"Those unguents which have a taste of earth are better," says Cicero, "than those which smack of saffron," it seeming to him more to the purpose to express himself by the word taste than smell. And such is the fact no doubt, that soil is the best which has the savour of a perfume. If the question should be put to us, what is this odour of the earth that is held in such estimation; our answer is that it is the same that is often to be recognized at the moment of sunset without the necessity even of turning up the ground, at the spots where the extremities of the rainbow have been observed to meet the earth: as also, when after long continued drought, the rain has soaked the ground. Then it is that the earth exhales the divine odour that is so peculiarly its own, and to which, imparted to it by the sun, there is no perfume however sweet that can possibly be compared. It is this odour which the earth, when turned up, ought to emit, and which, when once found, can never deceive any person: and this will be found the best criterion for judging of the quality of the soil. Such, too, is the odour that is usually perceived in land newly cleared when an ancient forest has been just cut down; its excellence is a thing that is universally admitted.] [Footnote 66: The _actus_ was the head land or as much land as a yoke of oxen could plough at a single spell without stopping, and measured 120 feet in length and four feet in width. Cf. Pliny, H.N. XVIII, 3. Hence the square of the head land became the basis of the Roman land measure. With the derivation of the _actus_ may be compared that of the English furlong (furrow-long) and the French _arpent_ (literally, head land).] [Footnote 67: On the socialistic principle of Strepsiades in Aristophanes' _Clouds_ that the use of geometry is to divide the land into _equal_ parts.]