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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。
CHAPTER IIITHE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE
SURFACE。
Rate at which various objects strewed on the surface of grass…
fields are covered up by the castings of wormsThe burial of a
paved pathThe slow subsidence of great stones left on the
surfaceThe number of worms which live within a given spaceThe
weight of earth ejected from a burrow； and from all the burrows
within a given spaceThe thickness of the layer of mould which the
castings on a given space would form within a given time if
uniformly spread outThe slow rate at which mould can increase to
a great thicknessConclusion。
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 fo