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 

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

 Lve the name of this Neudeckian stage. 



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



)resent height, advanced in the northern United States and 



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



:eeping nearly equal pace with the continued retreat of the ice 



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



.tlantic to the Rocky Mountains the mainly retreating but often 



luctuating ice margin formed many belts of knolly and hilly 



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



iver basins which slope northward or northeastward were ob- 



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



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



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



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



>recursors of the present five great lakes from Superior to 



)ntario. The very grand development of the marginal moraines 



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



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



md 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 



nithern and eastern margins of the great Baltic glacier. 



During the maximum extent of the glacial Lake Warren, held 



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



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



ippears to have reached from Lake Superior over Lakes Michigan, 



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



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



r ork, is correlated by Leverett with the Lockport moraine. 



'his and later American stages, all of minor importance and 



duration in comparison with the preceding, can not probably be 



3hown to be equivalent with Geikie's European divisions belong- 



ig 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 f ossilif- 



jrous 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 



