the formation of vegetable mould-第29章
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down walls now project only 0。75 of an inch above its level。 The
field； which was in pasture； here sloped from north to south； at an
angle of 30 degrees； 40 seconds。 The nature of the ground at some
little distance on each side of the corridor is shown in the
section。 It consisted of earth full of stones and other debris；
capped with dark vegetable mould which was thicker on the lower or
southern than on the northern side。 The pavement was nearly level
along lines parallel to the side…walls； but had sunk in the middle
as much as 7。75 inches。
A small room at no great distance from that represented in Fig。 13；
had been enlarged by the Roman occupier on the southern side； by an
addition of 5 feet 4 inches in breadth。 For this purpose the
southern wall of the house had been pulled down； but the
foundations of the old wall had been left buried at a little depth
beneath the pavement of the enlarged room。 Mr。 Joyce believes that
this buried wall must have been built before the reign of Claudius
II。； who died 270 A。D。 We see in the accompanying section； Fig。
15； that the tesselated pavement has subsided to a less degree over
the buried wall than elsewhere； so that a slight convexity or
protuberance here stretched in a straight line across the room。
This led to a hole being dug； and the buried wall was thus
discovered。
We see in these three sections； and in several others not given；
that the old pavements have sunk or sagged considerably。 Mr。 Joyce
formerly attributed this sinking solely to the slow settling of the
ground。 That there has been some settling is highly probable； and
it may be seen in Fig。 15 that the pavement for a width of 5 feet
over the southern enlargement of the room； which must have been
built on fresh ground； has sunk a little more than on the old
northern side。 But this sinking may possibly have had no
connection with the enlargement of the room； for in Fig。 13 one
half of the pavement has subsided more than the other half without
any assignable cause。 In a bricked passage to Mr。 Joyce's own
house； laid down only about six years ago； the same kind of sinking
has occurred as in the ancient buildings。 Nevertheless it does not
appear probable that the whole amount of sinking can be thus
accounted for。 The Roman builders excavated the ground to an
unusual depth for the foundations of their walls； which were thick
and solid； it is therefore hardly credible that they should have
been careless about the solidity of the bed on which their
tesselated and often ornamented pavements were laid。 The sinking
must； as it appears to me； be attributed in chief part to the
pavement having been undermined by worms； which we know are still
at work。 Even Mr。 Joyce at last admitted that this could not have
failed to have produced a considerable effect。 Thus also the large
quantity of fine mould overlying the pavements can be accounted
for； the presence of which would otherwise be inexplicable。 My
sons noticed that in one room in which the pavement had sagged very
little； there was an unusually small amount of overlying mould。
As the foundations of the walls generally lie at a considerable
depth； they will either have not subsided at all through the
undermining action of worms； or they will have subsided much less
than the floor。 This latter result would follow from worms not
often working deep down beneath the foundations； but more
especially from the walls not yielding when penetrated by worms；
whereas the successively formed burrows in a mass of earth； equal
to one of the walls in depth and thickness； would have collapsed
many times since the desertion of the ruins； and would consequently
have shrunk or subsided。 As the walls cannot have sunk much or at
all； the immediately adjoining pavement from adhering to them will
have been prevented from subsiding； and thus the present curvature
of the pavement is intelligible。
The circumstance which has surprised me most with respect to
Silchester is that during the many centuries which have elapsed
since the old buildings were deserted； the vegetable mould has not
accumulated over them to a greater thickness than that here
observed。 In most places it is only about 9 inches in thickness；
but in some places 12 or even more inches。 In Fig。 11； it is given
as 20 inches； but this section was drawn by Mr。 Joyce before his
attention was particularly called to this subject。 The land
enclosed within the old walls is described as sloping slightly to
the south； but there are parts which； according to Mr。 Joyce； are
nearly level； and it appears that the mould is here generally
thicker than elsewhere。 The surface slopes in other parts from
west to east； and Mr。 Joyce describes one floor as covered at the
western end by rubbish and mould to a thickness of 28。5 inches； and
at the eastern end by a thickness of only 11。5 inches。 A very
slight slope suffices to cause recent castings to flow downwards
during heavy rain； and thus much earth will ultimately reach the
neighbouring rills and streams and be carried away。 By this means；
the absence of very thick beds of mould over these ancient ruins
may； as I believe； be explained。 Moreover most of the land here
has long been ploughed； and this would greatly aid the washing away
of the finer earth during rainy weather。
The nature of the beds immediately beneath the vegetable mould in
some of the sections is rather perplexing。 We see； for instance；
in the section of an excavation in a grass meadow （Fig。 14）； which
sloped from north to south at an angle of 30 degrees 40 seconds；
that the mould on the upper side is only six inches and on the
lower side nine inches in thickness。 But this mould lies on a mass
（25。5 inches in thickness on the upper side） 〃of dark brown mould；〃
as described by Mr。 Joyce； 〃thickly interspersed with small pebbles
and bits of tiles； which present a corroded or worn appearance。
The state of this dark…coloured earth is like that of a field which
has long been ploughed； for the earth thus becomes intermingled
with stones and fragments of all kinds which have been much exposed
to the weather。 If during the course of many centuries this grass
meadow and the other now cultivated fields have been at times
ploughed； and at other times left as pasture； the nature of the
ground in the above section is rendered intelligible。 For worms
will continually have brought up fine earth from below； which will
have been stirred up by the plough whenever the land was
cultivated。 But after a time a greater thickness of fine earth
will thus have been accumulated than could be reached by the
plough； and a bed like the 25。5…inch mass； in Fig。 14； will have
been formed beneath the superficial mould； which latter will have
been brought to the surface within more recent times； and have been
well sifted by the worms。
Wroxeter； Shropshire。 The old Roman city of Uriconium was founded
in the early part of the second century； if not before this date；
and it was destroyed； according to Mr。 Wright； probably between the
middle of the fourth and fifth century。 The inhabitants were
massacred； and skeletons of women were found in the hypocausts。
Before the year 1859； the sole remnant of the city above ground；
was a portion of a massive wall about 20 ft。 in height。 The
surrounding land undulates slightly； and has long been under
cultivation。 It had been noticed that the corn…crops ripened
prematurely in certain narrow lines； and that the snow remained
unmelted in certain places longer than in others。 These
appearances led； as I was informed； to extensive excavations being
undertaken。 The foundations of many large buildings and several
streets have thus been exposed to view。 The space enclosed within
the old walls is an irregular oval； about 1 mile in length。 Many
of the stones or bricks used in the buildings must have been
carried away； but the hypocausts； baths； and other underground
buildings were found tolerably perfect； being filled with stones；
broken tiles； rubbish and soil。 The old floors
