Accession No

4473

Brief Description

surveying compass, by E. R. Watts and Son, English, mid-20th Century

Origin

England; London

Maker

E. R. Watts and Son

Class

surveying

Earliest Date

1900

Latest Date

1948

Inscription Date

Material

metal (brass, oxidized brass, white metal, steel); glass; wood; cloth (felt)

Dimensions

overall height 200mm; diameter 112mm box length 169mm; breadth 133mm; height 47mm

Special Collection

Provenance

Transferred from the Department of Geography, University of Cambridge, on 18/03/1994.

Inscription

‘E.R. Watts & Son.
London. Eng.
Ottawa & Winnipeg.’ (on one of the sights)

Description Notes

surveying compass, by E.R. Watts, mid C20th, with detachable tripod mount. Main instrument has compass with raised degree scale divided 0 - 90˚ - 0 - 90˚ - 0 numbered by 10˚ graduated to 1˚. Also a Vernier scale and magnetic variation scale around the west point. Cardinal points marked by initials. Two orthogonal bubble levels. Steel needle with locking bar. Outer ring of compass carries two slit and thread sights and can be rotated to adjust the compass for magnetic variation. Screw-fit tripod connector with alt-azimuth mount. Fitted wooden box with felt lining.

Card with note detailing donation was inside lid of box - now moved to OHF (21/10/2014).

Condition good; complete

References

Events

Description
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.

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.

From display label:

Magnetic compass fitted with sights so as to take bearings with reference to the magnetic meridian. This instrument is also known of as a ‘circumferentor’. The circular scale on this instrument is divided at intervals of 1 degree of arc, giving 360 divisions.

31/08/2006
Created by: updated by Ruth Horry on 31/08/2006

FM:40673