FOSSIL INVERTEBRATED ANIMALS. 465 



coarse shelly limestone, and which are foreign to the strata of 

 the environs of Paris ; but they are worn and mutilated. Frag- 

 ments of siliceous wood are also found there, and many bodies 

 carried away from the chalk strata. 



The waters which swept off the enormous masses of rock 

 in this valley, and which deposited rolled flints as far as the 

 elevation of Montrouge and that of the forest of St. Germain, 

 must have been considerably elevated above those places to 

 have been capable of making such deposition upon them. 



We cannot doubt but that a violent current, which admits 

 neither of appreciation nor comparison, deposited this stratum. 

 Regarding the direction of this current, some doubts indeed 

 may be raised, but there is every reason to believe that it 

 proceeded in the direction of the actual course of the Seine. 

 The volume of water was so considerable, that the declivity of 

 the soil which causes that river to flow in the direction which 

 it at present takes, might not perhaps be sufficient to establish 

 this conjecture ; but the pieces of red granite which have been 

 found at Issy and the Bois de Boulogne, which are also found 

 in the basins of the Oise and Marne, and which are thought 

 to have been detached from those of Burgundy, countenance 

 the opinion that the torrent came from that side rather than 

 from the side of Normandy, where no similar granite is to be 

 found. 



The rounded flints, which we find on the shores of the sea, 

 have been forced to take this form by the periodical return of 

 the flux and reflux, which rolls them for a considerable time in 

 the same place. But this is not the case with stones of the 

 stratum of which we have been speaking, which have been 

 worn and rounded by rolling together in the direction of the 

 torrent, and constantly removing to a greater distance from the 

 place where they were first seized by the inundation. 



The sand with which the bottom of the Seine is spread at 

 the present day is composed, like that of the plain of Grenelle, 

 of small fragments of granite or of quartz, which have remained 



2 H 



