Dod Protractor and Parallel Rule

This brass semicircular protractor is divided by single degrees and marked by tens from 10° to 90° to 10°. It is attached with metal screws to a set of brass parallel rules. Brass S-shaped hinges connect the rules to each other. The bottom left screw on the parallel rules does not attach to the bottom piece. A rectangular brass arm is screwed to the center of the protractor. A thin brass piece screwed to the arm is marked with a small arrow for pointing to the angle markings. The protractor is stored in a wooden case, which also contains a pair of metal dividers (5-1/4" long).
The base of the protractor is signed: L. Dod, Newark. Lebbeus Dod (1739–1816) manufactured mathematical instruments in New Jersey and is credited with inventing the parallel rule protractor. He served as a captain of artillery during the Revolutionary War and made muskets. His three sons, Stephen (1770–1855), Abner (1772–1847), and Daniel (1778–1823), were also noted instrument and clock makers. The family was most associated with Mendham, N.J. (where a historic marker on N.J. Route 24 indicates Dod's house), but Dod is known to have also lived at various times in Newark.
ID number MA*310890 is a similar protractor and parallel rule. Compare also to a Dod instrument owned by the Metropolitan Museum of Art in New York,
References: Bethuel Lewis Dodd and John Robertson Burnet, "Biographical Sketch of Lebbeus Dod," in Genealogies of the Male Descendants of Daniel Dod . . . 1646–1863 (Newark, N.J., 1864), 144–147; Alexander Farnham, "More Information About New Jersey Toolmakers," The Tool Shed, no. 120 (February 2002),; Deborah J. Warner, “Surveyor's Compass,” National Museum of American History Physical Sciences Collection: Surveying and Geodesy,; Peggy A. Kidwell, "American Parallel Rules: Invention on the Fringes of Industry," Rittenhouse 10, no. 39 (1996): 90–96.
Currently not on view
Object Name
protractor and parallel rule
date made
late 1700s
Dod, Lebbeus
Physical Description
leather (overall material)
wood (overall material)
brass (overall material)
overall: 2.9 cm x 33.5 cm x 14 cm; 1 5/32 in x 13 3/16 in x 5 1/2 in
place made
United States: New Jersey, Newark
ID Number
accession number
catalog number
Science & Mathematics
Parallel Rules
Parallel Rule
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Parallel Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Ruth A. Ming
Additional Media

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