Link (unit)
The link (usually abbreviated as "l.", "li." or "lnk."), sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. A link is exactly 66⁄100 of a foot, or exactly 7.92 inches.
The unit is based on Gunter's chain, a metal chain 66 feet long with 100 links, that was formerly used in land surveying. Even after the original tool was replaced by later instruments of higher precision, the unit itself was commonly used in this application throughout the English-speaking world (e.g. in the United States customary system of measurements and the Imperial system). The length of the foot, and hence the link, varied slightly from place to place and time to time, but in modern times the difference between, say, the US survey foot and the international foot is two parts per million. The link fell out of general use in the 20th century.
Edmund Gunter designed and introduced the Gunter's chain in England in 1620. By correlating traditional English land measurements with the new decimal number system (which had just replaced Roman numerals), it combined ease and flexibility in taking surveying measurements in the field with ease of calculating results afterwards. It rapidly gained acceptance in English surveying practice, which also began to adopt the tool's chain and link lengths as units of measure within the English system of units. As English dominions grew over time, its system of measures came to be used in many parts of the world.
When the American colonies broke their ties with Great Britain in 1776, they needed to establish a system of units that fell under their own political authority. While they adopted many of the British units, the length of the yard (which determined all other units of length) was by necessity governed by the length of a physical artifact. The one in American possession was slightly different in actual length from the British one, due to imprecision of manufacture. It was of only minor significance at the time.
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