SOME UNSOLVED PROBLEMS IN GEOLOGY. 69 



Arctic explorers, holds that it is probable that the interior of Green- 

 land is itself verdant in summer, and is at this moment preparing to 

 attempt to reach this interior oasis. Nor is it difficult, with the aid of 

 the facts cited by Woeickoff and Whitney,* to perceive the cause of 

 the exceptional condition of Greenland. To give ice and snow in 

 large quantities, two conditions are required first, atmospheric hu- 

 midity ; and, secondly, cold precipitating regions. Both of these 

 conditions meet in Greenland. Its high coast-ranges receive and con- 

 dense the humidity from the sea on both sides of it and to the south. 

 Hence the vast accumulation of its coast snow-fields, and the intense 

 discharge of the glaciers emptying out of its valleys. When extreme 

 glacialists point to Greenland, and ask us to believe that in the glacial 

 age the whole continent of North America as far south as the latitude 

 of 40 was covered with a continental glacier, in some places several 

 thousands of feet thick, we may well ask, first, what evidence there is 

 that Greenland, or even the Antarctic Continent, at present shows such 

 a condition ; and, secondly, whether there exists a possibility that the 

 interior of a great continent could ever receive so large an amount of 

 precipitation as that required. So far as present knowledge exists, it 

 is certain that the meteorologist and the physicist must answer both 

 questions in the negative. In short, perpetual snow and glaciers must 

 be local, and can not be continental, because of the vast amount of 

 evaporation and condensation required. These can only be possible 

 where comparatively warm seas supply moisture to cold and elevated 

 land ; and this supply can not, in the nature of things, penetrate far 

 inland. The actual condition of interior Asia and interior America in 

 the higher northern latitudes affords positive proof of this. In a state 

 of partial submergence of our northern continents, we can readily 

 imagine glaciation by the combined action of local glaciers and great 

 ice-floes ; but, in whatever way the phenomena of the bowlder clay 

 and of the so-called terminal moraines are to be accounted for, the 

 theory of a continuous continental glacier must be given up. 



I can not better indicate the general bearing of facts, as they pre- 

 sent themselves to my mind in connection with this subject, than by 

 referring to a paper by Dr. G. M. Dawson on the distribution of drift 

 over the great Canadian plains east of the Rocky Mountains. f I am 

 the more inclined to refer to this, because of its recency, and because 

 I have so often repeated similar conclusions as to Eastern Canada and 

 the region of the Great Lakes. 



The great interior plain of Western Canada, between the Lauren- 

 tian axis on the east and the Rocky Mountains on the west, is seven 

 hundred miles in breadth, and is covered with glacial drift, presenting 

 one of the greatest examples of this deposit in the world. Proceed- 



*" Memoir on Glaciers," Geological Society of Berlin, 1881; "Climatic Changes," 

 Boston, 1883. 



\ " Science," July 1, 1883. 



