d be spread into
strata by mere heat, is to me incomprehensible."--It is only upon the
last sentence that I am here to remark: This, I believe, will be a
sufficient specimen of our author's understanding, with regard at least
to my Theory which he is here examining.

The reader will see what I have said upon the subject of coal, by
turning back to the second section of the preceding chapter. I had given
almost three quarto pages upon that subject, endeavouring to explain how
all the different degrees of _infusibility_ were produced, by means of
heat and distillation, in strata which had been originally more or less
oily, bituminous, and _fusible_; and now our author says, that it is
incomprehensible to him, how coal, _an infusible substance_, could be
spread into strata by mere heat.--So it truly may, either to him or to
any other person; but, it appears to me almost as incomprehensible, how
a person of common understanding should read my Dissertation, and impute
to it a thing so contrary to its doctrine.

Nothing can better illustrate the misconceived view that our author
seems to have taken of the two opposite theories, (_i. e_. of
consolidation by means of heat, and by means of water alone,) than
his observation upon the case of mineral alkali. To that irrefragable
argument (which Dr Black suggested) in proof of this substance having
been in a state of fusion in the mineral regions, our author makes the
following reply; "What then will our author say of the vast masses
of this salt which are found with their full quantity of water of
crystallization?"--There is in this proposition, insignificant as it may
seem, a confusion of ideas, which it certainly cannot be thought worth
while to investigate; but, so far as the doctrine of the aqueous theory
may be considered as here concerned, it will be proper that I should
give some answer to the question so triumphantly put to me.

Our author is in a mistake in supposing that Dr Black had written any
thing upon the subject; he had only suggested the argument of this
example of mineral alkali to me, as I have mentioned; and, the use I
made of that argument was to corroborate the example I had given of sal
gem. If, therefore, our author does not deny the inference from the
state of that mineral alkali, his observation upon it must refer to
something which this other example of his is to prove on the opposite
side, or to support the aqueous instead of the igneous theory; and,