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
31 2 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.
SUMMARY OF THE FOUR FOREGOING CASES.
(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
74