Theodolite in an octagonal wooden box.
Base- Diameter 6.5" (16.5cm) is graduated 0-180 by 1 degree in each half, with three verniers, each marked to 30.It is fitted with two knobs, one to turn the instrument in azimuth, the other to clamp it. A tripod mounting socket, fitted with four levelling screws, is attached to a spigot at the centre of the underside of the base.
Compass-Diameter 5.5" (14cm) with a blued steel needle with arrow heads at each end, is mounted at the centre of the base. The compass is graduated quadrantally in degrees.
Vertical arc -Diameter 5.5" (14cm) with a mounting for a telescope is mounted above the base, and has rack teeth cut in its outer edge. It is graduated on one side 70-0-70 by 1 degree with vernier (30-0-30), and on the other side 15-0-15 (with veriner 20-0-20). Vernier scale is carried on a brass support with an ivory-ended spindle for turning arc in altitde. A spirit level in brass casing 2.25" (5.7cm) long is mounted on the lower part of the arc.
Telescope -A modern replacement fitted with plain glass, no lenses. A similar instrument is illustrated in Gardiner, 'General Surveying Improved' (London, 1735)