Accession No
2563
Brief Description
compass by Siemens & Halske, 2nd 1/2 19th C.
Origin
Berlin; Germany
Maker
Siemens & Halske
Class
magnetism
Earliest Date
1850
Latest Date
1900
Inscription Date
Material
metal (brass, steel); glass
Dimensions
diameter 125mm; height 27mm
Special Collection
Provenance
Transferred from Institute of Astronomy, University of Cambridge, Cambridge, England, 5/6/1980.
Inscription
‘Siemens & Halske BERLIN’
Description Notes
Brass compass with silvered scale and steel needle, part of astronomical or surveying instrument. Divided 0 - 90˚ - 0 - 90˚ - 0, subdivided to 1˚. Knurled screw beneath for clamping needle.
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:43603
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