Perch (unit of measure)
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Perch, is a rather unique term, being known as a unit of length, area, and volume used since Ancient Rome, and in the middle ages in France and the British Isles to at least the mid 1800s. As a unit of area, official Australian town planning documents drawn as late as mid-twentieth-century were using the term.
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[edit] Origin
The word perch is from the French perche, derived from the Latin pertica, meaning a pole or staff.[1][2] 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.
[edit] Length
The perch as a lineal measure in Rome, was 10 feet[3], and in France varied from 10 feet (perche romanie) to 22 feet[4] (perche d'arpent - apparently 1/10th of "the range of an arrow".[5] - 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[6], 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 24 feet; and even as late as 1820, a House of Commons report notes lengths of 16.5, 18, 21, 24, and even 25 feet[7]. In Ireland, a perch was standardized at 21 feet, making an Irish chain, furlong and mile proportionately longer by 27.27% than the "standard" English measure.[8]
[edit] Area
As a unit of area, a square perch (as standardized to equal 16.5 feet) is equal to a square rod, or 30¼ square yards. There are 40 square perches to a rood, 160 square perches to an acre (1 square perch is 0.00625 acres). Obviously, regional interpretations of perch would yield different results.
The metric conversion for a perch as area is 25.29 square metres
[edit] 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 1 foot in width, for a volume (nominal) of 24.75 cubic feet.
[edit] See also
Systems of measurement History of measurement
[edit] References
- ^ Websters 20th Century Unabridged Dictionary, ISBN 0-529-04852-3
- ^ Wictionary, Perch
- ^ http://en.wikipedia.org/wiki/Ancient_Roman_units_of_measurement#Length
- ^ http://fr.wikipedia.org/wiki/Perche_%28unit%C3%A9%29
- ^ http://fr.wikipedia.org/wiki/Arpent
- ^ Encyclopedia Britannica, English measure
- ^ 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.
- ^ Units: P
