292 OBJECTIONS TO THE 



deduced by M. D'Archiac from the consideration of these 

 observations, and specially from those concerning the valley 

 of the Seine, is " Que les courants diluviens ne venaient 

 point d'une direction unique mais qu'ils convergaient des 

 bords du bassin vers son centre, suivant les depressions pre- 

 existantes, et que leur elevation ou leur force de transport ne 

 suffisait pas pour faire passer les debris qu'ils charriaient d'une 

 de ces vallees dans Vautre" * 



Considering, however, all these facts, remembering that 

 the constituents of these river- drift gravels, are, in all cases, 

 derived from beds now in situ along the valley, that they 

 have not only followed the lines of these valleys, but have 

 done so in the direction of the present waterflow, and 

 without in any case passing across from one river system 

 to another, it seems quite unnecessary to call in the assistance 

 of diluvial waves, or indeed any other agency than that of 

 the rivers themselves. 



There are, however, certain facts in the case which have 

 been regarded by most geologists as fatal to this hypothesis, 

 and which prevented M. D'Archiac, and we may add the 

 French geologists generally, from adopting an explanation so 

 simple and so obvious. These difficulties appear to have 

 been two-fold ; or at least the two principal were, firstly, 

 the large sandstone blocks which are scattered throughout 

 the river gravels of Northern and Central France ; and, 

 secondly, the height at which the upper level gravels stand 

 above the present water line. We will consider these two 

 objections separately. 



It must be admitted that the presence of the sandstone blocks 

 in the gravels appear at first sight to be irreconcileable with 

 our hypothesis. In some places they occur frequently, and are 

 of considerable size ; the largest I have myself seen is repre- 

 sented in the section, fig. 141, taken close to the railway 

 * i.e. p. 163. 



