that he could know nothing about their original heights. In Knole Park a
mound had been thrown up behind the rifle-targets, which appeared to have
been formed of earth originally supported by square blocks of turf. The
sides sloped, as nearly as I could estimate them, at an angle of 45 or
50 with the horizon, and they were covered, especially on the northern
side, with long coarse grass, beneath which many worm-castings were
found. These had flowed bodily downwards, and others had rolled down as
pellets. Hence it is certain that as long as a mound of this kind is
tenanted by worms, its height will be continually lowered. The fine
earth which flows or rolls down the sides of such a mound accumulates at
its base in the form of a talus. A bed, even a very thin bed, of fine
earth is eminently favourable for worms; so that a greater number of
castings would tend to be ejected on a talus thus formed than elsewhere;
and these would be partially washed away by every heavy shower and be
spread over the adjoining level ground. The final result would be the
lowering of the whole mound, whilst the inclination of the sides would
not be greatly lessened. The same result would assuredly follow with
ancient embankments and tumuli; except where they had been formed of
gravel or of nearly pure sand, as such matter is unfavourable for worms.
Many old fortifications and tumuli are believed to be at least 2000 years
old; and we should bear in mind that in many places about one inch of
mould is brought to the surface in 5 years or two inches in 10 years.
Therefore in so long a period as 2000 years, a large amount of earth will
have been repeatedly brought to the surface on most old embankments and
tumuli, especially on the talus round their bases, and much of this earth
will have been washed completely away. We may therefore conclude that
all ancient mounds, when not formed of materials unfavourable to worms,
will have been somewhat lowered in the course of centuries, although
their inclinations may not have been greatly changed.
_Fields formerly ploughed_. From a very remote period and in many
countries, land has been ploughed, so that convex beds, called crowns or
ridges, usually about 8 feet across and separated by furrows, have been
thrown up. The furrows are directed so as to carry off the surface
water. In my attempts to ascertain how long a time these crowns and
furrows last, when ploughed land has been converted into pasture,
obstacles of many kinds were encountered. It is rarely known when a
field was last ploughed; and some fields which were thought to have been
in pasture from time immemorial were afterwards discovered to have been
ploughed only 50 or 60 years before. During the early part of the
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