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length 66 feet (4 poles)
In 1620, an English mathematician and astronomer named Edmund Gunter described a surveyor's chain with 100 links, measuring 66 feet (22 yards or 4 poles) overall. With this design, one square chain equals 484 square yards, ten square chains equal an acre, and 80 chains equal a mile. Gunther's design proved extremely popular in English lands. This example belonged to John Johnson (1771-1841), the Surveyor General of Vermont. It is made of steel, with round handles at either end, brass tallies every 10 links, and swivels every 25 links. Each link is joined to the next by three rings, and each unit is 7.92 inches long.