280 DENUDATION TO LAND Chap. VI. 



the former cnse 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 ledges, 

 my son could not ascertain. Nor could he 

 feel sure how much of the earth on the middle 

 and bare parts, consisted of disintegrated 

 worm-castings which had 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 oank 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 em- 

 bankments only a foot or two iu length were 

 still present. The slope became steeper lower 

 down the hill, and the regular ledges then re- 

 appeared. Another of my sons observed, on 



