Paris line

Physical unit
Unit name	Paris line
Unit symbol	${\ displaystyle \ mathrm {{} ^ {\ prime \ prime \ prime}}}$
Physical quantity (s)	length
Formula symbol	${\ displaystyle l}$
dimension	${\ displaystyle {\ mathsf {L}}}$
In SI units	${\ displaystyle \ mathrm {1 ^ {\ prime \ prime \ prime} = 2 {,} 2558 ... \; mm}}$
Derived from	inch
See also: Old weights and measures (France)

The Parisian line is an old measure of length that was used as a reference unit across Europe in the 17th to 19th centuries .

definition

The "Paris line" is derived from the "Paris foot" in the duodecimal system .

symbol	unit	Length in mm (rounded)	divides into
1'	Parisian foot (pied)	324.840	12 Paris inches (pouces)
1''	Paris Customs (pouce)	027.070	12 Parisian lines (lignes)
1'''	Paris line (ligne)	002.256	12 scruples (douzièmes)
1''''	Scruples (douzième)	000.188

In 1799 the original meter was set to 443,296 Parisian lines. This means that a Paris line is around 2.2558 mm long.

For a long time in the 19th century, the Paris line and the meter were used in parallel as a reference unit for local linear measurements. The problem with all conversions is the large, unwieldy prime factor 1979, which appears in the sequence of digits 443296. 443296 = 2 ⁵ x 7 x 1979. Rounding from 443.296 to 443.3 results in the prime factors 11 × 13 × 31, ie no common prime factor for the unrounded sequence of digits 443296. Often, rounded values were used for further calculations, which led to error propagation. Therefore, depending on the source, there are significant variations in many historical units.

use

This reference measure was used in science, e.g. B. Newton , watchmakers , typesetters , opticians and in historical metrology .

A movement with the size of 11.5 lines therefore has a diameter of 25.9 mm.
In measurement technology , the sensitivity of tubular vials was given in arc seconds per line.
The wick widths of oil and kerosene lamps are also traditionally indicated in lines . Over time, the unit of measurement was used more and more to classify the lamp size. A lamp with a 14-line wick was a 14-line lamp, which included a 14-line draft glass and a tank with a 14-line thread (vase ring).
The traditional measurement system of typography uses the Didot point defined as the ¹ ⁄ ₆ Parisian line as the unit of measurement .

The typographical representation of the unit character can be used as triple lines carried, the Unicode is U+2034in HTML can &#8244be used. The triple application of the apostrophe is visually similar .