138 MR. E. HULL ON THE VESTIGES OF EXTINCT 



subsequent to the Northern Drift. Bearing this in mind, 

 and recollecting the clear evidence which the roches mou- 

 tonnees, frequently enclosed by marine drift, afford of 

 having been formed by glaciers before the deposition of 

 the same formation, we have here a sequence of three dis- 

 tinct, though connected, periods : the first, in which the 

 glaciers descended down the main valleys; the second, 

 when the land of Wales had sunk at least 2300 feet, du- 

 ring which the Till or Drift was spread over the flanks of 

 the mountains; and the third, when the land had been 

 elevated, and glaciers again descended from the heights 

 ploughing out the Drift, and forming moraines for embank- 

 ments to lakes and tarns. 



The striations of the rock surfaces of Anglesea appear 

 to be altogether disconnected with the glacier system of 

 Caernarvonshire. The strise and grooves generally range 

 W. 30° S.,* and are probably the result of icebergs strand- 

 ing and scoring the bottom as they floated from the 

 mountains of Westmoreland. 



The Lake District. — The existence of former glaciers 

 amongst the mountains of Westmoreland and Cumberland 

 having been announced by Agassizf and Buckland,f these 

 great observers have left but very slight details of the phe- 

 nomena upon which their conclusions were established. 

 The truth is, that the evidence on this subject for all the 

 highland districts of Britain is of so analogous a nature, 

 and so incapable of being misinterpreted, that a few special 

 cases were enough for their general purpose, that of estab- 

 lishing an interesting and novel theory. 



Both these authors, however, notice in several localities 

 on the southern and eastern sides of the district, examples 

 of scored and grooved surfaces, and the mammilar bosses 



* Ramsay, Quarterly Journal, vol. viii. p. 374. 



t Proceedings oftlie Geological Society, vol. iii. pt. ii. p. 328. 



X Hid. pp. 345 et seq. 



