Accession No

0100

Brief Description

pocket compass by W & S Jones, c.1800

Origin

London; England

Maker

W & S Jones

Class

magnetism

Earliest Date

1800

Latest Date

1800

Inscription Date

Material

wood; glass; metal (brass, steel)

Dimensions

box length 78mm; breadth 79mm; thickness 24mm

Special Collection

Robert Whipple collection

Provenance

Purchased by Robert Stewart Whipple from J. Whitaker, Cambridge, on 24/05/1923. It was repaired by G. Green on 06/1925.

Inscription

‘W and S JONES LONDON’ (compass rose)

Description Notes

Paper rose with 32 points and scale divided 0 - 90˚ - 0 - 90˚ - 0, numbered by 10˚, graduated to 1˚. Steel needle with locking bar. Glass held in place by brass ring. Mounted in wooden box with hinged lid.

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:43339