Images(9)

variation compass

Datecirca 1818

Inventory Number5128

ClassificationVariation Compass

Subject

Maker Henri Gambey 1787 - 1847

User Department of Physics, Harvard University founded 1884

User John Farrar ? 1779 - 1853

Cultural Region

Place of Origin

Place of Use

Dimensions18.6 × 29.7 × 41.5 cm (7 5/16 × 11 11/16 × 16 5/16 in.)

Material

DescriptionInstrument of three major parts connected only by a screw under the compass needle: Bronze base of T shape with a leveling screw at end of each limb. Above that a rectangular frame bottom short end of which is curved. On left hand limb a sight at each end. On top of short limb a spirit level; a second one on right hand limb. Curved limb graduated by degrees and thirds of degrees from 5 to 65 and numbered by tens from 10 to 60.

Box compass with bronze back and wooden frame. Base extends to support 5" long brass magnifying telescope which sights end of needle, and then into vernier graduated by degrees from 0 to 20 and numbered by tens from 0 to 20. Inside box on bronze base inscribed maker's name. Mounted in center, needle with quartz bearing.

Signedengraved on plate at bottom of compass box: Gambey à Paris

Inscribedon left-hand limb stamped twice: 8-29

Curatorial RemarksPlease clean up the "dimensions" box as this is complex.

FunctionUsed to measure magnetic variation, the angle difference between the geographic and the magnetic north.

The base is oriented along the north-south meridian using the sights on the side. Then the compass box is rotated so that the needle is centered, which is checked with the scope. Finally, the magnetic declination can the be read from the scale and vernier.

ProvenanceStamps typical with instrument coming from the Physics Department, Harvard University. Jefferson Physical Laboratory, Harvard University; transferred to CHSI May 1948.

Historical AttributesDesigned by William Ritchie and destined for Harvard ("The University of Cambridge in America"); used by Francois Arago as early as 1818 and probably also used by John Farrar, Hollis Professor of Mathematics and Natural Philosophy at Harvard. The stamps with numbers on the instrument indicate that much later, in the last decades of the 19th century and first decades of the 20th, the instrument continued to be used by the Harvard Physics Department.