Vol. 70.] THE GLACIAL GEOLOGY OF EAST LANCASHIRE. 231 



the position of the overflow-channels the extent of the lakes and 

 the direction of the drainage at different stages of the retreat of 

 the ice, he assumed that the relative heights of the surfaces of the 

 country were the same as at present. The speaker, however, 

 believed that the accumulation of man} 7- hundreds of feet of ice on 

 the lower ground would result in a depression of that portion of 

 the region relatively to the area left uncovered, while the subsequent 

 disappearance of the ice would cause a gradual reverse movement. 

 Such movements should be allowed for in dealing with the problems 

 presented by the facts recorded in the paper. 



The Author, in reply to Mr. Tiddeman, instanced the well- 

 defined boundary between the North- Western and the Bibblesdale 

 Drifts and the almost complete absence of boulders of igneous rocks 

 from the latter, as evidence that the ice-streams which deposited 

 these two types of Drift did not commingle to any appreciable 

 extent. 



The - Author informed Prof. David that marine deposits are 

 widely distributed among the Drift : thus, marine shells had been 

 obtained by Mr. Bolton from the Boulder Clay at Bacup. 



Replying to Dr. Evans, the Author stated that he had carefully 

 considered the influence of a possible warping of the land-surface 

 upon the overflow-channels, but that a simpler interpretation was 

 sufficient to explain the few difficulties that occur. 



In conclusion, he thanked the Fellows for their kind appreciation 

 of his work. 



Q. J. G. S. No. 278. 



