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 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. {259}
The steep, grass-covered sides of a mountainous valley in Westmoreland,
called Grisedale, was marked in many places with innumerable lines of
miniature cliffs, with almost horizontal, little ledges at their bases.
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 boulder-clay and moraine rubbish. Nor, as far as I could judge, was
the formation of these little cliffs at all closely connected with the
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 the mountain sides; and in
thus sliding, had yielded and cracked in horizontal lines, transversely
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