Accession No

2884

Brief Description

marine compass, by Edward John Dent, English, 1850 (c)

Origin

England; London

Maker

Dent, Edward John

Class

navigation

Earliest Date

1850

Latest Date

1850

Inscription Date

Material

paper (card); metal (brass); wood

Dimensions

box breadth 270mm; depth 275mm; height 183mm

Special Collection

Provenance

Purchased from Saul Muskowitz, Massachusetts, USA; Spring Catalogue 1982, Item 205, 1982.

Inscription

‘DENT INVENTOR &
PATENTEE LONDON
141
CHRONOMETER MAKER TO THE QUEEN.’
(Directions for use inside lid.)

Description Notes

Dry card compass; 128 point rose; fleur-de-lys north; brass mounts; painted interior and cross-bar; ON/OFF switch; mounted in gimbals; octagonal wooden box; card lifting screw below bowl; dip adjusting screws on threaded arms.

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:43044