James Croll — Transport of Wastdale Crag Blocks. 19 



In my paper on tlie Boulder-clay of Caithness, I had represented 

 the ice entering the North Sea from the east coast of Scotland and 

 England, as all passing round the North of Scotland. But the 

 reviewer suggests that the ice entering at places to the south of, say, 

 Flamborough Head, would be deflected southwards instead of north- 

 wards, and thus ]Dass over England. " It is improbable, however," 

 says the writer, " that this joint ice-sheet would, as Mr. Croll sup- 

 poses, all find its way round the north of Scotland into the deep sea. 

 The southern uplands of Scotland, and probably also the mountains 

 of Northumberland, propelled, during the coldest part of the Glacial 

 period, a land ice-sheet in an eastward direction. This sheet would 

 be met by another streaming outward from the south-western part of 

 Norway — in a diametrically opposite direction. In other words, an 

 imaginary line might be drawn representing the course of some 

 particular boulder in the moraine profonde from England met by a 

 boulder from Norway, in the same straight line. With a dense ice- 

 sheet to the north of this line, and an open plain to the south, it is 

 clear that all the ice travelling east or west from points to the south 

 of the starting-points of our two boulders, would be ' shed ' off to 

 the south. There would be a point somewhere along the line, at 

 which the ice would turn as on a pivot — this point being nearer 

 England or Scandinavia, as the degree of pressure exercised by the 

 respective ice-sheets should determine. There is very little doubt 

 that the point in question would be nearer England. Further, the 

 direction of the joint ice-sheet could not be due south, unless the 

 pressure of the component ice-sheets should be exactly equal. In 

 the event of that from Scandinavia pressing with greater force, the 

 direction would be to the south-west. This is the direction in 

 which the drifts described by Mr. Lucy have travelled." 



I can perceive no physical objection to this modification of the 

 theory. What the ice seeks is the path of least resistance, and along 

 this path it will move, whether it may lie to the south or to the 

 north. And it is not at all improbable that an outlet to the ice 

 would be foxmd along the natural hollow formed by the Yalleys of 

 the Trent, Avon, and Severn. Ice moving in this direction would 

 no doubt pass down the Bristol Channel and thence into the Atlantic. 



Might not the shedding of the North of England ice-sheet 

 to the north and south, somewhere not far from Stainmoor, ac- 

 count for the remarkable fact pointed out by Mr. Searles Wood, 

 that the Boulder-clay, with Shap boulders, to the north of the 

 Wold is destitute of Chalk, while on the other hand, the 

 chalky Boulder-clay to the south of the Wold is destitute of 

 Shap boulders ? The ice which passed over Wastdale Crag moved 

 to the E.N.E., and did not cross the Chalk of the Wold ; while 

 the ice which bent round to the south by the Wold came from the 

 district lying to the south of Wastdale Crag, and, consequently, did 

 not carry with it any of the granite from that Crag. In fact, Mr. 

 Searles Wood has himself represented on the map accompanying his 

 Memoir this shedding of the ice north and south. 



These theoretical considerations are, of course, advanced for what 



