ACTUS, a Roman measure of land, which formed the basis of the whole system of land measurement. In that system the name actus (from ago), which originally meant a way between fields for beasts of burthen to pass (or, as some say, the length of a furrow), was given to such a way when of definite width and length, and also to a square piece of land of the same length. The former was called actus minimus or simplex, and was 120 feet (Roman) long by 4 feet wide (Varro, L. L. iv.4, or v.34, Müller; Colum. v.1 §5, ed. Schneider; Festus, s.v. iter inter vicinos IV. pedum latum). The actus quadratus, which was the square unit in the system of Roman land-measurement, was of the same length as the actus minimus, and of a width equal to its length: it was thus 120 feet square, and contained 14,400 square feet. It was the half of a juger (Colum. l.c.; Varro, l.c., and R. R. i.10 §2, ed. Schneider). The following are the etymological explanations of the word: Actus vocabatur, in quo boves agerentur cum aratro, uno impetu justo (Plin. xviii.3); Ut ager quo agi poterat, sic qua agi actus (Varro, L. L. l.c.). The actus furnishes an example of the use of the number twelve among the Romans, its length being twelve times the standard DECEMPEDA. Columella (l.c. § 6) says that the Gauls called the actus quadratus, aripennis; 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 ii.).