80 T. BELT ON THE DRIFT OE DEVON AND CORNWALL. 



10. The Drift of Devon and Cornwall, its Origin, Correlation 

 with that of the South-east of England, and Place in the 

 Glacial Series. By Thomas Belt, Esq., E.G.S. (Read No- 

 vember 3, 1875.) 



[Abridged.] 



1. Introduction. — If we separate the southern counties from the 

 rest of England by a line following up the Thames to near Ciren- 

 cester, then along the southern boundary of Gloucestershire to the 

 Severn at the mouth of the Avon, we get an irregular strip of 

 country, shaped somewhat like a fish, of which Kent forms the 

 head, and Cornwall the tail. Excepting, perhaps, some of the 

 hills of Somersetshire, this part of England appears to have been 

 entirely free from the action of land-ice in the Glacial period; 

 and there are no glaciated rock-surfaces, no true till, and no mo- 

 raines. Along with, and, as I believe, in consequence of, this 

 freedom from ice-action, there is also an utter absence of those frag- 

 mentary marine shells which, further north, are found in drift on 

 both the eastern and western coasts, where the great streams of ice 

 from the north, after crossing arms or channels of the sea, advanced 

 upon the land — and the presence of which, as they are never found 

 above heights to which the circumpolar ice reached, and for other 

 reasons I have urged, is due, not to the submergence of the land 

 beneath the ocean, but to portions of the ocean-bed having been 

 carried up by the rising ice*. 



The purpose of the present paper is to describe the surface -geology 

 of the counties of Devon and Cornwall, to examine the theories that 

 have been proposed to account for the origin of the drift beds, to give 

 my own views on the same question, and to support them by apply- 

 ing the theory to the drift beds of the whole of the south of 

 England. 



2. Drift beds of Devon and Cornwall. — The superficial deposits 

 of Devon and Cornwall consist of two divisions : — a. Upland de- 

 posits (on the tops and sides of hills, mostly more than 300 feet above 

 the present sea-level, and reaching up to about 1200 . feet ; these 

 consist of gravels, clays, and transported boulders left in frag- 

 mentary patches, and evidently have had at one time a much 

 greater extension) ; b. Lowland deposits (gravels, clays, and boulders 

 spread out in more persistent and regular beds at low levels ; they 

 are most strongly developed in the valleys, but are not confined to 

 them). 



a. Upland deposits. — The whole of the surface of Dartmoor is 

 sprinkled over with large blocks of granite, some of which are of 

 enormous size. On the road from Tavistock to Princetown, about a 

 mile west of Merriville bridge, one of the numerous excavations 

 made in search of stream-tin exhibits the following section : — 



* Nature, May 14 & 28, 1874. 



