Smithsonian - National Museum of American History, Behring Center

 
Physical Sciences Collection - Surveying and Geodesy

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Alidade - click to enlarge

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Alidade

Catalogue number:
PH*247911

Inscriptions:
"U.S.G.S. No. 25"

Dimensions:
base 18 inches long; telescope 9 inches long

Discussion:
This alidade has a telescope with level mounted below, and a vertical arc that is silvered, graduated to degrees, and read by vernier to single minutes. The base has six round holes, two short level vials, and a beveled edge with a 12-inch scale that is divided to sixteenths of an inch. The United States Geological Survey transferred this instrument to the Smithsonian in 1907, describing it as a "preliminary type" of alidade devised for the Survey about 1890.

Further Information:

Alidade

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