t the top, a
lining of dead leaves extends downward for a few inches, and in day time
a plug of the same material is the outside door. At night the worm comes
to the surface, and casts out the pellets of earth swallowed. The burrow
grows in length by the amount of earth scraped off by the long snout
and swallowed. The daily amount of excavation done is fairly estimated
by the castings observed each morning on the surface.

One earthworm's work for the farmer is not very much, but consider how
many are at work, and what each one is doing. It is boring holes through
the solid earth, and letting in the surface water and the air. It is
carrying the lower soil up to the surface, often the stubborn subsoil,
that no plough could reach. It is burying and thus hastening the decay
of plant fibre, which lightens heavy soil and makes it rich because it
is porous. Moreover, the earthworms are doing over and over again this
work of fining and turning over the soil, which the plough does but
seldom.

By the continuous carrying up of their castings, the earthworms
gradually bury manures spread on the surface. The collapse of their
burrows and the making of new ones keep the soil constantly in motion.
The particles are being loosened and brought into contact with the soil
water, that dissolves, and thus frees for the use of feeding roots, the
plant food stored in the rock particles that compose the mineral part of
the soil.

The weight of earth brought to the surface by worms in the course of a
year has been carefully estimated. Darwin gives seven to eighteen tons
per acre as the lowest and highest reports, based on careful collecting
of castings by four observers, working on small areas of totally
different soils. In England, earthworms have done a great deal more
toward burying boulders and ancient ruins than any other agency. They
eagerly burrow under heavy objects, the weight of which causes them to
crush the honeycombed earth. Undiscouraged, the earthworms repeat their
work.

"Long before man existed, the land was regularly ploughed, and continues
still to be ploughed by earthworms. It may be doubted whether there are
many other animals which have played so important a part in the history
of the world as have these lowly organized creatures."

After years of study, Charles Darwin came to this conclusion. The more
we study the lives of these earth-consuming creatures, the more fully do
we believe what the great nature student