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exhibited no signs of having been penetrated by worms； and although
the overlying fine mould closely resembled that which in many
places has certainly been accumulated by worms； yet it seemed
hardly possible that this mould could have been brought up by worms
from beneath the apparently sound floor。 It seemed also extremely
improbable that the thick walls； surrounding the room and still
united to the concrete； had been undermined by worms； and had thus
been caused to sink； being afterwards covered up by their castings。
I therefore at first concluded that all the fine mould above the
ruins had been washed down from the upper parts of the field； but
we shall soon see that this conclusion was certainly erroneous；
though much fine earth is known to be washed down from the upper
part of the field in its present ploughed state during heavy rains。
Although the concrete floor did not at first appear to have been
anywhere penetrated by worms； yet by the next morning little cakes
of the trodden…down earth had been lifted up by worms over the
mouths of seven burrows； which passed through the softer parts of
the naked concrete； or between the interstices of the tesserae。 On
the third morning twenty…five burrows were counted； and by suddenly
lifting up the little cakes of earth； four worms were seen in the
act of quickly retreating。 Two castings were thrown up during the
third night on the floor； and these were of large size。 The season
was not favourable for the full activity of worms； and the weather
had lately been hot and dry； so that most of the worms now lived at
a considerable depth。 In digging the two trenches many open
burrows and some worms were encountered at between 30 and 40 inches
beneath the surface； but at a greater depth they became rare。 One
worm； however； was cut through at 48。5； and another at 51。5 inches
beneath the surface。 A fresh humus…lined burrow was also met with
at a depth of 57 and another at 65。5 inches。 At greater depths
than this； neither burrows nor worms were seen。
As I wished to learn how many worms lived beneath the floor of the
atriuma space of about 14 by 9 feetMr。 Farrer was so kind as to
make observations for me； during the next seven weeks； by which
time the worms in the surrounding country were in full activity；
and were working near the surface。 It is very improbable that
worms should have migrated from the adjoining field into the small
space of the atrium； after the superficial mould in which they
prefer to live； had been removed。 We may therefore conclude that
the burrows and the castings which were seen here during the
ensuing seven weeks were the work of the former inhabitants of the
space。 I will now give a few extracts from Mr。 Farrer's notes。
Aug。 26th； 1877； that is； five days after the floor had been
cleared。 On the previous night there had been some heavy rain；
which washed the surface clean； and now the mouths of forty burrows
were counted。 Parts of the concrete were seen to be solid； and had
never been penetrated by worms； and here the rain…water lodged。
Sept。 5th。Tracks of worms； made during the previous night； could
be seen on the surface of the floor； and five or six vermiform
castings had been thrown up。 These were defaced。
Sept。 12th。During the last six days； the worms have not been
active； though many castings have been ejected in the neighbouring
fields； but on this day the earth was a little raised over the
mouths of the burrows； or castings were ejected； at ten fresh
points。 These were defaced。 It should be understood that when a
fresh burrow is spoken of； this generally means only that an old
burrow has been re…opened。 Mr。 Farrer was repeatedly struck with
the pertinacity with which the worms re…opened their old burrows；
even when no earth was ejected from them。 I have often observed
the same fact； and generally the mouths of the burrows are
protected by an accumulation of pebbles； sticks or leaves。 Mr。
Farrer likewise observed that the worms living beneath the floor of
the atrium often collected coarse grains of sand； and such little
stones as they could find； round the mouths of their burrows。
Sept。 13th； soft wet weather。 The mouths of the burrows were re…
opened； or castings were ejected； at 31 points； these were all
defaced。
Sept。 14th； 34 fresh holes or castings； all defaced。
Sept。 15th； 44 fresh holes； only 5 castings； all defaced。
Sept。 18th； 43 fresh holes； 8 castings； all defaced。
The number of castings on the surrounding fields was now very
large。
Sept。 19th； 40 holes； 8 castings； all defaced。
Sept。 22nd； 43 holes； only a few fresh castings； all defaced。
Sept。 23rd； 44 holes； 8 castings。
Sept。 25th； 50 holes； no record of the number of castings。
Oct。 13th； 61 holes； no record of the number of castings。
After an interval of three years； Mr。 Farrer； at my request； again
looked at the concrete floor； and found the worms still at work。
Knowing what great muscular power worms possess； and seeing how
soft the concrete was in many parts； I was not surprised at its
having been penetrated by their burrows； but it is a more
surprising fact that the mortar between the rough stones of the
thick walls； surrounding the rooms； was found by Mr。 Farrer to have
been penetrated by worms。 On August 26th； that is； five days after
the ruins had been exposed； he observed four open burrows on the
broken summit of the eastern wall （W in Fig。 8）； and； on September
15th； other burrows similarly situated were seen。 It should also
be noted that in the perpendicular side of the trench （which was
much deeper than is represented in Fig。 8） three recent burrows
were seen； which ran obliquely far down beneath the base of the old
wall。
We thus see that many worms lived beneath the floor and the walls
of the atrium at the time when the excavations were made； and that
they afterwards almost daily brought up earth to the surface from a
considerable depth。 There is not the slightest reason to doubt
that worms have acted in this manner ever since the period when the
concrete was sufficiently decayed to allow them to penetrate it；
and even before that period they would have lived beneath the
floor； as soon as it became pervious to rain； so that the soil
beneath was kept damp。 The floor and the walls must therefore have
been continually undermined； and fine earth must have been heaped
on them during many centuries； perhaps for a thousand years。 If
the burrows beneath the floor and walls； which it is probable were
formerly as numerous as they now are； had not collapsed in 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