66 



Types of Aquatic Environment 



The Lakes of the Yahara Valley in Southern Wisconsin 

 are of another type . They occupy broad , shallow basins 

 formed by the deposition of barriers of glacial drift 



in the preglacial course of 

 the Yahara River. Their 

 outlet is through Rock 

 River into the Missis- 

 sippi. Their shores are 

 indented with numerous 

 bays, and bordered ex- 

 tensively by marshes. 

 The surrounding plain is 

 dotted with low rounded 

 hills, some of which rise 

 abruptly from the water, 

 making attractive shores. 

 The city of Madison is 

 the location of the Uni- 

 versity of Wisconsin , 

 which Professor Birge has 

 made the center of the 

 most extensive and care- 

 ful study of lakes yet 

 undertaken in America. 

 The area, elevation and 

 depth of these lakes is as 

 follows : 



FIG. 



1 6. The four-lake region of 

 Madison, Wisconsin. 



LakeKegonsa . 

 " Wabesa . 

 Monona . 

 " Mendota 



