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

This 21" German silver hinged parallel rule has two knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges. 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 right end of the upper blade is marked: CAPT. FIELD'S IMP^D. The center of the lower blade is marked: U. S. C. & G. S. NO. H. 398. The left end has the firm's "HUSUN" logo for the London instrument maker H. Hughes & Son, with a sun above the letters and waves below the letters. A circle around the logo is marked: REGISTERED TRADE MARK (/) G^T BRITAIN.

Capt. William Andrew Field (about 1796–1871) of Britain 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 November 6, 1923, and last issued it on February 16, 1924. Compare to MA.309661 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, http://collections.rmg.co.uk/collections/objects/42814.html; Science Museum Group, "Henry Hughes and Son Limited," Collections Online – People, http://collectionsonline.nmsi.ac.uk/detail.php?type=related&kv=58792&t=people.

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