Accession No

1279

Brief Description

7-inch transit theodolite, by Matthew Berge and by Thomas Jones, English, 1805 (c)

Origin

England; London

Maker

Berge, Matthew [telescope] Jones, Thomas [horizontal circle]

Class

surveying

Earliest Date

1805

Latest Date

1805

Inscription Date

Material

metal (brass); glass

Dimensions

length 277mm; breadth 175mm; height 320mm

Special Collection

Provenance

Transferred from the Cavendish Laboratory.

Inscription

‘Berge London Late Ramsden.’ (on telescope)
‘Thomas Jones Charing Cross LONDON’ (on horizontal circle)

Description Notes

Transit theodolite, by Berge and by Thomas Jones, English, c. 1805

Brass throughout. 3 parts.

1. Telescope with rack and pinion focus (screw missing). Inverting eyepiece. Transits over objective. Bubble mounted outside vertical circle which is very small and divided 0 - 90 - 0˚ twice, subdivided to 30’ of arc. Read by 2 opposing verniers to 2’ of arc. Clamp for vertical circle.
2. ‘A’ frame. Bubble mounted on horizontal circle with second at right angles. No graduations. Horizontal circle graduated 0 - 180˚ twice and to 20’ of arc. Read by 2 verniers to 1’ of arc. Clamp and motion screw for vernier plate. Compass mounted centrally. Silvered scale divided 0 - 90 - 0 twice, subdivided to 1˚. Locking bar.
3. Brass tripod with levelling screws, central thread for attachment to instrument

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:44909