Detail from a model (scale 1:48) of a Chinese astronomical clock, copied from Su Song's 'New Design for a Mechanised Armillary Sphere and Celestial Globe' (1092). Su Song (1020-1101) was a Chinese astronomer and inventor who was ordered by the emperor to construct a complex armillary clock. The original clock-tower was 37 feet high overall. The clock mechanism drove the armillary sphere mounted on top of the tower, while inside the tower a celestial globe was rotated once in a sidereal day by the clock. The time of day was shown by 'jacks' appearing in apertures in the sides of the tower and was also sounded audibly. This image shows shows the water wheel, which has 36 buckets, and the sump below used to collect the water falling from the buckets.
© Science Museum / Science & Society Picture Library