Carrington's Patent Rolling Parallel Rule

Carrington's Patent Rolling Parallel Rule

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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.
Currently not on view
Object Name
parallel rule
date made
mid 19th century
Carrington, James
place made
United States: Connecticut, Wallingford
Physical Description
metal (overall material)
wood (overall material)
overall: 2.2 cm x 35.6 cm x 4.9 cm; 7/8 in x 14 1/32 in x 1 15/16 in
ID Number
accession number
catalog number
Credit Line
Warshaw Collection of Business Americana
Drafting, Engineering
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Parallel Rules
Data Source
National Museum of American History
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I have a Carrington’s patent parallel rule that is marked as being manufactured by WIlliam Hull, Wallingford Ct. There are no dates on it and the body and roller appear to be different kinds of mahogany, the rollers being lighter in color. The ends look like gunmetal to me. The ruler still runs true and the rollers are still straight and round.

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