks used in India. One type had 30 bowls, arranged on the ground along the circumference of a circle
Every 48 minutes, the sinking of a bowl would be followed by the release of the bowl in the next adjacent device. I assume human intervention to reset the clock was required only once a day, not every 48 minutes.
The second type of clock mentioned by the Hindu prince was a rotating statue on top of an elephant. Each time the bowl sank, the statue would return to its starting position.
Source is page 225 of “A History of Engineering In Classical and Medieval Times” by Donald Hill (1984), which cites V. Ragavan, “Yantras Or Mechanical Contrivances In Ancient India”, transaction no. 10, (1952) page 23.
I assume that this type of clock was also capable of running 24 hours before requiring human intervention. [It would be illogical for both types of clocks to be in use if one could run 24 hours without human intervention but the other type required frequent human intervention.]
In the year 1206, al-Jazari described his increasingly complex sinking bowl water clocks he built for his wealthy customers. The most complicated of these was the elephant clock, which I presume was similar to the elephant clock described centuries earlier by a Hindu prince in India.
The elephant clock displayed the number of equal-length hours since sunrise by uncovering silver discs. At his latitude in what is now Turkey, this could be as much as 15 hours in the summer or as little as 9 hours in the winter.
Each morning at sunrise, the clock operator would load 18 to 30 balls in the top of the clock, one for each half hour. A bowl (attached by 3 hinges in series to the inside wall of a water tank hidden inside the elephant statue) had a piece of agate mounted near its bottom. In manufacturing the clock, a hole would be drilled through the agate, and gradually increased in size until it took exactly a half hour for the bowl to sink because of water entering the hole near the bottom of the bowl.
The elephant clock used the sinking bowl to pull on a pulley rope wrapped around a wheel under a statue of a scribe. As the statue rotated, the enormous pen he held pointed to the minutes of the clock face drawn on the floor.
When the bowl sank completely, it would pull on a chain which released a ball from the top of the clock into the mouth of the dragon-serpent on the left. This caused the neck of the dragon-serpent on the left to gradually fall, resulting in the head of the dragon-serpent almost biting the elephant. It also caused the elephant driver to hit the elephant. As the head of the dragon-serpent fell, its tail rose, pulling a chain that reset the bowl.
The ball would be released from the mouth of the dragon-serpent to hit the cymbal on the left to make a loud noise. With the dragon-serpent no longer pulled down by the weight of the ball, it would return to its starting position. A weight at the opposite end of the pulley rope pulled the scribe back to his starting position.
The gradual sinking of the bowl would repeat until a half hour later when a ball would be released into the mouth of the other dragon-serpent. This caused different motions of the elephant driver and ended with the ball hitting the other cymbal.
Al-Jazari’s previous clocks used bowls with vertical sides.
The hemisphere shape of the bowl of the elephant clock would have increased its tendency to run faster at the beginning of the half hour cycle. The boat-shaped bowl in the diagram is not the bowl used in the elephant clock, but the bowl of a different clock al-Jazari built. The author of the internet article may have deliberately depicted the wrong bowl to make the elephant clock look more dramatic.
The clock face had 15 markings spaced at intervals of 15° for displaying 30 minutes at 2-minute intervals.
If the hole is very small in any water clock, the much higher viscosity of cold water would cause it to run much slower in the winter than in the summer.
Click to download pdf document explaining it http://www.thetech.org/sites/default/files/activity_6.pdf
The following video shows the clock in motion: http://www.youtube.com/watch?v=doYPp-gaJ0o Both of these internet links show an incorrect illustration of the bowl shape, and omit mention of the hinges.
The quotation from the traveler Ibn Battuta is entirely fake except for his age and the year he left Tangiers. Ibn Battuta never saw the elephant clock, and wrote about the people he met during his travels, his duties as a sharia law judge, and about the threat of Arab highway robbers, not about Muslim inventions.
The elephant handler hit the elephant with an axe blade, not with a mallet. The narration was altered to hide the animal cruelty.
The depiction of scholars in the video is from a painting of a late 16th century observatory in Istanbul. The traveler traveled in the early 14th century, so he could not have written about technology of 250 years later. [I read the multi-volume English translation of the book, and there is no mention of technology except for a Mongolian marching band, and no mention of scholars except for a Jewish medical doctor despised by the traveler, and Quran scholars.
THEME OF ELEPHANT CLOCK
The theme of this clock was perhaps Greeks writing about an ancient myth of India that elephants traveling through the forest would be attacked by enormous gold-scaled dragon-serpents hiding in the trees http://www.theoi.com/Thaumasios/DrakonesIndikoi.html
The tower on the elephant looks like a hilltop astronomical observatory.
CHINESE WATER CLOCKS
Chinese water clocks used a very different design, based on the weight of the water causing the see-saw with a bucket to rotate and temporarily cut off the flow of water.
Image by al-Jazari, via Wikimedia Commons.
image credit https://commons.wikimedia.org/wiki/File:Al-jazari_elephant_clock.png#mw-jump-to-license