Su Song's astronomical clock tower and the water-wheel escapement
A tower about nine metres (30 feet) high built in the Song capital Kaifeng: an armillary sphere turned at the top, a celestial globe inside, and figures in windows announced the time. Everything was driven by a scoop water-wheel that turned in jerks: a scoop filled, outweighed, and a lever mechanism let the wheel advance by one spoke and locked it again. Su Song described the device in a book of 1090, with drawings of every part.
Price considers this an independent invention of the mechanical escapement, that is, of dividing a steady motion into equal portions. European clocks with a weight and verge appeared two centuries later; Price allows that the Chinese device may have been their source, but does not claim it.
Here for the first time one sees that steady going can be obtained not from a smooth flow of water but by counting identical steps. Every mechanical clock rests on the same principle.
Why this date
reliable. The tower was built at Kaifeng in 1088-1092; Price dates Su Song's description, Xin yixiang fayao, to 1090.
Other links
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The weight-driven mechanical clock with verge escapement
parallel to · Confidence: medium
A mechanical escapement appears both in Su Song's water-wheel clock in China and in the European weight-driven clock. Price does not decide how they are related: he calls the Chinese escapement an independent invention not found in the European line, and at once allows that it may have been the basis of European horology. There is no document of transmission, so the link is shown as a parallel.
Dispute: Price himself hesitates: he calls the Chinese escapement an independent invention and at once allows ('may have been') that it was the basis of European horology, tentatively proposing a transmission from the East around 1100. There is no document of transmission, so the link is shown as a parallel.
Link sources
- Price D. J. de S. «On the Origin of Clockwork, Perpetual Motion Devices, and the Compass», United States National Museum Bulletin 218, Washington: Smithsonian Institution, 1959, Project Gutenberg, «The Chinese Tradition» (1959) Verified 4 Oct 2026
this stem reveals the crucial independent invention of a mechanical escapement, a feature not found in the European stem
- Price D. J. de S. «On the Origin of Clockwork, Perpetual Motion Devices, and the Compass», United States National Museum Bulletin 218, Washington: Smithsonian Institution, 1959, Project Gutenberg, «The Chinese Tradition» (1959) Verified 4 Oct 2026
the medieval Chinese escapement may have been the basis of European horology
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- Price D. J. de S. «On the Origin of Clockwork, Perpetual Motion Devices, and the Compass», United States National Museum Bulletin 218, Washington: Smithsonian Institution, 1959, Project Gutenberg, «The Chinese Tradition» (1959) Verified 4 Oct 2026
Node sources
- Price D. J. de S. «On the Origin of Clockwork, Perpetual Motion Devices, and the Compass», United States National Museum Bulletin 218, Washington: Smithsonian Institution, 1959, Project Gutenberg, «The Chinese Tradition» (1959) Verified 4 Oct 2026
written by Su Sung in A.D. 1090
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.