North American Geophysical Gravimeter

Description
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.
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.
Ref: G. E. Sweet, The History of Geophysical Prospecting (Los Angeles, 1966).
L. L. Nettleton, Gravity and Magnetics in Oil Prospecting (New York, 1976), p.62.
Advertisements for North American gravimeters in Geophysics 11 (1946): 28; 14 (1949): 62; and 16 (1951): 28.
Object Name
gravity meter, North American
maker
North American Geophysical Co.
Measurements
overall: 44 cm x 27.5 cm x 30 cm; 17 5/16 in x 10 13/16 in x 11 13/16 in
place made
United States: Texas, Houston
ID Number
AG*MHI-P-9376
catalog number
MHI-P-9376
accession number
281132
subject
Measuring & Mapping
Natural Resources
See more items in
Work and Industry: Agriculture
Data Source
National Museum of American History, Kenneth E. Behring Center

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