Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/304

 long ago, by Playfair, who, in 1802, wrote, "in the permanence of a coat of vegetable mould on the surface of the earth, we have a demonstrative proof of the continued destruction of the rocks."

Ancient encampments and tumuli.—É. de Beaumont adduces the present state of many ancient encampments and tumuli and of old ploughed fields, as evidence that the surface of the land undergoes hardly any degradation. But it does not appear that he ever examined the thickness of the mould over different parts of such old remains. He relies chiefly on indirect, but apparently trustworthy, evidence that the slopes of the old embankments are the same as they originally were; and it is obvious that he could know nothing about their original heights. In Knole Park a mound had been thrown up behind the rifle-targets, which appeared to have been formed of earth originally supported by square blocks of turf. The sides sloped, as nearly as I could estimate them, at an angle of 45° or 50° with the horizon, and they were covered, especially on the northern side, with long coarse grass,