- GLACIAL DRIFTS IN MINNESOTA 
401 
‘"mixed” till, the planing over of a moraine under a clay-till 
“over-ridden moraine,” clay moraines, and sandy or mixed mo¬ 
raines, give a large range of phenomena. 
Since the Wisconsin Kewatin and the Kansan Kewatin glaciers 
came from the northwest, and presumably from the same place by 
the same route and over the same shales, the till of this last 
glacier, which is most like that of the old one, is taken to be the 
normal product. More and smaller boulders, more gravel de¬ 
posits, and higher outwash plains are seemingly the natural results 
of this glacier’s coming over the weathered and washed surface 
of the older one. In line with this view is the observed fact that 
the Patrician glacier with a still more stony drift, built morainic 
hills that are rougher, deeper and more obstructive than are even 
those of the Wisconsin Patrician materials. 
In conclusion it may be noted that only glaciers coming from 
the Kewatin centre went beyond the south boundary line of Min¬ 
nesota on the west of the “Driftless Area.” Of these, the first, 
or Nebraskan, may be characterized as that which moved most 
easily and farthest. The second, or Kansan, is the “great drift” 
in its extent and thickness in southern Minnesota. The third, or 
Wisconsin, was the most disturbing to streams and topography. 
These differences have appeared to be the main essential charac¬ 
teristics of those glacial drifts. A fuller discussion of them may 
be better made after all the work of Frank Leverett in Minnesota 
has’ been published. Enough of that work has appeared now, 
however, to justify some discussion of main problems. Those 
differences which are characterized in the three drifts have, of 
course, been formerly considered largely as induced upon them by 
time and erosion. But, what conditions of erosion could in time 
reduce the stony moraines of the Wisconsin drift to remnants of 
till such as that of Minnesota, or Iowa, in the Kansan and Ne¬ 
braskan drifts, is not known or easily suggested. 
It is, moreover, easily observed that the youngest Kewatin till 
in northeast Minnesota is as deeply leached as the Kansan till is in 
southwestern Minnesota, and that criteria of that kind as to ero¬ 
sion and leaching have much weight only when not counterbalanced 
by broader considerations. It would be obviously futile to con¬ 
tend that the Wisconsin Kewatin above the Patrician has great 
