Accession No

2209

Brief Description

prismatic compass, by Hughes Owens Company Ltd., Canadian, 1915 (c)

Origin

Canada

Maker

Hughes Owens Company Ltd.

Class

magnetism; navigation

Earliest Date

1915

Latest Date

1915

Inscription Date

Material

metal (alloy); paper (card); glass

Dimensions

length 83mm; breadth 55mm; thickness 22mm

Special Collection

Provenance

Transferred from Department of Geography, University of Cambridge, Cambridge, England, 05/1969.

Inscription

‘THE HUGHES OWENS CO Ltd
MONTREAL, TORONTO, WINNIPEG, VANCOUVER’

Description Notes

Metal alloy enclosed box. Card graduated 0-360˚ in single degrees with 4 points. Glazed eccentric window under prism. Slit sight over prism. Folding window sight (wire missing) opposite. Locking bar.

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:43379