532 



SCIENCE. 



[N. S. Vol. II. No. 43. 



lation, covering the Aftonian forest beds, 

 and extending again into Iowa, to a distance 

 of 350 miles or more from its most northern 

 indentation by the Aftonian retreat, and 

 re-advancing about 150 miles in Illinois, 

 while its boundary eastward from Ohio 

 probably remained with little change. 



The Polandian stage of renewed growth 

 of the European ice sheet, probably ad- 

 vancing its boundaries in some portions 

 hundreds of miles from the Helvetian re- 

 treat. 



II. The Champlain EjJoch. 



5. Champlain subsidence; ISTeudeckian 

 STAGE. Depression of the ice-burdened 

 areas mostly somewhat below their present 

 heights, as shown by fossiliferous marine 

 beds overlying the glacial drift up to 300 

 feet above the sea in Maine, 560 feet at 

 Montreal, 300 to 400 feet from south to 

 north in the basin of Lake Champlain, 300 

 to 500 feet southwest of Hudson and James 

 bays, and similar or less altitudes on the 

 coasts of British Columbia, the British 

 Isles, Germany, Scandinavia and Spitz- 

 bergen. 



Glacial recession from the lowan boun- 

 daries was rapid under the temperate (and 

 in summers warm or hot) climate belong- 

 ing to the more southern parts of the drift- 

 bearing areas when reduced from their 

 great preglacial elevation to their present 

 height or lower. The finer portion of the 

 englacial drift, swept down from the 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 Mis- 

 soui'i, the Mississippi and the Rhine. 

 Marine beds reaching to a maximum height 

 of about 375 feet at Neudeck, in western 

 Prussia, give the name of this stage. 



6. Wisconsin stage. Moderate reeleva- 

 tion of the land in the northern United 

 States and Canada, advancing as a perma- 



nent wave from south to north and north- 

 east ; continued retreat of the ice along 

 most of its extent, but its maximum ad- 

 vance in southern ISTew England, with fluc- 

 tuations and the formation of prominent 

 marginal moraines ; great glacial lakes on 

 the northern borders of the United States. 

 The Mecklenburgian stage in Europe. 

 Conspicuous moraine accumulations in 

 Sweden, Denmark, Germany and Finland, 

 on the southern and eastern margins of the 

 great Baltic glacier. ISTo extensive glacial 

 re-advance between the lowan and Wiscon- 

 sin stages, either in North America or 

 Eui-ope. 



7. Waeeen stage. Maximum extent of 

 the glacial Lake Warren, held on its north- 

 east side by the retreating ice border, one 

 expanse of water, as mapped by Spencer, 

 Lawson, Taylor, Gilbert and others, 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, IST. Y., corre- 

 lated by Leverett with the Lockport mor- 

 raine. 



This and later American stages, all of 

 minor importance and duration in compari- 

 son with the jjreceding, cannot probably be 

 shown to be equivalent with Geikie's Euro- 

 pean divisions belonging in the same time. 



8. Toronto stage. Slight glacial oscil- 

 lations, with temperate climate nearly as 

 now, at Toronto and Scai'boro', Out., indi- 

 cated by interbedded deposits of till and 

 fossiliferous stratified gravel, sand and claj\ 

 Although the waning ice sheet still occa- 

 pied a vast area on the northeast, and twice 

 re-advanced, with deposition of much till, 

 during the formation of the Scarboro' fos- 

 siliferous drift series, the climate then, de- 

 termined bjr the Champlain low altitude of 

 the land, bj^ the proximity of the large gla- 

 cial lake Algonquin, succeeding the larger 

 lake Warren, and by the eastward and 

 northeastward surface atmospheric currents 



