164 MAN AND THE GLACIAL PERIOD. 



" The glacial geology of the Trent Valley from Burton 

 to Nottingham has been ably dealt with by Mr. R. M. 

 Deeley,* who recognises a succession which may be gener- 

 alised as follows : (1.) A lower series containing rocks de- 

 rived from the Pennine chain ; (2.) A middle series con- 

 taining rocks from the eastward (chalky boulder-clay, 

 etc.) ; and (3.) An upper series with Pennine rocks. Mr. 

 Deeley thinks the Pennine debris may have been brought 

 by glaciers flowing down the valleys of the Dove, the Wye, 

 and the Derwent ; but, while recognising the importance 

 of the testimony adduced, especially that of the boulders, 

 I am compelled to reserve judgment upon this point until 

 something like moraines or other evidences of local glaciers 

 can be shown in those valleys. In their upper parts there 

 is not a sign of glaciation. Some of the deposits de- 

 scribed must have been laid down by land-ice ; while the 

 conformation of the country shows that during some stages 

 of glaciation a lake must have existed into which the dif- 

 ferent elements of the converging glaciers must have pro- 

 jected. This condition will account for the remarkable 

 commingling of boulders observed in some of the deposits. 

 Welsh, Cumbrian, and Scottish rocks occur in the western 

 portion of the Trent Valley. The overflow of the extra- 

 morainic lake would find its way into the valleys of the 

 Avon and Severn, and may be taken to account for the 

 abundance of flints in some of the gravels. 



" The Isle of Man. — This little island in mid-seas con- 

 stituted in the early stages of the Glacial epoch an inde- 

 pendent centre of glaciation, and from some of its valleys 

 ice-streams undoubtedly descended to the sea ; but with 

 the growth of the great Irish Sea Glacier the native ice 

 was merged in the invading mass, and at the climax of the 

 period the whole island was completely buried, even to its 

 highest peak (Snae Fell, 2,054 feet), beneath the ice. The 



* Quarterly Journal Geological Society, vol. xlii, p. 437. 



