, verdatres,
rougeatres, jaunatres, bleuatres, tachetees, veinees, etc. Leur clarte
n'est pas moins variable, que leur couleur, il y en a de presqu'opaques,
comme aussi de presque transparentes, sur tout la, ou la calcedoine
predomine.

"Le quartz s'y trouve comme dans les pierres de la premiere section, c,
a, d, crystallise, en groupes dans de petites cavites; quelquefois aussi
en veines. La calcedoine y est de meme, ou bien en mamelons, ou bien en
stalactites, lorsqu'elle a de la place pour s'y deposer.

"Un phenomene encore plus curieux que cela est cette belle pyrite
sulphureuse jaune, comme de l'or, qui est quelquefois parsemee par tout
la substance de petrifications agathisees, et qui apparemment y fut
deposee apres la dite metamorphose a la faveur des petits pores, qui y
etoient restes ouverts."

I would beg that mineralists, who use such language as this, would
consider if it contains a distinct idea of the operation which they
would thereby describe, or if it does not contain either a contradiction
or an inconceivable proposition. It supposes a calcareous body to be
metamorphosed, somehow by means of the mountain acid, into a siliceous
body. But, finding many bodies of pyrites contained within that solid
flint, it is said, that, when the calcareous body was flintified, there
were left in it cavities which were afterwards filled with pyrites. Let
us reflect a moment upon this doctrine. These cavities were first open
to the outside of the flinty body; but now the pyrites with which they
had been filled is insulated in the solid flint. Here three things are
required; first, The calcareous body is to be flintified, at the same
time leaving the body full of small cavities open to the outside;
secondly, These cavities are to be filled with pyrites; lastly, These
mineral bodies are to be so inclosed within the flint, as to leave no
vestige of the former processes. This marly mountain itself, which had
been formed of loose materials gathered together at the bottom of the
sea, was first to be filled with pyrites, in various shapes, by means of
the phlogistic and the acid of the mountain. Here is proposed to us an
operation which is totally unknown, or of which we have no kind of
idea. But, let us suppose pyrites formed in this mountain, (of whatever
chemical substances), by means of water; Why should water again undo
that pyrites, in order to form other concretions? And, Why should the
flint be formed first with cavi