TOWARDS the end of the 11th century, while tardy Europeans kept time with sundials, Su Sung of China completed his masterpiece: a water clock of great intricacy and accuracy.

• 11世纪末的时候，迟缓的欧洲人还在用日冕仪计时，而中国的苏松[音译]已经完成了他的杰作：一座非常复杂而又走时准确的水钟。