This is a plaster cast of an original green schist shadow clock. The clock consists of a straight base with a raised crospiece at one end. The base, on which is inscribed a scale of six time divisions, is placed in an east-west direction with the crospiece at the east end in the morning and the west end in the afternoon. The pasage of time is measured by the movement of the shadow of the base.
© Science Museum / Science & Society Picture Library