time that, in other parts,
the spherical figures of the calcedony enter the solid body of the
spar, and thus impress their mammelated figures into that part which is
contiguous. It is therefore inconceivable, that these appearances
could have been produced in any other manner than by those two bodies
concreting from a simply fluid state.

There are in jaspers and agates many other appearances, from whence the
fusion of those substances may be concluded with great certainty and
precision; but it is hoped, that what has been now given may suffice for
establishing that proposition without any doubt.

It must not be here objected, That there are frequently found siliceous
crystals and amethysts containing water; and that it is impossible
to confine water even in melted glass. It is true, that here, at the
surface of the earth, melted glass cannot, in ordinary circumstances, be
made to receive and inclose condensed water; but let us only suppose a
sufficient degree of compression in the body of melted glass, and we
can easily imagine it to receive and confine water as well as any
other substance. But if, even in our operations, water, by means of
compression, may be made to endure the heat of red hot iron without
being converted into vapour, what may not the power of nature be able to
perform? The place of mineral operations is not on the surface of the
earth; and we are not to limit nature with our imbecility, or estimate
the powers of nature by the measure of our own.[10]

[Note 10: This is so material a principle in the theory of consolidating
the strata of the earth by the fusion of mineral substances, that I beg
the particular attention of the reader to that subject. The effect of
compression upon compound substances, submitted to increased degrees of
heat, is not a matter of supposition, it is an established principle
in natural philosophy. This, like every other physical principle, is
founded upon matter of fact or experience; we find, that many compound
substances may with heat be easily changed, by having their more
volatile parts separated when under a small compression; but these
substances are preserved without change when sufficiently compressed.
Our experiments of this kind are necessarily extremely limited; they
are not, however, for that reason, the less conclusive. The effects of
increasing degrees of heat are certainly prevented by increasing degrees
of compression; but the rate at which the different ef