a line 100 yards in length. This latter amount in a damp state would
weigh 111 2 pounds. Thus a considerable weight of earth is continually
moving down each side of every valley, and will in time reach its bed.
Finally this earth will be transported by the streams flowing in the
valleys into the ocean, the great receptacle for all matter denuded from
the land. It is known from the amount of sediment annually delivered
into the sea by the Mississippi, that its enormous drainage-area must on
an average be lowered .00263 of an inch each year; and this would suffice
in four and half million years to lower the whole drainage-area to the
level of the sea-shore. So that, if a small fraction of the layer of
fine earth, 0.2 of an inch in thickness, which is annually brought to the
surface by worms, is carried away, a great result cannot fail to be
produced within a period which no geologist considers extremely long.
* * * * *
Arch ologists ought to be grateful to worms, as they protect and preserve
for an indefinitely long period every object, not liable to decay, which
is dropped on the surface of the land, by burying it beneath their
castings. Thus, also, many elegant and curious tesselated pavements and
other ancient remains have been preserved; though no doubt the worms have
in these cases been largely aided by earth washed and blown from the
adjoining land, especially when cultivated. The old tesselated pavements
have, however, often suffered by having subsided unequally from being
unequally undermined by the worms. Even old massive walls may be
undermined and subside; and no building is in this respect safe, unless
the foundations lie 6 or 7 feet beneath the surface, at a depth at which
worms cannot work. It is probable that many monoliths and some old walls
have fallen down from having been undermined by worms.
* * * * *
Worms prepare the ground {284} in an excellent manner for the growth of
fibrous-rooted plants and for seedlings of all kinds. They periodically
expose the mould to the air, and sift it so that no stones larger than
the particles which they can swallow are left in it. They mingle the
whole intimately together, like a gardener who prepares fine soil for his
choicest plants. In this state it is well fitted to retain moisture and
to absorb all soluble substances, as well as for the process of
nitrification. The bones of dead animals, the harder parts of insects,
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