328 J. D. Dana — New England and the Upper 



Fourthly. Among the prominent glacial investigators, one 

 has been on both sides of the question. Having studied 

 glacial phenomena long and faithfully in New England, 

 Warren Upham explained the facts which he had observed on 

 the theory of one advancing and retreating glacier, and found 

 evidence of its terminal moraine and another halt moraine in 

 the islands south of New England and on part of the adjoin- 

 ing main land. But after some years of study in Minnesota 

 and the neighboring States and over the region northward 

 through Manitoba, he adopted the theory of two glacial epochs. 

 Returning again to New England and revising the facts there 

 presented, he was led back to his former opinion, as he has 

 announced in his recent papers. Since no geologist in America 

 is better acquainted with the facts on the two sides, or more 

 faithful and earnest in glacial investigation, these changes in 

 his conclusions have special interest. 



Fifthly. As the above review of facts makes manifest, the 

 division among geologists on the question, and the differences 

 in intensity of opinion, are to a large extent geographical. 



The cause of this sectional divergence in views deserves con- 

 sideration. The writer has come to the conclusion that the 

 cause is largely meteorological : that the geological differences in 

 opinion are a consequence not only of differences in observed 

 facts in the west as compared with those of the east, but back 

 of these, in meteorological differences in the two regions dur- 

 ing the Glacial -period. 



At the present time the glaciated areas of eastern and central 

 North America differ widely in hygrometric conditions. For 

 New England and three-fourths of the State of New York 

 the mean annual precipitation, according to Schott's maps, 

 varies from 38 to 42 inches — a broad coast region, nearly half 

 the breadth of New England, excepted over which it amounts 

 in some parts to 50 inches ; while for Wisconsin, it varies from 

 32 to 38 inches, and for the larger part of Minnesota, from 20 

 to 32 inches. North of New England in British America 

 east of Hudson's Bay the annual precipitation is from 32 to 

 20 inches ; but to the west of this region over Manitoba and 

 beyond, it is 20 to 10 inches. 



Here is a large present difference between the eastern and 

 western regions, affecting snow-falls as well as rain-falls. 



Now in the Glacial period, this eastern region would not 

 only have had the same great advantage as now of proximity 

 to the Atlantic Ocean, but also that of greater height than 

 now. The evidence appears to be conclusive that along the 

 Atlantic side of the continent from southern New England 



