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Show 282 DENUDA1'ION TO LAND CrrAP. VI. of every prominence at nearly the salne 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 becorne more regular and horizontal by some of the castings rolling laterally from the higher to the lower parts, which would thus be raised. .A.ny projection beneath a ledge would not afterwards receive distintegrated matter from above, and would tend to be obliterated by rain and other atmospheric agencies. There is some analogy between the formation, as her~ supposed, of these ledges, and that of the npples of wind-drifted sand as described by Lyell.* The steep, grass-covered sides of a mountainous valley in W est.moreland, cal~ed Grisedale, was marked in many places with innumerable, almost horizontal, l~ttle l~~ge.s, to rather lines of miniature chffs. lhmr formation was in no way connected with the action of worms, for castings could no~ anywhere be seen (and their absence lS ~n inexplicable fact) although the tu:f lay m many places over a considerable thlckness of * 'Elements of Geology,' 1865, P· 20· CrrAP. VI. LEDGES ON lULL-SIDES. 283 boulder-clay and moraine rubbish. Nor, as far as I could judge, was the formation of these little cliffs at all closely connected with tl1e trampling of cows or sheep. It appeared as if the whole superficial, somewhat argillaceous earth, while partially held together by the roots of the grasses, had slided a little way down tl1e mountain sides; and in thus sliding, had yielded and cracked in horizontal lines, transversely to the slope. Castings blown to leeww·d ~y the wind.-We have seen that moist castings :flow, and that disintegrated castings roll down any inclined surface; and we shall now see that castings, recently ejected on lev~l grass-covered surfaces, are blown during gales of wind accompanied by rain to leeward. This has been observed by me many times on many fields during several successive years. After such gales, the castings present a gently inclined and smooth, or sometimes furrowed, surface to windward, while they are steeply inclined or precipitous to leeward, so that they resemble on a miniature scale glacier-ground hillocks of rock. They are often cavernous on the |