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Telescopic Alidade for Plane Table, by E. R. Watts & Son Ltd., 1944

Inventory Number 11273

Acknowledgement: © History of Science Museum, University of Oxford, inv.11273

Item type
Object
Provenance
Transferred from the Dept. of Earth Sciences per Dr. J. G. Olliver
Primary inscriptions
on case "ALlDADE. 1."
Other inscriptions
INSTRUMENT NO. 24137 DATE 18/2/44
Physical material
metal
Glass
plastic
water
Object type
Alidade
Dimensions
Height: 384mm Width: 173mm Depth: 108mm Weight: 3200g
Inventory No
11273
Accession Number
1987-20/5

Description

The alidade has a telescopic shaft with an eyepiece at one end, a lens at the other, an upwards-protruding copper alloy knob and is mounted above a sextant. Below the sextant is a moving arm with a lens. At the edge of the base, a long thin flap opens out about 45°, has a mirror on one side and reveals a horizontal spirit level. A shaft that has four protruding knobs and a vertical spirit level attaches the frontal elements to a long, thick metal rectangle with a strip that lifts up from the rest of the object but is attached via an arm at each end. It has a small ball-shaped handle for ease of lifting.

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