A surveyor's chain that is 66 ft (20 m) long, consisting of a series of 100 metal links each 7.92 in (20.1 cm) long and fastened together with rings. It served as the legal unit of length for surveys of U.S. public lands, but has been superseded by steel or metal tapes graduated in chains and links. Named after Edmund Gunter (1581-1626), English mathematician and astronomer, who invented the device about 1620.