LECTURES. 59 



places. Everywhere is evidence of a great glacial 

 sheet, of immense thickness, passing over mountains 

 five and six thousand feet high, which left boulders 

 of a similar nature upon their tops and each of their 

 sides. I think that the ice in some places must have 

 been at least fifteen thousand feet thick. It moved 

 in a North-South direction. In Siberia, Asia, and in 

 the United States, gigantic animals were found im- 

 bedded in the ice, in perfect preservation, and show- 

 ing the contents of the stomach, proving that they 

 must have been overpowered suddenly, perhaps by 

 frost. I think that our large and small rivers are the 

 result of the melting of these glaciers. 



"Drift phenomena must be studied locally. There 

 must have occurred local ice which distributed itself 

 in plains different from that which came down from 

 the mountains. The idea that the glacial period was 

 simply an extension of the Arctic ice is nullified by 

 the fact that at the southernmost limit of that ice 

 sheet is a large moraine. The drift wanes in dis- 

 tinctness from north southward. This period, there- 

 fore, was not an enlargement of the northern glaciers. 

 In America are intimations of local glaciers, but they 

 are few; for example, in the White Mountains, on the 

 coast of Maine, and especially at Mt. Desert. The 

 characteristic of drift in America is that it extends 

 over a plain evenly, and without indications of lat- 

 eral moraines. The hills on the borders of Lake 

 Superior are scarred over their whole surface, slope and 

 summit. Indications that this action has been even 

 from north southward is, that the south side of the 

 rocks is not polished, but the boulders are rough and 

 unmarked. In some places there are deviations of 

 much less extent running from 20 to 30, sometimes 

 almost at right angles with the main line: these are 

 indications of local glaciers these often run north- 

 west and southeast. Another peculiarity of Ameri- 

 can glaciers is that most of our boulders are rounded 

 those of Europe and Scotland are angular; where 

 we have circumscribed glaciers we have rounded 



