478 OSBORN AND REEDS PREHISTORY OF MAN IN EUROPE 



Reeds diagram (figure 13), but unfortunately there is in America the 

 difficult "Iowan" question to complicate correlation ; until this is settled, 

 we do not know whether there were four or five glacial stages in America. 

 Our last, or Wisconsin, stage is so complex that it is not an easy matter 

 to correlate any part of it with the corresponding part of the Wiirm 

 stage of Europe or with the last glaciation of the north of Europe. 

 Leverett is unable to come to a definite opinion as to whether 'the Third 

 Glaciation of Europe is the correlative of the Illinoian or of the Iowan 

 of America ; the drift of the Third Glaciation in Germany and in Holland 

 is thin or scanty like our Iowan. This leaves the Second and First 

 glaciations of Europe, which seem to correlate with the Second and First 

 glaciations of America. 



(10) Coming to the question of harmonizing Penck's interpretations 

 with those of De Geer, Leverett is not clear as to the precise way in 

 which the one interpretation would fit into the other. There is in this 

 case the need for further careful field-work to clear up the matter satisfac- 

 torily. He states that he would not venture an opinion as to whether 

 the morainic system which separates De Geers "Gothiglacial" from his 

 "Finiglacial" is the correlative of Penck's moraines of the Daun sub- 

 stage, or whether the Daun moraines find their equivalent in later 

 moraines of Sweden. It is unlikely that the Daun moraines are older 

 than those which mark the division between Gothiglacial and Finiglacial 

 in Sweden. In De Geer's "Quaternary sea bottoms in western Sweden" 

 [and Antev's (1917.1) "Post-Glacial marine shell-beds in Bohuslan"' 

 we have evidence of remarkable diastrophic complexity, which would serve 

 to show the danger of following Deperet in his idea of simplicity of earth 

 movements. 



(11) Leverett notices that De Geer seems to think that his determina- 

 tion of 11,000 years for the time since the ice disappeared from the 

 northern part of the Baltic region is inconsistent with the American esti- 

 mate of over 30,000 years for the duration of Niagara Falls, and says 

 it is perhaps four times too long. This leads Leverett to remark that it 

 is likely that the ice in North America was reduced to a small area on 

 the east side of Hudson Bay at the time it was melting out of the north 

 end of the Baltic basin. In that case Niagara history is much longer. 

 The part that corresponds to the life of Lake Algonquin would entirely 

 precede it, and probably a considerable part of the life of Lake Nipissing. 

 It seems to Leverett, therefore, that we are under no necessity of dis 

 carding the estimate of about 30,000 years for the life of Niagara. The 

 estimate is, however, of a less refined nature than that made by De Geer, 

 and is so understood by those of us who have followed Spencer and also 



