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|Description||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)|
|Place made||London, England|
|Credit||National Maritime Museum, Greenwich, London, Caird Collection|
|Materials||glass; ivory; brass|
|Measurements||Overall: 170 x 163 x 295 x 165 mm|
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