262 MESSES. E. H. EASTALL AND J. EOMANES ON [Aug. 1909, 



more powerful and tended to displace the Scandinavian ice towards 

 the east. In the later stages of glaciation the supply of houlders of 

 Scottish origin appears to have diminished, since they are rare to 

 the east of Cambridge, and in the Chalky Boulder-Clay of East 

 Anglia local rocks predominate. 



The common occurrence of almost all rock-types at Hitchin and 

 Bedford must be due to the movement of the ice-sheets having 

 been controlled by the Chalk escarpment which runs in a general 

 south-westerly direction. 



The map which accompanies this paper (p. 251) is primarily in- 

 tended to show the distribution of the localities mentioned, but a 

 line has been drawn to indicate approximately the limit of the 

 common occurrence of rocks of Scottish origin. To the west of 

 this line they are abundant, while to the east of it they show a 

 rapid diminution. An exhaustive examination of several gravel- 

 pits at Chippenham, east of Newmarket, and near Mildenhall failed 

 to reveal the presence of any rocks of Scottish or other northern 

 origin. The line therefore probably represents the boundary be- 

 tween the Scottish and the Scandinavian ice when the former had 

 reached its maximum extension. 



Finally, we have much pleasure in expressing our gratitude to 

 Dr. Bonney for the kind help and encouragement which we have 

 received from him during the progress of this work. 



Discussion. 

 The Peesident (Prof. Sollas) commented on the value of the paper, 

 as affording exact knowledge concerning the distribution and origin 

 of boulders in the Drift. The Red Chalk, however, was represented 

 by travelled boulders much farther to the west than Bedford : he had 

 himself found examples of this rock in fluvio-glacial gravels exposed 

 in a pit near Burmington, not far from Chipping Norton. This 

 might possibly be explained by an originally greater extension to 

 the west of the outcrop of the Bed Chalk. Evidence seemed to. be 

 accumulating in favour of the occurrence of two glacial episodes in 

 these islands ; but, considering the results obtained in North America 

 and the Alps, it was surprising that so far no proof had been 

 obtained of a larger number. 



Prof. Bonney said that he felt sure the Society would agree that 

 they had not often listened to a paper more lucidly presented or 

 more valuable for its facts. These afforded opportunities for a very 

 wide discussion, but he would restrict himself, as far as possible, 

 to indicating their importance. The Authors had traced boulders 

 of Scandinavian rocks over a district extending beyond Cambridge 

 to Bedford and Hitchin. Supposing these to have entered by the 

 "Wash, that would be a journey, in. a direct line from the coast, of 

 nearly 55 miles in the one case and over 60 miles in the other. 

 Here, then, we had boulders, moving in a south-westerly direction, 

 crossing a stream from Scotland and Northern England, which had 



