Accession No

1600

Brief Description

circumferentor and theodolite with tripod, by Heath and Wing, English, 1750 (c)

Origin

England; London

Maker

Heath and Wing Heath, T.

Class

surveying

Earliest Date

1740

Latest Date

1765

Inscription Date

Material

metal (brass); wood; glass

Dimensions

theodolite on tripod height 1580mm; depth 610mm; breadth 620mm 2 sights height 144mm; depth 39mm; breadth 33mm 2 sights height 128mm; breadth 33mm; depth 35mm Circle diameter 304 mm; Compass diameter 150 mm; Telescope length 312 mm box (for tripod?) length 690mm; breadth 105mm; height 103mm; 2nd box (for theodolite?) length 352mm; breadth 360mm; height 205mm

Special Collection

Provenance

Purchased from Sotheby's 18/10/1971. Purchased with the aid of a 50% grant from the Victoria and Albert Museum.

Inscription

Made by Heath and Wing London (on telescope)
T. Heath Fecit (on circle)

Description Notes

Brass; Pierced 4 spoked circle graduated 0 - 360° to 1°. Read by one vernier on alidade arm to 5’. Other arm index only. Also graduated for ‘Breadth’ 100 - 0 - 100 ‘left’ and ‘right’. Compass mounted centrally on vernier plate; silvered 16 point rose with fluer-de-lis North; calibrated 0 - 90 - 0°twice and 0 - 360° an single degrees. Bubble set in compass face. Slit and window sights slot onto vernier arm to form alidade. These can be replaced by telescope and pierced altitude semi-circle. Push focus; inverting telescope; cross hairs; sliding objective and eye piece covers. . Bubble mounted over telescope. The whole mounted on an index arm over the semi-circle which is graduated 90- 0 - 90° to 1° and is read by vernier to 5’. Scales of ‘Depren’ and ‘Elevan’ 100 - 0 ‘FEET’. Also ‘DeH: Hypo: and Base’ 25 - 0 - 25. The whole mounted on parallel plates with 4 levelling feet and fitting for tripod. Key to adjust fittings. Three two part wooden legs with brass ferrules and fittings. Fitted boxes for instrument and tripod legs.
fair condition, compass glass cracked

References

Events

Description
Theodolite

The Theodolite is a relatively, simple tool used for measuring angles, both horizontal and vertical. Although primarily used in surveying the theodolite can be applied to both Meteorology and Navigation. It works 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.

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.
The circumferentor is an instrument that derives from the reverse side of an astrolabe. It is used to measure horizontal angles, or vertical angles by suspending the instrument from its shackle.

Circumferentor

The circumferentor was described by Arthur Hopton in 1611, though passing references had been made to it in earlier works. It became one of the standard pieces of equipment of the surveyor throughout the 17th and 18th centuries.
31/08/2006
Created by: updated by Ruth Horry on 31/08/2006

FM:39639