As you go on beyond the sea-wall, you find what it is eating up. The
whole low cliff is going visibly. But whither is it going? To form
new soil in the aestuary. Now you will not wonder how old harbours
so often become silted up. The sea has washed the land into them.
But more, the sea-currents do not allow the sands of the aestuary to
escape freely out to sea. They pile it up in shifting sand-banks
about the mouth of the aestuary. The prevailing sea-winds, from
whatever quarter, catch up the sand, and roll it up into sand-hills.
Those sand-hills are again eaten down by the sea, and mixed with the
mud of the tide-flats, and so is formed a mingled soil, partly of
clayey mud, partly of sand; such a soil as stretches over the greater
part of all our lowlands.
Now, why should not that soil, whether in England or in Scotland,
have been made by the same means as that of every aestuary.
You find over great tracts of East Scotland, Lancashire, Norfolk,
etc., pure loose sand just beneath the surface, which looks as if it
was blown sand from a beach. Is it not reasonable to suppose that it
is? You find rising out of many lowlands, crags which look exactly
like old sea-cliffs eaten by the waves, from the base of which the
waters have gone back. Why should not those crags be old sea-cliffs?
Why should we not, following our rule of explaining the unknown by
the known, assume that such they are till someone gives us a sound
proof that they are not; and say--These great plains of England and
Scotland were probably once covered by a shallow sea, and their soils
made as the soil of any tide-flat is being made now?
But you may say, and most reasonably "The tide-flats are just at the
sea-level.
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