Universal equinoctial dial for latitudes 0°-75° North. The base-plate is shield-shaped and is supported by three levelling screws. A circular disc is set on top of this. Hinged to its North end is an hour-circle segment. This supports the gnomon apparatus which consists of a sliding strip that moves within a U-shaped outer section and to which is attached a lens mounted within a flat brass ring. The latitude arc is hinged to the West side of the circular disc. A hinged brass gallows arm on the opposite side to the latitude arc supports a string and brass plumb bob, which hangs over a brass pin marker.

This dial has no compass and is self-orienting by means of the lens gnomon. If the gnomon apparatus is set for the correct declination of the sun, the dial will be correctly oriented when the lens focuses a point of light on the central line of the inner rim of the hour arc, and the position of the light will give the time. The inclusion of a lens allows the instrument to be used even when the sun is obscured by light cloud.

This type of dial was illustrated and described in detail in the second edition (1774) of Bedos de Celles' 'La Gnomonique Pratique'. Bedos de Celles believed it to be the best of all forms of portable dial and very easy to use. The dial is inscribed 'Meurand Quay de L horloge du Palais a Paris . 1780 . n . 32 .' on the circular disc on the base-plate. It has a red lined black leather shield-shaped case, edged with gold.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.