The Formation of Vegetable Mould through the action of worms with observations of their habits
Charles Darwin

Part 2 out of 4

feet. In a bed of fine sand overlying the chalk, which had never
been disturbed, a worm was cut into two at 55 inches, and another
was found here at Down in December at the bottom of its burrow, at
61 inches beneath the surface. Lastly, in earth near an old Roman
Villa, which had not been disturbed for many centuries, a worm was
met with at a depth of 66 inches; and this was in the middle of

The burrows run down perpendicularly, or more commonly a little
obliquely. They are said sometimes to branch, but as far as I have
seen this does not occur, except in recently dug ground and near
the surface. They are generally, or as I believe invariably, lined
with a thin layer of fine, dark-coloured earth voided by the worms;
so that they must at first be made a little wider than their
ultimate diameter. I have seen several burrows in undisturbed sand
thus lined at a depth of 4 ft. 6 in.; and others close to the
surface thus lined in recently dug ground. The walls of fresh
burrows are often dotted with little globular pellets of voided
earth, still soft and viscid; and these, as it appears, are spread
out on all sides by the worm as it travels up or down its burrow.
The lining thus formed becomes very compact and smooth when nearly
dry, and closely fits the worm's body. The minute reflexed
bristles which project in rows on all sides from the body, thus
have excellent points of support; and the burrow is rendered well
adapted for the rapid movement of the animal. The lining appears
also to strengthen the walls, and perhaps saves the worm's body
from being scratched. I think so because several burrows which
passed through a layer of sifted coal-cinders, spread over turf to
a thickness of 1.5 inch, had been thus lined to an unusual
thickness. In this case the worms, judging from the castings, had
pushed the cinders away on all sides and had not swallowed any of
them. In another place, burrows similarly lined, passed through a
layer of coarse coal-cinders, 3.5 inches in thickness. We thus see
that the burrows are not mere excavations, but may rather be
compared with tunnels lined with cement.

The mouths of the burrow are in addition often lined with leaves;
and this is an instinct distinct from that of plugging them up, and
does not appear to have been hitherto noticed. Many leaves of the
Scotch-fir or pine (Pinus sylvestris) were given to worms kept in
confinement in two pots; and when after several weeks the earth was
carefully broken up, the upper parts of three oblique burrows were
found surrounded for lengths of 7, 4, and 3.5 inches with pine-
leaves, together with fragments of other leaves which had been
given the worms as food. Glass beads and bits of tile, which had
been strewed on the surface of the soil, were stuck into the
interstices between the pine-leaves; and these interstices were
likewise plastered with the viscid castings voided by the worms.
The structures thus formed cohered so well, that I succeeded in
removing one with only a little earth adhering to it. It consisted
of a slightly curved cylindrical case, the interior of which could
be seen through holes in the sides and at either end. The pine-
leaves had all been drawn in by their bases; and the sharp points
of the needles had been pressed into the lining of voided earth.
Had this not been effectually done, the sharp points would have
prevented the retreat of the worms into their burrows; and these
structures would have resembled traps armed with converging points
of wire, rendering the ingress of an animal easy and its egress
difficult or impossible. The skill shown by these worms is
noteworthy and is the more remarkable, as the Scotch pine is not a
native of this district.

After having examined these burrows made by worms in confinement, I
looked at those in a flower-bed near some Scotch pines. These had
all been plugged up in the ordinary manner with the leaves of this
tree, drawn in for a length of from 1 to 1.5 inch; but the mouths
of many of them were likewise lined with them, mingled with
fragments of other kinds of leaves, drawn in to a depth of 4 or 5
inches. Worms often remain, as formerly stated, for a long time
close to the mouths of their burrows, apparently for warmth; and
the basket-like structures formed of leaves would keep their bodies
from coming into close contact with the cold damp earth. That they
habitually rested on the pine-leaves, was rendered probable by
their clean and almost polished surfaces.

The burrows which run far down into the ground, generally, or at
least often, terminate in a little enlargement or chamber. Here,
according to Hoffmeister, one or several worms pass the winter
rolled up into a ball. Mr. Lindsay Carnagie informed me (1838)
that he had examined many burrows over a stone-quarry in Scotland,
where the overlying boulder-clay and mould had recently been
cleared away, and a little vertical cliff thus left. In several
cases the same burrow was a little enlarged at two or three points
one beneath the other; and all the burrows terminated in a rather
large chamber, at a depth of 7 or 8 feet from the surface. These
chambers contained many small sharp bits of stone and husks of
flax-seeds. They must also have contained living seeds, for on the
following spring Mr. Carnagie saw grass-plants sprouting out of
some of the intersected chambers. I found at Abinger in Surrey two
burrows terminating in similar chambers at a depth of 36 and 41
inches, and these were lined or paved with little pebbles, about as
large as mustard seeds; and in one of the chambers there was a
decayed oat-grain, with its husk. Hensen likewise states that the
bottoms of the burrows are lined with little stones; and where
these could not be procured, seeds, apparently of the pear, had
been used, as many as fifteen having been carried down into a
single burrow, one of which had germinated. {40} We thus see how
easily a botanist might be deceived who wished to learn how long
deeply buried seeds remained alive, if he were to collect earth
from a considerable depth, on the supposition that it could contain
only seeds which had long lain buried. It is probable that the
little stones, as well as the seeds, are carried down from the
surface by being swallowed; for a surprising number of glass beads,
bits of tile and of glass were certainly thus carried down by worms
kept in pots; but some may have been carried down within their
mouths. The sole conjecture which I can form why worms line their
winter-quarters with little stones and seeds, is to prevent their
closely coiled-up bodies from coming into close contact with the
surrounding cold soil; and such contact would perhaps interfere
with their respiration which is effected by the skin alone.

A worm after swallowing earth, whether for making its burrow or for
food, soon comes to the surface to empty its body. The ejected
earth is thoroughly mingled with the intestinal secretions, and is
thus rendered viscid. After being dried it sets hard. I have
watched worms during the act of ejection, and when the earth was in
a very liquid state it was ejected in little spurts, and by a slow
peristaltic movement when not so liquid. It is not cast
indifferently on any side, but with some care, first on one and
then on another side; the tail being used almost like a trowel.
When a worm comes to the surface to eject earth, the tail
protrudes, but when it collects leaves its head must protrude.
Worms therefore must have the power of turning round in their
closely-fitting burrows; and this, as it appears to us, would be a
difficult feat. As soon as a little heap has been formed, the worm
apparently avoids, for the sake of safety, protruding its tail; and
the earthy matter is forced up through the previously deposited
soft mass. The mouth of the same burrow is used for this purpose
for a considerable time. In the case of the tower-like castings
(see Fig. 2) near Nice, and of the similar but still taller towers
from Bengal (hereafter to be described and figured), a considerable
degree of skill is exhibited in their construction. Dr. King also
observed that the passage up these towers hardly ever ran in the
same exact line with the underlying burrow, so that a thin
cylindrical object such as a haulm of grass, could not be passed
down the tower into the burrow; and this change of direction
probably serves in some manner as a protection.

Worms do not always eject their castings on the surface of the
ground. When they can find any cavity, as when burrowing in newly
turned-up earth, or between the stems of banked-up plants, they
deposit their castings in such places. So again any hollow beneath
a large stone lying on the surface of the ground, is soon filled up
with their castings. According to Hensen, old burrows are
habitually used for this purpose; but as far as my experience
serves, this is not the case, excepting with those near the surface
in recently dug ground. I think that Hensen may have been deceived
by the walls of old burrows, lined with black earth, having sunk in
or collapsed; for black streaks are thus left, and these are
conspicuous when passing through light-coloured soil, and might be
mistaken for completely filled-up burrows.

It is certain that old burrows collapse in the course of time; for
as we shall see in the next chapter, the fine earth voided by
worms, if spread out uniformly, would form in many places in the
course of a year a layer 0.2 of an inch in thickness; so that at
any rate this large amount is not deposited within the old unused
burrows. If the burrows did not collapse, the whole ground would
be first thickly riddled with holes to a depth of about ten inches,
and in fifty years a hollow unsupported space, ten inches in depth,
would be left. The holes left by the decay of successively formed
roots of trees and plants must likewise collapse in the course of

The burrows of worms run down perpendicularly or a little
obliquely, and where the soil is at all argillaceous, there is no
difficulty in believing that the walls would slowly flow or slide
inwards during very wet weather. When, however, the soil is sandy
or mingled with many small stones, it can hardly be viscous enough
to flow inwards during even the wettest weather; but another agency
may here come into play. After much rain the ground swells, and as
it cannot expand laterally, the surface rises; during dry weather
it sinks again. For instance, a large flat stone laid on the
surface of a field sank 3.33 mm. whilst the weather was dry between
May 9th and June 13th, and rose 1.91 mm, between September 7th and
19th of the same year, much rain having fallen during the latter
part of this time. During frosts and thaws the movements were
twice as great. These observations were made by my son Horace, who
will hereafter publish an account of the movements of this stone
during successive wet and dry seasons, and of the effects of its
being undermined by worms. Now when the ground swells, if it be
penetrated by cylindrical holes, such as worm-burrows, their walls
will tend to yield and be pressed inwards; and the yielding will be
greater in the deeper parts (supposing the whole to be equally
moistened) from the greater weight of the superincumbent soil which
has to be raised, than in the parts near the surface. When the
ground dries, the walls will shrink a little and the burrows will
be a little enlarged. Their enlargement, however, through the
lateral contraction of the ground, will not be favoured, but rather
opposed, by the weight of the superincumbent soil.

