The Drum Tower of Datong, China

Datong 's Drum Tower dates from the Ming Dynasty, with many later repairs and restorations.  Due to its proximity to the "barbarian" frontier, it served variously as the Northern Wei capital from 439-535, a secondary capital under the Liao (916-1125) and Jin (1115-1234), and a military headquarters during the Ming Dynasty.   I was surprised to learn that it was also a clock, or at least a timekeeper. Drummers would make noise at various times of day, and the whole village could hear them. 

The mechanical clock is an invention we all use today. According to historical research, the world's first clock was invented by Yi Xing, a Buddhist monk and mathematician of the Tang Dynasty (618－907). Yi's clock operated with water steadily dripping on a wheel that made a full revolution every 24 hours. It permitted the exact determinations of the time of dawn and dusk, full and new moons, tarrying and hurrying. Moreover, there were two wooden jacks standing on the horizon surface, having one a bell and the other a drum in front of it, the bell being struck automatically to indicate the hours, and the drum being beaten automatically to indicate the quarters.  So pay no attention to those who say the mechanical clock is a European invention.  It was first made in China.

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