'The Karnak Clepsydra', Egyptian celestial diagram, c 1400 BC.
© Science Museum / Science & Society Picture Library
A copy (made in 1939) of the hieroglyphics and other figures embosed on the outside of an Egyptian water clock or 'clepsydra' which was discovered in the Temple of Karnak, Luxor, Upper Egypt, and dates from the rule of King Amenhophis III (1415- 1380 BC). The top row shows a series of planet gods and the 36 decan stars - the great celestial timekeepers of the ancient Egyptians. In the middle are various constellations and deities and, on the bottom row, a calendar of months and month gods.