Geodetic Transit

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This transit marked "USC&GS No. 18" was designed by E. G. Fischer, chief mechanician of the U. S. Coast and Geodetic Survey. It is one of two identical instruments that were built in the Survey's instrument shop in 1888–1889. These instruments were said to be "the most complete and best constructed transits the Survey has ever had for longitude." They had about the same optical power as the transits that Troughton & Simms had made in the 1840s, but weighed substantially les. When packed in two boxes for transportation, each new instrument weighed "only" about 350 pounds. John Clacey made the objective lenses, and Edward Kahler made the eyepieces.
G. N. Saegmuller offered an apparently identical instrument for $900. He termed it a "Coast Survey Transit. No. 30" and noted that the Survey used instruments of this sort "for time observations only."
Ref: Edwin Smith, "A Description of Two New Portable Transit Instruments for Longitude Work," Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1889 (Washington, D.C., 1890), Appendix No. 9.
G. N. Saegmuller, Descriptive Price–List of First–Class Engineering & Astronomical Instruments (Washington, D.C., 1903), p. 75.
Currently not on view
aperture: 3 1/2 in; 8.89 cm
telescope: 39 1/2 in; 100.33 cm
ID Number
accession number
catalog number
Credit Line
U.S. Coast & Geodetic Survey
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Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History