We have already observed, that all the strata of the earth are composed
either from the calcareous relicts of sea animals, or from the
collection of such materials as we find upon our shores. At a gross
computation, there may perhaps be a fourth part of our solid land, which
is composed from the matter that had belonged to those animals. Now,
what a multitude of living creatures, what a quantity of animal economy
must have been required for producing a body of calcareous matter
which is interspersed throughout all the land of the globe, and which
certainly forms a very considerable part of that mass! Therefore, in
knowing how those animals had lived, or with what they had been fed, we
shall have learned a most interesting part of the natural history of
this earth; a part which it is necessary to have ascertained, in order
to see the former operations of the globe, while preparing the materials
of the present land. But, before entering upon this subject, let us
examine the other materials of which our land is formed.
Gravel forms a part of those materials which compose our solid land; but
gravel is no other than a collection of the fragments of solid stones
worn round, or having their angular form destroyed by agitation in
water, and the attrition upon each other, or upon similar hard bodies.
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