244 



A Yorkshire Glacial Problem. 



of ice action in tlie rest of the district that is most remarkable, 

 especially to those who have tramped through the clean cut 

 overflow valleys of Cleveland and the Hambleton Hills. It is 

 hard to believe that the evidence in the two extreme ends of the 

 county must be ascribed to the same period. 



This, of course, sug-g-ests that the g-laciation of the North of 

 England may have been a more complex affair than we had 

 been led to believe. Evidence is beginning to accumulate which 

 tends to indicate that there may have been an inter-glacial 

 period of some sort. That is, there was some disturbing or 

 modifying influence at work, on the removal of which the 

 numerous ice sheets had changed their direction of flow and 

 carried a diff"erent assemblage of erratics. A hint of this was 

 given many years ago when the late Prof. Green described the 

 Barnsley Boulder Clay. Here we had two distinct beds with 

 a difference in the included boulders. Mr. J. W. Stather's 

 investigation of the vertical range of the Cheviot and Carbon- 

 iferous Limestone erratics in the East Yorkshire Boulder Clay 

 indicated a very great diff"erence between the upper Red Clay 

 and the lower hard ash-coloured clay, while the eroded surface 

 of the lower bed, with its overlying clay, gravel, and sand, on 

 which the Red Clay rests, is very suggestive. Recent cuttings 

 in the Derwent Valley, Derbyshire, disclosed several interesting 

 sections showing an upper red bed and a lower purple Boulder 

 Clay, each with its characteristic erratics. This evidence of 

 ■a break and change in the glacial conditions is too widespread 

 to be ignored.'-'" 



For the solution of the problem we can only review the 

 somewhat limited data available, (i) We have the Crosspool 

 erratics very suggestive of a connection with the Vale of York 

 glacier. (2) The almost entire absence of drift in the district 

 S. and S.W. (3) Occurrence of erratics of a similar character 

 towards the N. and N.E. This all points to the deposit having 



*It must be borne in mind that whilst there unquestionably is evidence 

 of one or more divisions in the glacial series, representing- different con- 

 ditions ot" ice-flow, etc., it does not necessarily imply the existence of an 

 Interglacial Epoch, i.e., a distinct warm period between two separate and 

 distinct Glacial Epochs. At present the view generally accepted is that 

 put forward by P. F. Kendall in Wright's ' Man and the Glacial Period,' 

 viz., that the so-called Inter-glacial beds can be accounted for on the 

 assumption of one Ice Ag"e, during- which there were many oscillations in 

 the movement of the ice-front, some quite possibly being of very long 

 duration. Additional evidence may, of course, necessitate a chang-e in this 

 view. — Eds. 



Naturalist, 



