History of Science & Technology

Henry Gregory

Azimuth Compass, 18th century

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Live auction begins on:

July 15, 06:00 PM GMT

Estimate

5,000 - 8,000 USD

Bid

3,000 USD

Lot Details

Description

English Azimuth compass, London, 4th quarter of 18th century, in brass bowl, mounted in gimbals and weighted at the bottom, set in European oak case (14.75 x 14.6 x 9.25 inches). Compass engraved with “H. Gregory, Neare the India House, LONDON.”

Engraved paper compass card (8 inch diameter) marked with compass points and directions, with North represented by a fleur de lis. Compass card reads “GILBERT…near the India House LONDON.”

Paper overlay (1.75 inch diameter) reads “JOHN GRAY [illegible] LIVERPOOL,” likely added later.

18th-century instrument maker Henry Gregory (1744-1782) sold an azimuth compass to the explorer James Cook for his second voyage to the southern Pacific on the HMS Resolution from 1772-1775 according to the ship’s logbook.

This compass allowed the navigator to use the sun’s bearing to determine variation from true north. To use it, the bowl is rotated until the crosswires under the glass cover align with the cardinal points on the card. The index arm on the side of the bowl is turned until the shadow is cast on the slit of the upright sight. The horizontal alidade then demonstrates the sun’s bearing.

Few of these compasses survive today, though examples of azimuth compasses made by Henry Gregory are included in the collections of the Smithsonian American History Museum and the National Maritime Museum in Greenwich, UK.