William J. Peters of the United States 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 U.S.G.S., which transferred this stenometer to
the Smithsonian in 1907, reported that "Distances up to 1 or 2 miles can be determined with
sufficient accuracy for reconnaissance work." This stenometer is 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, 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.
N.M.A.H. accession file #47,736.