Ligne


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. The loi du 19 frimaire an VIII states that one metre is equal to exactly 443.296 French lines.
It is vestigially retained today by French and Swiss watchmakers to measure the size of watch movements, in button making, and ribbon manufacture.

Current use

Watchmaking

There are 12 lignes to one French inch. The standardized conversion for a ligne is 2.2558291 mm, and it is abbreviated with the letter L or represented by the triple prime,. One ligne is the equivalent of 0.0888 international inch.
This is comparable in size to the British measurement called "line", used prior to 1824.

Buttonmaking

In the 18th 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 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 to measure buttons, probably introduced by German immigrants. It remains in US use today for buttons and snaps.

Hatmaking

Ligne is used in measuring the width of ribbons in men's hat bands, at 11.26 per inch.