8/6 EDITORIAL 



From the close of the later Wisconsin to the present, - - i unit 

 From the earliest Wisconsin (Shelbyville moraine) 



to the present, - - - - - - - - 2>^ units 



From the lowan to the present, ------ 5 " 



From the Illinois invasion of Iowa to the present, - - - 8 " 



From the Kansan to the present, - - - - - 15 " 



From the sub-Aftonian (Albertan) to the present, - - - x " 



Four of the investigators previously named who have seen 

 this memorandum are disposed to increase the figure for the 

 Kansan, and some of them would alter other figures in the same 

 direction, with perhaps a reduction of the estimate for the 

 lowan. After the estimate had been made it was observed that 

 the intervals form a symmetrical diminishing series. The 

 temperature variations of the period might therefore be repre- 

 sented by an oscillating curve with declining waves. 



T. C. C. 



