Octant in Mahogany Case
Spencer Barrett & Co., London: 3rd Qtr. 19th C.
Spencer Barrett Octant


Box, closed

Box, closed

Box, opened

Box, opened

Box label

John Bruce label on box

Spencer Barrett & Co. (instrument maker)
John Bruce (act. 1865-96) (seller)
London: 3rd Quarter 19th Century
Ebony and brass, with glass lenses, mirror fittings, engraved ivory inlay
In original mahogany fitted keystone box
13.5 x 11 inches, sextant without box

Octant in ebony frame, with ivory arc, brass index arm, two horizon mirrors, three rectangular sun shades, three round horizon shades, and a peep hole. This example measures from minus 0 to plus 105 degrees. It was produced by Spencer Barrett & Co., London, and sold by John Bruce, Liverpool.

An octant is a portable instrument using a small mirror to determine latitude at sea with reference to the sun, the horizon, and the position of celestial bodies. It has an arc exceeding 45 degrees. Like the one shown here, those made during the 19th century typically have ebony frames, brass index arms, and ivory graduated scales under a vernier (moveable scale). A similar Spencer Barrett & Co. octant, but without the round horizon shades, is in the collection of the Smithsonian National Museum of American History.

Spencer Barrett & Co. was a manufacturer of navigational instruments in London, England, during the mid 19th century. The company supplied octants to various sellers in Britain and the U.S., who added their own label to the cases.

John Bruce was a seller of chronometers and nautical instruments in Liverpool, England, active between 1865 and 1896. The firm’s label lists marine barometers, sextants, quadrants and telescopes among the products sold.

Ivory engraved plate: "Spencer Barrett & Co. London.”

Partial Paper Label: “John Bruce, Chronometer, [missing] & Nautical Instrume[nts]. Salthouse Buildings, 26, Wappi[ng] opposite the South end Salthouse Dock, Liverpool. Marine & Pocket Chronometers, Marine Barometers, Sextants, Quadrants, Telescopes & Light Glasses. Gold & Silver...Chronometers c[lea]ned, adjusted....”

Condition: Generally very good with the usual overall wear and oxidation. All parts present and working. Mahogany box very good, with nice patina, some minor age cracks and warping. John Bruce paper label oxidized, soiled, abraded, with minor chips and losses, but substantially intact.


“Octant (definition).” Smithsonian National Museum of American History. http://americanhistory.si.edu/collections/navigation/type.cfm?typeid=4 (24 June 2009).

“Spencer, Barrett & Co. Octant.” Smithsonian National Museum of American History. http://americanhistory.si.edu/collections/navigation/object.cfm?recordnumber=1197564 (24 June 2009).

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