Accession No

1460

Brief Description

surveying compass, by Lennel, French, 1780 (c)

Origin

France; Paris

Maker

Lennel

Class

magnetism

Earliest Date

1780

Latest Date

Inscription Date

Material

wood (oak); paper; metal (silver)

Dimensions

box length 177mm; breadth 163mm; height 29mm

Special Collection

Provenance

Inscription

‘Lennel Eleve et Successeur de Mr Canivet Paris’ (on face)

Description Notes

Oak box. Compass. 8 point paper rose. Fleur-de-lis north. Graduated 0-90-0˚ twice clockwise. Silvered scale graduated 1-360˚ in single degrees. Half blued needle. Locking bar operated by decorative handle with screw thread. Sights along one edge of compass in wooden case; pivots around central point. 3 plates in base with holes for attachment to tripod. Sliding 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:43371