Details
A late 18th-century lacquered-brass theodolite,
signed on the horizontal plate Ramsden London, the telescope with rack and pinion focusing, suspended bubble level, cross-wire tensioners, object glass of pale green tint, and lens cap, located by twin clamps on the upper limb of the vertical half circle, the axis supported by twin inverted-V supports, the vertical circle divided on one side 80°-0-70°, with vernier on the pinion mounting for the external rack gear, the other side with two scales, the upper divided 30°-0-30°, the lower 100°-0-100°, the horizontal plate with level and cross-bubble, the compass box incorporated with the vertical supports, the finely engraved silvered dial divided in four quadrants, the plain steel bar needle with jewelled cap, the dial divided in four quadrants, the upper stepped horizontal circle divided 0°-360°, the horizontal circle adjusted by internal rack and pinion gear, with chamfered scale and single vernier, raised on a four-screw tripod mounting with tangent screw fine adjustment and butterfly-nut clamp, the instrument -- 11in. (28cm.) high, contained in a mahogany case, with a reproduction of a portrait of Jesse Ramsden pasted to the interior of the lid, the case with brass swing handle -- 14in. (35.5cm.) high
See Colour Illustration and Detail
signed on the horizontal plate Ramsden London, the telescope with rack and pinion focusing, suspended bubble level, cross-wire tensioners, object glass of pale green tint, and lens cap, located by twin clamps on the upper limb of the vertical half circle, the axis supported by twin inverted-V supports, the vertical circle divided on one side 80°-0-70°, with vernier on the pinion mounting for the external rack gear, the other side with two scales, the upper divided 30°-0-30°, the lower 100°-0-100°, the horizontal plate with level and cross-bubble, the compass box incorporated with the vertical supports, the finely engraved silvered dial divided in four quadrants, the plain steel bar needle with jewelled cap, the dial divided in four quadrants, the upper stepped horizontal circle divided 0°-360°, the horizontal circle adjusted by internal rack and pinion gear, with chamfered scale and single vernier, raised on a four-screw tripod mounting with tangent screw fine adjustment and butterfly-nut clamp, the instrument -- 11in. (28cm.) high, contained in a mahogany case, with a reproduction of a portrait of Jesse Ramsden pasted to the interior of the lid, the case with brass swing handle -- 14in. (35.5cm.) high
See Colour Illustration and Detail