Three-ring universal equinoctial ring dial for all latitudes. Standard dial (see related terms) except for the following details:-

The dial has a suspension ring attached to a bracket which moves in the grooved outer edges of the meridian ring. On the bracket is a Vernier scale, which allows the latitude to be set to 1'. The meridian ring carries the latitude scales and a table of latitudes consisting primarily of places in France. The equinoctial ring, on which is an hour scale, is secured in an open position by hinged stops that are riveted to the meridian ring.

On the declination ring are degree scales and crossing bars that are set at right-angles to each other across the centre of the ring. An alidade is attached on each side of the declination ring and a friction-tight pivot allows movement of alidades either independently or together. On each one is a sight with three pinhole sights, one central, the other two equidistant from the centre. The presence of the outer pinholes means that the time can be read even at noon when the meridian ring would obscure the sun's rays from the central pinhole.
This is a rather large and heavy instrument. The double alidade allows the user to measure the difference in altitude of two different objects. The hinged stops for the equinoctial ring are unusual, as are some of the town names that appear in the table of latitudes: 'Chaumont en Bassigny', 'Chalons-sur-Marne' and 'Langres'. They suggest that the original owner probably lived in the Ardennes. The dial is signed 'Baradelle fils AParis. 1774' on the meridian ring.

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