Clocks, Chinese & Japanese Water-balance escapement, Chinese, 1088

Clocks, Chinese & Japanese Water-balance escapement, Chinese, 1088. Working model (scale 1:6). The original was used in Su Song's astronomical clock-tower (tour horloge astronomique a energie hydraulique de Su Song) of 1088. Su Song (1020-1101) was a Chinese astronomer and inventor who was ordered by the emperor to construct a complex armillary clock. With his advisers, he built a full-scale working model in wood which was tested before the metal parts were cast. The water-balance escapement represents a 'missing link' between earlier water clocks, whose timekeeping depended upon measuring changes in the waterlevel, and the all-mechanical escapement clock developed in Europe towards the end of the 13th century. ©SSPL/Science Museum