Distribution of Worms.--Earth-worms are found in all parts of the
world, and some of the genera have an enormous range. {41} They
inhabit the most isolated islands; they abound in Iceland, and are
known to exist in the West Indies, St. Helena, Madagascar, New
Caledonia and Tahiti. In the Antarctic regions, worms from
Kerguelen Land have been described by Ray Lankester; and I found
them in the Falkland Islands. How they reach such isolated islands
is at present quite unknown. They are easily killed by salt-water,
and it does not appear probable that young worms or their egg-
capsules could be carried in earth adhering to the feet or beaks of
land-birds. Moreover Kerguelen Land is not now inhabited by any

In this volume we are chiefly concerned with the earth cast up by
worms, and I have gleaned a few facts on this subject with respect
to distant lands. Worms throw up plenty of castings in the United
States. In Venezuela, castings, probably ejected by species of
Urochaeta, are common in the gardens and fields, but not in the
forests, as I hear from Dr. Ernst of Caracas. He collected 156
castings from the court-yard of his house, having an area of 200
square yards. They varied in bulk from half a cubic centimeter to
five cubic centimeters, and were on an average three cubic
centimeters. They were, therefore, of small size in comparison
with those often found in England; for six large castings from a
field near my house averaged 16 cubic centimeters. Several species
of earth-worms are common in St. Catharina in South Brazil, and
Fritz Muller informs me "that in most parts of the forests and
pasture-lands, the whole soil, to a depth of a quarter of a metre,
looks as if it had passed repeatedly through the intestines of
earth-worms, even where hardly any castings are to be seen on the
surface." A gigantic but very rare species is found there, the
burrows of which are sometimes even two centimeters or nearly 0.8
of an inch in diameter, and which apparently penetrate the ground
to a great depth.

In the dry climate of New South Wales, I hardly expected that worms
would be common; but Dr. G. Krefft of Sydney, to whom I applied,
after making inquiries from gardeners and others, and from his own
observations, informs me that their castings abound. He sent me
some collected after heavy rain, and they consisted of little
pellets, about 0.15 inch in diameter; and the blackened sandy earth
of which they were formed still cohered with considerable tenacity.

The late Mr. John Scott of the Botanic Gardens near Calcutta made
many observations for me on worms living under the hot and humid
climate of Bengal. The castings abound almost everywhere, in
jungles and in the open ground, to a greater degree, as he thinks,
than in England. After the water has subsided from the flooded
rice-fields, the whole surface very soon becomes studded with
castings--a fact which much surprised Mr. Scott, as he did not know
how long worms could survive beneath water. They cause much
trouble in the Botanic garden, "for some of the finest of our lawns
can be kept in anything like order only by being almost daily
rolled; if left undisturbed for a few days they become studded with
large castings." These closely resemble those described as
abounding near Nice; and they are probably the work of a species of
Perichaeta. They stand up like towers, with an open passage in the

A figure of one of these castings from a photograph is here given
(Fig. 3). The largest received by me was 3.5 inches in height and
1.35 inch in diameter; another was only 0.75 inch in diameter and
2.75 in height. In the following year, Mr. Scott measured several
of the largest; one was 6 inches in height and nearly 1.5 in
diameter: two others were 5 inches in height and respectively 2
and rather more than 2.5 inches in diameter. The average weight of
the 22 castings sent to me was 35 grammes (1.25 oz.); and one of
them weighed 44.8 grammes (or 2 oz.). All these castings were
thrown up either in one night or in two. Where the ground in
Bengal is dry, as under large trees, castings of a different kind
are found in vast numbers: these consist of little oval or conical
bodies, from about the 1/20 to rather above 1/10 of an inch in
length. They are obviously voided by a distinct species of worms.

The period during which worms near Calcutta display such
extraordinary activity lasts for only a little over two months,
namely, during the cool season after the rains. At this time they
are generally found within about 10 inches beneath the surface.
During the hot season they burrow to a greater depth, and are then
found coiled up and apparently hybernating. Mr. Scott has never
seen them at a greater depth than 2.5 feet, but has heard of their
having been found at 4 feet. Within the forests, fresh castings
may be found even during the hot season. The worms in the Botanic
garden, during the cool and dry season, draw many leaves and little
sticks into the mouths of their burrows, like our English worms;
but they rarely act in this manner during the rainy season.

Mr. Scott saw worm-castings on the lofty mountains of Sikkim in
North India. In South India Dr. King found in one place, on the
plateau of the Nilgiris, at an elevation of 7000 feet, "a good many
castings," which are interesting for their great size. The worms
which eject them are seen only during the wet season, and are
reported to be from 12 to 15 inches in length, and as thick as a
man's little finger. These castings were collected by Dr. King
after a period of 110 days without any rain; and they must have
been ejected either during the north-east or more probably during
the previous south-west monsoon; for their surfaces had suffered
some disintegration and they were penetrated by many fine roots. A
drawing is here given (Fig. 4) of one which seems to have best
retained its original size and appearance. Notwithstanding some
loss from disintegration, five of the largest of these castings
(after having been well sun-dried) weighed each on an average 89.5
grammes, or above 3 oz.; and the largest weighed 123.14 grammes, or
4.33 oz.,--that is, above a quarter of a pound! The largest
convolutions were rather more than one inch in diameter; but it is
probable that they had subsided a little whilst soft, and that
their diameters had thus been increased. Some had flowed so much
that they now consisted of a pile of almost flat confluent cakes.
All were formed of fine, rather light-coloured earth, and were
surprisingly hard and compact, owing no doubt to the animal matter
by which the particles of earth had been cemented together. They
did not disintegrate, even when left for some hours in water.
Although they had been cast up on the surface of gravelly soil,
they contained extremely few bits of rock, the largest of which was
only 0.15 inch in diameter.

Dr. King saw in Ceylon a worm about 2 feet in length and 0.5 inch
in diameter; and he was told that it was a very common species
during the wet season. These worms must throw up castings at least
as large as those on the Nilgiri Mountains; but Dr. King saw none
during his short visit to Ceylon.

Sufficient facts have now been given, showing that worms do much
work in bringing up fine earth to the surface in most or all parts
of the world, and under the most different climates.


Rate at which various objects strewed on the surface of grass-
fields are covered up by the castings of worms--The burial of a
paved path--The slow subsidence of great stones left on the
surface--The number of worms which live within a given space--The
weight of earth ejected from a burrow, and from all the burrows
within a given space--The thickness of the layer of mould which the
castings on a given space would form within a given time if
uniformly spread out--The slow rate at which mould can increase to
a great thickness--Conclusion.

We now come to the more immediate subject of this volume, namely,
the amount of earth which is brought up by worms from beneath the
surface, and is afterwards spread out more or less completely by
the rain and wind. The amount can be judged of by two methods,--by
the rate at which objects left on the surface are buried, and more
accurately by weighing the quantity brought up within a given time.
We will begin with the first method, as it was first followed.

Near Mael Hall in Staffordshire, quick-lime had been spread about
the year 1827 thickly over a field of good pasture-land, which had
not since been ploughed. Some square holes were dug in this field
in the beginning of October 1837; and the sections showed a layer
of turf, formed by the matted roots of the grasses, 0.5 inch in
thickness, beneath which, at a depth of 2.5 inches (or 3 inches
from the surface), a layer of the lime in powder or in small lumps
could be distinctly seen running all round the vertical sides of
the holes. The soil beneath the layer of lime was either gravelly
or of a coarse sandy nature, and differed considerably in
appearance from the overlying dark-coloured fine mould. Coal-
cinders had been spread over a part of this same field either in
the year 1833 or 1834; and when the above holes were dug, that is
after an interval of 3 or 4 years, the cinders formed a line of
black spots round the holes, at a depth of 1 inch beneath the
surface, parallel to and above the white layer of lime. Over
another part of this field cinders had been strewed, only about
half-a-year before, and these either still lay on the surface or
were entangled among the roots of the grasses; and I here saw the
commencement of the burying process, for worm-castings had been
heaped on several of the smaller fragments. After an interval of
4.75 years this field was re-examined, and now the two layers of
lime and cinders were found almost everywhere at a greater depth
than before by nearly 1 inch, we will say by 0.75 of an inch.
Therefore mould to an average thickness of 0.22 of an inch had been
annually brought up by the worms, and had been spread over the
surface of this field.

Coal-cinders had been strewed over another field, at a date which
could not be positively ascertained, so thickly that they formed
(October, 1837) a layer, 1 inch in thickness at a depth of about 3
inches from the surface. The layer was so continuous that the
over-lying dark vegetable mould was connected with the sub-soil of
red clay only by the roots of the grasses; and when these were
broken, the mould and the red clay fell apart. In a third field,
on which coal-cinders and burnt marl had been strewed several times
at unknown dates, holes were dug in 1842; and a layer of cinders
could be traced at a depth of 3.5 inches, beneath which at a depth
of 9.5 inches from the surface there was a line of cinders together
with burnt marl. On the sides of one hole there were two layers of
cinders, at 2 and 3.5 inches beneath the surface; and below them at
a depth in parts of 9.5, and in other parts of 10.5 inches there
were fragments of burnt marl. In a fourth field two layers of
lime, one above the other, could be distinctly traced, and beneath
them a layer of cinders and burnt marl at a depth of from 10 to 12
inches below the surface.

