:''For the French river of the same name see
Ligne River''.
The 'ligne' (from the
French word meaning "
line") is a unit of length that was in use prior to the French adaptation of the
metric system in the late
1700s, and is still used by French and
Swiss wristwatch makers to measure the size of a watch movement. (For example, ''
Girard-Perregaux'' will introduce a new 12 ligne chronograph movement.) In this usage there are 12 ligne 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, ′′′.
This is comparable in size to the British measurement called "line" (one twelfth of an imperial inch).
In the eighteenth century the term ''ligne'' came into use among
German button makers, where it was used 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 1/40th 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. Its use was again to measure buttons, and was probably introduced by German immigrants.
See also
★
Horology