[Note 39: The description of those insulated siliceous bodies, containing in their closed cavities all the usual concretions of calcedony and crystals, as well as full of small pyrites floating in the solid flint, are extremely interesting to a mineral system, or such a geological theory as should explain the present state of things in those strata that had been formed by deposits of known materials at the bottom of the sea; they are indeed such appearances as may be found, more or less, in all consolidated strata. But it is this author's explanation of that petrifaction which is our present object to consider; and, as he is so particular in giving us his theory upon the subject, it is easy to detect the error of his reasoning. Were those naturalists who explain things only in general, by saying that water is the agent, and infiltration the means employed by nature;--were these naturalists, I say, to give us as particular a description of their process, it would appear as inconsistent with the nature of things as that which we have from this author, who examines nature very minutely, and who sees distinctly that the infiltrating theory is inapplicable for the explanation of those petrifactions.] The third section has for title, "_Generation du Silex et Quartz de la Pierre Puante_." Here we find an example worthy of being recorded, as contributing to throw great light upon those mineral operations; however, the opinion of our author and mine, upon this subject, differ widely. He proceeds thus: "Cette pierre n'est, comme chacun le sçait, qu'une pierre calcaire contenant du bitume. "Nos montagnes n'en contiennent seulement pas de simples couches, mais il y en a même de grandes bancs fort épais. "Le caillou, ou silex qui s'y génère, forme, tantôt de gros blocs informes, qui occupent des cavités dans l'intérieure des montagnes, tantôt, enfin, en forme de filons. "J'ai remarqué cette métamorphose sur trois endroits différens, dans chacun des quels la nature a autrement opéré.