500 W. UPHAM STAGES OF THE ICE AGE 



dons climatic changes implied in the glaciation conld permit complete 

 repetition of the continental ice-sheets in America and Europe, and ex- 

 tend them in each case to so nearly the same maximum limits in the 

 earlier and later parts of the Glacial period. It is better, until proofs are 

 obtained more fully in the central regions of the drift areas on each con- 

 tinent, to regard their time of glaciation as one and continuous, with 

 much areal oscillation, such as is proverbial of weather, during both the 

 general stages of growth and departure. 



All the ground that was relinquished by the ice-sheet during its Afto- 

 nian recession, which doubtless reached north to the southern part of the 

 Eed Eiver valley, nearly to the head of the Mississippi, and to the vicinity 

 of James Bay, became again deeply enveloped by the snowfall and ice- 

 fields of the Kansan and Illinoian stages, spreading in the basin of the 

 Missouri and Mississippi rivers somewhat farther than the previous Ne- 

 braskan limit. The Keewatin glacial outflow southward extended at the 

 maximum of the Kansan stage to the lower part of the Kansas River, to 

 the Missouri below Kansas City, and to the Mississippi on the northeast 

 boundary of Missouri. In the States of Illinois, Indiana, and Ohio the 

 Labradorian glaciation later attained its maximum of the Illinoian stage, 

 depositing the outermost drift over the northern watershed of the Ohio 

 River, and in the vicinity of Cincinnati it extended beyond this river into 

 the edge of Kentucky. 



Along the upper course of the Missouri the border of the Keewatin ice- 

 field at its Kansan maximum limit crossed that river to the drift bound- 

 ary in Nebraska, South and North Dakota, and eastern Montana. Far- 

 ther west the Cordilleran outflow of both the Nebraskan and Kansan 

 stages seems generally to have been surpassed by the Wisconsin stage, 

 which is thought also to have produced the greatest extension of local 

 glaciers upon the more southern Cordilleran ranges, to Colorado and 

 California. 



In the greater part of New York and New England, where interglacial 

 formations are very scantily developed or absent, the icefield of Nebraskan 

 time may have persisted through the Aftonian interval and forward dur- 

 ing the Kansan and later glacial stages to the Champlain stage, in which 

 the Glacial period ended. The maximum thickness and area of the ice- 

 sheet east of the Hudson River was reached by the late Wisconsin mo- 

 raine-forming stage. 



Much drift that had been eroded and borne far from its sources during 

 the very long Nebraskan glaciation, having afterward in Aftonian time 

 rested from its travel, was again in part gathered up into the Kansan, 



