OBJECTIONS TO THE PROPOSED THEORY. 367 



composes des memes roches que celles que les rivieres actuelles 

 entrainent dans les vallees, et sont les debris des seules mon- 

 tagnes de la Lozin, du Tanargue et du Me'zene, qui entourent 

 le bassin du Vivarais."* 



Again : 



"Le diluvium des vallees de 1'Aisne et de 1'Aire ne ren- 

 ferme que les debris plus ou moms roules des terrains que ces 

 rivieres coupent dans leur cours."f 



Finally, Mr. Prestwich has pointed out that the same thing 

 holds good in various English rivers. The conclusion 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 direc- 

 tion unique, mais qu'ils convergaient des bords du bassin vers 

 son centre, suivant les depressions preexistantes, et que leur 

 elevation ou leur force de transport ne suffisait pas pour faire 

 passer les debris quils cliarriaient d'une de ces valUes dans 



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, as well as the French 

 geologists generally, from adopting an explanation apparently 

 so simple and so obvious. These difficulties appear to have 



* D'Archiac, 1. c. p. 160. 



t Malbos. Bull. Geol. vol. iii. p. 631. $ 1. c. p. 163. 



