Telescopic Alidade

This alidade has a telescope with a level mounted above, and a vertical circle that is silvered, graduated to 30 minutes, and read by vernier to single minutes. The base has two perpendicular level vials. The U.S. Geological Survey transferred it to the Smithsonian in 1907, describing it as a "preliminary type" of alidade devised for the Survey about 1890.
Currently not on view
Object Name
alidade (telescopic)
base: 20 in; 50.8 cm
telescope: 10 1/4 in; 26.035 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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