654 THE ICE AGE IN NORTH AMERICA. 



Winchell as belonging to the age of the glacial deposits 

 which here line the trough of the Mississippi. A little later, 

 Miss Franc E. Babbitt examined the locality more carefully, 

 and found a large number of additional implements. 

 Her discoveries were first reported in a paper read before 

 the Minnesota Historical Society in February, 1880. A 

 fuller account was presented at the meeting of the Ameri- 

 can Association for the Advancement of Science at Minne- 

 apolis in August, 1883. At that time also the subject was 

 thoroughly canvassed by the numerous geologists present, 

 and a paper was read upon the subject by Mr. Warren 

 Upham, to whose work upon the surface geology of the 

 Northwest we have so often had occasion to refer. To get 

 the whole subject before our readers we can do no better 

 than to append the principal portion of an elaborate paper 

 read by Mr. Upham before the Boston Society of Natural 

 History, on December 31, 1887, which will be the more 

 readily understood by reason of the previous chapters of the 

 present volume detailing the general results of Mr. Upham's 

 work in that region : 



The recession of the ice-sheet of the last Glacial epoch in 

 Minnesota seems to be clearly marked by as many as ten 

 stages of halt or readvance, in which distinct marginal mo- 

 raines were accumulated, besides the moraine on the limits 

 of its farthest extent. Six summers of geologic field-work 

 in that State have been spent by the writer chiefly in the 

 examination of its glacial and modified drift, of these mo- 

 raines, and of the beaches and deltas of the glacial Lake 

 Agassi z, which was formed in the valley of the Eed River of 

 the North and of Lake Winnipeg by the barrier of the 

 departing ice-sheet. In their bearings upon this subject, my 

 observation and study of that region convince me that the 

 rude implements and fragments of quartz discovered at Little 

 Falls were overspread by the glacial flood-plain of the Mis- 

 sissippi River, while most of the northern half of Minnesota 

 was still covered by the ice, contemporaneously with its for- 

 mation of the massive moraines of the Leaf Hills and with 



