Gurley Locke Level (binocular)

In 1886 William Gurley obtained a patent (#353,406) for a Locke level with the vial inside the telescope tube. He described it as "a short, compact, cheap, durable, efficient, easily adjustable, and well–incased telescopic leveling–instrument, having a very large and clear field, and requiring but one eye to be used by an engineer or surveyor in quickly taking preliminary or approximate levels with the instrument held by hand." Maria Gurley, William's wife and executrix of his estate, obtained a patent (#360,805) for a binocular version of this instrument in 1887. Here the tube on the right holds the usual lenses of an opera glass, while the tube on the left holds the level vial, prism, and cross wires of the level. The monocular was soon selling for $12, and the binocular for $15, and both remained on the market for about 30 years. This example is marked "W. & L. E. GURLEY TROY N. Y." The Interstate Commerce Commission transferred it to the Smithsonian in 1962.
Ref: W. & L. E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N.Y., 1893), pp. 225–226.
Currently not on view
Object Name
W. & L. E. Gurley
overall: 3 3/8 in x 4 5/8 in x 2 1/16 in; 8.5725 cm x 11.7475 cm x 5.23875 cm
place made
United States: New York, Troy
ID Number
catalog number
accession number
Measuring & Mapping
Surveying and Geodesy
See more items in
Medicine and Science: Physical Sciences
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center
W. & L. E. Gurley. Manual of the Prinicipal Instruments Used in American Engineering and Surveying; 30th Edition

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