This theodolite magnetometer is based on the design that the U.S. Coast and Geodetic Survey developed in 1892-1893. It is similar in many ways to the instrument that the Survey had been using since the early 1880s, but with several new features. One is the octagonal shape of the collimating magnets. Another is the black velvet screen that connects the telescope with the suspension box: this cuts off stray light and eliminates the problems that had been caused by the glass window in the earlier form. It is marked "FAUTH & CO. WASHN D.C. 941" and "T.M.C.I. 1." The serial number suggests that it was made around 1895.
This instrument belonged to the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. Internal records indicate that D.T.M. purchased it from Kolesch & Co. in New York in 1906 (for $175), sent it to Bausch, Lomb, Saegmuller Co. for repairs (another $120), and kept it in service until 1919.
Ref: Edwin Smith, "Notes on Some Instruments Recently Made in the Instrument Division of the Coast and Geodetic Survey Office," Annual Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1894, Appendix No. 8.
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