but was in one spot 6 inches in thickness. On the north-west side of the
hill, either no embankment had ever been thrown up above the ditch, or it
had subsequently been removed; so that here there was nothing to prevent
worm-castings, earth and stones being washed into the ditch, at the
bottom of which the mould formed a layer from 11 to 22 inches in
thickness. It should however be stated that here and on other parts of
the slope, the bed of mould often contained fragments of chalk and flint
which had obviously rolled down at different times from above. The
interstices in the underlying fragmentary chalk were also filled up with
mould.
My son examined the surface of this hill to its base in a south-west
direction. Beneath the great ditch, where the slope was about 24 , the
mould was very thin, namely, from 11 2 to 21 2 inches; whilst near the base,
where the slope was only 3 to 4 , it increased to between 8 and 9 inches
in thickness. We may therefore conclude that on this artificially
modified hill, as well as in the natural valleys of the neighbouring
Chalk Downs, some fine earth, probably derived in large part from
worm-castings, is washed down, and accumulates in the lower parts,
notwithstanding the percolation of an unknown quantity into the
underlying chalk; a supply of fresh earthy matter being afforded by the
dissolution of the chalk through atmospheric and other agencies.
CHAPTER VII.
CONCLUSION.
Summary of the part which worms have played in the history of the
world Their aid in the disintegration of rocks In the denudation of the
land In the preservation of ancient remains In the preparation of the
soil for the growth of plants Mental powers of worms Conclusion.
WORMS have played a more important part in the history of the world than
most persons would at first suppose. In almost all humid countries they
are extraordinarily numerous, and for their size possess great muscular
power. In many parts of England a weight of more than ten tons (10,516
kilogrammes) of dry earth annually passes through their bodies and is
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