Gurley began offering telescopic alidades in 1884, explaining that “This instrument, which has been so largely employed abroad in topography and map drawing, is now fast coming into use in our own country, especially in colleges and schools where the study of surveying is pursued.” This example belonged to Gettysburg College and is marked “W. & L. E. GURLEY TROY, N.Y.” The lack of serial number indicates that it was made before 1908. It has an erecting telescope with level above, and a vertical circle that is graduated to 30 minutes and read by vernier to single minutes. There is also a box compass with level vials, a plumbing bar, and a plumb bob.
Ref: W. & L. E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N.Y., 1893), pp. 215-224.
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