John Roger Arnold Box Chronometer
date: label: date made
content: ca 1825
name: label: maker
content: John Roger Arnold
notes: label: Description
content: This instrument, made by John Roger Arnold about 1825, is a specialized timekeeper for finding longitude at sea. The chronometer was part of the James Arthur Collection at New York University, and the university donated a portion of the collection, including the chronometer, to the Smithsonian in 1984.
label: Description
content: To find longitude at sea, a chronometer was set to the time of a place of known longitude, like Greenwich, England. 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.
label: Description
content: John Roger Arnold (1769-1843) learned watchmaking from his father, chronometer pioneer John Arnold, and Abraham Louis Breguet. The Arnolds were in business as Arnold & Son between 1787 and 1799, when the father died. In 1805 John Roger Arnold accepted the English Board of Longitude’s posthumous award to his father for improvements to the marine chronometer, which included simplifications that permitted others to undertake batch production of chronometers—a detached escapement, a helical balance spring and a temperature-compensated balance. The younger Arnold continued the business and between 1830 and 1840 took in partner Edward John Dent. In that decade, the firm made about 600 chronometers.
label: Description
content: Mechanism details:
label: Description
content: Escapement: Arnold, spring detent
label: Description
content: Duration: 8-day
label: Description
content: Power source: Spring drive with chain and fusee
label: Description
content: Balance spring: helical, blued steel
label: Description
content: Balance: J. R. Arnold with built-in aux. comp. Patented in 1821 (#4531)
label: Description
content: Inscription: "Jn. R. Arnold _ London. Invt et Fecit No 491" on backplate
label: Description
content: Dial details:
label: Description
content: Engraved and silvered brass
label: Description
content: Indicates hours, minutes, seconds
label: Description
content: Inscription: “ARNOLD. / London / No 491" on dial
label: Description
content: Blued steel spade hands
label: Description
content: Brass bowl; bayonet-fitted bezel; convex, plain crystal
label: Description
content: No box
label: Description
content: No winding key, sprung dust cover over winding work
label: Description
content: References:
label: Description
content: 1. Gould, Rupert T. <i>The Marine Chronometer.</i> London: Holland Press, 1960.
label: Description
content: 2. Mercer, Tony. <i>Chronometer Makers of the World.</i> Essex: NAG Press, 1991.
label: Description
content: 3. Mercer, Vaudrey. <i>John Arnold & Son, Chronometer Makers, 1762-1843.</i> London: The Antiquarian Horological Society, 1972.
label: Description
content: 4. Mercer, Vaudrey. <i>The Life and Letters of Edward John Dent, Chronometer Maker and some account of his Successors.</i> London: The Antiquarian Horological Society, 1977.
label: Description
content: 5. Whitney, Marvin E. <i>The Ship's Chronometer.</i> Cincinnati: American Watchmakers Institute Press, 1985.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
setName: label: See more items in
content: Work and Industry: Mechanisms
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content: Time and Navigation
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content: Measuring & Mapping
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1984.0416.014
label: accession number
content: 1984.0416
label: catalog number
content: 1984.0416.014
objectType: label: Object Name
content: box chronometer without case
physicalDescription: label: Physical Description
content: brass (overall material)
label: Physical Description
content: glass (part: material)
label: Measurements
content: overall: 2 1/2 in x 3 3/4 in; 6.35 cm x 9.525 cm