You will see now why I have begun with the soil in the field; because
it is the uppermost, and therefore latest, of all the layers; and
also for this reason, that, if Sir Charles Lyell's theory be true--as
it is--then the soils and rocks below the soil of the field may have
been made in the very same way in which the soil of the field is
made. If so, it is well worth our while to examine it.
You all know from whence the soil comes which has filled up, in the
course of ages, the great aestuaries below London, Stirling, Chester,
or Cambridge.
It is river mud and sand. The river, helped by tributary brooks
right and left, has brought down from the inland that enormous mass.
You know that. You know that every flood and freshet brings a fresh
load, either of fine mud or of fine sand, or possibly some of it
peaty matter out of distant hills. Here is one indisputable fact
from which to start. Let us look for another.
How does the mud get into the river? The rain carries it thither.
If you wish to learn the first elements of geology by direct
experiment, do this: The next rainy day--the harder it rains the
better--instead of sitting at home over the fire, and reading a book
about geology, put on a macintosh and thick boots, and get away, I
care not whither, provided you can find there running water.
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