Capt. Field's Improved Hinged Parallel Rule Signed Henry Hughes & Son

This 21" German silver hinged parallel rule has two small knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges. An indentation is on both blades at the center of the rule, with a line marking the center. 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.
The center of the top blade is marked: U. S. C. & G. S. NO. 331. The right end of the top blade is marked: CAPT. FIELD'S IMPD. The right end of the lower blade is marked: H. HUGHES & SON LTD. LONDON. The left end has the firm's "HUSUN" logo, with a sun above the letters and waves below the letters.
Capt. William Andrew Field (about 1796–1871) of England added a 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. Henry Hughes & Son made marine and aeronautical navigational instruments in London from 1828 to 1947 and incorporated in 1903. According to the accession file, the U.S. Coast & Geodetic Survey acquired this rule on August 21, 1919, and last issued it on September 5, 1922. Compare to MA*309662 and MA*309663.
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,; Science Museum Group, "Henry Hughes and Son Limited," Collections Online – People,
Currently not on view
Object Name
parallel rule
date made
H. Hughes & Son, Ltd.
Physical Description
brass (overall material)
german silver (overall material)
overall: 1.1 cm x 53.3 cm x 7.3 cm; 7/16 in x 20 31/32 in x 2 7/8 in
place made
United Kingdom: England, London
ID Number
catalog number
accession number
Parallel Rules
Science & Mathematics
Measuring & Mapping
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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