When the water, in flood, begins to find a place where it can run, it begins with its weak inundation to scrape away and lift the lighter things, and it deposits them where the current becomes weak; and as it grows it lifts heavier things, such as sand, and carries it over the first things and there leaves it; and although the water may not increase, still by its persistence it goes on lifting, little by little, from the place where it runs, but because of their heaviness it does not carry them so far forward as the first, lighter ones; and if it then lifts still heavier things, it deposits them proportionally near the place from which it took them.

On restoring soil to places laid bare and scoured by the courses of the waters, on a hill or on a mountain or other slopes.

One must, by means of the rains, or else, having the convenience of other waters, make channels or the mouths of rivers pass through places where they flow with a great current, so that they become turbid with the earth they lift; and arrange that, when they reach the place where you want them to deposit the said earth, such water-channels divide into many little branches of water in the manner of furrows, and their fury slackens and clears.