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 taken out of the mine, and preserved in their cabinet.
Footnote 40:[ (return) ] Vid. Essais de Minéralogie 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 gypsum in which it is concreted; but that in having the humidity evaporated, by being taken out of the mine and exposed to the dry air, those portions of calcedony, which did not before appear, may be perceived by becoming more opaque[41].
Footnote 41:[ (return) ] From the description given in this treatise, and from the drawings both of M. de Carosi and M. Macquart, I find a very valuable inference to be made, so much the more interesting, as I have not found any example of the like before. This arises from the intimate connection which is here to be perceived between agate and gypsum. Now, upon this principle, that the agate-calcedony had been formed by fusion, a truth which, from the general testimony of minerals, I must presume, it is plain, that those nodules of gypsum had been in the fluid state of fusion among those marly strata, and that the gypseous bodies had been penetrated variously with the siliceous substance of the calcedony.
The description of those siliceous penetrations of gypsum is followed by this conclusion: "En voila assez, je crois pour faire voir que le silex ci-décrit est effectivement une émanation du gypse, et non pas une matière hétérogène amenée d'autre part et déposée, ou nous la voyons." In this instance our author had convinced himself that the calcedony concretions had not been formed, as he and other mineralists had before supposed, by means of infiltration; he has not, however, substituted any thing more intelligible in its stead. I do not pretend that we understand mineral fusion; but only that such mineral fusion is a thing demonstrable upon a thousand occasions; and that thus is to be explained the petrification and consolidation of the porous and naturally incoherent strata of the earth.
There is, however, a subject in which I can more freely accuse this author of being deceived. This naturalist says, that calcareous stones become silex by a certain chemical operation; and that those flinty bodies, in being exposed upon the surface of the earth, out of their natural bed, are again, by a contrary chemical operation, changed from flint to a calcareous substance. I will give it in his own words, (p. 56.)
"Cela dit, venons au fait. Tout silex progénéré de chaux, détaché de son lieu natal, et exposé aux changemens de saisons, s'amollit, reçoit de crevasses, perd sa transparence, devient, enfin, tout-à-fait opaque, le phlogistique s'en évapore, l'acide en est détaché, lavé, et de terre vitrescible, qu'il étoit, il redevient chaux, comme il étoit auparavant."
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 Sabloneuse.
"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.