North American Geophysical Gravimeter

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.
Currently not on view
North American Geophysical Co.
place made
United States: Texas, Houston
overall: 44 cm x 27.5 cm x 30 cm; 17 5/16 in x 10 13/16 in x 11 13/16 in
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Work and Industry: Agriculture
Measuring & Mapping
Natural Resources
Data Source
National Museum of American History


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