2 A NATURALIST IN THE GREAT LAKES REGION 



where high clay bluffs stand at the water's edge, as at Fort 

 Sheridan or Lakeside, and see, during a storm, the pounding 

 waves gnawing at their bases. As they are undermined the 

 unsupported upper portions slide down, carrying the vegetation, 

 even the trees, the soil, and contained bowlders into the insatiable 

 maw of the lake (Fig. i), all to be ground up by the wave action 

 and deposited in time out in quiet water as beds of sand or clay, 



FIG. i. Clay.'oluffs near Winnetka on shore of Lake Michigan, showing 

 erosion. The bfise is torn up by waves and the whole unsupported side is moving 

 down, as sh()w n by shrubs and trees in various stages of transit from top to bottom. 



or transported and thrown up on shore in sandy or muddy 

 beaches. This process of wave erosion and deposition goes on 

 ceaselessly and has been going on for ages, not only on the shores 

 of Lake Michigan, but wherever land masses are exposed to the 

 attacks of the waves. Serried ranks of billows (Fig. 2) armed 

 with rock fragments hurl themselves in relentless fury on the 

 slow-retreating land. The softer portions of the shores, even 

 the rock-bound shores, in the age-long battle are worn away 

 rapidly and form deep bays. The more resistant sections stand 



