458 MB. E. M. DEELEY ON THE PLEISTOCENE 



stage to the shelter afforded it by the high land to the east and 

 north. In this area the Chalky Clay is a silty de^^osit with a few 

 flints and qnartz or qnartzite pebbles. 



In addition to the evidence furnished by the presence of great 

 numbers of Cretaceous boulders in the Chalky Clay, an indication of 

 the direction of the ice-flow of this stage has, in one instance at 

 least, been left upon the rocky floor over which it moved. In the 

 Stanton tunnel, south of Nottingham, Mr. Teall found the Lias 

 limestone, upon which the Chalky Clay rested, striated from the 

 east-north-east to west-south-west. 



The Pennine rocks in this Boulder-clay have been derived from 

 the Older Pleistocene deposits over which the ice passed. If we 

 regarded them as having been derived directly from the Pennine 

 Chain we should be forced to admit an ice-flow from this direction 

 as weU — an inference totally at variance with the distribution of 

 the Boulder-clay and its associated deposits. 



The abnormal direction of the ice-flow most probably owed its 

 existence to a period of intense cold coupled with a considerable 

 depression of the Pennine axis. This would result in the approach 

 of Continental ice without the interference of local English glaciers. 



When I come to treat of the Chalky Gravel, it will be seen that I 

 regard the gravels in the west of Staffordshire as representing aU 

 the Middle Pleistocene stages, the Great Chalky Boulder-clay never 

 having been formed in the open water then existing on the west side 

 of the watershed. 



Upon the Melton Sand the subglacial streams deposited silty 

 sandy Boulder-clays in the partially land- and ice-locked valleys of 

 the east of England. In the majority of cases these sands and silty 

 Boulder-clays, together with older deposits, have been overridden 

 and converted into uustratified moraine. 



Although, as we have seen, the Great Chalky Boulder-clay is ex- 

 tensively distributed over the country and sections of it are of toler- 

 ably frequent occurrence, it generally maintains such a wonderfully 

 uniform lithological character that a description of all the sections 

 would involve constant repetition. I have therefore confined my- 

 self to sections where its relationship to deposits of other stages is 

 shown, or where it presents peculiar characteristics. In the pre- 

 vious stage those sections which show the passage of the Melton 

 Sand into Chalky Clay have been noticed. As these sections throw 

 considerable light upon the formation of this Boulder-clay, I propose 

 to state briefly the opinions at which I have arrived. 



The late Mr. Searles Y. Wood contended that the Great Chalky 

 Boulder-clay was formed by an ice-sheet depositing and overriding 

 the mud-bank which it formed at its seaward face. I am inclined 

 to support a somewhat similar view in preference to the theory 

 which attributes its formation wholly to land-ice. The presence 

 of stratified sand and gravel at its base is evidence that the Trent 

 basin was submerged when the ice-sheet advanced over it. It has 

 been argued that the absence of moUuscan remains is conclusive 

 evidence against its aquatic origin. This is, no doubt, a difficulty ; 



