The U.S. Coast and Geodetic Survey designed and built this 4-meter base bar, No. 6, and transferred it to the Smithsonian in 1914. It is probably one of the secondary slide contact bars that was lent to the U.S. Geological Survey in the early 1880s. J. Howard Gore, of the Geological Survey, found that “Four meter bars were preferred to those six meters long, since they are more easily transported and are less liable to injury by careless handling.”
Ref: Report of Mr. J. Howard Gore, Dec. 11, 1881, in Third Annual Report of the United States Geological Survey (Washington, 1883), pp. 30-32.
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