Telescopic Alidade

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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 six large circular holes, and a circular level vial. 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
base: 26 in; 66.04 cm
telescope: 11 1/2 in; 29.21 cm
overall: 8 13/16 in x 26 in x 3 1/2 in; 22.38375 cm x 66.04 cm x 8.89 cm
ID Number
catalog number
accession number
Credit Line
U.S. Geological Survey
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Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History