CAUSES, STAGES, AND TIME OF THE ICE AGE. 367 



ice fields by the abundant waters of their melting and of rains, 

 was spread on the lower lands and along valleys in front of the 

 departing ice as the loess of the Missouri, the Mississippi, and the 

 Rhine. Marine beds reaching a maximum height of about three 

 hundred and seventy-five feet at Neudeck, in western Prussia, 

 give the name of this Neudeckian stage. 



A moderate re- elevation of the land, to approximately its 

 present height, advanced in the northern United States and 

 Canada as a permanent wave from south to north and northeast, 

 keeping nearly equal pace with the continued retreat of the ice 

 along most of its extent. Throughout all the distance from the 

 Atlantic to the Rocky Mountains the mainly retreating but often 

 fluctuating ice margin formed many belts of knolly and hilly 

 drift, called marginal moraines. It is also to be noted that the 

 river basins which slope northward or northeastward were ob- 

 structed by the waning ice sheet, so that they were temporarily 

 filled by great glacial lakes, as Lake Agassiz, in the basin of the 

 Red River of the North and of Lake Winnipeg, and a very remark- 

 able series of lakes in the basin of the St. Lawrence, the glacial 

 precursors of the present five great lakes from Superior to 

 Ontario. The very grand development of the marginal moraines 

 in Wisconsin (scarcely, however, surpassing Minnesota) led to the 

 application of the name Wisconsin to this stage of the Ice age 

 and to its drift. In Europe this is named by Geikie the Meck- 

 lenburgian stage. Conspicuous moraine accumulations were 

 formed in Sweden, Denmark, Germany, and Finland, on the 

 southern and eastern margins of the great Baltic glacier. 



During the maximum extent of the glacial Lake Warren, held 

 on its northeast side by the retreating ice border, one expanse of 

 water, as mapped by Spencer, Lawson, Taylor, Gilbert, and others, 

 appears to have reached from Lake Superior over Lakes Michigan, 

 Huron, and Erie, to the southwestern part of Lake Ontario. Its 

 latest southern beach, traced east by Gilbert to Crittenden, New 

 York, is correlated by Leverett with the Lockport moraine. 

 This and later American stages, all of minor importance and 

 duration in comparison with the preceding, can not probably be 

 shown to be equivalent with Geikie's European divisions belong- 

 ing to the same time. 



In the next ensuing Toronto stage, slight glacial oscillations, 

 with temperate climate nearly as now at Toronto and Scarborough, 

 Ontario, are indicated by interbedded deposits of till and fossilif- 

 erous stratified gravel, sand, and clay. Although the waning ice 

 sheet still occupied a vast area on the northeast, and twice read- 

 vanced with deposition of much till during the formation of the 

 Scarborough f ossilif erous drift series, the climate then, determined 

 by the Champlain low altitude of the land, by the proximity of 



