PELORUS COMPASS

Brass compass rose mounted on gimbals. "ALEX R. DOBBIE & SON GLASGOW (symbol)". "SHIPS HEAD" on rim of case. Pointer & sighting vanes pivoted at centre of compass rose with full circle horizontally & half circle for vertical angle measurements. (vert. scale marked "S.LAT." & "N. LAT." Horizontal circle marked "A.M. & P.M." Bought at auction sale at Clifford's 181 High Street, Fremantle on 5 October 1963. Provenance unknown. Ref. Peter Kemp (ed). "The Oxford Companion to SHIPS & THE SEA", OUP, London 1976. "PELORUS, a circular ring fitted to the rim of a compass bowl and carrying two sighting vanes used for taking azimuths (bearings) of celestial objects. The ring can be easily revolved and the compass bearing read off by sighting the vanes on the required object. Alternatively, the ring can be fitted to a `dumb' compass which can be set by hand to the course of a ship before taking a bearing. The word comes from the name of Hannibal's pilot, probably a Greek who sided with the Carthaginians, and assisted Hannibal to get his troops across to Europe and kept him in tough with Carthage by sea. This instrument same in principle, though different in design.

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