Magazine article UNESCO Courier

The Mechanical Clock

Magazine article UNESCO Courier

The Mechanical Clock

Article excerpt

The Chinese did not invent the first clock of any kind, merely the first mechanical one. Water clocks had existed since Babylonian times, and the earliest Chinese got them indirectly from that earlier civilization of the Middle East.

The world's first mechanical clock was built by the Chinese Tantric Buddhist monk and mathematician Yixing (683-727). This was actually an astronomical instrument which served as a clock, rather than simply a clock. A contemporary text describes it:

"[It] was made in the image of the round heavens and on it were shown the lunar mansions in their order, the equator and the degrees of the heavenly circumference. Water, flowing into scoops, turned a wheel automatically, rotating it one compTete revolution in one day and night [24 hours]. Besides this, there were two rings fitted around the celestial sphere outside, having the sun and moon threaded on them, and these were made to move in circling orbit. ... And they made a wooden casing the surface of which represented the horizon, since the instrument was half sunk in it. It permitted the exact determinations of the time of dawns and dusks, full and new moons, tarrying and hurrying. Moreover, there were two wooden jacks standing on the horizon surface, having one a bell and the other a drum in front of it, the bell being struck automatically to indicate the hours, and the drum being beaten automatically to indicate the quarters. All these motions were brought about by machinery within the casing, each depending on wheels and shafts, hooks, pins and interlocking rods, stopping devices and locks checking mutually [i.e. the escapement]".

Yixing's clock was, like water clocks, subject to the vicissitudes of the weather. In order to keep the water in them from freezing, torches generally burnt beside them. Therefore, in the next great clock of which we have accounts in China, mercury was substituted for water because of the freezing problem. This clock was built by Zhang Sixun in 976 AD. Zhang Sixun's clock was apparently much larger than Ylxing's. It was certainly far more complex. The dynastic history of the time describes it:

"... a tower of three storeys each over 3 metres in height, within which was concealed all the machinery. …

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