Truman Gravity Meter No. 1

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.
Because gravitational anomalies are often associated with petroleum deposits, geologists measure the force of gravity in areas where they suspect oil might be found. The gravimeters that came into use for this purpose in the 1930s were more rugged and easier to manage than the gravity pendulums and torsion balances that had used since the early years of the 20th century. This gravimeter, which reads to one part in ten million, was the first gravimeter that was sufficiently accurate and dependable for oil exploration. It was designed by Orley Hosmer Truman, built by the Humble Oil and Refining Co., and put into use in 1931. Humble donated it to the Smithsonian in 1960.
Ref: Notes prepared by D. H. Gardner, August 19, 1959, in NMAH accession file.
O. H. Truman, "Notes on the Truman Gravity Meter No. 1" (Feb. 26, 1962), and letter to P. W. Bishop, Jan. 10, 1963, in NMAH curatorial file.
L. L. Nettleton, Geophysical Prospecting for Oil (New York: McGraw-Hill, 1940),p. 32.
Currently not on view
Object Name
gravity meter
date made
ca 1931
Humble Oil and Refining Co.
overall: 33 in x 24 in; 83.82 cm x 60.96 cm
ID Number
catalog number
accession number
See more items in
Work and Industry: Petroleum
Measuring & Mapping
Natural Resources
Data Source
National Museum of American History, Kenneth E. Behring Center


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