Su Song Completes His Astronomical Clock Tower

1090

In Kaifeng, the engineer Su Song finished constructing a water-powered astronomical clock tower standing forty feet tall. Its three levels housed an armillary sphere for observation, a celestial globe tracking planetary motions, and wooden automata that struck the hours and displayed plaques announcing the time. An endless chain drive - the world's first - linked the mechanism. The clock ran continuously for thirty-five years before Jurchen invaders dismantled it and carted it north.