Semicircular Protractor

This semicircular brass protractor is divided by single degrees and marked by tens from 10° to 170° in both the clockwise and counterclockwise directions. The degree lines are crude and likely engraved by hand rather than by machine. A rounded notch is at the origin point. There is no maker's mark. The Department of Entomology in the National Museum of Natural History acquired this object in the late 19th century for use in research. Since inexpensive (10–25 cents) machine-divided brass protractors were widely available during this time period, it is not clear why the curators purchased an instrument that was so poorly manufactured. The protractor may have been made closer to the late 18th century.
Currently not on view
Object Name
date made
19th century
Physical Description
brass (overall material)
overall: .1 cm x 9.5 cm x 4.7 cm; 1/32 in x 3 3/4 in x 1 27/32 in
ID Number
accession number
catalog number
Science & Mathematics
See more items in
Medicine and Science: Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Transfer from National Museum of Natural History

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