orated from them. On the other hand, coaly substances are
destitute of fusibility and volatility, in proportion as they have
been exposed to greater degrees of heat, and to other circumstances
favourable to the dissipation of their more volatile and fluid parts.

If, therefore, in mineral bodies, we find the two extreme states of this
combustible substance, and also the intermediate states, we must either
conclude, that this particular operation of heat has been thus actually
employed in nature, or we must explain those appearances by some other
means, in as satisfactory a manner, and so as shall be consistent with
other appearances.

In this case, it will avail nothing to have recourse to the false
analogy of water dissolving and crystallising salts, which has been so
much employed for the explanation of other mineral appearances. The
operation here in question is of a different nature, and necessarily
requires both the powers of heat and proper conditions for evaporation.

Therefore, in order to decide the point, with regard to what is the
power in nature by which mineral bodies have become solid, we have
but to find bituminous substance in the most complete state of coal,
intimately connected with some other substance, which is more generally
found consolidating the strata, and assisting in the concretion of
mineral substances. But I have in my possession the most undoubted proof
of this kind. It is a mineral vein, or cavity, in which are blended
together coal of the most fixed kind, quartz and marmor metallicum. Nor
is this all; for the specimen now referred to is contained in a rock
of this kind, which every naturalist now-a-days will allow to have
congealed from a fluid state of fusion. I have also similar specimens
from the same place, in which the coal is not of that fixed and
infusible kind which burns without flame or smoke, but is bituminous or
inflammable coal.

We have hitherto been resting the argument upon a single point, for the
sake of simplicity or clearness, not for want of those circumstances
which shall be found to corroborate the theory. The strata of fossil
coal are found in almost every intermediate state, as well as in those
of bitumen and charcoal. Of the one kind is that fossil coal which melts
or becomes fluid upon receiving heat; of the other, is that species of
coal, found both in Wales and Scotland, which is perfectly infusible in
the fire, and burns like coals, without flame or smoke.