68 THE DENUDANTS, ETC. 



is evident that previous to that time, the last occupier 

 of the hills was ice ; consequently we are forced to 

 believe that in such elevated situation the glaciers died 

 out, leaving little or no rock detritus after them. 



At one time we put much more faith in the abrad- 

 ing powers of ice than we now do, but experience 

 teaches that first impressions are sometimes deceptive, 

 and that often the more a subject is studied the more 

 apparent becomes the necessity of modifying first 

 ideas. Undoubtedly, under favourable circumstances, 

 ice must be capable of executing a considerable 

 amount of work. This is also true of all the other 

 denudants, but none of them can operate with advan- 

 tage unless it has received aid from its fellow- workers. 

 If ice, as long as it continued moving, had the same 

 denuding powers, we could have no such thing as an 

 empty rock basin, as the ice when it finally melted 

 would be full of blocks and debris, and would more 

 or less fill up the hollow. If, however, ice has less 

 opportunities of denuding the longer it works, we 

 might in time have an ice pretty nearly pure, so 

 that when it finally melted there would only be a 

 mere trace of drift left by it; and this seems to 

 have been the case in many of the rock basins in 

 lar-Connaught, as the only deposit in them is a 

 peaty one of a quite recent age. 



