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Weights and Measures: Avoirdupois

Systems of Weight. - There are three principal systems of weights in general use: avoirdupois weight, the universal standard, except as to the weight of the precious metals, jewels, and drugs; troy weight used in coinage and by jewelers (who also make use of a standard unit in weighing jewels called the carat); and apothecaries' weight, used by druggists and physicians. Avoirdupois weight, so called from the Norman Avon du poids, "goods of weight," is derived from the imperial standard pound above mentioned, equal to 700 troy grains. The grain is the same in both avoirdupois and troy weight. Formerly the ton consisted of 2,240 pounds, and the hundredweight of 112 pounds, divided into four quarters of 28 pounds each. And this practice continues in Great Britain and in the United States customhouse. In the ordinary commerce of the United States, however, it has become customary, as a matter of convenience, to reckon 100 pounds to the hundredweight, and 2,000 pounds to the ton; and this practice has been legalized in some of the States.