Accession No

2178

Brief Description

magnetic compass, 1/2 20th C.

Origin

England

Maker

Class

magnetism

Earliest Date

1900

Latest Date

1950

Inscription Date

Material

metal (white metal, brass); plastic (perspex, 2 others)

Dimensions

diameter 187mm; height 110mm

Special Collection

Provenance

Transferred from Department of Geography, University of Cambridge, Cambridge, England, 05/1969.

Inscription

‘TYPE P4A NO 45501T’ (rim)

Description Notes

Grey-painted brass casing carries compass set on system of shock-absorbing springs. Compass set in black plastic and glazed with perspex. Degree scale divided [0] - [360] numbered by 10 subdivided to 1 with cardinal and quadrantal points marked. 8-point needle suspended on screw pivot with short crossing bar to mark North. Pairs of parallel lines across centre of compass at 10˚ either side of cardinal points. Casing marked ‘AFT’ at north end of scale.

Condition fair; complete

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:44425