A piece of waste, swampy land was enclosed, drained, ploughed,
harrowed and thickly covered in the year 1822 with burnt marl and
cinders. It was sowed with grass seeds, and now supports a
tolerably good but coarse pasture. Holes were dug in this field in
1837, or 15 years after its reclamation, and we see in the
accompanying diagram (Fig. 5), reduced to half of the natural
scale, that the turf was 1 inch thick, beneath which there was a
layer of vegetable mould 2.5 inches thick. This layer did not
contain fragments of any kind; but beneath it there was a layer of
mould, 1.5 inch in thickness, full of fragments of burnt marl,
conspicuous from their red colour, one of which near the bottom was
an inch in length; and other fragments of coal-cinders together
with a few white quartz pebbles. Beneath this layer and at a depth
of 4.5 inches from the surface, the original black, peaty, sandy
soil with a few quartz pebbles was encountered. Here therefore the
fragments of burnt marl and cinders had been covered in the course
of 15 years by a layer of fine vegetable mould, only 2.5 inches in
thickness, excluding the turf. Six and a half years subsequently
this field was re-examined, and the fragments were now found at
from 4 to 5 inches beneath the surface. So that in this interval
of 6.5 years, about 1.5 inch of mould had been added to the
superficial layer. I am surprised that a greater quantity had not
been brought up during the whole 21.5 years, for in the closely
underlying black, peaty soil there were many worms. It is,
however, probable that formerly, whilst the land remained poor,
worms were scanty; and the mould would then have accumulated
slowly. The average annual increase of thickness for the whole
period is 0.19 of an inch.

Two other cases are worth recording. In the spring of 1835, a
field, which had long existed as poor pasture and was so swampy
that it trembled slightly when stamped on, was thickly covered with
red sand so that the whole surface appeared at first bright red.
When holes were dug in this field after an interval of about 2.5
years, the sand formed a layer at a depth of 0.75 in. beneath the
surface. In 1842 (i.e., 7 years after the sand had been laid on)
fresh holes were dug, and now the red sand formed a distinct layer,
2 inches beneath the surface, or 1.5 inch beneath the turf; so that
on an average, 0.21 inch of mould had been annually brought to the
surface. Immediately beneath the layer of red sand, the original
substratum of black sandy peat extended.

A grass field, likewise not far from Maer Hall, had formerly been
thickly covered with marl, and was then left for several years as
pasture; it was afterwards ploughed. A friend had three trenches
dug in this field 28 years after the application of the marl, {42}
and a layer of the marl fragments could be traced at a depth,
carefully measured, of 12 inches in some parts, and of 14 inches in
other parts. This difference in depth depended on the layer being
horizontal, whilst the surface consisted of ridges and furrows from
the field having been ploughed. The tenant assured me that it had
never been turned up to a greater depth than from 6 to 8 inches;
and as the fragments formed an unbroken horizontal layer from 12 to
14 inches beneath the surface, these must have been buried by the
worms whilst the land was in pasture before it was ploughed, for
otherwise they would have been indiscriminately scattered by the
plough throughout the whole thickness of the soil. Four-and-a-half
years afterwards I had three holes dug in this field, in which
potatoes had been lately planted, and the layer of marl-fragments
was now found 13 inches beneath the bottoms of the furrows, and
therefore probably 15 inches beneath the general level of the
field. It should, however, be observed that the thickness of the
blackish sandy soil, which had been thrown up by the worms above
the marl-fragments in the course of 32.5 years, would have measured
less than 15 inches, if the field had always remained as pasture,
for the soil would in this case have been much more compact. The
fragments of marl almost rested on an undisturbed substratum of
white sand with quartz pebbles; and as this would be little
attractive to worms, the mould would hereafter be very slowly
increased by their action.

We will now give some cases of the action of worms, on land
differing widely from the dry sandy or the swampy pastures just
described. The chalk formation extends all round my house in Kent;
and its surface, from having been exposed during an immense period
to the dissolving action of rain-water, is extremely irregular,
being abruptly festooned and penetrated by many deep well-like
cavities. {43} During the dissolution of the chalk, the insoluble
matter, including a vast number of unrolled flints of all sizes,
has been left on the surface and forms a bed of stiff red clay,
full of flints, and generally from 6 to 14 feet in thickness. Over
the red clay, wherever the land has long remained as pasture, there
is a layer a few inches in thickness, of dark-coloured vegetable

A quantity of broken chalk was spread, on December 20, 1842, over a
part of a field near my house, which had existed as pasture
certainly for 30, probably for twice or thrice as many years. The
chalk was laid on the land for the sake of observing at some future
period to what depth it would become buried. At the end of
November, 1871, that is after an interval of 29 years, a trench was
dug across this part of the field; and a line of white nodules
could be traced on both sides of the trench, at a depth of 7 inches
from the surface. The mould, therefore, (excluding the turf) had
here been thrown up at an average rate of 0.22 inch per year.
Beneath the line of chalk nodules there was in parts hardly any
fine earth free of flints, while in other parts there was a layer,
2.25 inches in thickness. In this latter case the mould was
altogether 9.25 inches thick; and in one such spot a nodule of
chalk and a smooth flint pebble, both of which must have been left
at some former time on the surface, were found at this depth. At
from 11 to 12 inches beneath the surface, the undisturbed reddish
clay, full of flints, extended. The appearance of the above
nodules of chalk surprised me, much at first, as they closely
resembled water-worn pebbles, whereas the freshly-broken fragments
had been angular. But on examining the nodules with a lens, they
no longer appeared water-worn, for their surfaces were pitted
through unequal corrosion, and minute, sharp points, formed of
broken fossil shells, projected from them. It was evident that the
corners of the original fragments of chalk had been wholly
dissolved, from presenting a large surface to the carbonic acid
dissolved in the rain-water and to that generated in soil
containing vegetable matter, as well as to the humus-acids. {44}
The projecting corners would also, relatively to the other parts,
have been embraced by a larger number of living rootlets; and these
have the power of even attacking marble, as Sachs has shown. Thus,
in the course of 29 years, buried angular fragments of chalk had
been converted into well-rounded nodules.

Another part of this same field was mossy, and as it was thought
that sifted coal-cinders would improve the pasture, a thick layer
was spread over this part either in 1842 or 1843, and another layer
some years afterwards. In 1871 a trench was here dug, and many
cinders lay in a line at a depth of 7 inches beneath the surface,
with another line at a depth of 5.5 inches parallel to the one
beneath. In another part of this field, which had formerly existed
as a separate one, and which it was believed had been pasture-land
for more than a century, trenches were dug to see how thick the
vegetable mould was. By chance the first trench was made at a spot
where at some former period, certainly more than forty years
before, a large hole had been filled up with coarse red clay,
flints, fragments of chalk, and gravel; and here the fine vegetable
mould was only from 4.125 to 4.375 inches in thickness. In another
and undisturbed place, the mould varied much in thickness, namely,
from 6.5 to 8.5 inches; beneath which a few small fragments of
brick were found in one place. From these several cases, it would
appear that during the last 29 years mould has been heaped on the
surface at an average annual rate of from 0.2 to 0.22 of an inch.
But in this district when a ploughed field is first laid down in
grass, the mould accumulates at a much slower rate. The rate,
also, must become very much slower after a bed of mould, several
inches in thickness, has been formed; for the worms then live
chiefly near the surface, and burrow down to a greater depth so as
to bring up fresh earth from below, only during the winter when the
weather is very cold (at which time worms were found in this field
at a depth of 26 inches) and during summer, when the weather is
very dry.

A field, which adjoins the one just described, slopes in one part
rather steeply (viz., at from 10 degrees to 15 degrees); this part
was last ploughed in 1841, was then harrowed and left to become
pasture-land. For several years it was clothed with an extremely
scant vegetation, and was so thickly covered with small and large
flints (some of them half as large as a child's head) that the
field was always called by my sons "the stony field." When they
ran down the slope the stones clattered together, I remember
doubting whether I should live to see these larger flints covered
with vegetable mould and turf. But the smaller stones disappeared
before many years had elapsed, as did every one of the larger ones
after a time; so that after thirty years (1871) a horse could
gallop over the compact turf from one end of the field to the
other, and not strike a single stone with his shoes. To anyone who
remembered the appearance of the field in 1842, the transformation
was wonderful. This was certainly the work of the worms, for
though castings were not frequent for several years, yet some were
thrown up month after month, and these gradually increased in
numbers as the pasture improved. In the year 1871 a trench was dug
on the above slope, and the blades of grass were cut off close to
the roots, so that the thickness of the turf and of the vegetable
mould could be measured accurately. The turf was rather less than
half an inch, and the mould, which did not contain any stones, 2.5
inches in thickness. Beneath this lay coarse clayey earth full of
flints, like that in any of the neighbouring ploughed fields. This
coarse earth easily fell apart from the overlying mould when a spit
was lifted up. The average rate of accumulation of the mould
during the whole thirty years was only .083 inch per year (i.e.,
nearly one inch in twelve years); but the rate must have been much
slower at first, and afterwards considerably quicker.

The transformation in the appearance of this field, which had been
effected beneath my eyes, was afterwards rendered the more
striking, when I examined in Knole Park a dense forest of lofty
beech-trees, beneath which nothing grew. Here the ground was
thickly strewed with large naked stones, and worm-castings were
almost wholly absent. Obscure lines and irregularities on the
surface indicated that the land had been cultivated some centuries
ago. It is probable that a thick wood of young beech-trees sprung
up so quickly, that time enough was not allowed for worms to cover
up the stones with their castings, before the site became unfitted
for their existence. Anyhow the contrast between the state of the
now miscalled "stony field," well stocked with worms, and the
present state of the ground beneath the old beech-trees in Knole
Park, where worms appeared to be absent, was striking.

