itted that every solid body is crystallised, we thus know no more of
the geology of this earth, or understand as little of the general theory
of mineral concretion, as we did before;--we cannot, from that, say
whether it be by the operation of solution or of fusion which had
produced the perceived effect.

[Note 37: Journal de Physique; Avril 1753.]

M. de Carosi has wrote a treatise upon certain petrifactions[38]. In the
doctrine of this treatise there is something new or extraordinary. It
will therefore be proper to make some observations on it.

[Note 38: Sur la Generation du Silex et du Quartz en partie.
Observations faites en Pologne 1783, a Cracovie.]

The object of this treatise is to describe the generation of silex and
quartz, with their modifications or compositions, formed within mineral
bodies of a different substance. The natural history contained in this
little treatise is well described and sufficiently interesting. But It
is chiefly in order to examine the means which, according to the theory
of this treatise, are employed in petrifying bodies, that I consider it
in this place.

The first section of this treatise has for title, _Generation du Caillou
et du Quartz de la terre calcaire pure_. It may be worth while to
compare the natural history of this part of the earth with the flint and
chert found in our chalk and lime-stone countries. I shall therefore
transcribe what is worth observing upon that subject (p. 5.).

"Nous rencontrons chez nous dans les parties le plus montagneuses, et
les moins couvertes de terreau, ou tout-au plus de sable, entre de purs
rochers calcaires une quantite incroyable de cailloux (silex) tant en
boules, que veines, couches, et debris. Au premier coup d'oeil l'on
s'imagine que ce font des debris de montagnes eloignees, qui y furent
amenes par les eaux, mais, en examinant la chose de plus pres, on est
convaincu, que ce sont tout au contraire, des parties detachees des
montagnes de la contree. Car il y a sur presque toute l'etendue de nos
montagnes calcaires une couche, ou pour mieux dire, un banc compose
de plusieurs couches de base calcaire, mais qui ou sont parsemees
irregulierement de boules, de rognons, de veines, et de petits filons
de silex, ou qui contiennent cette pierre en filon, veines, et couches
paralleles, et regulierement disposees. Les boules et rognons de silex
y font depuis moins de la grandeur d'une petite noisette, jusqu'au
diametre de plus de six pouce