This instrument is marked "No. 1 U.S.G.S." The horizontal circle and vertical arc are silvered, graduated to 30 minutes, and read by verniers to single minutes. A trough compass and level vial sit atop the telescope; a circular level sits on the horizontal circle. A micrometer attachment, sometimes termed a gradientor, measures the elevation of the telescope with great precision. The words "New November 15 87" are scratched on the underside of the horizontal plate.The U.S. Geological Survey transferred it to the Smithsonian in 1907.
Currently not on view
Object Name
date made
associated institution
U.S. Department of the Interior. U.S. Geological Survey
horizontal circle: 3 1/2 in; 8.89 cm
telescope: 8 1/2 in; 21.59 cm
needle: 5 1/4 in; 13.335 cm
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
Credit Line
U.S. Geological Survey

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