Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/296

 of every prominence at nearly the same level, and would indent the turf between them; and such intermediate indentations would again arrest the castings. An irregular ledge when once formed would also tend to become more regular and horizontal by some of the castings rolling laterally from the higher to the lower parts, which would thus be raised. Any projection beneath a ledge would not afterwards receive disintegrated matter from above, and would tend to be obliterated by rain and other atmospheric agencies. There is some analogy between the formation, as here supposed, of these ledges, and that of the ripples of wind-drifted sand as described by Lyell.

The steep, grass-covered sides of a mountainous valley in Westmoreland, called Grisedale, was marked in many places with innumerable, almost horizontal, little ledges, or rather lines of miniature cliffs. Their formation was in no way connected with the action of worms, for castings could not anywhere be seen (and their absence is an inexplicable fact) although the turf lay in many places over a considerable thickness of