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Show 280 DENUDATION TO LAND CHAP. VI. the former case 4 and in the latter only 3 inches. The grass grew more vigorously on the outer edges of the ledges than on any other part of the slope, and here formed a tufted fringe. Their middle part was bare, but whether this had been caused by the trampling of sheep, which sometimes frequent the lodges, my son could not ascertain. Nor could he feel sure how n1uch of the earth on the middle and bare parts, consisted of disintegrated worm-castings which l1ad rolled down from above· but he felt convinced that some had ' thus originated ; and it was manifest that the ledges with their grass-fringed edges would arrest any small object rolling down from above . ..At one end or side of the bank bearing these ledges, the surface consisted in parts of bare chalk, and here the ledges were very irregular. ..At the other end of the bank, the slope suddenly became less steep, and here the ledges ceased rather abruptly; but little embankments only a foot or two in length were ~till present. The slope became steeper lower down the hill, and the regular ledges then reappeared. Another of my sons observed, on CHAP. VI. LEDGES ON ITILL-SIDES. 281 the inland 8ide of Beachy llead, where the surface sloped at about 25°, many short little embankments like those just mentioned. They extended horizontally and were from a few inches to two or three feet in length. They supported tufts of grass growing vigorously. The average thickness of the mould of which they were formed, taken from nine measurements, was 4 · 5 inches ; while that of the mould above and beneath them was on an average only 3·2 inches, and on each side, on the same level, 3·1 inches. On the upper parts of the slope, these embankments showed no signs of having been trampled on by sheep, but in the lower parts such signs were fairly plain. No long continuous ledges had here been formed. If the little embankments above the Corniche road, which Dr. King saw in the act of formation by the accumulation of disintegrated and rolled worm-castings, were to become confluent along horizontal lines, ledges would be formed. Each embankment would tend to extend laterally by the lateral extension of the arrested castings; and animals grazing on a steep slope would almost certainly make use |
