Accession No

0328

Brief Description

mariner’s azimuth compass, by Joseph da Costa Miranda, Portuguese, 1711

Origin

Portugal; Lisbon

Maker

Miranda, Joseph da Costa

Class

magnetism; navigation

Earliest Date

1711

Latest Date

1711

Inscription Date

1711

Material

wood; glass; metal (brass); paper

Dimensions

length 263mm; width 237mm; height 123mm

Special Collection

Robert Whipple collection

Provenance

Purchased from A. Fleming, Ltd in 09/1928.

Inscription

‘Joseph da Costa
Miranda afez em
Lisbon Anno 1711’ (reverse of card)

Description Notes

Mariner’s azimuth compass, by Joseph da Costa Miranda, Portuguese, 1711.

Wooden-cased amplitude magnetic compass. Square wooden case, inlaid, glazed on top and partially on two sides. Interior painted gold and red. 2 wooden studs for gimbals. four brass pins. Two fiducial threads in glazed sides. Separate wooden base, decorated in red and gold on top, central brass point for compass card. Decorated compass card. 32 point inner rose; outer scale divided 0 - 90 - 0 - 90 - 0, numbered by 10˚, subdivided to 1˚. Raised edges to E and W each graduated 45 - 0 - 45, divided to 1˚. Reverse has single bar magnet held by central brass nut. Also a pin to the North, and the ends are held in place. Card wooden with printed paper rose.

References

Events

Description
Magnetic compass
The magnetic compass consists of a magnetic needle attached to a compass card, graduated into angular points, and is used for navigation. The first known dry pivoted compass is dated as early as 1269.

A simple bar magnet is fixed beneath the compass card, its north-seeking end fastened under the elaborate fleur-de-lis on the card. As the ship changes course, the card swings, keeping the fleur-de-lis pointing to magnetic north.

The magnetic north pole is located at some distance from the geographic pole, around which the Earth rotates. This location drifts slowly over the centuries and at present lies in the Queen Elizabeth Islands, off northern Canada, between 100° and 110° W.

04/08/2008
Created by: Dr Anita McConnell on 04/08/2008

FM:39877