Hamilton No. 1 Box Chronometer
date: label: date made
content: 1941
label: date made
content: 1956
name: label: maker
content: Hamilton
notes: label: Description
content: This instrument is a specialized timekeeper for determining longitude at sea. It is serial no. 1 from a run of approximately 10,000 similar timekeepers made by Hamilton Watch Co, Lancaster, PA in 1942.
label: Description
content: World War II created a dire chronometer shortage for the United States. Before the war, most chronometers for American military and civilian customers were imported. Only a few American firms—including William Bond & Son of Boston and the New York establishments of John Bliss Inc. and T.S. and J. D. Negus—finished chronometers from parts imported from European makers. Chronometer making was a craft, with only a few hundred produced in any given year. When the war started in 1941, European suppliers of parts and finished instruments halted exports to the United States.
label: Description
content: Anticipating the arrival of war, the U.S. Naval Observatory had asked American domestic watch manufacturers in 1939 for their participation in mass-producing chronometers. Domestic watch manufacturers Hamilton and Elgin agreed to undertake the design and production, but only Hamilton’s product met Navy accuracy requirements. Hamilton delivered two prototypes to the Navy on 27 February 1942, which passed with an error rate of 1.55 seconds per day. The firm went on during the war to mass-produce 8900 more chronometers for the Navy, 1500 for merchant shipping and 500 for the Army. Between 1942 and 1944, the price dropped from $625 to $390 per timekeeper.
label: Description
content: Hamilton’s design for its Model 21 chronometer did not copy traditional European standards. Instead the design introduced key changes to improve accuracy. The modifications included changes to the escapement and the chronometer’s oscillating unit—the balance and hairspring assembly.
label: Description
content: 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.
label: Description
content: References:
label: Description
content: 1. Dick, Steven J. <i>Sky and Ocean Joined: The U. S. Naval Observatory 1830-2000.</i> Cambridge: Cambridge University Press, 2003.
label: Description
content: 2. Whitney, Marvin. <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 States: Pennsylvania, Lancaster
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
creditLine: label: Credit Line
content: Department of the Navy. Bureau of Ships
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: ME.314825
label: catalog number
content: 314825
label: accession number
content: 210893
objectType: label: Object Name
content: chronometer
label: Object Name
content: box chronometer
physicalDescription: label: Physical Description
content: brass (overall material)
label: Physical Description
content: steel (overall material)
label: Physical Description
content: glass (overall material)
label: Physical Description
content: wood (overall material)
label: Measurements
content: overall - chronometer case: 7 1/2 in x 8 in x 7 3/4 in; 19.05 cm x 20.32 cm x 19.685 cm
label: Measurements
content: overall - carrying case: 9 1/2 in x 12 in x 10 in; 24.13 cm x 30.48 cm x 25.4 cm
label: Measurements
content: overall - from catalog card: 7 1/2 in x 7 1/2 in x 7 1/2 in; 19.05 cm x 19.05 cm x 19.05 cm