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 71 2 ounces; so that the weight of those on a square yard
would have been 4 lb. 31 2 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 91 2 oz., or 5 lb. 51 2
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 21 2 oz., or 1 lb. 61 2 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. 131 2 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
72