Accession No

2460

Brief Description

4-inch transit theodolite by Stanley, c. 1926

Origin

London; England

Maker

Stanley

Class

surveying

Earliest Date

1926

Latest Date

1926

Inscription Date

Material

metal (brass, 1 other); glass; wood

Dimensions

box length 412mm; breadth 162mm; height 155mm; height 304mm; horizontal circle diameter 120mm; telescope length 217mm

Special Collection

Provenance

Transferred from Department of Engineering, University of Cambridge, Cambridge, England, 09/1979.

Inscription

‘STANLEY LONDON 11779 Patent’ (on horizontal circle)

Description Notes

Metal alloy with black fininsh and brass screws. Telescope with rack and pinion focus moving the objective. Ray shade; cross hairs. Bubble mounted over telescope; graduated to 1/16”. Clipping screw adjustment. Vertical circle with scale subdivided to 30’, read by 2 opposing verniers and microscopes. Clamp (inside frame) and motion screws for vertical circle. ‘U’ frame with 2 mutually perpendicular bubble levels on horizontal circle. Horizontal circle subdivided to 30’ and read by verniers and microscopes. Clamp and motion screws for vernier plate and horizontal circle. 3 levelling feet on tribrach limbs into a clamped trivet base. Plumb-bob. Trough compass with scale divided 5˚ - 0 - 5˚ slots underneath horizontal circle; locking bar. Fitted wooden box with oil well.

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 that is still used today.

FM:42880