Astronomical and navigational instruments, Compasses

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Azimuth compass

NAV0288
Astronomical and navigational instruments

Object connections:

Collection Astronomical and navigational instruments, Compasses
Gallery locationNot on display
Publication(s)Treasures of the National Maritime Museum
Gloria Clifton and Nigel Rigby
View this book in the library

Object details:

Object ID NAV0288
Description This compass was designed to allow the navigator to take the sun's bearing as a way of determining the variation of the compass from true north. It is mounted in brass gimbals within a wooden case with carrying handles. The compass card is marked in degrees and compass points, with north decorated with a fleur-de-lys. It has a single iron needle with a brass cap that rests on a brass spike projecting from the bottom of the bowl. The brass cover has an index arm fixed to one side, which can rotate so that the alidade (which is a modern replacement) moves across a degree scale. To use the compass, the bowl is rotated until a pair of cross-wires under the glass cover line up with the cardinal points on the compass card. The index arm, which is pivoted at the side of the bowl, is turned until the shadow of the thread is thrown onto the slit of the upright sight. The horizontal alidade then indicates the sun's bearing on the scale engraved on the compass cover. In principle, the diagonals on the scale allow the bearing to be read to an accuracy of 5 minutes, although this accuracy was not possible in practice. The name of the maker, 'J. Fowler LONDON', is engraved on the compass cover, probably referring to John Fowler. The compass card has the name 'H. GREGORY neare the India House LONDON.' on it, referring to Henry Gregory, who was apprenticed to John Fowler in 1732 and worked in London until the 1780s.
Date made compass bowl circa 1720; compass card circa 1760

Artist/Maker Fowler, J
Gregory, H.
Fowler, J.
Place made London, England
Credit National Maritime Museum, Greenwich, London
Materials paper; steel; textile tread; wood; brass
Measurements Overall: 454 x 453 x 240 mm
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