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
base: 20 in; 50.8 cm
telescope: 10 1/4 in; 26.035 cm
overall: 8 9/16 in x 20 in x 4 in; 21.74875 cm x 50.8 cm x 10.16 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