268 M. Marcel de Serres on the Deposition of 



moellon always occurs superior to marls, which, in the oceanic 

 basins, and particularly in that of Paris, are themselves above 

 the calcaire grossier, there results that, if two parallel series be 

 established, representing the tertiary beds of the Paris basin, 

 and those of the Mediterranean basins, and proceeding from the 

 common term A, blue clayey marls, we should have in the Paris 

 basin, A blue marls. A' upper marine sands ; while, in the 

 Mediterranean basin we should have A blue marls. A' calcaire 

 moellon, A" marine sands ; a series which, having for its last 

 or upper term, a more elevated stage, indicates, in consequence, 

 that the sands of the Mediterranean formations have been de- 

 posited posteriorly to the sands of the Paris basin, or at least 

 that they have followed the deposition of calcareous rocky 

 banks, and have immediately succeeded the blue marls. 



But it is remarkable, that, while the second tertiary limestone 

 is wanting in most of the organic basins, and, in particular, in 

 that of Paris *, the first, or that lying under the bone gypsum, 

 seems not to have been deposited in the basins of the south of 

 France. In fact, most of those which are observed there, and 

 we might almost say all, belong to the second tertiary marine 

 limestone, or calcaire moellon. It is of this limestone that nearly 

 all the towns of the south of France are built -f, of which it will 

 suffice to mention Marseilles, Nimes, Montpellier, Beziers, and 

 Narbonne ; and that the most remarkable monuments, whether 

 ancient or modem, such as the triumphal arch of Orange, the 

 Pont du Gard, a portion of the Arense of Nimes, and the beau- 

 tiful aqueduct of the Peyrou, near Montpellier, have been con- 



• This assertion of M. Marcel de Serres is not correct, if we admit the 

 facts, such as they have been represented by the authors of the geological 

 description of the neighbourhood of Paris ; for the beds of solid limestone, 

 worked at Nanteuie-le-Haudouin, are considered, in that work, as belonging 

 to the marine formation lying above the gypsum containing bones ; and it 

 has not yet been proved that these naturalists have been deceived in this de- 

 termination, although some geologists appear inclined to consider the lime- 

 stone in question as the upper part of the calcaire grossier. 



+ It appears to be the same in Italy and Spain, where the calcaire moel- 

 lon, as well as the fresh-water limestone, are largely employed in building. 

 It would be useful to observe the different materials used in building, in or- 

 der to form a correct idea of the extent and development of the various for- 

 mations of a country. 



