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Of typical form, the glass enclosed compass with magnetic needle, the silvered compass face with finely engraved triangular directional points, fleur-de-lis northern pointer, and maker's name "Rittenhouse and Potts," with circular conforming brass compass cover, centered within brass twin folding sight vanes.
The Rittenhouse brothers of Philadelphia manufactured innovative mathematical and scientific instruments, notably compasses, which were widely admired at the time for their reliability and fine craftsmanship, and are still prized by American surveyors today. David began as clockmaker and later made compasses and other instruments. He mentored his younger brother, Benjamin, who also became a master craftsman, making highly decorated fine compasses and clocks.
It is uncertain as to whether David invented the vernier compass, which helps surveyors compensate for the difference between true north and magnetic north, or whether he based his version on a European design. It is undisputed, however, that he introduced the vernier compass to North America, and that Benjamin popularized the feature, so that in the 19th century vernier compasses were generically referred to "Rittenhouse compasses." Compasses based upon the Rittenhouse design were the definitive instrument for public land surveys until the 1840s, and continued to be used through most of the 19th century.
This compass was made by Benjamin in collaboration with William Lukens Potts, who worked with him from 1796-98 before striking out on his own.
Uzes, Francois D. Bud. "The Brothers Rittenhouse, ACSM/ASPRS International Proceedings: 1994." http://www.odyssey.maine.edu/gisweb/spatdb/acsm/ac94127.html