74 THE ILLINOIS GLACIAL LOBE. 



lacks support because of the absence of a system of ridges leading up from 

 the west. It is perhaps opposed by the direction of the neighboring stria 

 at Alton, which is southwestward, parallel with the ridges, instead of south- 

 eastward toward them. This hypothesis, therefore, is held lightly, but is 

 not rejected. 



The hypothesis that this system of ridges marks the western border of 

 a lobe which persisted in southern Illinois after the withdrawal of the ice 

 from western Illinois is apparently supported by the distribution of the 

 ridges. This is especially true of the southeastward extension of the belt 

 across Randolph and Jackson counties which, in a measure, encircles the 

 supposed lobe. This hypothesis apparently is the best-supported one of 

 the group. 



The hypothesis that rock hills may constitute nuclei for the ridges was 

 suggested by the occurrence of such hills in western Shelby County, in the 

 midst of the system of ridges, but no evidence was found elsewhere along 

 the belt which would support this view. Indeed, the majority of ridges 

 have such abruptness that they can scarcely be supposed to carry an equally 

 abrupt ridge of rock. The formations in that region are largely shale or 

 shaly sandstone which, in all probability, would be preserved only in low 

 hills and ridges with gentle slope. 



The hypothesis that the ridges are remnants of a sheet of drift which 

 once covered this region to the height of their crests is presented in the 

 Illinois Geological Reports as an explanation for their occurrence. This 

 hypothesis involves such a vast amount of erosion as to be entirely unsup- 

 ported by the features of the region, and is therefore no longer considered 

 applicable. 



BUFFALO HART MORAI1ST3. 



The Buffalo Hart moraine is well defined for a distance of about 15 

 miles in eastern Sangamon and southwestern Logan counties, passing from 

 the Sangamon River near Mount Auburn northwestward past Buffalo and 

 Buffalo Hart to Elkhart. It consists of knolls of considerable prominence, 

 somewhat closely aggregated, many of which are 30 or 40 feet and a few 

 75 or 80 feet or more in height. Among the knolls there are sloughs and 

 shallow basins, giving the surface a subdued type of knob-and-basin topog- 



