But, we have
reason to believe, it is not in the nature of things to change the
infusible species, so as to make it fusible or oily. Now, that this body
was not formed originally in its present state, must appear from this,
that the stratum here considered is perfectly solid; but, without
fusion, this could not have been attained; and the coal is now supposed
to be infusible. Consequently, this fixed substance, which is now,
properly speaking, a perfect coal, had been originally an oily
bituminous or fusible substance. It is now a fixed substance, and an
infusible coal; therefore, it must have been by means of heat and
distillation that it had been changed, from the original state in which
this stratum had been formed.
We have thus, in the examination of coal strata upon chemical
principles, received a certain lesson in geology, although this does not
form a proper distinction by which to specify those strata in general,
or explain the variety of that mineral. For, in this manner, we
could only distinguish properly two species of those strata; the one
bituminous or inflammable; the other proper coal, burning without smoke
or flame.
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