A narrow path running across part of my lawn was paved in 1843 with
small flagstones, set edgeways; but worms threw up many castings
and weeds grew thickly between them. During several years the path
was weeded and swept; but ultimately the weeds and worms prevailed,
and the gardener ceased to sweep, merely mowing off the weeds, as
often as the lawn was mowed. The path soon became almost covered
up, and after several years no trace of it was left. On removing,
in 1877, the thin overlying layer of turf, the small flag-stones,
all in their proper places, were found covered by an inch of fine

Two recently published accounts of substances strewed on the
surface of pasture-land, having become buried through the action of
worms, may be here noticed. The Rev. H. C. Key had a ditch cut in
a field, over which coal-ashes had been spread, as it was believed,
eighteen years before; and on the clean-cut perpendicular sides of
the ditch, at a depth of at least seven inches, there could be
seen, for a length of 60 yards, "a distinct, very even, narrow line
of coal-ashes, mixed with small coal, perfectly parallel with the
top-sward." {45} This parallelism and the length of the section
give interest to the case. Secondly, Mr. Dancer states {46} that
crushed bones had been thickly strewed over a field; and "some
years afterwards" these were found "several inches below the
surface, at a uniform depth."

The Rev. Mr. Zincke informs me that he has lately had an orchard
dug to the unusual depth of 4 feet. The upper 18 inches consisted
of dark-coloured vegetable mould, and the next 18 inches of sandy
loam, containing in the lower part many rolled pieces of sandstone,
with some bits of brick and tile, probably of Roman origin, as
remains of this period have been found close by. The sandy loam
rested on an indurated ferruginous pan of yellow clay, on the
surface of which two perfect celts were found. If, as seems
probable, the celts were originally left on the surface of the
land, they have since been covered up with earth 3 feet in
thickness, all of which has probably passed through the bodies of
worms, excepting the stones which may have been scattered on the
surface at different times, together with manure or by other means.
It is difficult otherwise to understand the source of the 18 inches
of sandy loam, which differed from the overlying dark vegetable
mould, after both had been burnt, only in being of a brighter red
colour, and in not being quite so fine-grained. But on this view
we must suppose that the carbon in vegetable mould, when it lies at
some little depth beneath the surface and does not continually
receive decaying vegetable matter from above, loses its dark colour
in the course of centuries; but whether this is probable I do not

Worms appear to act in the same manner in New Zealand as in Europe;
for Professor J. von Haast has described {47} a section near the
coast, consisting of mica-schist, "covered by 5 or 6 feet of loess,
above which about 12 inches of vegetable soil had accumulated."
Between the loess and the mould there was a layer from 3 to 6
inches in thickness, consisting of "cores, implements, flakes, and
chips, all manufactured from hard basaltic rock." It is therefore
probable that the aborigines, at some former period, had left these
objects on the surface, and that they had afterwards been slowly
covered up by the castings of worms.

Farmers in England are well aware that objects of all kinds, left
on the surface of pasture-land, after a time disappear, or, as they
say, work themselves downwards. How powdered lime, cinders, and
heavy stones, can work down, and at the same rate, through the
matted roots of a grass-covered surface, is a question which has
probably never occurred to them. {48}

The Sinking of great Stones through the Action of Worms.--When a
stone of large size and of irregular shape is left on the surface
of the ground, it rests, of course, on the more protuberant parts;
but worms soon fill up with their castings all the hollow spaces on
the lower side; for, as Hensen remarks, they like the shelter of
stones. As soon as the hollows are filled up, the worms eject the
earth which they have swallowed beyond the circumference of the
stones; and thus the surface of the ground is raised all round the
stone. As the burrows excavated directly beneath the stone after a
time collapse, the stone sinks a little. {49} Hence it is, that
boulders which at some ancient period have rolled down from a rocky
mountain or cliff on to a meadow at its base, are always somewhat
imbedded in the soil; and, when removed, leave an exact impression
of their lower surfaces in the underlying fine mould. If, however,
a boulder is of such huge dimensions, that the earth beneath is
kept dry, such earth will not be inhabited by worms, and the
boulder will not sink into the ground.

A lime-kiln formerly stood in a grass-field near Leith Hill Place
in Surrey, and was pulled down 35 years before my visit; all the
loose rubbish had been carted away, excepting three large stones of
quartzose sandstone, which it was thought might hereafter be of
some use. An old workman remembered that they had been left on a
bare surface of broken bricks and mortar, close to the foundations
of the kiln; but the whole surrounding surface is now covered with
turf and mould. The two largest of these stones had never since
been moved; nor could this easily have been done, as, when I had
them removed, it was the work of two men with levers. One of these
stones, and not the largest, was 64 inches long, 17 inches broad,
and from 9 to 10 inches in thickness. Its lower surface was
somewhat protuberant in the middle; and this part still rested on
broken bricks and mortar, showing the truth of the old workman's
account. Beneath the brick rubbish the natural sandy soil, full of
fragments of sandstone was found; and this could have yielded very
little, if at all, to the weight of the stone, as might have been
expected if the sub-soil had been clay. The surface of the field,
for a distance of about 9 inches round the stone, gradually sloped
up to it, and close to the stone stood in most places about 4
inches above the surrounding ground. The base of the stone was
buried from 1 to 2 inches beneath the general level, and the upper
surface projected about 8 inches above this level, or about 4
inches above the sloping border of turf. After the removal of the
stone it became evident that one of its pointed ends must at first
have stood clear above the ground by some inches, but its upper
surface was now on a level with the surrounding turf. When the
stone was removed, an exact cast of its lower side, forming a
shallow crateriform hollow, was left, the inner surface of which
consisted of fine black mould, excepting where the more protuberant
parts rested on the brick-rubbish. A transverse section of this
stone, together with its bed, drawn from measurements made after it
had been displaced, is here given on a scale of 0.5 inch to a foot
(Fig. 6). The turf-covered border which sloped up to the stone,
consisted of fine vegetable mould, in one part 7 inches in
thickness. This evidently consisted of worm-castings, several of
which had been recently ejected. The whole stone had sunk in the
thirty-five years, as far as I could judge, about 1.5 inch; and
this must have been due to the brick-rubbish beneath the more
protuberant parts having been undermined by worms. At this rate
the upper surface of the stone, if it had been left undisturbed,
would have sunk to the general level of the field in 247 years; but
before this could have occurred, some earth would have been washed
down by heavy rain from the castings on the raised border of turf
over the upper surface of the stone.

The second stone was larger that the one just described, viz., 67
inches in length, 39 in breadth, and 15 in thickness. The lower
surface was nearly flat, so that the worms must soon have been
compelled to eject their castings beyond its circumference. The
stone as a whole had sunk about 2 inches into the ground. At this
rate it would have required 262 years for its upper surface to have
sunk to the general level of the field. The upwardly sloping,
turf-covered border round the stone was broader than in the last
case, viz., from 14 to 16 inches; and why this should be so, I
could see no reason. In most parts this border was not so high as
in the last case, viz., from 2 to 2.5 inches, but in one place it
was as much as 5.5. Its average height close to the stone was
probably about 3 inches, and it thinned out to nothing. If so, a
layer of fine earth, 15 inches in breadth and 1.5 inch in average
thickness, of sufficient length to surround the whole of the much
elongated slab, must have been brought up by the worms in chief
part from beneath the stone in the course of 35 years. This amount
would be amply sufficient to account for its having sunk about 2
inches into the ground; more especially if we bear in mind that a
good deal of the finest earth would have been washed by heavy rain
from the castings ejected on the sloping border down to the level
of the field. Some fresh castings were seen close to the stone.
Nevertheless, on digging a large hole to a depth of 18 inches where
the stone had lain, only two worms and a few burrows were seen,
although the soil was damp and seemed favourable for worms. There
were some large colonies of ants beneath the stone, and possibly
since their establishment the worms had decreased in number.

The third stone was only about half as large as the others; and two
strong boys could together have rolled it over. I have no doubt
that it had been rolled over at a moderately recent time, for it
now lay at some distance from the two other stones at the bottom of
a little adjoining slope. It rested also on fine earth, instead of
partly on brick-rubbish. In agreement with this conclusion, the
raised surrounding border of turf was only 1 inch high in some
parts, and 2 inches in other parts. There were no colonies of ants
beneath this stone, and on digging a hole where it had lain,
several burrows and worms were found.

At Stonehenge, some of the outer Druidical stones are now
prostrate, having fallen at a remote but unknown period; and these
have become buried to a moderate depth in the ground. They are
surrounded by sloping borders of turf, on which recent castings
were seen. Close to one of these fallen stones, which was 17 ft
long, 6 ft. broad, and 28.5 inches thick, a hole was dug; and here
the vegetable mould was at least 9.5 inches in thickness. At this
depth a flint was found, and a little higher up on one side of the
hole a fragment of glass. The base of the stone lay about 9.5
inches beneath the level of the surrounding ground, and its upper
surface 19 inches above the ground.

A hole was also dug close to a second huge stone, which in falling
had broken into two pieces; and this must have happened long ago,
judging from the weathered aspect of the fractured ends. The base
was buried to a depth of 10 inches, as was ascertained by driving
an iron skewer horizontally into the ground beneath it. The
vegetable mould forming the turf-covered sloping border round the
stone, on which many castings had recently been ejected, was 10
inches in thickness; and most of this mould must have been brought
up by worms from beneath its base. At a distance of 8 yards from
the stone, the mould was only 5.5 inches in thickness (with a piece
of tobacco pipe at a depth of 4 inches), and this rested on broken
flint and chalk which could not have easily yielded to the pressure
or weight of the stone.

