Portable variation compass,
Date: 1852-1930
Inventory Number: 1998-1-1650
Classification: Variation Compass
Subject:
Maker: J. H. Steward Ltd (fl. 1852 - 1930)
Cultural Region:
Place of Origin:
Dimensions:
1.9 x 2 x 10 cm (3/4 x 13/16 x 3 15/16 in.)
Description:
Metal rectangular casing with glass front and a nob on the top; inside is a metal needle mounted on brass; notched scales on top and bottom of casing, measuring angle from a central zero. The scale ranges 5° (unmarked) on either side.
Signedengraved in italics on the side: (cursive) J. H. Steward / STRAND, LONDON.
FunctionA trough or variation compass, used to determine the angle difference between the geographic and the magnetic north.
This one was probably used to align and draw lines parallel to the earth's magnetic field on a plane table.
This one was probably used to align and draw lines parallel to the earth's magnetic field on a plane table.