Accession No

0359

Brief Description

surveying compass, by George Adams Jnr., English, 1790 (c)

Origin

England; London; Fleet Street

Maker

Adams, George (Jnr.)

Class

magnetism

Earliest Date

1790

Latest Date

1790

Inscription Date

Material

metal (brass); wood (mahogany); paper

Dimensions

box length 177mm; breadth 177mm; thickness 35mm

Special Collection

Robert Whipple collection

Provenance

Purchased from Antique Art Galleries, Cambridge, on 03/08/1927. G. Green repaired the ‘hinge etc.’ in 07/1930.

Inscription

‘MADE BY G:ADAMS IN FLEET STREET. LONDON.’ (on rose)

Description Notes

Brass compass set in mahogany box. Folding slit and window sights at 0/360˚ and 180˚. Paper rose; 32 point; graduated 0-360˚ by 10˚ to 1˚. Brass scale over graduated 0-90-0˚ twice in single degrees. Blued needle. Locking bar.

References

Events

Description
Magnetic compass
The magnetic compass consists of a magnetic needle attached to a compass card, graduated into angular points, and is used for navigation. The first known dry pivoted compass is dated as early as 1269.

The compass indicates the direction of the magnetic pole but there are problems caused by the difference between magnetic and true north (true north being the useful reading). The variation between the two must be calculated in order to obtain an accurate reading. True north was sometimes simply offset from the direction of magnetic north, but this did not allow for geographical variation. For this, charts were needed. The iron used in building ships during 19th century also led to problems because the magnetism of iron affected the compasses on board.
18/10/2002
Created by: Saffron Clackson on 18/10/2002

FM:43367