The weight-driven mechanical clock with verge escapement
A clock in which a falling weight turns toothed wheels, while an escapement (a verge with a foliot) lets the wheel advance one tooth at a time, dividing time into equal beats. The inventor is unknown. In 1271 Robertus Anglicus, teaching in Paris or Montpellier, writes that clockmakers are trying to make a wheel that completes exactly one revolution a day, but have not yet succeeded.
Before them time was measured by the sun and by water, and a summer hour was longer than a winter one. The mechanism for the first time gave equal hours, the same by day and night, in every season.
A similar escapement had been built in China two hundred years earlier by Su Song. Whether the two inventions are connected is unknown.
Why this date
approximate. The 1911 Britannica places the first clocks in Europe in the 13th century. In 1271 Robertus Anglicus writes that craftsmen are trying to make a wheel that turns exactly once a day but have not yet succeeded; this passage is taken as the lower bound for the invention. There is no exact date for the first working mechanism.
Other links
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Su Song's astronomical clock tower and the water-wheel 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
- Encyclopædia Britannica, 11- (1911), «Clock», 6, Wikisource (1911) Verified 4 Oct 2026
The earliest clocks seem to have come into use in Europe during the 13th century.
- 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, «Mechanized Astronomical Models» (1959) Verified 4 Oct 2026
The date of this passage, 1271, has been taken as a _terminus post quem_ for the invention of the mechanical clock.
"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.