Accession No

3733

Brief Description

magnetic compass, by Lenoir, French, 1800 (c)

Origin

France; Paris

Maker

Lenoir

Class

magnetism

Earliest Date

1800

Latest Date

1800

Inscription Date

Material

wood; glass; metal (steel, copper, brass?); paper

Dimensions

length 150mm; breadth 80mm; thickness 27mm

Special Collection

Provenance

Purchased from Tesseract, Hastings-on-Hudson, New York, USA, 1989.

Inscription

‘Lenoir a Paris.’ (face of dial)

Description Notes

Magnetic compass, Lenoir, French, c. 1800.

Wooden cased compass (sliding lid missing) with a glazed compartment (with brass frame (?); 27-1-2000) for a steel needle moving over a restricted arc of 30 degrees on either side of zero. There is a printed compass rose and a copper degree scale, numbered by 10, divided to 1. Lenoir is known to have used copper in other magnetic instruments to avoid the danger of local deviation.

Condition: good; incomplete (lid missing).

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:43473