Mechanical equinoctial dial for latitudes 0°-90° North. The dial has a circular base with three turned feet. Set into the centre of the base is a silvered compass. On the base-plate, there is a circular bubble level and the equation of time is marked. The main part of the dial has a thick ring set in the plane of the meridian. This consists of two rings, the inner one to be adjusted for latitude. Pivoted within this ring is a further ring carrying a shaped alidade. It comprises two lenses and a circle whose centre is marked and on which the light falls after passing through the lenses. On the axis of the declination ring, and within the ring itself, is an hour dial, which does not move with the ring but remains fixed. The action of turning the declination ring until the sun's rays fall through the two lenses of the alidade on to the centre of the bottom circle causes the hands on the hour dial to turn and indicate the correct time.

This instrument is a form of standing universal equinoctial ring dial.The inclusion of a table with the equation of time allows the dial time to be adjusted to mean time for regulating clocks and watches. There is French wording on the dial indicating that it was made for the foreign market, probably as a commissioned piece given the high quality of the workmanship. On the declination ring, it is signed 'Wm DEANE Fecit in Crane Court Fleet Street LONDON'. There are similar dials in the British museum (registration no. 1894,6-23.4) and the Whipple museum (accession no. Wh: 0319).

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