DISCUSSION. 



Professor N. S. Shaler : I should like to ask Mr. Russell if the facts 

 observed by him in Alaska are consistent with the supposition that the non- 

 glaciated portion of the country was beneath the level of the sea during the 

 glacial epoch '? 



Mr. Russell: My observations do not favor such an hypothesis. Just 

 where the coast line was in Alaska during the glacial epoch remains to be 

 determined. 



President T. C. Chamberlin : I should like to inquire as to the relative 

 age of the glaciation. Is it young or old? 



Mr. Russell: The records are extremely fresh. On limestone hills near 

 Lake Lebarge, which could not have been protected by superficial deposits 

 since the glaciers retreated, fine striations still remain. The glaciation is 

 perhaps fresher in appearance than it is in the Sierra Nevada mountains. 



President Chamberlin : The observations of Mr. Russell have a very 

 important bearing on our general conceptions of the Pleistocene period, 

 especially as to its great agency. It seems that we can now safely say that 

 this agency was excluded from the northwestern corner of our continent. It 

 also appears from evidence from Siberia that glaciers may be excluded from 

 that still more extended region ; for, while there are evidences of glaciation 

 in the mountains on the southern border of Siberia, it does not appear that 

 the extent there was more than would be accounted for by a slight increase 

 in the precipitation of that region. The Pleistocene glaciation gathered 

 about the north Atlantic, while the region of the north Pacific was free from it. 



Professor Shaler : I am very glad to testify along with the last speaker 

 as to the importance of these observations. I think they enable us to bring 

 the glacial question — the question of the last glacial period — down to a very 

 simple issue. I think I could safely undertake to re-create a glacial period 

 in this part of the continent, if we could only manage the rainfall, leaving 

 the temperature as it is. We have, for instance, at Mount Washington the 

 conditions which just approach glaciation. I am inclined to think if the 

 average rainfall there were twelve inches greater than at present, that 

 amount coming in the form of snow, we would be likely to have a small 

 glacial cap on the top of the mountain. Such an ice-cap would breed its 

 own climate. A considerable increase of the snow-fall in New England 

 would, I think, most likely set up glaciation over a large part of its surface. 



President Chamberlin: Coincident with this limitation in distribution, 

 we are approaching a demonstration — if we have not already reached it — 

 that in the first glacial epoch pre-eminently, and in the second glacial 

 epoch measurably, there was a low condition of the surface; and the old 



XXI— Bun. Gf.ol. Soc. Am., Vol. 1, 1889. (155 



