Molyneux & Sons Box Chronometer

This instrument is a specialized timekeeper for finding longitude at sea. It was made by the firm Robert Molyneux & Sons of London, England, between 1832 and 1845. The U.S. Navy Bureau of Ships transferred it to the Smithsonian in 1953.
To find longitude at sea, a chronometer would be set to the time of a place of known longitude, like Greenwich, England, the prime meridian. That time, carried to a remote location, could be compared to local time. Because one hour of difference in time equals 15 degrees difference in longitude, the difference in time between the chronometer and local time would yield local longitude. The instruments require careful handling to keep precise time. Although the original box for this instrument has not survived, most chronometers are fitted in a wooden box in a gimbal to remain level and compensate for the movement of a ship at sea.
Robert Molyneux was a maker of chronometers and precision clocks in England. He was trained by Thomas Earnshaw and went into business for himself in the 1820s. In 1832 he moved his London business from 44 Devonshire Street to 30 Southampton Row and partnered with his son Henry in 1835. In 1842 the chronometer firm Birchall & Appleton moved to that address.
Mechanism details:
Escapement: Earnshaw spring detent
Duration: 56-hour
Power source: Spring drive with chain and fuse
Balance spring: helical, blued steel
Dial details:
Engraved and silvered brass
Indicates hours, minutes, seconds, and winding level up and down
Inscription: “Molyneux & Sons / 30 Southampton Row, London / No 1436 / U.S. Army.”
Blued steel spade hands
Brass bowl with fittings to insert in gimbal
No box
No winding key
1. Britten, Frederick James. Old Clocks and Watches & Their Makers. London: E. & N. Spon Limited, 1922.
2. Gould, Rupert T. The Marine Chronometer. London: Holland Press, 1960.
3. Mercer, Tony. Chronometer Makers of the World. Essex: N.A.G. Press, 1991.
4. Whitney, Marvin. The Ship’s Chronometer. Cincinnati: American Watchmakers Institute Press, 1985.
5. Wood, Christopher. “Robert Molyneux's Astronomical Clocks and Chronometers,” Antiquarian Horology 9 no. 4 (1975).
Object Name
box chronometer, without case
date made
Molyneaux & Sons
Physical Description
brass (overall material)
glass (overall material)
steel (overall material)
bezel - from catalog card: 4 in; 10.16 cm
backplate - from catalog card: 2 29/32 in; 7.366 cm
overall: 2 1/8 in x 4 1/2 in; 5.3975 cm x 11.43 cm
place made
United Kingdom: England, London
ID Number
catalog number
accession number
Time and Navigation
Measuring & Mapping
See more items in
Work and Industry: Mechanisms
Time and Navigation
Time and Navigation, National Air and Space Museum
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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