What would you say but: The pond has
not been always full. It has at some time or other been dry enough
to let a whole copse grow up inside it?
And if you found--as you will actually find along some English
shores--under the sand hills, perhaps a bed of earth with shells and
bones; under that a bed of peat; under that one of blue silt; under
that a buried forest, with the trees upright and rooted; under that
another layer of blue silt full of roots and vegetable fibre; perhaps
under that again another old land surface with trees again growing in
it; and under all the main bottom clay of the district--what would
common sense tell you? I leave you to discover for yourselves. It
certainly would not tell you that those trees were thrust in there by
a violent convulsion, or that all those layers were deposited there
in a few days, or even a few years; and you might safely indulge in
speculations about the antiquity of the aestuary, and the changes
which it has undergone, with which I will not frighten you at
present.
It will be fair reasoning to argue thus. You may not be always right
in your conclusion, but still you will be trying fairly to explain
the unknown by the known.
But have Rain and Rivers alone made the soil?
How very much they have done toward making it you will be able to
judge for yourselves, if you will read the sixth chapter of Sir
Charles Lyell's new "Elements of Geology," or the first hundred pages
of that admirable book, De la Beche's "Geological Observer;" and
last, but not least, a very clever little book called "Rain and
Rivers," by Colonel George Greenwood.
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