A straight rod was fixed horizontally (by the aid of a spirit-
level) across a third fallen stone, which was 7 feet 9 inches long;
and the contour of the projecting parts and of the adjoining
ground, which was not quite level, was thus ascertained, as shown
in the accompanying diagram (Fig. 7) on a scale of 0.5 inch to a
foot. The turf-covered border sloped up to the stone on one side
to a height of 4 inches, and on the opposite side to only 2.5
inches above the general level. A hole was dug on the eastern
side, and the base of the stone was here found to lie at a depth of
4 inches beneath the general level of the ground, and of 8 inches
beneath the top of the sloping turf-covered border.

Sufficient evidence has now been given showing that small objects
left on the surface of the land where worms abound soon get buried,
and that large stones sink slowly downwards through the same means.
Every step of the process could be followed, from the accidental
deposition of a single casting on a small object lying loose on the
surface, to its being entangled amidst the matted roots of the
turf, and lastly to its being embedded in the mould at various
depths beneath the surface. When the same field was re-examined
after the interval of a few years, such objects were found at a
greater depth than before. The straightness and regularity of the
lines formed by the imbedded objects, and their parallelism with
the surface of the land, are the most striking features of the
case; for this parallelism shows how equably the worms must have
worked; the result being, however, partly the effect of the washing
down of the fresh castings by rain. The specific gravity of the
objects does not affect their rate of sinking, as could be seen by
porous cinders, burnt marl, chalk and quartz pebbles, having all
sunk to the same depth within the same time. Considering the
nature of the substratum, which at Leith Hill Place was sandy soil
including many bits of rock, and at Stonehenge, chalk-rubble with
broken flints; considering, also, the presence of the turf-covered
sloping border of mould round the great fragments of stone at both
these places, their sinking does not appear to have been sensibly
aided by their weight, though this was considerable. {50}

On the number of worms which live within a given space.--We will
now show, firstly, what a vast number of worms live unseen by us
beneath our feet, and, secondly, the actual weight of the earth
which they bring up to the surface within a given space and within
a given time. Hensen, who has published so full and interesting an
account of the habits of worms, {51} calculates, from the number
which he found in a measured space, that there must exist 133,000
living worms in a hectare of land, or 53,767 in an acre. This
latter number of worms would weigh 356 pounds, taking Hensen's
standard of the weight of a single worm, namely, three grams. It
should, however, be noted that this calculation is founded on the
numbers found in a garden, and Hensen believes that worms are here
twice as numerous as in corn-fields. The above result, astonishing
though it be, seems to me credible, judging from the number of
worms which I have sometimes seen, and from the number daily
destroyed by birds without the species being exterminated. Some
barrels of bad ale were left on Mr. Miller's land, {52} in the hope
of making vinegar, but the vinegar proved bad, and the barrels were
upset. It should be premised that acetic acid is so deadly a
poison to worms that Perrier found that a glass rod dipped into
this acid and then into a considerable body of water in which worms
were immersed, invariably killed them quickly. On the morning
after the barrels had been upset, "the heaps of worms which lay
dead on the ground were so amazing, that if Mr. Miller had not seen
them, he could not have thought it possible for such numbers to
have existed in the space." As further evidence of the large
number of worms which live in the ground, Hensen states that he
found in a garden sixty-four open burrows in a space of 14.5 square
feet, that is, nine in 2 square feet. But the burrows are
sometimes much more numerous, for when digging in a grass-field
near Maer Hall, I found a cake of dry earth, as large as my two
open hands, which was penetrated by seven burrows, as large as

Weight of the earth ejected from a single burrow, and from all the
burrows within a given space.--With respect to the weight of the
earth daily ejected by worms, Hensen found that it amounted, in the
case of some worms which he kept in confinement, and which he
appears to have fed with leaves, to only 0.5 gram, or less than 8
grains per diem. But a very much larger amount must be ejected by
worms in their natural state, at the periods when they consume
earth as food instead of leaves, and when they are making deep
burrows. This is rendered almost certain by the following weights
of the castings thrown up at the mouths of single burrows; the
whole of which appeared to have been ejected within no long time,
as was certainly the case in several instances. The castings were
dried (excepting in one specified instance) by exposure during many
days to the sun or before a hot fire.


(Weight in ounces given in parenthesis--DP.)

(1.) Down, Kent (sub-soil red clay, full of flints, over-lying the
chalk). The largest casting which I could find on the flanks of a
steep valley, the sub-soil being here shallow. In this one case,
the casting was not well dried (3.98)

(2.) Down.--Largest casting which I could find (consisting chiefly
of calcareous matter), on extremely poor pasture land at the bottom
of the valley mentioned under (1.) (3.87)

(3.) Down.--A large casting, but not of unusual size, from a
nearly level field, poor pasture, laid down in a grass about 35
years before (1.22)

(4.) Down. Average weight of 11 not large castings ejected on a
sloping surface on my lawn, after they had suffered some loss of
weight from being exposed during a considerable length of time to
rain (0.7)

(5.) Near Nice in France.--Average weight of 12 castings of
ordinary dimensions, collected by Dr. King on land which had not
been mown for a long time and where worms abounded, viz., a lawn
protected by shrubberies near the sea; soil sandy and calcareous;
these castings had been exposed for some time to rain, before being
collected, and must have lost some weight by disintegration, but
they still retained their form (1.37)

(6.) The heaviest of the above twelve castings (1.76)

(7.) Lower Bengal.--Average weight of 22 castings, collected by
Mr. J. Scott, and stated by him to have been thrown up in the
course of one or two nights (1.24)

(8.) The heaviest of the above 22 castings (2.09)

(9.) Nilgiri Mountains, S. India; average weight of the 5 largest
castings collected by Dr. King. They had been exposed to the rain
of the last monsoon, and must have lost some weight (3.15)

(10.) The heaviest of the above 5 castings (4.34)

In this table we see that castings which had been ejected at the
mouth of the same burrow, and which in most cases appeared fresh
and always retained their vermiform configuration, generally
exceeded an ounce in weight after being dried, and sometimes nearly
equalled a quarter of a pound. On the Nilgiri mountains one
casting even exceeded this latter weight. The largest castings in
England were found on extremely poor pasture-land; and these, as
far as I have seen, are generally larger than those on land
producing a rich vegetation. It would appear that worms have to
swallow a greater amount of earth on poor than on rich land, in
order to obtain sufficient nutriment.

With respect to the tower-like castings near Nice (Nos. 5 and 6 in
the above table), Dr. King often found five or six of them on a
square foot of surface; and these, judging from their average
weight, would have weighed together 7.5 ounces; so that the weight
of those on a square yard would have been 4 lb. 3.5 oz. Dr. King
collected, near the close of the year 1872, all the castings which
still retained their vermiform shape, whether broken down or not,
from a square foot, in a place abounding with worms, on the summit
of a bank, where no castings could have rolled down from above.
These castings must have been ejected, as he judged from their
appearance in reference to the rainy and dry periods near Nice,
within the previous five or six months; they weighed 9.5 oz., or 5
lb. 5.5 oz. per square yard. After an interval of four months, Dr.
King collected all the castings subsequently ejected on the same
square foot of surface, and they weighed 2.5 oz., or 1 lb. 6.5 oz.
per square yard. Therefore within about ten months, or we will say
for safety's sake within a year, 12 oz. of castings were thrown up
on this one square foot, or 6.75 pounds on the square yard; and
this would give 14.58 tons per acre.

In a field at the bottom of a valley in the chalk (see No. 2 in the
foregoing table), a square yard was measured at a spot where very
large castings abounded; they appeared, however, almost equally
numerous in a few other places. These castings, which retained
perfectly their vermiform shape, were collected; and they weighed
when partially dried, 1 lb. 13.5 oz. This field had been rolled
with a heavy agricultural roller fifty-two days before, and this
would certainly have flattened every single casting on the land.
The weather had been very dry for two or three weeks before the day
of collection, so that not one casting appeared fresh or had been
recently ejected. We may therefore assume that those which were
weighed had been ejected within, we will say, forty days from the
time when the field was rolled,--that is, twelve days short of the
whole intervening period. I had examined the same part of the
field shortly before it was rolled, and it then abounded with fresh
castings. Worms do not work in dry weather during the summer, or
in winter during severe frosts. If we assume that they work for
only half the year--though this is too low an estimate--then the
worms in this field would eject during the year, 8.387 pounds per
square yard; or 18.12 tons per acre, assuming the whole surface to
be equally productive in castings.

In the foregoing cases some of the necessary data had to be
estimated, but in the two following cases the results are much more
trustworthy. A lady, on whose accuracy I can implicitly rely,
offered to collect during a year all the castings thrown up on two
separate square yards, near Leith Hill Place, in Surrey. The
amount collected was, however, somewhat less than that originally
ejected by the worms; for, as I have repeatedly observed, a good
deal of the finest earth is washed away, whenever castings are
thrown up during or shortly before heavy rain. Small portions also
adhered to the surrounding blades of grass, and it required too
much time to detach every one of them.

On sandy soil, as in the present instance, castings are liable to
crumble after dry weather, and particles were thus often lost. The
lady also occasionally left home for a week or two, and at such
times the castings must have suffered still greater loss from
exposure to the weather. These losses were, however, compensated
to some extent by the collections having been made on one of the
squares for four days, and on the other square for two days more
than the year.

