Solar Chronometer for latitude 0°-65° North. This instrument has a rectangular wooden stand with a baize-covered wooden rest. A brass plate is set on the wooden stand and engraved 'No. 112 G Ferguson's Solar Chronometer'. The instrument itself is a curved plate with struts across its horizontal diameter and down the vertical radius. Attached to one of the vertical struts is a ball joint which can move freely within a brass plate mounted in the stand, but which can also be locked by a brass screw on the right-hand side. This allows the instrument to be adjusted for latitude.

Across the width of the instrument at its lowest point is a curved latitude scale. A polar axis is fixed to the frame above the latitude scale. In the centre, it is reduced to two points, the shadow of whose meeting point indicates the time. Suspended from one end is a steel plumb bob and latitude indicator. Set against the curved plate is a card hour-plate. The hour-lines are drawn vertically but adjusted to the equation of time, and hence are curved so that the instrument always gives local mean time, rather than local solar time. A wooden cover can be set over the instrument and attached by two brass hook fasteners to the base. It has a brass carrying-handle on the top. The cover also contains an instruction booklet titled 'The 'FERGUSON' Solar chronometer and Astronomical Compass'. There are two separate cards, each beginning at one of the solstices. Another example of the solar chronometer is in the Science Museum, London (inventory no. 1922-104).

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