universal, in
relation to the strata of the earth, as having produced the various
degrees of solidity or hardness in these bodies.

I shall first remark, that a fortuitous collection of hard bodies, such
as gravel and sand, can only touch in points, and cannot, while in that
hard state, be made to correspond so precisely to each others shape as
to consolidate the mass. But if these hard bodies should be softened in
their substance, or brought into a certain degree of fusion, they
might be adapted mutually to each other, and thus consolidate the open
structure of the mass. Therefore, to prove the present point, we have
but to exhibit specimens of siliceous and calcareous strata which have
been evidently consolidated in this manner.

Of the first kind, great varieties occur in this country. It is,
therefore, needless to describe these particularly. They are the
consolidated strata of gravel and sand, often containing abundance of
feld-spar, and thus graduating into granite; a body, in this respect,
perfectly similar to the more regular strata which we now examine.

The second kind, again, are not so common in this country, unless
we consider the shells and coralline bodies in our lime-stones, as
exhibiting the same example, which indeed they do. But I have a specimen
of marble from Spain, which may be described, and which will afford the
most satisfactory evidence of the fact in question.

This Spanish marble may be considered as a species of pudding-stone,
being formed of calcareous gravel; a species of marble which, from Mr
Bowles' Natural History, appears to be very common in Spain. The gravel
of which this marble is composed, consists of fragments of other marbles
of different kinds. Among these, are different species of _oolites_
marble, some shell marbles, and some composed of a chalky substance, or
of undistinguishable parts. But it appears, that all these different
marbles had been consolidated or made hard, then broken into fragments,
rolled and worn by attrition, and thus collected together, along with
some sand or small siliceous bodies, into one mass. Lastly, This
compound body is consolidated in such a manner as to give the most
distinct evidence, that this had been executed by the operation of heat
or simple fusion.

The proof I give is this, That besides the general conformation of those
hard bodies, so as to be perfectly adapted to each other's shape, there
is, in some places, a mutual indentation of