The traditional British units of length or distance have been based on two standard lengths: the barleycorn (the length of a grain of barley) and the yard (the length of an arm, or sometimes defined as from the tip of the nose to the tip of the finger when an arm is outstretched). Other units have generally been defined in terms of those, though the perch or rod, as it was also known, had originally been defined as the total length of the left feet of the first sixteen men to leave church on Sunday morning, and the average length of those feet became the foot.
One of the earliest Anglo-Saxon standards was a bar designated "the yardstick," originating in the reign of Edgar.
The foot of St. Paul'sEdit
Sometime in the 12th century, a foot measurement was inscribed on the base of a column at St. Paul's Church in London. This foot, very close to a current foot in length, was termed the foot of St. Paul's.
Edward I's yardEdit
It appears that the earliest official definition of the yard (then referred to as the ulna) was in a statute of King Edward I (1272-1307). This statute also defined its sub- and aggregated divisions in the following words:
"It is remembered that the Iron Ulna of our Lord the King contains three feet and no more; and the foot must contain twelve inches, measured by the correct measure of this kind of ulna; that is to say, one thirty-sixth part [of] the said ulna makes one inch, neither more nor less... It is ordained that three grains of barley, dry and round make an inch, twelve inches make a foot; three feet make an ulna; five and a half ulna makes a perch (rod); and forty perches in length and four perches in breadth make an acre."
It should be noted that the length of the inch was there defined in terms of the length of grains of barley, as well as one thirty-sixth of an ulna; one wonders which took precedence.
Henry VII's yardEdit
Henry VII (1485-1509) established a standard, believed to be a direct copy of the 350-year-old standard of Edgar.
Elizabeth I's yardEdit
In 1588 Elizabeth I issued a new standard yard which remained the legal British yard for over 300 years until 1824, when it was superseded by an Act of Parliament under George IV. This act attempted to introduce systems of measures more widely into British society and remove inaccuracies associated with measurement.
The new yard became the first imperial standard and was actually a standard that had been commissioned by the Royal Society in 1742, which in turn had been based on an earlier Elizabethan standard.
The following table gives a listing of those traditional British units of length that survived into the twentieth century as British Imperial units. The length in terms of modern SI units would have varied somewhat over the course of time, but the values shown are the lengths of the final values of the correspondingly named units of the British imperial system since 1963:
|Name of unit||Value in terms of smaller units||Value (post-1963) in terms of the meter|
(For history after 1824, see the article on the British Imperial syatem.)