G. W. Bulman — Glacial Geology. 405 



are described by Mr. Clement Eeid ^ as " well-laminated ripple- 

 marked clays and marls with seams of fine false-bedded sand, 

 deposited on the hummocky surface of the First Till," and are in 

 turn overlaid by the Second Till. They have not yielded any 

 fossils except shell fragments derived from the Boulder Clay, and 

 Mr. Eeid is led to the following conclusions as to their origin : 



" The absence of all signs of life appears to point to a freshwater 

 origin for these beds, and for the similar unfossiliferous laminated 

 clays which are so common in glacial deposits in other parts of 

 England. Modern glacial lakes show a similar barren character " 

 (p. 88). 



Finally, Mr. Eeid does not consider that they afford evidence of 

 an inter-glacial warm climate : 



"After the deposition of the First Till, the ice appears to have 

 retreated, perhaps only for a few miles, leaving the Boulder Clay 

 with a curious hummocky surface, over which was deposited ripple- 

 marked clay and marl in thin beds. This deposit seems to be 

 glacial mud, such as would flow from beneath the ice, and be spread 

 over the surface lately abandoned. Such an evenly-bedded loam 

 cannot be taken as sufiScient evidence of an inter-glacial warm 

 climate, though it is traceable nearly continuously for at least four 

 miles ; for at the present day glaciers of the Alps and the ice of 

 Greenland advance and retreat short distances without any very 

 marked cause." ^ 



Nor do the sands which come between the second Till and the 

 Boulder clay or Stony loam afford any stronger evidence. They are 

 described as " fine false-bedded loamy sands, always chalky and 

 carboniferous, and of a peculiar pale tint, easily recognizable ; " 

 and they rest on the eroded surface of the Till, Like the beds 

 between the first and second Tills they have yielded no fossils. 



And this so-called Boulder-clay is a deposit of rather a curious 

 character. In general composition according to Mr. Eeid it is much 

 like the underlying till, but it contains bedded masses of sand of 

 which the bedding is often vertical. It perhaps marks an advance 

 of the ice less pronounced than that which produced the second Till, 

 and which permitted more freely the action of streams. 



The inconclusive nature of the evidence derived from the inter- 

 calated sands and gravels is further illustrated by a study of those 

 of South Lancashire as described by Mr. A. Strahan (Q.J.G.S. vol. 

 42, p. 362). 



According to Mr. Strahan these sands and gravels " usually 

 underlie Boulder-clay." Yet there is no evidence of glacial action 

 beneath them : " Lastly, it is almost invariably under Boulder-clay 

 that the rock has been found to be striated. Though the sands and 

 gravels are included among the glacial deposits, the Boulder-clays 

 alone show direct evidence of the action of ice." On the Welsh 

 coast, on the other hand, Boulder-clay is described lying beneath 

 marine drift: — "The occurrence of a tough blue basement clay 



1 Geology of the Country around Cromer, Mem. Geol. Surv. 



2 Ditto, p. 91. 



