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The subsidence of a floor； whilst it still remains nearly
horizontal； may at first appear improbable； but the case presents
no more real difficulty than that of loose objects strewed on the
surface of a field； which； as we have seen； become buried several
inches beneath the surface in the course of a few years； though
still forming a horizontal layer parallel to the surface。 The
burial of the paved and level path on my lawn； which took place
under my own observation； is an analogous case。 Even those parts
of the concrete floor which the worms could not penetrate would
almost certainly have been undermined； and would have sunk； like
the great stones at Leith Hill Place and Stonehenge； for the soil
would have been damp beneath them。 But the rate of sinking of the
different parts would not have been quite equal； and the floor was
not quite level。 The foundations of the boundary walls lie； as
shown in the section； at a very small depth beneath the surface；
they would therefore have tended to subside at nearly the same rate
as the floor。 But this would not have occurred if the foundations
had been deep； as in the case of some other Roman ruins presently
to be described。
Finally； we may infer that a large part of the fine vegetable
mould； which covered the floor and the broken…down walls of this
villa； in some places to a thickness of 16 inches； was brought up
from below by worms。 From facts hereafter to be given there can be
no doubt that some of the finest earth thus brought up will have
been washed down the sloping surface of the field during every
heavy shower of rain。 If this had not occurred a greater amount of
mould would have accumulated over the ruins than that now present。
But beside the castings of worms and some earth brought up by
insects； and some accumulation of dust； much fine earth will have
been washed over the ruins from the upper parts of the field； since
it has been under cultivation； and from over the ruins to the lower
parts of the slope； the present thickness of the mould being the
resultant of these several agencies。
I may here append a modern instance of the sinking of a pavement；
communicated to me in 1871 by Mr。 Ramsay； Director of the
Geological Survey of England。 A passage without a roof； 7 feet in
length by 3 feet 2 inches in width； led from his house into the
garden； and was paved with slabs of Portland stone。 Several of
these slabs were 16 inches square； others larger； and some a little
smaller。 This pavement had subsided about 3 inches along the
middle of the passage； and two inches on each side； as could be
seen by the lines of cement by which the slabs had been originally
joined to the walls。 The pavement had thus become slightly concave
along the middle； but there was no subsidence at the end close to
the house。 Mr。 Ramsay could not account for this sinking； until he
observed that castings of black mould were frequently ejected along
the lines of junction between the slabs； and these castings were
regularly swept away。 The several lines of junction； including
those with the lateral walls； were altogether 39 feet 2 inches in
length。 The pavement did not present the appearance of ever having
been renewed； and the house was believed to have been built about
eighty…seven years ago。 Considering all these circumstances； Mr。
Ramsay does not doubt that the earth brought up by the worms since
the pavement was first laid down； or rather since the decay of the
mortar allowed the worms to burrow through it； and therefore within
a much shorter time than the eighty…seven years； has sufficed to
cause the sinking of the pavement to the above amount； except close
to the house； where the ground beneath would have been kept nearly
dry。
Beaulieu Abbey； Hampshire。This abbey was destroyed by Henry
VIII。； and there now remains only a portion of the southern aisle…
wall。 It is believed that the king had most of the stones carried
away for building a castle； and it is certain that they have been
removed。 The positions of the nave and transepts were ascertained
not long ago by the foundations having been found； and the place is
now marked by stones let into the ground。 Where the abbey formerly
stood； there now extends a smooth grass…covered surface； which
resembles in all respects the rest of the field。 The guardian； a
very old man； said the surface had never been levelled in his time。
In the year 1853； the Duke of Buccleuch had three holes dug in the
turf within a few yards of one another； at the western end of the
nave； and the old tesselated pavement of the abbey was thus
discovered。 These holes were afterwards surrounded by brickwork；
and protected by trap…doors； so that the pavement might be readily
inspected and preserved。 When my son William examined the place on
January 5； 1872； he found that the pavement in the three holes lay
at depths of 6。75； 10 and 11。5 inches beneath the surrounding turf…
covered surface。 The old guardian asserted that he was often
forced to remove worm…castings from the pavement； and that he had
done so about six months before。 My son collected all from one of
the holes； the area of which was 5。32 square feet； and they weighed
7。97 ounces。 Assuming that this amount had accumulated in six
months； the accumulation during a year on a square yard would be
1。68 pounds； which； though a large amount； is very small compared
with what； as we have seen； is often ejected on fields and commons。
When I visited the abbey on June 22； 1877； the old man said that he
had cleared out the holes about a month before； but a good many
castings had since been ejected。 I suspect that he imagined that
he swept the pavements oftener than he really did； for the
conditions were in several respects very unfavourable for the
accumulation of even a moderate amount of castings。 The tiles are
rather large； viz。； about 5。5 inches square； and the mortar between
them was in most places sound； so that the worms were able to bring
up earth from below only at certain points。 The tiles rested on a
bed of concrete； and the castings in consequence consisted in large
part （viz。； in the proportion of 19 to 33） of particles of mortar；
grains of sand； little fragments of rock； bricks or tile； and such
substances could hardly be agreeable； and certainly not nutritious；
to worms。
My son dug holes in several places within the former walls of the
abbey； at a distance of several yards from the above described
bricked squares。 He did not find any tiles； though these are known
to occur in some other parts； but he came in one spot to concrete
on which tiles had once rested。 The fine mould beneath the turf on
the sides of the several holes； varied in thickness from only 2 to
2。75 inches； and this rested on a layer from 8。75 to above 11
inches in thickness； consisting of fragments of mortar and stone…
rubbish with the interstices compactly filled up with black mould。
In the surrounding field； at a distance of 20 yards from the abbey；
the fine vegetable mould was 11 inches thick。
We may conclude fro