ith mineral
coal, it is to be proved that the origin of this metallic body had been
fusion; and then it will appear, that all other mineral bodies must have
been more or less in fusion, or that they must have been consolidated
by means of heat, and not by any manner of solution or aqueous
infiltration. I therefore now proceed to take a view of the natural
history of coal strata,--a subject which mineralogists seem not inclined
to engage with, although the most ample data are to be found for that
investigation.

SECT. II.--Natural History of Coal Strata, and Theory of this
Geological Operation.

Fossil coal is the species of stratum best understood with regard to its
accidents, as being much sought after; at least, this is the case in
many parts of Britain, where it supplies the place of wood for burning.
This fossil body has the most distinguished character; for, being
inflammable or combustible in its nature, there is no other species of
stratum that may be confounded with it.

But, though coal be thus the most distinguishable mineral, and that
which is best understood in the science of mining, it is perhaps the
most difficult to be treated of in the science of mineralogy; for,
not having properly any distinguishable parts, we have nothing in the
natural constitution of this body, as we have in most other strata, to
lead us to the knowledge of its original state or first formation.

The varieties of coal are distinguished by their different manner of
burning; but, from appearances of this kind, no perfect judgement can be
formed with regard to the specific manner in which those strata had been
made; although, from chemical principles, some conclusion may be drawn
concerning certain changes which they have undergone since they had been
formed.

Thus we have one species of coal which is extremely fusible, abounds
with oil, and consequently is inflammable; we have another species again
which is perfectly fixed and infusible in the fire; therefore, we may
conclude upon principle, that, however, both those coals must have
undergone the operation of heat and fusion, in bringing them to their
present state, it is only the last that has become so much evaporated as
to become perfectly fixed, or so perfectly distilled, as to have been
reduced to a caput mortuum.

The argument here employed is founded upon this fact; that, from the
fusible species of coal, a caput mortuum may be formed by distillation,
and that this ch