Pocket shepherd's sundial, French, 19th century.
© Science Museum / Science & Society Picture Library
The shepherd's dial, also known as the pillar dial, traveller's dial or cylinder, was one of the simplest and most widely used portable sundials. It indicates the time of day from the sun's altitude, which also depends on the latitude and time of year. Consequently, each dial is designed for accuracy within a particular latitude and is adjustable to the correct date. The hours are marked in curves around the column. Sundials of this type were in common use until recently in the Pyrenees in France.