North American Geophysical Gravimeter
name: label: maker
content: North American Geophysical Co.
notes: label: Description
content: Gravimeters (gravity meters) are extremely precise instruments that measure the earth’s gravity at a specific location. Gravimeters are often used by prospectors to locate subterranean deposits of valuable natural resources (mainly petroleum) as well as by geodesists to study the shape of the earth and its gravitational field. Differences in topography, latitude, or elevation—as well as differences in subterranean density—all affect the force of gravity. Commonly, gravimeters are composed of a weight hanging on a zero-length spring inside a metal housing to negate the influence of temperature and wind. Gravity is then measured by how much the weight stretches the spring.
label: Description
content: This is an example of the gravimeter that the North American Geophysical Co. began advertising in 1945. It has a LaCoste-type zero-length spring, and a null system with a beam support. It is buoyancy compensated and, when new, accurate to within .01 of a milligal. It is read by microscope. It weighs 28 lbs. This particular unit was probably made sometime after 1950 when Reginald C. Sweet obtained a patent (#2,523,075) and assigned it to the North American Geophysical Co. Robert M. Iverson donated it to the Smithsonian in 1967.
label: Description
content: Ref: G. E. Sweet, <i>The History of Geophysical Prospecting</i> (Los Angeles, 1966).
label: Description
content: L. L. Nettleton, <i>Gravity and Magnetics in Oil Prospecting</i> (New York, 1976), p.62.
label: Description
content: Advertisements for North American gravimeters in <i>Geophysics</i> 11 (1946): 28; 14 (1949): 62; and 16 (1951): 28.
label: Location
content: Currently not on view
place: label: place made
content: United States: Texas, Houston
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content: Work and Industry: Agriculture
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content: Natural Resources
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content: Measuring & Mapping
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: AG.MHI-P-9376
label: catalog number
content: MHI-P-9376
label: accession number
content: 281132
objectType: label: Object Name
content: gravity meter, North American
physicalDescription: label: Measurements
content: overall: 44 cm x 27.5 cm x 30 cm; 17 5/16 in x 10 13/16 in x 11 13/16 in