382 CLIMATIC CONDITIONS OF THE GLACIAL EPOCH. 



and on or near the summits of the mountains, especially in New England, of 

 well-defined strias which do not run in conformity with the topography, but 

 cross the ranges obliquely, holding approximately the same general southerly 

 direction over a wide area of country, as if made by a body of ice not 

 hampered in its movement by local conditions. 



Those Avho have endeavored to account for the presence of such a glacial 

 covering over so large a part of the country, or to fix the place where it 

 originated and assign a cause for its motion in the direction demanded, have 

 had a difficult task to execute. The geologists who, as already mentioned, 

 have simply appealed to the condition of things in Greenland, as a perfectly 

 satisfactory illustration of the peculiarities of the Glacial epoch in North- 

 eastern America, and as removing all the difficulties which these present, are 

 greatly in error, as must have been made apparent by what has been stated 

 in the preceding pages. There is no motion of the glaciers in the Arctic 

 regions except down hill, and nothing abnormal in the mode of occurrence 

 of either snow or ice. 



Some have considered that the ice of Greenland extended down so far as 

 to cover the glaciated region of the Northern Drift. This theory seems not 

 only not in harmony with the direction of the striation and the general 

 topographical character of the intervening region, but to be from every 

 other point of view a climatological impossibility. Others have maintained 

 that the sudden ushering in of a period of intense cold would have caused 

 an immense fall of snow, and that this, becoming converted into ice, would 

 move in all directions from the region of greatest precipitation, because there 

 the snow would be heaped up so as to create a sufficient slope of itself with- 

 out the necessity of a previously existing high region for the purpose. Ac- 

 cordingly such areas of extraordinary precipitation have been located where 

 the divergence of the striation made it convenient to have them, regardless 

 of climatic and topographical conditions. Nothing approach ing this occurs 

 at the present day; and it is impossible to understand how it could have hap- 

 pened in former times, when, as we have every reason to believe, the laws 

 governing precipitation must have been similar to what they now ai-e. 



Professor Dana, whose authority is almost exclusively followed by the 

 younger workers in geology in this country, believes that the region from 

 which the continental glacier advanced was situated " over the Canada 

 water-shed, nearly north of Montreal." But this was only " its southern por- 

 tion." fioin which the " broad ice-range stretched northward and northeast- 



