Earth Inductor

As scientists discovered that even the best dip circles gave unreliable results, they began using earth inductors to determine magnetic dip. In 1912, the Department of Terrestrial Magnetism of the Carnegie Institution of Washington developed a new earth inductor for use at sea. It has three key elements: an improved gimbal stand, a means for rotating the coil without disturbing the gimbal rings, and a sensitive galvanometer.
This example is marked "D.T.M. C.I.W. E.I. N° 3." It is the third Carnegie marine earth inductor. When the Carnegie closed its program in terrestrial magnetism, it was lent to the U.S. Coast and Geodetic Survey. The U.S. Geological Survey acquired it in 1973 when it took over the geomagnetic program of the federal government, and transferred it to the Smithsonian in 1982.
Ref: J. A. Fleming, "Description of the C.I.W. Marine Earth
Inductor," Terrestrial Magnetism 18 (1912): 39-45.
C. W. Hewlett, "Report on the C.I.W. Marine Earth Inductor," Terrestrial Magnetism 18 (1912): 46-48.
Object Name
earth inductor
Date made
Carnegie Institution of Washington. Department of Terrestrial Magnetism
Physical Description
metal (overall material)
overall: 9 1/2 in; 24.13 cm
Place Made
United States: District of Columbia, Washington
ID Number
accession number
Measuring & Mapping
Science & Mathematics
Science & Scientific Instruments
Science & Scientific Instruments
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
U.S. Department of the Interior, U.S. Geological Survey

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