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Theodolite

NAV1451

Object connections:

Collection
User collections William Wales by NMMCollections
Gallery locationMaritime London Gallery (Floor plans)
Publication(s)Treasures of the National Maritime Museum
Gloria Clifton and Nigel Rigby
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Object details:

Object ID NAV1451
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)
Date made 1737

Artist/Maker Sisson, Jonathan
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
Parts
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