A space was selected (October 9th, 1870) for one of the squares on
a broad, grass-covered terrace, which had been mowed and swept
during many years. It faced the south, but was shaded during part
of the day by trees. It had been formed at least a century ago by
a great accumulation of small and large fragments of sandstone,
together with some sandy earth, rammed down level. It is probable
that it was at first protected by being covered with turf. This
terrace, judging from the number of castings on it, was rather
unfavourable for the existence of worms, in comparison with the
neighbouring fields and an upper terrace. It was indeed surprising
that as many worms could live here as were seen; for on digging a
hole in this terrace, the black vegetable mould together with the
turf was only four inches in thickness, beneath which lay the level
surface of light-coloured sandy soil, with many fragments of
sandstone. Before any castings were collected all the previously
existing ones were carefully removed. The last day's collection
was on October 14th, 1871. The castings were then well dried
before a fire; and they weighed exactly 3.5 lbs. This would give
for an acre of similar land 7.56 tons of dry earth annually ejected
by worms.

The second square was marked on unenclosed common land, at a height
of about 700 ft. above the sea, at some little distance from Leith
Hill Tower. The surface was clothed with short, fine turf, and had
never been disturbed by the hand of man. The spot selected
appeared neither particularly favourable nor the reverse for worms;
but I have often noticed that castings are especially abundant on
common land, and this may, perhaps, be attributed to the poorness
of the soil. The vegetable mould was here between three and four
inches in thickness. As this spot was at some distance from the
house where the lady lived, the castings were not collected at such
short intervals of time as those on the terrace; consequently the
loss of fine earth during rainy weather must have been greater in
this than in the last case. The castings moreover were more sandy,
and in collecting them during dry weather they sometimes crumbled
into dust, and much was thus lost. Therefore it is certain that
the worms brought up to the surface considerably more earth than
that which was collected. The last collection was made on October
27th, 1871; i.e., 367 days after the square had been marked out and
the surface cleared of all pre-existing castings. The collected
castings, after being well dried, weighed 7.453 pounds; and this
would give, for an acre of the same kind of land, 16.1 tons of
annually ejected dry earth.


(1.) Castings ejected near Nice within about a year, collected by
Dr. King on a square foot of surface, calculated to yield per acre
14.58 tons.

(2.) Castings ejected during about 40 days on a square yard, in a
field of poor pasture at the bottom of a large valley in the Chalk,
calculated to yield annually per acre 18.12 tons.

(3.) Castings collected from a square yard on an old terrace at
Leith Hill Place, during 369 days, calculated to yield annually per
acre 7.56 tons.

(4.) Castings collected from a square yard on Leith Hill Common
during 367 days, calculated to yield annually per acre 16.1 tons.

The thickness of the layer of mould, which castings ejected during
a year would form if uniformly spread out.--As we know, from the
two last cases in the above summary, the weight of the dried
castings ejected by worms during a year on a square yard of
surface, I wished to learn how thick a layer of ordinary mould this
amount would form if spread uniformly over a square yard. The dry
castings were therefore broken into small particles, and whilst
being placed in a measure were well shaken and pressed down. Those
collected on the Terrace amounted to 124.77 cubic inches; and this
amount, if spread out over a square yard, would make a layer 0.9627
inch in thickness. Those collected on the Common amounted to
197.56 cubic inches, and would make a similar layer 0.1524 inch in

These thicknesses must, however, be corrected, for the triturated
castings, after being well shaken down and pressed, did not make
nearly so compact a mass as vegetable mould, though each separate
particle was very compact. Yet mould is far from being compact, as
is shown by the number of air-bubbles which rise up when the
surface is flooded with water. It is moreover penetrated by many
fine roots. To ascertain approximately by how much ordinary
vegetable mould would be increased in bulk by being broken up into
small particles and then dried, a thin oblong block of somewhat
argillaceous mould (with the turf pared off) was measured before
being broken up, was well dried and again measured. The drying
caused it to shrink by 1/7 of its original bulk, judging from
exterior measurements alone. It was then triturated and partly
reduced to powder, in the same manner as the castings had been
treated, and its bulk now exceeded (notwithstanding shrinkage from
drying) by 1/16 that of the original block of damp mould.
Therefore the above calculated thickness of the layer, formed by
the castings from the Terrace, after being damped and spread over a
square yard, would have to be reduced by 1/16; and this will reduce
the layer to 0.09 of an inch, so that a layer 0.9 inch in thickness
would be formed in the course of ten years. On the same principle
the castings from the Common would make in the course of a single
year a layer 0.1429 inch, or in the course of 10 years 1.429 inch,
in thickness. We may say in round numbers that the thickness in
the former case would amount to nearly 1 inch, and in the second
case to nearly 1.5 inch in 10 years.

In order to compare these results with those deduced from the rates
at which small objects left on the surfaces of grass-fields become
buried (as described in the early part of this chapter), we will
give the following summary:-


The accumulation of mould during 14.75 years on the surface of a
dry, sandy, grass-field near Maer Hall, amounted to 2.2 inches in
10 years.

The accumulation during 21.5 years on a swampy field near Maer
Hall, amounted to nearly 1.9 inch in 10 years.

The accumulation during 7 years on a very swampy field near Maer
Hall amounted to 2.1 inches in 10 years.

The accumulation during 29 years, on good, argillaceous pasture-
land over the Chalk at Down, amounted to 2.2 inches in 10 years.

The accumulation during 30 years on the side of a valley over the
Chalk at Down, the soil being argillaceous, very poor, and only
just converted into pasture (so that it was for some years
unfavourable for worms), amounted to 0.83 inch in 10 years.

In these cases (excepting the last) it may be seen that the amount
of earth brought to the surface during 10 years is somewhat greater
than that calculated from the castings which were actually weighed.
This excess may be partly accounted for by the loss which the
weighed castings had previously undergone through being washed by
rain, by the adhesion of particles to the blades of the surrounding
grass, and by their crumbling when dry. Nor must we overlook other
agencies which in all ordinary cases add to the amount of mould,
and which would not be included in the castings that were
collected, namely, the fine earth brought up to the surface by
burrowing larvae and insects, especially by ants. The earth
brought up by moles generally has a somewhat different appearance
from vegetable mould; but after a time would not be distinguishable
from it. In dry countries, moreover, the wind plays an important
part in carrying dust from one place to another, and even in
England it must add to the mould on fields near great roads. But
in our country these latter several agencies appear to be of quite
subordinate importance in comparison with the action of worms.

We have no means of judging how great a weight of earth a single
full-sized worm ejects during a year. Hensen estimates that 53,767
worms exist in an acre of land; but this is founded on the number
found in gardens, and he believes that only about half as many live
in corn-fields. How many live in old pasture land is unknown; but
if we assume that half the above number, or 26,886 worms live on
such land, then taking from the previous summary 15 tons as the
weight of the castings annually thrown up on an acre of land, each
worm must annually eject 20 ounces. A full-sized casting at the
mouth of a single burrow often exceeds, as we have seen, an ounce
in weight; and it is probable that worms eject more than 20 full-
sized castings during a year. If they eject annually more than 20
ounces, we may infer that the worms which live in an acre of
pasture land must be less than 26,886 in number.

Worms live chiefly in the superficial mould, which is usually from
4 or 5 to 10 and even 12 inches in thickness; and it is this mould
which passes over and over again through their bodies and is
brought to the surface. But worms occasionally burrow into the
subsoil to a much greater depth, and on such occasions they bring
up earth from this greater depth; and this process has gone on for
countless ages. Therefore the superficial layer of mould would
ultimately attain, though at a slower and slower rate, a thickness
equal to the depth to which worms ever burrow, were there not other
opposing agencies at work which carry away to a lower level some of
the finest earth which is continually being brought to the surface
by worms. How great a thickness vegetable mould ever attains, I
have not had good opportunities for observing; but in the next
chapter, when we consider the burial of ancient buildings, some
facts will be given on this head. In the two last chapters we
shall see that the soil is actually increased, though only to a
small degree, through the agency of worms; but their chief work is
to sift the finer from the coarser particles, to mingle the whole
with vegetable debris, and to saturate it with their intestinal

Finally, no one who considers the facts given in this chapter--on
the burying of small objects and on the sinking of great stones
left on the surface--on the vast number of worms which live within
a moderate extent of ground on the weight of the castings ejected
from the mouth of the same burrow--on the weight of all the
castings ejected within a known time on a measured space--will
hereafter, as I believe, doubt that worms play an important part in


The accumulation of rubbish on the sites of great cities
independent of the action of worms--The burial of a Roman villa at
Abinger--The floors and walls penetrated by worms--Subsidence of a
modern pavement--The buried pavement at Beaulieu Abbey--Roman
villas at Chedworth and Brading--The remains of the Roman town at
Silchester--The nature of the debris by which the remains are
covered--The penetration of the tesselated floors and walls by
worms--Subsidence of the floors--Thickness of the mould--The old
Roman city of Wroxeter--Thickness of the mould--Depth of the
foundations of some of the Buildings--Conclusion.

