Accession No
2180
Brief Description
air compass, by H. Hughes and Son, English, 1930 (c)
Origin
England; London
Maker
H. Hughes and Son
Class
navigation; magnetism
Earliest Date
1930
Latest Date
1930
Inscription Date
Material
plastic (perspex); metal; wood; cloth (canvas)
Dimensions
box breadth 200mm; depth 185mm; height 109mm
Special Collection
Provenance
Transferred from Department of Geography, University of Cambridge, Cambridge, England, 05/1969.
Inscription
‘No. 11953’
Description Notes
Mark IIIA aperiodic compass. Liquid magnetic compass (liquid missing). Card divided into cardinal points (fleur-de-lys for N), subdivided to 32 points, and each point divided into 4. Surrounding circle divided into cardinal points (red N) and divided into 36 points, numbered 1 - 35, each subdivided into 5. Mounted in grey-painted metal casing, with securing lugs; one bevelled with short scale. Table of ‘MAGNETIC COURSE’ behind perspex cover
Wood box with canvas carrying handle.
Condition
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:43362
Images (Click to view full size):
