BY PROF. DAVID, RICHARD HELMS, AND E. F. PITTMAN. 45 



and slate nearly coincides with the trend of the Lake Albina 

 Valley (N. & S.), the area west of this line being granite, and 

 that to the east slate, the granite erratics have invaded the slate 

 area, but no slate erratics were noticed as having trespassed into 

 the granite area. 



Here, however, the fact must be remembered that the carry of 

 moraine material, especially superficial moraine, as distinct from 

 ground moraine, usually indicates the direction of ice movement 

 during late7' phases of glaciation when the ice, of perhaps, 

 originally, a mer de glace, has through reduction in volume been 

 split up into a number of small glaciers, the direction of move- 

 ment of which has had to conform to the trend of the valleys, 

 whereas the ice of the mer de glace, of the earlier phase of glacia- 

 tion, may have radiated out from its centre of movement more or 

 less independent of the physical features of the underlying rock 

 surface. Judged by the phenomena of " strike- side " and " lee- 

 side" alone, it appeared to one of us (Professor David) that the 

 ice which produced the grooved pavements in the Lake Albina 

 Valley probably moved from the east towards the west. Further 

 observation, however, will be necessary before this interesting 

 question can be settled. 



We are now also in a better position to estimate the maximum 

 thickness of the ice in the Snowy Valley, at the time when the 

 ridge from Mount Townsend, west of Lake Albina, was being 

 glaciated. 



If the surface level of the ice at Ramshead Pass was not less 

 than perhaps 7,150 feet, as seems probable, it would have been 

 possible for it to have had a fall of 250 feet to the top of the 

 ridge west of Lake Albina, even if it be assumed that the ice on 

 that ridge was at least 50 feet thick. This would give a fall (the 

 distance being two miles) of in round numbers 1 in 42, that is 

 an angle of inclination for the surface of the glacier of 1^°. It 

 is doubtful, however, whether ice will flow at such a low angle of 

 slope as 1J°, 3° being usually about the minimum angle of surface 

 slope observed in moving ice.* 



* The Great Ice Age. 