Archaeologists are probably not aware how much they owe to worms
for the preservation of many ancient objects. Coins, gold
ornaments, stone implements, &c., if dropped on the surface of the
ground, will infallibly be buried by the castings of worms in a few
years, and will thus be safely preserved, until the land at some
future time is turned up. For instance, many years ago a grass-
field was ploughed on the northern side of the Severn, not far from
Shrewsbury; and a surprising number of iron arrow-heads were found
at the bottom of the furrows, which, as Mr. Blakeway, a local
antiquary, believed, were relics of the battle of Shrewsbury in the
year 1403, and no doubt had been originally left strewed on the
battle-field. In the present chapter I shall show that not only
implements, &c., are thus preserved, but that the floors and the
remains of many ancient buildings in England have been buried so
effectually, in large part through the action of worms, that they
have been discovered in recent times solely through various
accidents. The enormous beds of rubbish, several yards in
thickness, which underlie many cities, such as Rome, Paris, and
London, the lower ones being of great antiquity, are not here
referred to, as they have not been in any way acted on by worms.
When we consider how much matter is daily brought into a great city
for building, fuel, clothing and food, and that in old times when
the roads were bad and the work of the scavenger was neglected, a
comparatively small amount was carried away, we may agree with Elie
de Beaumont, who, in discussing this subject, says, "pour une
voiture de materiaux qui en sort, on y en fait entrer cent." {53}
Nor should we overlook the effects of fires, the demolition of old
buildings, and the removal of rubbish to the nearest vacant space,

Abinger, Surrey.--Late in the autumn of 1876, the ground in an old
farm-yard at this place was dug to a depth of 2 to 2.5 feet, and
the workmen found various ancient remains. This led Mr. T. H.
Farrer of Abinger Hall to have an adjoining ploughed field
searched. On a trench being dug, a layer of concrete, still partly
covered with tesserae (small red tiles), and surrounded on two
sides by broken-down walls, was soon discovered. It is believed,
{54} that this room formed part of the atrium or reception-room of
a Roman villa. The walls of two or three other small rooms were
afterwards discovered. Many fragments of pottery, other objects,
and coins of several Roman emperors, dating from 133 to 361, and
perhaps to 375 A.D., were likewise found. Also a half-penny of
George I., 1715. The presence of this latter coin seems an
anomaly; but no doubt it was dropped on the ground during the last
century, and since then there has been ample time for its burial
under a considerable depth of the castings of worms. From the
different dates of the Roman coins we may infer that the building
was long inhabited. It was probably ruined and deserted 1400 or
1500 years ago.

I was present during the commencement of the excavations (August
20, 1877) and Mr. Farrer had two deep trenches dug at opposite ends
of the atrium, so that I might examine the nature of the soil near
the remains. The field sloped from east to west at an angle of
about 7 degrees; and one of the two trenches, shown in the
accompanying section (Fig. 8) was at the upper or eastern end. The
diagram is on a scale of 1/20 of an inch to an inch; but the
trench, which was between 4 and 5 feet broad, and in parts above 5
feet deep, has necessarily been reduced out of all proportion. The
fine mould over the floor of the atrium varied in thickness from 11
to 16 inches; and on the side of the trench in the section was a
little over 13 inches. After the mould had been removed, the floor
appeared as a whole moderately level; but it sloped in parts at an
angle of 1 degree, and in one place near the outside at as much as
8 degrees 30 minutes. The wall surrounding the pavement was built
of rough stones, and was 23 inches in thickness where the trench
was dug. Its broken summit was here 13 inches, but in another part
15 inches, beneath the surface of the field, being covered by this
thickness of mould. In one spot, however, it rose to within 6
inches of the surface. On two sides of the room, where the
junction of the concrete floor with the bounding walls could be
carefully examined, there was no crack or separation. This trench
afterwards proved to have been dug within an adjoining room (11 ft.
by 11 ft. 6 in. in size), the existence of which was not even
suspected whilst I was present.

On the side of the trench farthest from the buried wall (W), the
mould varied from 9 to 14 inches in thickness; it rested on a mass
(B) 23 inches thick of blackish earth, including many large stones.
Beneath this was a thin bed of very black mould (C), then a layer
of earth full of fragments of mortar (D), and then another thin bed
(about 3 inches thick) (E) of very black mould, which rested on the
undisturbed subsoil (F) of firm, yellowish, argillaceous sand. The
23-inch bed (B) was probably made ground, as this would have
brought up the floor of the room to a level with that of the
atrium. The two thin beds of black mould at the bottom of the
trench evidently marked two former land-surfaces. Outside the
walls of the northern room, many bones, ashes, oyster-shells,
broken pottery and an entire pot were subsequently found at a depth
of 16 inches beneath the surface.

The second trench was dug on the western or lower side of the
villa: the mould was here only 6.5 inches in thickness, and it
rested on a mass of fine earth full of stones, broken tiles and
fragments of mortar, 34 inches in thickness, beneath which was the
undisturbed sand. Most of this earth had probably been washed down
from the upper part of the field, and the fragments of stones,
tiles, &c., must have come from the immediately adjoining ruins.

It appears at first sight a surprising fact that this field of
light sandy soil should have been cultivated and ploughed during
many years, and that not a vestige of these buildings should have
been discovered. No one even suspected that the remains of a Roman
villa lay hidden close beneath the surface. But the fact is less
surprising when it is known that the field, as the bailiff
believed, had never been ploughed to a greater depth than 4 inches.
It is certain that when the land was first ploughed, the pavement
and the surrounding broken walls must have been covered by at least
4 inches of soil, for otherwise the rotten concrete floor would
have been scored by the ploughshare, the tesserae torn up, and the
tops of the old walls knocked down.

When the concrete and tesserae were first cleared over a space of
14 by 9 ft., the floor which was coated with trodden-down earth
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
atrium--a space of about 14 by 9 feet--Mr. 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

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

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

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 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

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 from these facts that when the abbey was destroyed
and the stones removed, a layer of rubbish was left over the whole
surface, and that as soon as the worms were able to penetrate the
decayed concrete and the joints between the tiles, they slowly
filled up the interstices in the overlying rubbish with their
castings, which were afterwards accumulated to a thickness of
nearly three inches over the whole surface. If we add to this
latter amount the mould between the fragments of stones, some five
or six inches of mould must have been brought up from beneath the
concrete or tiles. The concrete or tiles will consequently have
subsided to nearly this amount. The bases of the columns of the
aisles are now buried beneath mould and turf. It is not probable
that they can have been undermined by worms, for their foundations
would no doubt have been laid at a considerable depth. If they
have not subsided, the stones of which the columns were constructed
must have been removed from beneath the former level of the floor.

Chedworth, Gloucestershire.--The remains of a large Roman villa
were discovered here in 1866, on ground which had been covered with
wood from time immemorial. No suspicion seems ever to have been
entertained that ancient buildings lay buried here, until a
gamekeeper, in digging for rabbits, encountered some remains. {55}
But subsequently the tops of some stone walls were detected in
parts of the wood, projecting a little above the surface of the
ground. Most of the coins found here belonged to Constans (who
died 350 A.D.) and the Constantine family. My sons Francis and
Horace visited the place in November 1877, for the sake of
ascertaining what part worms may have played in the burial of these
extensive remains. But the circumstances were not favourable for
this object, as the ruins are surrounded on three sides by rather
steep banks, down which earth is washed during rainy weather.
Moreover most of the old rooms have been covered with roofs, for
the protection of the elegant tesselated pavements.

A few facts may, however, be given on the thickness of the soil
over these ruins. Close outside the northern rooms there is a
broken wall, the summit of which was covered by 5 inches of black
mould; and in a hole dug on the outer side of this wall, where the
ground had never before been disturbed, black mould, full of
stones, 26 inches in thickness, was found, resting on the
undisturbed sub-soil of yellow clay. At a depth of 22 inches from
the surface a pig's jaw and a fragment of a tile were found. When
the excavations were first made, some large trees grew over the
ruins; and the stump of one has been left directly over a party-
wall near the bath-room, for the sake of showing the thickness of
the superincumbent soil, which was here 38 inches. In one small
room, which, after being cleared out, had not been roofed over, my
sons observed the hole of a worm passing through the rotten
concrete, and a living worm was found within the concrete. In
another open room worm-castings were seen on the floor, over which
some earth had by this means been deposited, and here grass now

Brading, Isle of Wight.--A fine Roman villa was discovered here in
1880; and by the end of October no less than 18 chambers had been
more or less cleared. A coin dated 337 A.D. was found. My son
William visited the place before the excavations were completed;
and he informs me that most of the floors were at first covered
with much rubbish and fallen stones, having their interstices
completely filled up with mould, abounding, as the workmen said,
with worms, above which there was mould without any stones. The
whole mass was in most places from 3 to above 4 ft. in thickness.
In one very large room the overlying earth was only 2 ft. 6 in.
thick; and after this had been removed, so many castings were
thrown up between the tiles that the surface had to be almost daily
swept. Most of the floors were fairly level. The tops of the
broken-down walls were covered in some places by only 4 or 5 inches
of soil, so that they were occasionally struck by the plough, but
in other places they were covered by from 13 to 18 inches of soil.
It is not probable that these walls could have been undermined by
worms and subsided, as they rested on a foundation of very hard red
sand, into which worms could hardly burrow. The mortar, however,
between the stones of the walls of a hypocaust was found by my son
to have been penetrated by many worm-burrows. The remains of this
villa stand on land which slopes at an angle of about 3 degrees;
and the land appears to have been long cultivated. Therefore no
doubt a considerable quantity of fine earth has been washed down
from the upper parts of the field, and has largely aided in the
burial of these remains.

