Gurley Railroad Compass

Description
This instrument marked "W. & L. E. Gurley, Troy, N.Y." was made between 1868 when the Gurleys introduced a railroad compass with one vernier scale on the limb, and the middle of 1876 when the firm's engraving machine was up and running. New, it cost $70. It belonged to Bowdoin College. The upper plate carries the sights, two level vials, and the compass. The lower plate, wider than the upper, carries the circle which is graduated to 30 minutes, and read by vernier to single minutes. A tangent screw on the south arm moves the two plates relative to one another. There is a variation arc on the compass face that extends 30 degrees either way; the folded vernier is moved by a rack and pinion located on the north arm, and reads to 2 minutes. It has a blackened or bronzed finish, and a silver–plated face.
Ref: W.&L.E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N. Y., 1868), pp. 52–56.
W. Skerritt, "W.&L.E. Gurley's Engraving Machine," Rittenhouse 11 (1997): 97–100.
Location
Currently not on view
Object Name
compass (railroad)
date made
1868-1876
maker
W. & L. E. Gurley
Measurements
overall length: 15 5/8 in; 39.6875 cm
needle: 5 1/2 in; 13.97 cm
place made
United States: New York, Troy
ID Number
PH*329729
catalog number
329729
accession number
278336
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center

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