fects of those
powers proceed, or the measure of those different degrees of increase
that may be made without changing the constitution of the compound
substance, are not known; nor is there any limit to be set to that
operation, so far as we know. Consequently, it is a physical principle,
That the evaporation of volatile substances by heat, or the reparation
of them from a compound substance, consequently the effect of fire in
changing that compound substance, may be absolutely prevented by means
of compression.

It now remains to be considered, how far there is reason to conclude
that there had been sufficient degrees of compression in the mineral
regions, for the purpose of melting the various substances with which we
find strata consolidated, without changing the chemical constitution of
those compound substances.

Had I, in reasoning _a priori_, asserted, That all mineral bodies might
have been melted without change, when under sufficient compression,
there might have arisen, in the minds of reasoning men, some doubt with
regard to the certainty of that proposition, however probable it were to
be esteemed: But when, in reasoning _a posteriori_, it is found that all
mineral bodies have been actually melted, then, all that is required to
establish the proposition on which I have founded my theory, is to
see that there must have been immense degrees of compression upon the
subjects in question; for we neither know the degree of heat which had
been employed, nor that of compression by which the effect of the heat
must have been modified.

Now, in order to see that there had been immense compression, we have
but to consider that the formation of the strata, which are to be
consolidated, was at the bottom of the ocean, and that this place is to
us unfathomable. If it be farther necessary to show that it had been at
such unfathomable depth strata were consolidated, it will be sufficient
to observe, it is not upon the surface of the earth, or above the level
of the sea, that this mineral operation can take place; for, it is there
that those consolidated bodies are redissolved, or necessarily going
into decay, which is the opposite to that operation which we are now
inquiring after; therefore, if they were consolidated in any other place
than at the bottom of the sea, it must have been between that place of
their formation and the surface of the sea; but that is a supposition
which we have not any reason to make; therefo