Silchester, Hampshire.--The ruins of this small Roman town have
been better preserved than any other remains of the kind in
England. A broken wall, in most parts from 15 to 18 feet in height
and about 1.5 mile in compass, now surrounds a space of about 100
acres of cultivated land, on which a farm-house and a church stand.
{56} Formerly, when the weather was dry, the lines of the buried
walls could be traced by the appearance of the crops; and recently
very extensive excavations have been undertaken by the Duke of
Wellington, under the superintendence of the late Rev. J. G. Joyce,
by which means many large buildings have been discovered. Mr.
Joyce made careful coloured sections, and measured the thickness of
each bed of rubbish, whilst the excavations were in progress; and
he has had the kindness to send me copies of several of them. When
my sons Francis and Horace visited these ruins, he accompanied
them, and added his notes to theirs.

Mr. Joyce estimates that the town was inhabited by the Romans for
about three centuries; and no doubt much matter must have
accumulated within the walls during this long period. It appears
to have been destroyed by fire, and most of the stones used in the
buildings have since been carried away. These circumstances are
unfavourable for ascertaining the part which worms have played in
the burial of the ruins; but as careful sections of the rubbish
overlying an ancient town have seldom or never before been made in
England, I will give copies of the most characteristic portions of
some of those made by Mr. Joyce. They are of too great length to
be here introduced entire.

An east and west section, 30 ft. in length, was made across a room
in the Basilica, now called the Hall of the Merchants (Fig. 9).
The hard concrete floor, still covered here and there with
tesserae, was found at 3 ft. beneath the surface of the field,
which was here level. On the floor there were two large piles of
charred wood, one alone of which is shown in the part of the
section here given. This pile was covered by a thin white layer of
decayed stucco or plaster, above which was a mass, presenting a
singularly disturbed appearance, of broken tiles, mortar, rubbish
and fine gravel, together 27 inches in thickness. Mr. Joyce
believes that the gravel was used in making the mortar or concrete,
which has since decayed, some of the lime probably having been
dissolved. The disturbed state of the rubbish may have been due to
its having been searched for building stones. This bed was capped
by fine vegetable mould, 9 inches in thickness. From these facts
we may conclude that the Hall was burnt down, and that much rubbish
fell on the floor, through and from which the worms slowly brought
up the mould, now forming the surface of the level field.

A section across the middle of another hall in the Basilica, 32
feet 6 inches in length, called the AErarium, is shown in Fig. 10.
It appears that we have here evidence of two fires, separated by an
interval of time, during which the 6 inches of "mortar and concrete
with broken tiles" was accumulated. Beneath one of the layers of
charred wood, a valuable relic, a bronze eagle, was found; and this
shows that the soldiers must have deserted the place in a panic.
Owing to the death of Mr. Joyce, I have not been able to ascertain
beneath which of the two layers the eagle was found. The bed of
rubble overlying the undisturbed gravel originally formed, as I
suppose, the floor, for it stands on a level with that of a
corridor, outside the walls of the Hall; but the corridor is not
shown in the section as here given. The vegetable mould was 16
inches thick in the thickest part; and the depth from the surface
of the field, clothed with herbage, to the undisturbed gravel, was
40 inches.

The section shown in Fig. 11 represents an excavation made in the
middle of the town, and is here introduced because the bed of "rich
mould" attained, according to Mr. Joyce, the unusual thickness of
20 inches. Gravel lay at the depth of 48 inches from the surface;
but it was not ascertained whether this was in its natural state,
or had been brought here and had been rammed down, as occurs in
some other places.

The section shown in Fig. 12 was taken in the centre of the
Basilica, and though it was 5 feet in depth, the natural sub-soil
was not reached. The bed marked "concrete" was probably at one
time a floor; and the beds beneath seem to be the remnants of more
ancient buildings. The vegetable mould was here only 9 inches
thick. In some other sections, not copied, we likewise have
evidence of buildings having been erected over the ruins of older
ones. In one case there was a layer of yellow clay of very unequal
thickness between two beds of debris, the lower one of which rested
on a floor with tesserae. The ancient broken walls appear to have
been sometimes roughly cut down to a uniform level, so as to serve
as the foundations for a temporary building; and Mr. Joyce suspects
that some of these buildings were wattled sheds, plastered with
clay, which would account for the above-mentioned layer of clay.

Turning now to the points which more immediately concern us. Worm-
castings were observed on the floors of several of the rooms, in
one of which the tesselation was unusually perfect. The tesserae
here consisted of little cubes of hard sandstone of about 1 inch,
several of which were loose or projected slightly above the general
level. One or occasionally two open worm-burrows were found
beneath all the loose tesserae. Worms have also penetrated the old
walls of these ruins. A wall, which had just been exposed to view
during the excavations then in progress, was examined; it was built
of large flints, and was 18 inches in thickness. It appeared
sound, but when the soil was removed from beneath, the mortar in
the lower part was found to be so much decayed that the flints fell
apart from their own weight. Here, in the middle of the wall, at a
depth of 29 inches beneath the old floor and of 49.5 inches beneath
the surface of the field, a living worm was found, and the mortar
was penetrated by several burrows.

A second wall was exposed to view for the first time, and an open
burrow was seen on its broken summit. By separating the flints
this burrow was traced far down in the interior of the wall; but as
some of the flints cohered firmly, the whole mass was disturbed in
pulling down the wall, and the burrow could not be traced to the
bottom. The foundations of a third wall, which appeared quite
sound, lay at a depth of 4 feet beneath one of the floors, and of
course at a considerably greater depth beneath the level of the
ground. A large flint was wrenched out of the wall at about a foot
from the base, and this required much force, as the mortar was
sound; but behind the flint in the middle of the wall, the mortar
was friable, and here there were worm-burrows. Mr. Joyce and my
sons were surprised at the blackness of the mortar in this and in
several other cases, and at the presence of mould in the interior
of the walls. Some may have been placed there by the old builders
instead of mortar; but we should remember that worms line their
burrows with black humus. Moreover open spaces would almost
certainly have been occasionally left between the large irregular
flints; and these spaces, we may feel sure, would be filled up by
the worms with their castings, as soon as they were able to
penetrate the wall. Rain-water, oozing down the burrows would also
carry fine dark-coloured particles into every crevice. Mr. Joyce
was at first very sceptical about the amount of work which I
attributed to worms; but he ends his notes with reference to the
last-mentioned wall by saying, "This case caused me more surprise
and brought more conviction to me than any other. I should have
said, and did say, that it was quite impossible such a wall could
have been penetrated by earth-worms."

In almost all the rooms the pavement has sunk considerably,
especially towards the middle; and this is shown in the three
following sections. The measurements were made by stretching a
string tightly and horizontally over the floor. The section, Fig.
13, was taken from north to south across a room, 18 feet 4 inches
in length, with a nearly perfect pavement, next to the "Red Wooden
Hut." In the northern half, the subsidence amounted to 5.75 inches
beneath the level of the floor as it now stands close to the walls;
and it was greater in the northern than in the southern half; but,
according to Mr. Joyce, the entire pavement has obviously subsided.
In several places, the tesserae appeared as if drawn a little away
from the walls; whilst in other places they were still in close
contact with them.

In Fig. 14, we see a section across the paved floor of the southern
corridor or ambulatory of a quadrangle, in an excavation made near
"The Spring." The floor is 7 feet 9 inches wide, and the broken-
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

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 of various rooms
were covered with rubble. As I was anxious to know how thick the
mantle of mould and rubbish was, which had so long concealed these
ruins, I applied to Dr. H. Johnson, who had superintended the
excavations; and he, with the greatest kindness, twice visited the
place to examine it in reference to my questions, and had many
trenches dug in four fields which had hitherto been undisturbed.
The results of his observations are given in the following Table.
He also sent me specimens of the mould, and answered, as far as he
could, all my questions.


Trenches dug in a field called "Old Works."

(Thickness of mould in inches shown in parenthesis--DP.)

1. At a depth of 36 inches undisturbed sand was reached (20)

2. At a depth of 33 inches concrete was reached (21)

3. At a depth of 9 inches concrete was reached (9)

Trenches dug in a field called "Shop Leasows;" this is the highest
field within the old walls, and slopes down from a sub-central
point on all sides at about an angle of 2 degrees.

4. Summit of field, trench 45 inches deep (40)

5. Close to summit of field, trench 36 inches deep (26)

6. Close to summit of field, trench 28 inches deep (28)

7. Near summit of field, trench 36 inches deep (24)

8. Near summit of field, trench at one end 39 inches deep; the
mould here graduated into the underlying undisturbed sand, and its
thickness (24 inches) is somewhat arbitrary. At the other end of
the trench, a causeway was encountered at a depth of only 7 inches,
and the mould was here only 7 inches thick (24)

9. Trench close to the last, 28 inches in depth (24)

10. Lower part of same field, trench 30 inches deep (15)

11. Lower part of same field, trench 31 inches deep (17)

12. Lower part of same field, trench 36 inches deep, at which
depth undisturbed sand was reached (28)

13. In another part of same field, trench 9.5 inches deep stopped
by concrete (9.5)

14. In another part of same field, trench 9 inches deep, stopped
by concrete (9)

15. In another part of the same field, trench 24 inches deep, when
sand was reached (16)

16. In another part of same field, trench 30 inches deep, when
stones were reached; at one end of the trench mould 12 inches, at
the other end 14 inches thick (13)

Small field between "Old Works" and "Shop Leasows," I believe
nearly as high as the upper part of the latter field.

17. Trench 26 inches deep (24)

18. Trench 10 inches deep, and then came upon a causeway (10)

19. Trench 34 inches deep (30)


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