Accession No
2463
Brief Description
4-inch transit theodolite with tripod, by Troughton and Simms Ltd., English, 1915 (c)
Origin
England; London
Maker
Troughton and Simms Ltd.
Class
surveying
Earliest Date
1915
Latest Date
1915
Inscription Date
Material
metal (brass, other); glass; wood
Dimensions
box length 360mm; breadth 295mm; height 179mm tripod height 1480mm; maximum diameter 85mm; horizontal circle diameter 119mm; height 300mm; telescope length 238mm
Special Collection
Provenance
Transferred from Department of Engineering, University of Cambridge, Cambridge, England, 09/1979.
Inscription
‘TROGHTON & SIMMS Ltd
LONDON’ (on horizontal plate)
T.H [box lid outside]
Description Notes
Metal alloy construction with black finish and brass screws. Telescope with rack and pinion focus moving the objective. Inverting eyepiece with sliding focus. Ray shade; cross hairs. Vertical circle with silvered scale divided 0 - 90 - 0 - 90 - 0˚, subdivided to 20’ of arc; read by opposing veniers and microscopes to 30” of arc. Clamp and motion screws for vertical circle and clipping screws for levelling. ‘A’ frame with axis bearing adjustment. 2 mutually perpendicular bubbles mounted on horizontal plate. Horizontal circle with silvered scale divided 0 - 360˚ subdivided to 20’ of arc and read by verniers and hinged microscopes to 30” of arc. Clamp and motion screws for vernier plate and horizontal circle. 3 levelling feet on tribrach limbs. Trough compass with silvered scale divided 5 - 0 - 5˚ slots into horizontal circle below scale. Erecting lens. Sexagonal plumb-bob (not original). Trivet head with screw clamp for levelling feet and central threaded aperture for attachment to tripod. Fitted wooden box. Tripod
13 is instrument in fitted box with accessories
Incomplete; empty parts of fitted box
References
Events
Description
The Theodolite is a relatively, simple tool used for measuring angles, both horizontal and vertical. They work using the same principles as a protractor, the ‘point A’ is located and the angle noted, and then the telescope is pointed at ‘point B’ and the second angle is taken.
Although primarily used in surveying the theodolite can be applied to both Meteorology and Navigation.
Gemma Frisius proposed the idea behind the theodolite in 1533. At the time new methods of surveying were being used and by combining an Alidade, a magnetic compass and the degree scale on the back of an Astrolabe, the calculations made by modern theodolites could be observed. Unfortunately, this method was not practical due to the combination of instruments. The best of the attempts to simplify the process was the ‘theodolitus’, first described in print by Leonard Digges in 1571.
However, this instrument could only take measurements in the horizontal plane. Despite this it was still thought of as the ‘common’ Theodolite up to the late 18th century.
During the 19th century the Altazimuth Theodolite was considered the most useful theodolite, as it could measure on the horizontal and vertical planes. Three notable types of Altazimuth Theodolite were developed: The Everest Theodolite, the Plain Theodolite and the Transit Theodolite. It is the Transit Theodolite, which is still used today.
FM:42907
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