s crystaux n'aurons-nous
pas une boule de silex, avec de crystaux de quartz dans ses creux
interieurs."

The supposed case is this; a calcareous body is to be metamorphosed
into a siliceous nodule, having a cavity within it lined with quartz,
crystals, etc. M. de Carosi means to inform us how this may be done.
Now, as this process requires no other conditions than those that may
be found upon the surface of this earth, the proper way to prove this
hypothetical theory, would be to exhibit such a mineral body produced
by those means. But, even supposing that such a process were to be
exhibited, still it would remain to be explained, how this process,
which requires conditions certainly not be found at the bottom of the
sea, could be accomplished in that place, where the strata of the earth
had been deposited, accumulated, consolidated, and metamorphosed.

This mineral process, which has been now described, will no doubt revolt
the opinions of many of our chemists as well as naturalists; and I
should not have thought of transcribing it, but as an example of that
inconclusive reasoning which prevails in mineralogical writings upon
this subject.

But this is not all. We have, upon this occasion, a most remarkable
example of the fallaceous views that may be taken of things; and of the
danger to science when men of sense and observation form suppositions
for the explanation of appearances without that strict conformity with
the principles of natural philosophy which is requited on all occasions.
Both M. de Carosi, and also M. Macquart[40], to whom our author
communicated his ideas and proper specimens, assert, that from their
accurate experience, they find calcedony growing daily, not only in the
solid body of gypsum, etc. while in the mine, but also in the solid
stone when taktn out of the mine, and preserved in their cabinet.

[Note 40: Vid. Essais de Mineralogie par M. Macquart.]

What answer can be made to this positive testimony of these gentlemen,
by a person who has not seen any such a thing, and who has not the
opportunity of examining the cases in which those naturalists may have
perhaps been led into some delusion? Were I however to conjecture upon a
subject in which I have not any positive information, I should suppose
that some part of the calcedony, like the _oculus mundi_ when dipped in
water, may be so transparent, while containing some portion of humidity,
that it is not easily distinguishable from the gyp