HOW THE SOIL CAME. 33 



The whole continent of Greenland, about sixty times 

 the size of the State of Massachusetts, is now filled by 

 one vast bed of ice which is in many places more than 

 two thousand feet deep, and is spilling out through the 

 openings of the coast into Baffin's Bay and the Atlantic. 

 All these ice fields are doing the same things that were 

 formerly done upon the northern part of the United 

 States. 



Competent scientists are now studying them very 

 carefully; and all their evidence brings an overwhelming; 

 conviction to those who for the last twenty-five years 

 have been suspecting that the whole upper part of the 

 continent of North America was at one time a field o£ 

 moving ice. 



How it came to be so is now fairly well determined. 



Warren Upham, of the United States Geological Sur- 

 vey, has clearly shown that the northern region of our 

 continent was elevated before the glacial epoch as much 

 as one thousand feet in some places above its present 

 level. 



What heaving of the earth caused it may some day 

 be guessed ; but the fact of it is affirmed by such careful 

 students as Prof. George Frederick Wright and Prof. 

 William O. Crosby and many others. 



This great elevation pushed the heads of the White 

 Mountains so high into the cold that perpetual snow 

 clothed them. That snow chilled the air so that the 

 winter seasons grew longer and consequently a greater 

 amount of snow and ice formed to be melted during the 

 shortened summer. In the course of many years this, 

 combined with other causes,* produced glaciers in the 

 White Mountains as they now are in the Alps, 



*Mr. Upham calls attention to the fact that the Isthmus of Panama was not 

 elevated until about the time of the glacial epoch, and says : " It may be true 

 therefore, that the submergence of this isthmus was one of the causes of the 

 glacial period, the continuation of the equatorial oceanic current westward into 

 the Pacific having greatly diminished or wholly diverted the Gulf Stream, which 



