her 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.
Consequently, in finding masses of gravel in the composition of our
land, we must conclude, that there had existed a former land, on which
there had been transacted certain operations of wind and water, similar
to those which are natural to the globe at present, and by which new
gravel is continually prepared, as well as old gravel consumed or
diminished by attrition upon our shores.

Sand is the material which enters, perhaps in greatest quantity, the
composition of our land. But sand, in general, is no other than small
fragments of hard and solid bodies, worn or rounded more or less by
attrition; consequently, the same natural history of the earth, which
is investigated from the masses of gravel, is also applicable to those
masses of sand which we find forming so large a portion of our present
land throughout all the earth[16].

[Note 16: Sand is a term that denotes no particular substance; although
by it is commonly meant a siliceous substance, as being by far the most
prevalent. Sand is one of the modifications, of size and shape, in a
hard body or solid substance, which may be infinitely diversified. The
next modification to be distinguished in mineral bodies is that of
gravel; and this differs in