Leverett — Weathering and Erosion as Time Measures. 355 



terize portions of the Later Wisconsin moraines of the same 

 general region. This fact, and the fact that the outer portion 

 of the Earlier Wisconsin drift in Illinois carries a thin coating 

 of loess, is thought to indicate that a certain degree of aridity 

 prevailed during the culmination and the withdrawal of the 

 ice of this early part of the Wisconsin stage of glaciation. 

 The relatively arid conditions may account to some degree for 

 the poor development of drainage lines, which otherwise seem 

 rather inconsistent with the amount of toning down of knolls 

 and filling of basins which took place on the Earlier Wisconsin 

 moraines. The filling of basins would be accomplished rap- 

 idly under conditions of aridity, as is exemplified in our arid 

 western region. It is well, therefore, to keep this climatic 

 factor in mind when making a comparison of the amount of 

 erosion of the Earlier Wisconsin drift with the somewhat 

 younger Later Wisconsin drift. 



As may be seen from the above table (p. 351), the Wisconsin 

 drift is the only one of the series named in the Labrador and 

 Keewatin fields which is correlated with certainty. There is 

 a continuous belt of moraines connecting the Labrador and 

 Keewatin fields, but these moraines are of Later Wisconsin 

 age, and it yet remains to be determined whether the Earlier 

 Wisconsin drift is exposed outside the Later Wisconsin in the 

 Keewatin field. 



Probable European Correlatives of the Wisconsin Drift. 



In the European fields, Skandinavian and Alpine, and also 

 in Great Britain, there is a drift sheet which corresponds 

 closely in the amount of weathering with our Later Wisconsin 

 drift, while certain of the outer moraines of the north Ger- 

 man lowland and of Great Britain seem to correspond with 

 our Earlier Wisconsin. The complexity of the last stage of 

 glaciation seems, therefore, about as great in northwestern 

 Europe as in North America. In the Alps the Wiirm drift 

 has a freshness of contour very similar to that of the Later 

 Wisconsin moraines, while the " Verwaschene Wiirm," which 

 lies outside the Wiirm proper at a few points in northern 

 Switzerland, and also at a few points on the southern side of the 

 Alps, has a similar toning down to that displayed by our 

 Earlier Wisconsin moraines, of which it may prove to be the 

 correlative. 



The Upper Diluvium of the JSforth German Lowland is much 

 more extensive than the limits assigned by Geikie to the fourth 

 or Mecklenburgian drift. The great Baltic ridge seems, as 

 has been interpreted by several German geologists, to lie well 

 within the limits of the last glaciation, though it certainly 



