Tratis. N. V. Ac. Sci. 158 June 4, 



Alpine summits and the Arctic and Antarctic continents. To widen 

 and intensify the conditions which now produce glaciers would neces- 

 sarily induce an extension of snow and ice. Second, on the Cascade 

 mountains we find a copious precipitation of rain and snow, but no ice, 

 where great glaciers formerly existed. The snow-line is 7,000 feet 

 above the ocean ; and there the temperature is high enough to permit 

 the most vigorous growth of trees and smaller plants. The fir forests 

 here meet the snow-banks in actual mechanical conflict, and the front 

 ranks of trees, though of good size, are weighed down by the snow, 

 and grow prone and interlaced upon the ground. 



The snow-fields rise 3,000 to 4,000 feet above the snow-line, and there 

 are miniature glaciers at the heads of the valleys — relics of the great 

 glaciers that once filled these valleys to their mouths. The precipita- 

 tion remains, the snow fall remains, but the glaciers are gone ! 



Here we have just the conditions most favorable to the formation of 

 glaciers, according to the theory of those who regard them as thermal 

 phenomena, but no glaciers, because of the high annual temperature. 

 With a depression of temperature, which should cause the ram-bearing 

 winds from the Pacific to do all the year what they now do only in 

 winter, viz., heap up snow on the highlands, the mountain slopes and 

 draining valleys would soon be occupied by glaciers again. So if win- 

 ter conditions could be made permanent on the great water-shed of the 

 Canadian Highlands, and the flow of the St. Lawrence, Mississippi and 

 Red River be retained in the form of snow and ice, glaciers would 

 soon fill again the lake basins, over-ride the highest summits, and cover 

 with an ice-sheet all the old glaciated areas. Even if the evaporation 

 from adjacent seas was somewhat diminished by the cold, that would 

 not change the result, though it would prolong the lime. If the evap- 

 oration in the region surrounding the North and South poles is, as we 

 have demonstrative evidence, sufficient to produce continental glaciers 

 on Greenland and the Antarctic continent, it requires no argument to 

 show that like conditions would produce like results in what is now the 

 temperate zone. 



The relations which the ancient great lakes of the Far West bore to 

 the former glaciation of the same region is an interesting subject of in- 

 quiry. It has been suggested that it is the relation of cause and effect, 

 but this seems hardly possible. They may have been synchronous, and 

 to some extent co-operative phenomena, but the relationship was rather 

 fraternal than filial. The cause of the former great breadth of water- 

 surface was either an increased precipitation or a diminished evapora- 

 tion. We not only have no record of any change in the relationship of 

 the North American continent to the Pacific, in modern times geolog- 

 ically speaking, but the evidence against any change is conclusive. 



