74 McGEE MEMORIAL MEETING 



loam. This fact he attributed to the dual character of the ice ad- 

 vance. That he should have failed to detect the disparities in the 

 correlation of the several till-sheets is not to be wondered at, for no 

 detailed mapping of any part of the region had yet been done. It is, 

 then, no disparagement to his keen observational powers, his philo- 

 sophic insight into the order of nature, or his remarkable generalizing 

 faculties, to note this fact, for he chanced to be on the ground a full 

 decade too soon. Had he remained a few years longer in his native 

 State he doubtless would have been able to correctly correlate his 

 different drift-sections; but he was called into distant fields, and he 

 was unable until many years later to review his earlier work. 



The place where these depositional proofs of the complexity of the 

 Glacial period were first obtained is for several reasons of exceptional 

 interest. The section as originally displayed and described is now 

 fast disappearing. It is also this section which later gave the first 

 intimation of the eolic origin of American loess loams. It was here 

 that was found the first clue to the wonderful interlocking of the 

 southwestern loess deposit with the northeastern glacial tills. The 

 locality bids fair long to remain one of the classic geologic spots of 

 the continent. 



At this time and distance there are few of us who have any ade- 

 quate conception of the great difficulties which the Ice problem once 

 presented. Still fewer of us there are who understand from experi- 

 ence what it really means actively and determinedly to contend on 

 the battle-line of the unknowable. No one is in better position to 

 know intimately the intricacies of attempting to decipher the glacial 

 puzzles of that day than was McGee himself; and no one has stated 

 them more graphically. Here are his own words, as he sums up his 

 results in northeastern Iowa : 



The most startling induction of geology, if not of modern science, is the 

 glacial theory; but in the problem of these pages it is necessary to do more 

 than assume the existence and action of a great sheet of ice hundreds or 

 thousands of feet in thickness and hundreds or thousands of miles in ex- 

 tent. In order to explain the sum of the phenomena it is necessary to pic- 

 ture the great ice-sheet not only in its general form and extent, but in its 

 local features, its thickness, its direction and rate of movement over each 

 square league, the inclination of its surface both at top and bottom, and 



