54 



Probably our hills were still surrounded if not covered to their 

 highest points by glaciers, the gravels of the valleys being to some 

 extent the trail or drift consequent thereon. It is true we have 

 no evidence of glacial striation on our rocks, but their soft nature 

 is such that, had this been the case, atmospheric and other causes 

 would long since have obliterated them. 



But in another way I think I perceive evidence of glacial action. 

 It is well known that not only have we proof of this action on 

 the striated surfaces and edges of the rocks that have come within 

 its influence, but that also whei'e icebergs have stranded, or the 

 glaciers, as they have melted, have been moving forward, the beds 

 at their base have been deeply gi'ooved or channeled thereby. 

 Just this state of things exists in the stiff liassic clays on which 

 the mammal drift now lies in the Bath basin. Whenever it is 

 exposed it is seen to be cut up by deep and long continued 

 furrows, which are now filled by the trail or drift already 

 described. Evidence of this is also shown from the fact that whilst 

 the physical conditions of the district were the same as at the 

 present, bodies of fresh water must have occupied the table lands 

 around, for in no other way can, I think, the presence of fresh 

 water shells, mammalian and other remains, be accounted for, in 

 association with bog iron ore in most of our oolitic fissures. 



Man, then, it is now generally admitted co-existed with the 

 mammoth, the woolly rhinoceros, the cave tiger, the hyena, and 

 the other remains so abundantly found in our caverns and gravels. 

 As I have proceeded it will have occurred to you from the changes 

 indicated that his advent must be put back to a greatly 

 extended period. How far back this era must be placed will in 

 conclusion be a point of interest for our consideration. 



Speculations on this head come rather within the province of 

 the mathematician and the astronomer than the geologist, and I 

 shall have to refer you to a work just published by Mr. Croll, on 

 " The Physical Causes of Change and Time," in the Philosophical 

 Magazine. This gentleman has, in a series of tables, shown the 

 earth's eccentricity for the past 3,000,000 of years, and also for 

 1,000,000 years to come. In this way he has proved that there were 

 periods of great duration when our winters exceeded the summers. 



