16 M. D'Omalius D'Hali.oy on 



This is sufficiently evident with regard to the beds con- 

 taining lymneae, and those of the inferior white lime- 

 stone, which will easily be refered to the lower part of the 

 Paris gypsum formation. But the assertion requires expla- 

 nation as it respects the green marls and mill stone without 

 shells. Messrs. Cuvier and Brongniart, when advancing 

 their opinion upon what they have named fresh water forma- 

 tions, have shewn that circumspection which always accom- 

 panies true merit ; it might be said that they feared being 

 reproached for having given too much importance to their 

 discovery, by enlarging the extent of this new mode of 

 formation ; thus they have only attributed it to those rocks 

 whose origin is evident, and have not hazarded any opinion 

 respecting those in which animal remains did not exist. Yet 

 now that the idea is more familiarized, and that these for- 

 mations are known to be very abundant on the surface of the 

 globe, and that it may be said, if the expression be per- 

 mitted, that they do not cost nature more than the marine 

 formations, now, I say, we may allow ourselves to speak 

 with more confidence. I believe, for example, I have 

 been able to shew* that the siliceous limestone belongs 

 to the same mode of formation as that containing lym- 

 nea; and other freshwater shells. + This opinion affords 

 a double motive for attributing the mill-stone without shells 

 to the same origin ; for this mill-stone is known, on the one 

 hand, to have a great affinity to certain flints of the siliceous 

 limestone formation, and that, on the other, it so much re- 

 sembles the mill-stone with freshwater shells, that the authors 

 of the mineral geography of the environs of Paris, were at 



* Notice of the existence of freshwater limestone in the departments of 

 the Cher, &c. Journal des Mines, tome xxxii, p. 43. 



+ New observations, which will be publislied in the second edition of 

 our Essay on the Mincralogical Geography of the Environs of Paris, 

 induce us entirely to admit M. d'Halloy's opinion. We have now direct 

 proofs that the siliceous limestone forms a part of the first or lower fresh- 

 water formation; but we cannot admit the resemblance of the upper 

 millstones, whether they contain shells or not, to the flint of the siliceous 

 limestone. (Note of the Editor of the Annales des Mines.) 



