Line (unit)


The line was a small English unit of length, variously reckoned as,,, or of an inch. It was not included among the units defined in the Weights and Measures Act 1824, which established the British Imperial units of measurement system.

Size

The line was not recognized by any statute of the English Parliament but was usually understood as of a barleycorn, making it of an inch, and of a foot. The line was eventually decimalized as of an inch, without recourse to barleycorns.
The US button trade uses the same or a similar term but defined as one-fortieth of the US-customary inch.

In use

Botanists formerly used the unit to measure the size of plant parts. Linnaeus's Philosophia botanica includes the Linea in its summary of units of measurements, defining it as Linea una Mensurae parisinae ; Stearns gives its length as. Even after metrication, British botanists continued to employ tools with gradations marked as linea ; the British line is approximately and the Paris line approximately.
Entomologists in the UK and other European countries in the 1800s used lines as a unit of measurement for insects, at least for the relatively large mantids and phasmids. Examples include Westwood, in the UK, and de Haan in the Netherlands.
Gunsmiths and armament companies also employed the -inch line, in part owing to the importance of the German and Russian arms industries. These are now given in terms of millimeters, but the seemingly arbitrary mm caliber|7.62 mm (0.30 in) caliber] was originally understood as a 3-line caliber. The caliber used by the M2 Browning machine gun was similarly a 5-line caliber.

Other 'line' units

Other similar small units called lines include: