Accession No
2220
Brief Description
compass, marine, Dent's patent with Chetwynd's improvements, by E. Dent and Company, English, 1935 (c)
Origin
England; London; 61 Strand
Maker
E. Dent and Company
Class
navigation; magnetism
Earliest Date
1935
Latest Date
1935
Inscription Date
Material
liquids; metal (oxidised brass); wood
Dimensions
breadth 268mm; depth 260mm; height 205mm
Special Collection
Provenance
Cambridge University Department of Geography
Inscription
‘E. DENT & CO. LTD. 61, STRAND, LONDON’
‘WITH CHETWYND’S IMPROVEMENTS NO 55618’
‘DENT’
‘NO4’
‘DENT’S PATENT’ (on gimbal ring)
‘DENT’ (on fleur-de-lys)
Description Notes
Liquid, (azimuth?) compass with prismatic sight. Oxidised brass. Black and white 32-point card, divided (from N) 0-90-0-90-0 by 1o. Bar above with prismatic sight. Liquid-filled bowl, slung in gimbals and mounted on wooden stand.
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:44469
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