l appearances. Whether
warped by the prejudice of partial and erroneous theory, or deceived by
the inaccuracy of superficial observation, naturalists are apt to see
things in an improper light, and thus to reason from principles which
cannot be admitted, and, which often lead to false conclusions. A
naturalist, for example, comes to examine a cavity in the mines, he
there finds water dropping down all around him, and he sees the cavity
all hung with siliceous crystals; he then concludes, without hesitation,
that here is to be perceived cause and effect, or that he actually sees
the formation of those crystallizations from the operation of water. It
is thus that I have been told by men of great mineral knowledge, men who
must have had the best education upon that subject of mineralogy, and
who have the superintendance of great mineral concerns in Germany, that
they had actually seen nature at work in that operation of forming
rock-crystal;--they saw what I have now described; they could see no
more; but, they saw what had convinced them of that which, there is
every reason to believe, never happened. With regard to my theory,
I wish for the most rigorous examination; and do not ask for any
indulgence whatever, whether with regard to the principles on which the
theory is built, or for the application of the theory to the explanation
of natural appearances. But, let not geologists judge my theory by their
imperfect notions of nature, or by those narrow views which they take of
the present state of things;--let not mineralogists condemn my theory,
for no other reason but because it does not correspond with their false
principles, and those gratuitous suppositions by which they had been
pleased to explain to themselves every thing before. First let them look
into their own theory, and correct that erroneous principle, with regard
to the action of water, or the assumption of unknown causes, upon which
they have reasoned in forming their vague notions of the mineral region,
before they can be properly qualified to examine, impartially, a theory
which employs another principle. Every thing which has come under my
observation shall be, as far as I can, faithfully related; nor shall I
withhold those which neither the present theory, nor any other that I am
acquainted with, can, I think, explain.

Appearances cannot well be described except in relation to some theory
or general arrangement of the subject; because the particular det