bank was blown quite away by a strong south-west wind. Dr. King believes
that the wind removes the greater part of the old crumbling castings near
Nice. Several old castings on my lawn were marked with pins and
protected from any disturbance. They were examined after an interval of
10 weeks, during which time the weather had been alternately dry and
rainy. Some, which were of a yellowish colour had been washed almost
completely away, as could be seen by the colour of the surrounding
ground. Others had completely disappeared, and these no doubt had been
blown away. Lastly, others still remained and would long remain, as
blades of grass had grown through them. On poor pasture-land, which has
never been rolled and has not been much trampled on by animals, the whole
surface is sometimes dotted with little pimples, through and on which
grass grows; and these pimples consist of old worm-castings.
In all the many observed cases of soft castings blown to leeward, this
had been effected by strong winds accompanied by rain. As such winds in
England generally blow from the south and south-west, earth must on the
whole tend to travel over our fields in a north and north-east direction.
This fact is interesting, because it might be thought that none could be
removed from a level, grass-covered surface by any means. In thick and
level woods, protected from the wind, castings will never be removed as
long as the wood lasts; and mould will here tend to accumulate to the
depth at which worms can work. I tried to procure evidence as to how
much mould is blown, whilst in the state of castings, by our wet southern
gales to the north-east, over open and flat land, by looking to the level
of the surface on opposite sides of old trees and hedge-rows; but I
failed owing to the unequal growth of the roots of trees and to most
pasture-land having been formerly ploughed.
On an open plain near Stonehenge, there exist shallow circular trenches,
with a low embankment outside, surrounding level spaces 50 yards in
diameter. These rings appear very ancient, and are believed to be
contemporaneous with the Druidical stones. Castings ejected within these
circular spaces, if blown to the north-east by south-west winds would
form a layer of mould within the trench, thicker on the north-eastern
than on any other side. But the site was not favourable for the action
of worms, for the mould over the surrounding Chalk formation with flints,
was only 3.37 inches in thickness, from a mean of six observations made
at a distance of 10 yards outside the embankment. The thickness of the
mould within two of the circular trenches was measured every 5 yards all
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