Carrington's Patent Rolling Parallel Rule

A 14" trapezoidal mahogany frame with metal end pieces covers two mahogany rollers that rotate on metal shafts. A paper label is marked: CARRINGTON'S PATENT PARALLEL RULER, FOR COUNTING HOUSES, &C. The label is decorated with an eagle over a shield with arrows in its claws. The eagle's beak holds a banner marked: E PLURIBUS UNUM.

On April 14, 1832, James Carrington of Wallingford, Conn., patented a parallel ruler that was later manufactured by William Hill of Wallingford. The rollers were raised in order to prevent ink from smearing as the ruler was moved across a drawing. In 1849 the U.S. House of Representatives ordered six dozen of the rulers from R. Farnham, a stationer in Washington, D.C., for $2.30 per dozen. This suggests the rules were used relatively widely for a significant period of time. Before he built a dam and factory in Wallingford around 1830, Carrington was a supervisor and inspector at the Harpers Ferry and Springfield armories.

References: "American Patents," The Repertory of Patent Inventions 15 (1833): 24; "Power, Factories, Invention," in Centennial of Meriden: June 10–16, 1906 (Meriden, Conn.: Journal Publishing Co., 1906), 245; U.S. House of Representatives, Contracts for Stationery, 31st Congress, 1st Session, Miscellaneous, No. 16, December 31, 1849 (Washington, D.C., 1850), 16–17; Hiram Williams Beckwith, History of Montgomery County, Together With Historic Notes on the Wabash Valley (Chicago, 1881), 246; Merritt Roe Smith, Harpers Ferry Armory and the New Technology (Cornell: University Press, 1977), 203, 207, 229.

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