"U.S.G.S. No. 16"
base 18.5 inches long; telescope 11 inches long
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.