Accession No

2851

Brief Description

aircraft compass, purchased for adaptation as a surveying compass but never adapted, 1940 (c)

Origin

Maker

Class

magnetism; navigation

Earliest Date

1940

Latest Date

1940

Inscription Date

Material

metal; glass; wood

Dimensions

box breadth 179mm; depth 192mm; height 105mm

Special Collection

Provenance

Transferred from Sedgwick Musuem, Department of Earth Sciences, University of Cambridge, Cambridge, England, 05/1982.

Inscription

Description Notes

Khaki-painted air compass. Metal casing with securing lugs. Spring-mounted glazed compass marked with 4 cardinal points and divided clockwise 0 - 360˚ by 1˚.
Fitted box.

Condition

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:44423