[62] And there is a visible proof of the uninterrupted and everlasting vigour of the earth in the plants which spring from it, for being purified, either by the overflowing of rivers, as they say that Egypt is, or by annual rains, by such irrigation it refreshes and recruits its exhausted powers, and then, having rested for a while, it recovers its natural powers to the full extent of its original vigour, and then it begins again with a repetition of the production of similar things to those which it produced before to supply abundant food to every description of animal.