earth. But, our author answers, That the interior
parts _might have been in an original state of solidity_.--So might
they have been upon the surface of the earth, or on the summits of our
mountains; but, we are not inquiring What they _might have been_, but
What they truly _are_. It is from this actual state in which the solid
parts of the earth are found, that I have endeavoured to trace back the
different states in which they must have been; and, by generalising
facts, I have formed a theory of the earth. If this be a wrong principle
or manner of proceeding in a physical investigation, or if, proceeding
upon that principle, I have made the induction by reasoning improperly
on any occasion, let this be corrected by philosophers, who may reason
more accurately upon the subject. But to oppose a physical investigation
with this proposition, _that things might have been otherwise_, is to
proceed upon a very different principle,--a principle which, instead of
tending to bring light out of darkness, is only calculated to extinguish
that light which we may have acquired.

I shall afterwards have occasion to examine how far the philosophers,
who attribute to aqueous solution the origin of stony substances, have
proceeded in the same inductive manner of reasoning from effect to
cause, as they ought to do in physical subjects, and not by feigning
causes, or following a false analogy; in the mean time, I am to answer
the objections which have been made to the theory of the earth.

In opposition to the theory of consolidating bodies by fusion, our
author has taken great pains to show, that I cannot provide materials
for such a fire as would be necessary, nor find the means to make it
burn had I those materials. Had our author read attentively my theory he
would have observed, that I give myself little or no trouble about that
fire, or take no charge with regard to the procuring of that power, as I
have not founded my theory on the _supposition_ of subterraneous
fire, however that fire properly follows as a conclusion from those
appearances on which the theory is founded. My theory is founded upon
the general appearances of mineral bodies, and upon this, that mineral
bodies must necessarily have been in a state of fusion. I do not pretend
to prove, demonstratively, that they had been even hot, however that
conclusion also naturally follows from their having been in fusion. It
is sufficient for me to demonstrate, That those bodies