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The first measures of land were seed-measures. They are found in every country; they become fixed in course of time as the idea of geometric measurement arises; they survive in name giving the peasant a concrete idea of the extent of his fields.
Then came the estimation of land by the amount of ploughing, or sometimes of hand-digging, that could be done in a day, and by the extent that could be cultivated with a pair of oxen. Then came a system of geometric measurement, fixing the former seed-units or labour-units by measures of length and breadth, and finally the abstract idea of superficial area. These different systems have succeeded one another everywhere and in all time.
1. Seed-units.—The land that could be sown with a certain measure of seed-corn, wheat being the usual standard: Fr. _seterée_, _estrée_, _boisselée_, &c.; It. _moggio_; Sp. _fanega_; G. _scheffel_; Nor. _tunn-land_. These names correspond to corn-measures.
2. Day’s hand-labour units.—The land that could be tilled with spade or hoe in a day: the ‘Daieswork,’ about 10 square rods; Fr. _hommée_, _ouvrée_—20 square rods of vineyard.
3. Day’s ploughing units.—L. _jugerum_; It. _giornata_; Fr. _journal_, _arpent_; G. _morgen_, _joch_, _acker_; Du. _bouw_; Hind. _bigha_; Ar. _feddan_; Ir. _ardagh_. All about an English acre more or less.
4. Oxgang units.—The land that a boor with a yoke of oxen could keep in husbandry; about 7 acres of arable, about 30 acres including wood and pasture:
Yard-land; Du. _hoeve_. A group of oxgangs, generally of four yoke, made a Ploughland; Prov. _un mas de quatre couble_, a four-yoke farm.
5. Geometric units.—First, units of a certain shape based on the customary length of the furrow: Rood, 40 rods by 1 rod broad; Fr. _vergée_, _seillon_. Then small units of a square rod, the rod being of customary length; with large units, usually groups of roods, vergées, &c. Four roods side by side make the English or the Norman acre. A rood square or square furlong is the ‘acreme’ or 10-acre field.
Legal units of land were usually abstract, of so many square rods or fathoms, independently of any customary shape.
While smaller units, such as the superficial rod, can easily be conceived as square, the larger arable units have, or have had, a peculiar form which still attaches to them. The peasant, whose mind’s eye can perceive the square rod or toise or verge, refers the rood or the acre, the vergée or the arpent, to the familiar length of the furrow and to the breadth of the rod or of the four-rod acre-breadth equal to a cricket-pitch. These lengths and breadths will long be his essentially concrete standards of field-measurement.