1. The Yard, the Foot, the Inch
The term Yard, the Old English ‘gerde’ or ‘yerde,’ a wand or rod, became specially applied to a wand of 3 feet, or 4 spans; from this double mode of division and from its convenient length the cloth-yard of 3 feet became generally used. It has the convenience of being a half-fathom, and of being divisible not only into feet and inches, but also sexdecimally into units which are familiar as limb-lengths of the cubit and span system.
The half-yard corresponds to the Cubit.
The quarter-yard is a Span.[[12]]
The eighth is a Finger; women constantly measure linen approximately by the length of the bent middle finger.
The sixteenth is a Nail; this is the length of the half-finger, the last two joints of the middle finger.[[13]]
While the yard is lawfully divided into halves, quarters, eighths, and nails, it may also, as a measure of 3 feet, be divided into 36 inches. Yard-measures are usually divided in both ways, on one side into 16 nails, on the other into inches.
It is customary to say either a yard and a quarter, or 45 inches, or 3 feet 9 inches. Or to say either 58 inches or 4 feet 10 inches; but it is not customary to say a yard and 22 inches. We cease to use the yard as unit when we cannot express its fractions sexdecimally.
The Foot is lawfully divided into 12 inches; but there is nothing to prevent it being divided decimally, or otherwise, as convenient.
The Inch is divided according to convenience, either
Sexdecimally, into halves, quarters, &c., down to sixty-fourths. This is the usual division.
Duodecimally, into 12 lines.
Decimally, into tenths and hundredths.
Steel foot-rules usually show all three of these scales.
Some trades may have special scales. Thus type-founders divide the Inch into 6 ‘picas’ each = 2 lines, and the ‘pica’ into 12 points each = 1/6 line or 1/72 inch. Nonpareil type is 6 points; Brevier is 8 points.