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William J. Peters of the U. S. Geological Survey devised this type of instrument in 1898, while doing reconnaissance work in Alaska. G. N. Saegmuller, proprietor of Fauth & Co., explained its function: "Having a fixed base of known dimensions defined by targets, the measurement is made by bringing the images of the targets together by moving the halved objective by means of a micrometer screw." The Geological Survey transferred this example to the Smithsonian in 1907, reporting that "Distances up to 1 or 2 miles can be determined with sufficient accuracy for reconnaissance work."
This is actually a composite instrument. The prism monocular was probably made by Bausch & Lomb in Rochester, N.Y., according to the design developed by Zeiss in Jena, Germany, while Saegmuller made the divided object glass micrometer. It is notably different from the stenometer that Saegmuller was offering in 1901, and so is probably an early prototype. The words "U.S.G.S. No. 4" are scratched onto its surface.
Ref: George N. Saegmuller, Descriptive Price-List of First-Class Engineering & Astronomical Instruments (Washington, D.C., 1901), p. 108.
Currently not on view
Object Name
Fauth & Co.
place made
United States: District of Columbia, Washington
overall: 2 in x 3 1/4 in x 4 3/4 in; 5.08 cm x 8.255 cm x 12.065 cm
overall: 2 in x 3 5/16 in x 4 11/16 in; 5.08 cm x 8.41375 cm x 11.90625 cm
ID Number
catalog number
accession number
Credit Line
U.S. Geological Survey
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History
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