Phelps & Gurley Transit

This is a good example of instrument makers feeling their way towards a good design, but not quite getting it right. It is marked "Phelps & Gurley" and "Troy, N.Y." and dates from the period 1845-1851 when Jonas Phelps and William Gurley were in business together. Several elements of its design originated with Oscar Hanks, the mathematical instrument maker with whom Phelps and Gurley both apprenticed. W. & L. E. Gurley made a similar instrument that they called a Vernier Transit Compass.
The variation arc at the south side of the compass extends 20 degrees either way; the vernier reads to 2 minutes. There are level vials at North and West. The small vertical circle is read by vernier to 10 minutes.
William H. Skerritt, Catalog of the Charles E. Smart Collection of Antique Surveying Instruments (Troy, N.Y., 1996), p. 29.
Currently not on view
Object Name
Phelps & Gurley
overall: 7 in; 17.78 cm
needle: 5 in; 12.7 cm
vertical circle: 3 1/2 in; 8.89 cm
telescope: 9 3/4 in; 24.765 cm
place made
United States: New York, Troy
ID Number
accession number
catalog number
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
Skerritt, William H.. Catalog of the Charles E. Smart Collection of Antique Surveying Instruments
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