Perch (unit of measure)

A perch is as a unit of measurement used for length, area, and volume in a number of different systems of measurement. Its name derives from the Ancient Roman unit, the "pertica".

Origin

The word perch is from the French perche, derived from the Latin pertica, meaning a pole or staff. [Websters 20th Century Unabridged Dictionary, ISBN 0-529-04852-3] [Wictionary, Perch] Originating in Roman antiquity, it spread with the Roman Empire and was likely re-introduced to England with the Norman Conquest of 1066. In the Roman Empire, France and England, it also could mean area (square perches), and among operative masons of the middle ages, volume.

Length

The perch as a lineal measure in Rome, was convert|10|ft|m, and in France varied from 10 feet (perche romanie) to 22 feet (perche d'arpent - apparently 1/10th of "the range of an arrow". - about 220 feet). To confuse matters more, by ancient Roman definition, an arpent equaled 120 Roman feet.

In England, the perch was officially discouraged in favor of the rod as early as the 15th century [Encyclopedia Britannica, English measure] , however local customs maintained its use. While the rod as a survey measure was standardized by Edmund Gunter in England in 1607 as 1/4 of a chain (of 66 feet), or 16 1/2 feet (5 1/2 yards) in length, in the 13th century perches were recorded in lengths of 18, 20, 22 and convert|24|ft|m; and even as late as 1820, a House of Commons report notes lengths of 16.5, 18, 21, 24, and even convert|25|ft|m [United Kingdom. House of Commons Report (Second) of Commissioners to Consider the Subject of Weights and Measures, 13 July 1820. Parliamentary Papers 1820. (HC314) Pages 473-512.] . In Ireland, a perch was standardized at convert|21|ft|m, making an Irish chain, furlong and mile proportionately longer by 27.27% than the "standard" English measure. [ [http://www.unc.edu/~rowlett/units/dictP.html Units: P ] ]

Area

As a unit of area, a square perch (the perch being standardized to equal 16.5 feet) is equal to a square rod, 30¼ square yards, 25.29 square metres or convert|0.00625|acre|m2. There are 40 square perches to a rood, 160 square perches to an acre This unit was usually referred to as a "perch" or "pole" even though "square perch" and "square pole" were the more precise terms. Confusingly, "rod" was used as a unit of area but it meant a rood.

Obviously, regional interpretations of perch would yield different results.

Volume

Used in stone or brick masonry, a perch has a volume of one perch length (nominally 16.5 feet), by 1 and one half foot high, by convert|1|ft|m|sing=on in width, for a volume (nominal) of convert|24.75|cuft|m3.

ee also

*Systems of measurement
*History of measurement

References