The Formation of Ledges on Mountain-Slopes and Hill-Sides

Abstract

IT is well known that Darwin attributed to the castings of earthworms the principal part in the formation of these ledges; although he mentions in his book the case of a valley in Westmoreland, where it was “in no way connected with the action of worms.” “It appeared,” he concludes, “as if the whole superficial, somewhat argillaceous earth, while partially held together by the roots of the grasses, had slided a little way down the mountainsides; and in that sliding, had yielded and cracked in horizontal lines, transversely to the slope.”¹