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ACTUS a Roman measure of land, which formed the basis of the whole system of land measurement. The word actus sometimes denotes a way between fields, along which cattle could be driven (Dig. 8, 1, 5; 5, 4, &c.). Varro (L. L. 5.34, Müller) asserts that the name of the measure was derived from this, but couples this remark with an absurd derivation of ager: ut ager quo agi poterat, sic qua agi actus. According to Varro, Columella (5.1, 5, on the authority of Varro) and Festus, s.v. the actus simplex or minimus was 120 (Roman) feet long and 4 feet wide. The actus quadratus, or simply actus, was a square of 120 feet each way, containing thus 14,400 square feet. Pliny (18.9) says of it: actus in quo boves agerentur cum aratro uno impetu justo (i.e. without turning) ; hic erat cxx pedum. Mommsen (Hist. 1.215) explains actus, “the driving,” to be properly a measure of labour, denoting the half-day's work, with reference to the marked division of the day in Italy by the noon-tide siesta. The jugerum, or “yoking,” the double of the actus, would thus denote the day's work. This is far more probable than the earlier explanations. The actus furnishes an example of the combination of the duodecimal with the decimal system, its length being twelve times the standard DECEMPEDA Columella (l.c. § 6) says that the Gauls called the actus quadratus, arepennis; but this could only be an approximate identification, for the actus quadratus is somewhat smaller than the great French arpent and much larger than the small arpent. (Compare ACNA; Niebuhr, Hist. of Rome, vol. ii. Appendix I.)


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    • Pliny the Elder, Naturalis Historia, 18.9
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