296 THE ILLINOIS GLACIAL LOBE. 



phenomena. By one interpretation the portion of the ridge from Hampshire 

 northward is considered a continuation of the Blooming-ton system, while 

 the portion south from Hampshire is merely a spur projecting- back from 

 the reentrant angle formed near that village. The difference in the contours 

 of these two portions of the ridge may in this case he due to a different 

 position in reference to the ice margin, the portion north from Hampshire 

 being formed at the extreme margin of the ice sheet and the portion south 

 from Hampshire at some distance back from the margin. The submarginal 

 position would seem to be a sufficient cause for the smoothness of contour. 



By a second interpretation the Marengo Ridge is made later than the 

 outer ridge of the Bloomington system, and its entire length considered a 

 marginal accumulation. Its great relief above the outer ridge of the 

 Bloomington system at Hampshire, where it crosses that ridge, so strongly 

 favors this interpretation that for some years it was given more weight by 

 the writer than other interpretations, though the absence of a gravel out- 

 wash on the west border of the portion south from Hampshire left room for 

 doubt. 



A third interpretation suggested itself when revisiting the region with 

 a view to reaching a more satisfactory conclusion concerning correlations. 

 By this interpretation the outer ridge of the Bloomington system is con- 

 sidered to pass eastward across the Marengo Ridge and to join the composite 

 belt lying- east of that ridge. The portion of the Marengo Ridge north of 

 Hampshire would, in this case, have stood outside the ice sheet, while the 

 portion south of Hampshire would have been overridden by it. If the 

 weakness of the outer ridge of the Bloomington system at the point where 

 it connects with the Marengo Ridge is continued eastward some difficulty 

 would be experienced in tracing it over the more bulky and more sharply 

 morainic Marengo Ridge. The abrupt change in the contour of the Marengo 

 Ridge at the point where the outer ridge of the Bloomington system con- 

 nects with it seems to give support to this interpretation, as well as to the 

 first interpretation. 



Until further light is thrown upon the subject, the value of each of 

 these interpretations must remain an open question. At present the writer 

 is unable to exclude any of them, nor does any one of them seem decidedlv 

 1 utter sustained by the phenomena than the others. 



