Here is no question with regard to mere opinion, but to matter of fact; and, in this case, nothing is more evident, than that upon the surface of this earth, that is, in the examinable parts above the level of the sea, there is no transition either of calcareous bodies into flint, nor of flinty bodies into calcareous substance. Calcareous matter is constantly dissolved by water, when it is exposed to the washing of that fluid; and it is even dissolved out of the most perfect union or combination with siliceous substance, and the most solid composition of an insoluble body, as may be perceived in the decaying of feld-spar. A superficial view of flints, which have come out of a body of chalk, may have created such an opinion, which will not either bear the light of chemical or mineral investigation. The subject of these chalk flints will be minutely examined in its proper place. Our author has carefully examined the subject of flintification; and the country where he makes his observations would seem to be well disposed for such a research. He has had great opportunity and inclination to examine the subject which he writes upon; and he has given a distinct account of what be has seen. His description of the flintification of sand-stone is extremely interesting. I will therefore transcribe it, both as a valuable portion of natural history, and also in order to contrast this author's opinion, with regard to the means employed by nature in petrifying bodies, and that which I maintain to be the general consolidating operation of the globe. It is Section V. _Generation du Caillou du Silex du Grès, ou Pierre Sablonneuse_. "Tout grès est susceptible de cette métamorphose quant au grain et quant à la couleur; depuis la bréccia quartzeuse jusqu'à la pierre à rasoir; et depuis le grès blanc jusqu'au brun et presque noirâtre, tient ou non tient, dur, ou presque friable, c'est indifférent, toutes ces variétés donnent du silex, et surtout de la calcédoine, de la cornaline, et des agathes. Quant au ciment je l'y ai toujours remarqué calcaire et faisant effervescence avec les acides dans les endroits de la pierre qui n'étoient point encore changés; et jamais je n'ai vu ce changement dans du grès dont le ciment fut ou quartzeux ou argileux et réfractaire. Ainsi le ciment entre pour quelque chose dans ce changement.