Capt. Field's Improved Hinged Parallel Rule

This 21" German silver hinged parallel rule has two small knobs for positioning the instrument. Brass pins secure the hinges. The top blade is marked: U. S. C. & G. S. NO. 323. A fleur-de-lis or letter H appears above the mark. The edges of the top blade are marked as a rectangular protractor, and the edges of the bottom blade are marked for nautical compass points.
Capt. William Andrew Field (about 1796–1871) of England added the protractor and compass scales to hinged parallel rules in 1854. This made it easier for ship navigators to move the rule without losing track of the ship's course. According to the accession file, the U.S. Coast & Geodetic Survey acquired this rule on July 23, 1919, and last issued it on March 18, 1920. Compare to MA*309661 and MA*309662.
References: "Field's Parallel Rule," The Nautical Magazine and Naval Chronicle 23, no. 5 (May 1854): 280; Peggy A. Kidwell, "American Parallel Rules: Invention on the Fringes of Industry," Rittenhouse 10, no. 39 (1996): 90–96; National Maritime Museum, "Captain Field's Improved Parallel Rule," Object ID NAV0602,
Currently not on view
Object Name
parallel rule
date made
Physical Description
german silver (overall material)
overall: 1.1 cm x 53.6 cm x 7.3 cm; 7/16 in x 21 3/32 in x 2 7/8 in
ID Number
catalog number
accession number
Science & Mathematics
Measuring & Mapping
Parallel Rules
See more items in
Medicine and Science: Mathematics
Parallel Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Transfer from U.S. Department of Commerce, Coast & Geodetic Survey
Additional Media

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