Railroad Compass
date: label: date made
content: 1868-1876
name: label: maker
content: W. & L. E. Gurley
notes: label: Description
content: 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.
label: Description
content: Ref: W.&L.E. Gurley, <i>A Manual of the Principal Instruments Used in American Engineering and Surveying</i> (Troy, N. Y., 1868), pp. 52–56.
label: Description
content: W. Skerritt, "W.&L.E. Gurley's Engraving Machine," <i>Rittenhouse</i> 11 (1997): 97–100.
label: Location
content: Currently not on view
place: label: place made
content: United States: New York, Troy
setName: label: See more items in
content: Medicine and Science: Physical Sciences
label: See more items in
content: Surveying and Geodesy
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content: Measuring & Mapping
publisher: label: Related Publication
content: W. & L. E. Gurley. Manual of the Prinicipal Instruments Used in American Engineering and Surveying; 11th Edition
creditLine: label: Credit Line
content: Bowdoin College, Department of Physics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.329729
label: catalog number
content: 329729
label: accession number
content: 278336
objectType: label: Object Name
content: Surveyor's Compass (Railroad)
physicalDescription: label: Measurements
content: overall length: 15 5/8 in; 39.6875 cm
label: Measurements
content: needle: 5 1/2 in; 13.97 cm
label: Measurements
content: overall in case: 5 7/16 in x 16 5/8 in x 9 3/8 in; 13.81125 cm x 42.2275 cm x 23.8125 cm