Su Song's astronomical clock at Kaifeng

1111

In the Song capital, the polymath official Su Song completed and described a thirty-foot-tall water-driven clock tower with an armillary sphere, celestial globe, and bell-striking puppets, accurate to within seconds a day. The machine would be dismantled by the Jurchen invaders a few years later. Su Song's treatise on the mechanism, illustrated with detailed diagrams, survives as one of the great documents of medieval Chinese engineering.