77 



merits may be greatly abraded. The determination of 

 relative age in types cannot then safely be made in recent 

 deposits, but old types must be made out in old deposits 

 which cannot contain late ones. Wear and rudeness of 

 manufacture are no proof of age, and peculiarities of work 

 and shape without the assistance of geological position are 

 fallacious guides. 



Part II. 



It is not only to rivers, however, that so much and 

 apparently such rapid denudation has to be credited, even 

 with a rainfall much greater than at present. It is largely 

 to snow and ice. Therefore a few remarks as to the 

 evidence of their work is offered. I do not use the phrase 

 *'the glacial epoch" because any term implying a sharply 

 defined time in which this district was ice-bound is in- 

 applicable to the subject. Since the day the crests of our 

 hills emerged from a sea covered with bergs, ice and snow 

 have apparently held this county to the exclusion of a 

 truly genial climate, and although it is not strictly glacial 

 now, the improvement appears as if commencing but 

 yesterday, compared with the long ages of cold preceding 

 the remission. 



But first it is necessary to say a few words as to the 

 present mode of surface denudation. 



The growth of plants and tillage, &c., by disturbing 

 the soil at the surface, works it into a confused light 

 mass, usually of a dark grey colour which is known as 

 vegetable soil or humus, and which covers the ground. 

 The action of wind and rain with frost is apparent enough, 

 in tearing down rocks and washing them about, and this 

 also contributes to the formation of vegetable soil. The 

 finer particles are frequently left as flood loams on the 

 low land beside streams, while the coarser are borne down 

 by the current until checked by the sea. 



