|This article needs additional citations for verification. (December 2008)|
|2.256×10−3 m||2.2558 mm|
|US customary units (Imperial units)|
|7.401×10−3 ft||88.81×10−3 in|
The ligne or line or Paris line, is a historic unit of length used in France and elsewhere prior to the adoption of the metric system in the late 18th century, and used in various sciences after that time. It is vestigially retained today by French and Swiss watchmakers to measure the size of watch movements, in button making, and ribbon manufacture.
There are 12 lignes to one French inch (pouce). The standardized conversion for a ligne is 2.2558291 mm (1 mm = 0.443296 ligne), and it is abbreviated with the letter L or represented by the triple prime, ‴. One ligne is the equivalent 0.0888 inch.
In the 9th century German button makers began to use the term ligne to measure the diameter of buttons. The consensus definition was that a ligne was the measurement of a round wick, folded flat. In this sense it measures 1⁄40 of an inch, but not exactly, for there were several inches in the kingdoms and petty states of Germany at that time.
Such a measurement became the American measurement called "line," being one-fortieth of the US-customary inch, used measure buttons, probably introduced by German immigrants. It remains in US use today for buttons and snaps.
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