474 OSBORN AND REEDS PREHISTORY OE MAN IN EUROPE 



a slight amount of stream-work to remove this barrier and lower it to 

 the 30-meter terrace, 



(3) An important feature of Deperet' s theory is that he attributes the 

 elevation and depression of the shorelines chiefly to upward or downward 

 movements of the sea (eustatic theory ), as distinguished from upward 

 or downward movements of the land (epirogenic theory). Leverett 

 remarks, therefore, that it may be profitable to attempt to set forth the 

 amount of variation in level (that is, eustatic) which the sea is likely 

 to have had, and thus determine whether it is necessary to call in any 

 uplifts and subsidences of the land (that is, diastrophic ) . The fluctua- 

 tions of the sea seem to depend entirely upon the amount abstracted in 

 forming ice-sheets, and in returning the water again, by the melting of 

 the ice. On this subject Penck has written several papers, but probably 

 the best discussion is that by Daly in his paper, '"The Glacial-control 

 theory of coral reefs" (1915.1). On page 173 it is pointed out that an 

 average lowering of the sea of 25 fathoms (46 meters) is likely to have 

 occurred in all the stages of glaciation. This he later raised a little, 

 making it 50-60 meters, or a maximum of about 200 feet. If the earth 

 should become ice-free the sea level would probably be raised somewhere 

 between 11 and 37 meters above the present sea level. This wide range 

 is due to our lack of knowledge of the amount of ice in the existing ice- 

 sheets. There may then, in preglacial time, have been a sealevel from 

 11 to 37 meters higher than the present sealevel. In the glacial stages 

 the sea may have been 50 meters or 60 meters lower than the present. 

 In the interglacial stages the sealevel is likely to have been about the same 

 as at present, unless the Antarctic and Greenland ice-sheets were com- 

 pletely melted, in which case it would have stood 11-37 meters higher 

 than at present. 



(4) According to Leverett, it follows that if there were no diastrophic 

 movements, the shorelines of the several glacial stages would have been 

 so far below the present sealevel that they would have no exposure in 

 the region discussed by Deperet. So that any reference he makes to 

 shorelines of glacial age that are visible must involve the work of dias- 

 trophism to bring them to view. It appears to Leverett that Deperet 

 is radically wrong in trying to rule out diastrophism, and at "the same 

 time to have the glacial shorelines high enough to be visible above the 

 present sealevel. It is, perhaps, of still more importance to note that if 

 there had been no diastrophism the sea could not have reached a level 

 more than 11 to 37 meters above the present, and that, too, in an ice-free 

 condition of the earth. The Quaternary marine shorelines at 100 meters 

 and 55-60 meters are thus entirely too high to be in accord with an 



