570 Correspondence. 



Altogether "we believe tlie history of the cavern deposits on the 

 Lesse to belong to that ancient river history which geologists now 

 comprehend as the period of the loio-level drifts of Mr. Prestwich; a 

 period when, as we know, in this country, climatal adaptations, and 

 many of the animals of the period, were very different from the 

 present. Since that period the great mammalia which once inhabited 

 Europe have become extinct, and all our rivers, like the river Lesse, 

 flow in deeper hollows excavated in the hard strata which forms the 

 bottom of their valley. 



We consider the drift phenomena of the caverns on the Lesse to 

 bear the same relation to the existing physical condition of the 

 country as our old Severn and Avon loio-level valley drifts bear to 

 the existing rivers, their silted up lakes and alluvial plains. We see 

 no reason for attributing a more ancient history to the human remains 

 of the "Trou de Naulette," than to the numerous other examples 

 given by Sir Charles Lyell in his "Antiquity of Man," where human 

 bones, or human implements, have been found in cavern deposits 

 associated with the remains of the extinct animals. 



The principal interest attached to the caves on the Lesse is owing 

 to the great number of human relics that have been found there ; 

 and I may here observe, that the particular cave, in which the very 

 remarkable jaw was found, lying close by the bones of the rhinoceros, 

 is considered by Dr. Dupont to have been a den of the hysena, for 

 here were found the coprolites of that animal, and also a considerable 

 number of gnawed bones of elephant and other animals. The 

 rhinoceros bone in question presents strong marks of the hyaena's 

 canines. 



C OI^IilB S IPO IsTIDIE nisTCIE] . 



RIVER-DENUDATION OF VALLEYS. 

 To the Editor of the Geological Magazine. 



Sir, — The attempt of Mr. Green, in the November number of the 

 Magazine, to render ridiculous my explanation of the physical facts 

 connected with the valleys of Lancashire and Yorkshire, which facts 

 he allows I have accurately given, will scarcely be acknowledged as 

 a fair way of meeting my arguments. 



My views — which I advanced with diffidence — may be erroneous, 

 and whenever they are shown to be so on physical grounds, I am 

 ready to abandon them ; but, as it seems to me, the attempt of my 

 colleague to prove them illogical has only resulted in exposing him- 

 self to the charge of being still more illogical, and of mis-stating my 

 argument. 



Taking the case of Todmorden valley, he puts my argument thus : 



" We know that Jones, heavily shod, etc., has often been seen in 

 the neighbourhood of what is now the vale of Todmorden. 



"We do not know for certain that any stream has run through 

 this valley. 



" It is, therefore, less incredible that the valley should have been 



