Darling, Brown & Sharpe Astronomical Linear Slide Rule

This large mahogany linear astronomical slide rule is covered with strips of German silver. There are two slides, each of which have scales on both sides. Each slide has a knob near one end for moving it; these may be unscrewed and attached on the reverse side. One slide is marked COLLIMATION on one side and AZIMUTH on the other. The other slide is marked LEVEL AZIMUTH on one side and REFRACTION on the other. The base has four identical, unlabeled logarithmic scales, each of which runs from 1 to 10 twice (with a bit more at each end).
On the center portion of the base, the instrument is marked Darling Brown & Sharpe Providence R.I. Darling, Brown & Sharpe did business under that name from 1866 to 1892. For additional company history, see 1977.0460.01. According to records of the United States Naval Observatory, this slide rule was purchased for $154.00 in December 1887. Few slide rules specifically for astronomy survive, so these large and expensive objects were probably not widely used. Compare to two late 19th-century rules held by the Powerhouse Museum, http://www.powerhousemuseum.com/collection/database/?irn=233017.
Reference: Ledger of Instruments Purchased by the U.S. Naval Observatory, ca. 1845–1906, United States Naval Observatory, Washington, D.C.
Currently not on view
Object Name
slide rule
date made
Darling, Samuel
Brown & Sharpe Manufacturing Company
Physical Description
german silver (laminate material)
mahogany (overall material)
overall: 6.9 cm x 112 cm x 15.4 cm; 2 23/32 in x 44 3/32 in x 6 1/16 in
place made
United States: Rhode Island, Providence
ID Number
catalog number
accession number
Science & Mathematics
Slide Rules
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Transfer from U.S. Naval Observatory
Additional Media

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