128 GEOLOGY OF EASTERN WISCONSIN. 



OHAPTEE II 

 HYDKOLOGY. 



Drainage. On the average, about 165,512,000,000 barrels of water 

 fall annually upon the district under discussion. Of this, about one- 

 half is lost by evaporation and absorption, and the remainder runs 

 away, constituting the drainage of the district. Were the slope of 

 the surface much increased, the water would be discharged so rapidly 

 as to do much permanent damage by erosion and the rapid removal of 

 our fertile soil. "Were its inclination much less, the drainage would 

 be imperfect, and our noble water powers destroyed. In the golden 

 mean presented, a mutual adaptation to the twin industries, agricul- 

 ture and manufacture is fortunately secured. The drainage of the 

 region forms part of two great systems, the Mississippi and the St. 

 Lawrence. Perhaps one-fourth belongs to the former and the remain- 

 der to the latter. 



The watershed between these systems is very peculiar. On the 

 Illinois line, the divide is within three and one-half miles of Lake 

 Michigan, and is only 160 feet above that body of water, while the 

 surface to the west continues to rise by undulations to 400 feet and 

 upwards. A little north of the state line, several of the streams, no- 

 tably the White river, the outlet of Lake Geneva, flow to the north- 

 east, and yet reach the Mississippi. 



From the state boundary, the line of the watershed pursues a north- 

 westerly course, becoming more and more elevated till it passes the 

 Kettle range at about 500 feet above Lake Michigan, whence it con- 

 tinues still to the northwest till it suddenly drops 200 feet into the 

 Green Bay and Eock river valley, whence it curves more to the west, 

 until, on the highlands of Metomen, at about 400 feet elevation, it 

 turns abruptly southward, giving rise to another anomaly. The 

 streams that here flow east discharge into the Mississippi, while those 

 that flow west empty into Lake Michigan. Following the watershed 

 onward from this point, it gradually curves to the westward, descend- 

 ing to the portage between the Fox and Wisconsin rivers, where its 

 elevation is little more than 200 feet. From thence it pursues a 



