Protractor and Ruler Scale

Description
This steel semicircular protractor is divided by half-degrees and is marked by tens from 360 to 180 and from 180 to 0, both in the counterclockwise direction. A 3/8" line is engraved at the origin point. On its left side, the protractor slides along a steel bar or straight edge. Two thumbscrews at the top of the protractor hold in place a removable scale, which is divided into units of four and marked by 40s from 0 to 720. Forty units correspond to approximately one centimeter. The bottom of each screw is marked "2." The scale moves approximately 60 units to the left or right by turning a third screw against a serrated edge on the scale.
An additional scale accompanies the object. This scale is divided by fifties and marked by thousands from 0 to 12,000. Ten units correspond to approximately 1.5 centimeters. The protractor was originally stored in a mahogany case, apparently discarded by 1959. The protractor was purchased by the U.S. Geological Survey between 1879 and 1907.
See also ID number MA.247968.
Location
Currently not on view
date made
1879-1907
maker
W. & L. E. Gurley
Gurley, Lewis E.
Gurley, William
place made
United States: New York, Troy
Physical Description
steel plate (overall material)
copper (overall material)
Measurements
overall: 2 cm x 23 cm x 30.5 cm; 25/32 in x 9 1/16 in x 12 in
ID Number
MA.247967
accession number
47736
catalog number
247967
Credit Line
Transfer from U.S. Geological Survey
subject
Mathematics
Protractor
Surveying
See more items in
Medicine and Science: Mathematics
Protractors
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center

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