6 A NATURALIST IN THE GREAT LAKES REGION 



little runnel is starting out from some grassy depression (Fig. 5), 

 pass the fairly level upper stretches where it meanders, cutting 

 an irregular course as it grows by minor tributaries, enter the 

 V-shaped valley (Fig. 6) in which it is flowing with irresistible 

 vigor straight for its goal a valley that deepens and widens with 

 every advance and finally arrive where for a few rods it may 

 proceed a placid little river just before it enters the lake. 



FIG. 6. A later stage, the deep V-shaped ravine 



Valleys which exemplify similar stages of development are 

 seen where the stream cuts its way down through the rock, only 

 in this case the valley sides are likely to be very precipitous if 

 the cutting is at all recent, since it takes much longer for the 

 forces of erosion to crumble down the valley sides. No better 

 illustration of such valleys cut out of the rock can be found than 

 those exhibited in the neighborhood of Starved Rock on the 

 Illinois River, Oregon on the Rock River, and the Dalles of 

 the Wisconsin (Fig. 7), all beauty spots easily accessible from 

 Chicago. Standing on the top of Starved Rock, the -valley 

 lies spread out before your eye, bounded on either side by 



