THE GLACIAL PERIOD 



61 



showing the compass point from which the glacier came here. 

 At times the scratches cross each other, indicating at least local 

 changes in the direction of movement of the ice (Fig. 41). 



At last in its onward flow the glacier pushed its way south- 

 ward into a region so warm that the front of the glacier melted 

 away as rapidly as new ice arrived. The bulk of the coarse 

 rock fragments it was carrying, together with much of the finer 



FIG. 41. Grooves and scratches on bed rock due to glacial erosion, Stony 

 Island, Chicago. 



stuff, was deposited along this line where the glacier front stood 

 perhaps for hundreds of years, piling up in great unsorted heaps 

 as the moving ice continually brought fresh supplies. Thus it 

 formed out of this debris pillaged from a continent the terminal 

 moraine. The Illinois glacier is the first one to leave undisputed 

 evidence of itself in our state ; it pushed south approximately to 

 the present location of the Ohio River and deposited its terminal 

 moraine. This glacier, therefore, extended past our present loca- 



