Telescopic Aildade

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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 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: 18 1/2 in; 46.99 cm
telescope: 11 in; 27.94 cm
overall: 8 1/8 in x 18 5/8 in x 3 3/4 in; 20.6375 cm x 47.3075 cm x 9.525 cm
ID Number
catalog number
accession number
Credit Line
U.S. Geological Survey
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History


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