This instrument is marked "D.T.M. C.I.W. N° 19." Designed and built by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington in 1912, it incorporates an astronomical telescope and magnetometer for the determination of magnetic declination and horizontal intensity, and a dip circle with a Lloyd-Creak attachment for the determination of inclination and intensity. It is relatively light and easy to manipulate. It was used for a few years and then set aside when the universal magnetometer with earth inductor came into use.
This magnetometer was probably transferred to the U.S. Coast and Geodetic Survey after the Carnegie Institution closed its geomagnetic program. 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, "Two New Types of Magnetometers Made by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington," Terrestrial Magnetism 16 (1911): 1-12.
Carnegie Institution of Washington, Land Magnetic Observations, 1911-1913 (Washington, D.C., 1915), pp. 7-8.
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