456 OSCAR H. HERS HEY 



that case the longest feeders would have come from the heart of 

 the serpentine area on the east and the conditions for the dis- 

 tribution of the serpentine would have been at least equally as 

 favorable as for the granite. The serpentine-bearing drift appears 

 to me to be more nearly normal than the other. It is fair to 

 acknowledge that the earliest glaciation undoubtedly incorporated 

 in its drift preglacial river deposits in which serpentine occurred 

 in proportion lo its outcrop area but this does not fully explain 

 the contrast. It was the peculiar or abnormal character of the 

 later glaciers which caused granite erratics to be present in the 

 drift in a proportion entirely in excess of the outcrop area that 

 caused the difference. 



Further, the more uniform temperature of a low altitude 

 climate would enable the early glaciers to run farther down the 

 valleys even though thinner at a given distance from the end 

 than the later glaciers and perhaps containing no more ice. 

 Earlier glaciation was less vigorous than later glaciation. Prob- 

 ably the climate was colder at a given altitude than during the 

 last glacial stage and the ice was sluggish. There seems to have 

 been less tendency for the formation of large moraines than later. 



At about the time of the last glacial stage, the country was 

 uplifted and brought under high altitude conditions. The glaciers 

 formed rapidly in the shadow of the peaks, but when they ran 

 out into the open, into strong sunlight, they were soon pinched 

 off by melting. 



The character of the climate during the last glacial stage was 

 similar to the present, except for a general lower temperature. 

 Therefore, the altitude may have been at least as high as the 

 present. The character of the climate during an early glacial 

 stage seems to have been similar to that which now belongs to 

 a lower altitude than the present, except for a general lower 

 temperature. These mountains might have been, in an early 

 glacial stage, 3,000 feet lower than at present, but not more, as a 

 depression to that amount would nearly submerge the Summer- 

 ville basin. Glaciation occurring at such an altitude would, 

 judging from observations made near the coast, yield products 

 similar to the earlier drift discussed in this paper. 



