the course of time in the manner formerly explained, the underlying earth
would have been riddled with passages like a sponge; and as this was not
the case, we may feel sure that they have collapsed. The inevitable
result of such collapsing during successive centuries, will have been the
slow subsidence of the floor and of the walls, and their burial beneath
the accumulated worm-castings. 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.
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