Public domain
Science and research. Mineral prospecting. Intensity of the earth's magnetic field, something a mining engineer needs to know if he is looking for vital metals under the crust of the earth, may be measured by the horizontal magnetometer and the vertical magnetometer shown here. Three engineering stu
From the collection of Library of Congress. Free to download, adapt and use — no permission needed.
Credit lineScience and research. Mineral prospecting. Intensity of the earth's magnetic field, something a mining engineer needs to know if he is looking for vital metals under the crust of the earth, may be mea. 1942-01-01. United States. Office Of War Information, Feininger, Andreas. Farm Security Administration/Office of War Information Collection, Library of Congress. Public domain.
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