Portable column sundial, 1587.
© Science Museum / Science & Society Picture Library
This small ivory column, or pillar, sundial is signed 'D Stephanus, FF, 1587'. It has two gnomons, one for summer and one for winter and indicates Italian hours. Pillar dials consist of a hollow tube with a gnomon fixed horizontally into a slot at the top so that it is in line with the correct month. The dial is then turned so that the shadow cast by the gnomon falls directly onto the pillar, the end of the shadow indicating the correct time on the hour scale.