Smithsonian - National Museum of American History, Behring Center

 
Physical Sciences Collection - Surveying and Geodesy

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Telescopic Alidade - click to enlarge

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Telescopic Alidade

Catalogue number:
PH*247912

Inscriptions:
"U.S.G.S. No. 16"

Dimensions:
base 18.5 inches long; telescope 11 inches long

Discussion:
This alidade has an inverting telescope, and a vertical arc that is silvered, graduated to 20 minutes, and read by vernier to single minutes. The pedestal is painted maroon. The base, also maroon, has floral decorations at either end, a circular level vial, and a beveled edge with an 18-inch scale that is divided to fiftieths 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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