Tablet sundial, German, 1648.
© Science Museum / Science & Society Picture Library
This engraved ivory pocket sundial has a string gnomon which can be adjusted for five different latitudes and five corresponding hour scales are provided on the horizontal dial. In addition there are two small vertical styles, reading Italian and Babylonian hours respectively, and a small horizontal style showing equal hours on a dial at the top of the opened lid. The dial also indicates the length of day and the position of the sun in the zodiac.