Octagonal Louis XVI sundial and compas, French, early 18th Century.
© Science Museum / Science & Society Picture Library
Made by Baradelle of Paris, France, this pocket sundial is of the 'Butterfield' type, named after its originator who worked in Paris until 1724. Most horizontal sundials with fixed gnomons show the time correctly only in the latitude for which they are designed, but this type of sundial allows the shadow-casting part of the gnomon to be pivoted so that its inclination can be varied. There are also four separated hour scales surrounding the compas, suitable for use in different latitudes. On the underside of the dial there is a table giving the latitudes of 27 important towns in various European countries.