W. & L. E. Gurley introduced this type of instrument--a railroad compass with one vernier on the limb--in 1868. This example has a hand-engraved signature, and so was made before the middle of 1876, when Gurley’s engraving machine was up and running. 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. A variation arc on the compass face 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. The compass has a blackened or bronzed finish, and a silver–plated face. New, it cost $65.
The "Fagg & Bowe 1870" signature scratched on the inside of this compass refers to George S. Fagg and Archibald H. Bowe, who began working for Gurley in 1866. The "Edward Meister Baltimore 1872" signature refers to an independent instrument maker in Baltimore, Md. The "Geo. Shilling 1904 Wash. D.C." signature refers to an independent instrument maker in Washington, D.C. The "J. Heim 1885" signature has not been identified.
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.
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