854 



GEOLOCY 



on plains, plateaus, and mountains, indiscriminately, though not 

 usually in equal amounts, (b) The drift is sometimes so disposed 

 as to make the surface rougher than it would be otherwise, and 

 sometimes so as to give it less relief. This is illustrated by Figs. 

 568 and 569. (c) It is measurably independent of present drainage 

 basins, so far as its constitution is concerned. Thus, materials from 



I 



Fig. 566. Foliated till. (Photo, by Jefferson.) 



one drainage basin are found in the drift of other drainage basins 

 so commonly as to make it clear that present divides did not con- 

 stitute divides to the ice. (d) Various sorts of material in the drift 

 at certain points are so related to their sources as to make it clear 

 that they were carried upwards, sometimes hundreds of feet, from 

 their original sites, (e) A considerable area in southwestern Wis- 

 consin, and the adjacent parts of Illinois, Iowa, and Minnesota, is 

 without drift. This driftless area is neither notably higher nor 

 lower than its surroundings, and glacial ice seems to be the only 



