12 ILLINOIS BIOLOGICAL MONOGRAPHS [12 



that the river beds form a series of connecting channels between the 

 various lakes. 



After the formation of the lakes, it was a simple matter, as has been 

 said, to establish connections between the lakes by means of river systems. 

 The second source of water in the lakes is springs, which are extremely 

 abundant throughout the region. Practically all of the lakes, whether they 

 have inlet and outlet or not, are spring fed. These springs are the termini 

 of great under ground water systems, and arise in the bottom of the lakes 

 as bubbling streams. Nothing is known at the present time concerning the 

 abundance of these springs in any lake, but data at hand indicate that 

 they are numerous. In many places along the shores these springs have 

 been "captured" and show an output of a vast quantity of marvelously 

 clear, cold water, which is none other than the famous "Waukesha water" 

 for which the county is well known. The temperature at which these 

 springs enter the lakes is very low, the temperature of nine springs, taken 

 in June, being as follows: 5.1, 5.4, 5.0, 4.8, 5.8, 5.6, 5.0, 4.9, and 5.0 degrees 

 centigrade. 



The medial moraine, to which I have previously referred, divides the 

 county into two primary drainage areas, namely that of 1) the Rock river 

 and 2) the Fox river. The northwestern third of the county contributes 

 either directly or indirectly to the Rock river, while the southeastern 

 third contributes to the Fox river drainage basin. Both of these rivers are 

 tributaries to the Mississippi within the boundaries of Illinois, the Rock 

 river entering directly, the Fox river by its union with the Illinois river. 

 The northeastern third of the county lies outside of the Mississippi drain- 

 age, its one river, the Menomonee, flowing almost due east into Lake 

 Michigan. 



There are five river systems within the county, and these may be tabu- 

 lated as follows: 



1. Rock river tributaries: 



1. Ashippun river. 



2. Oconomowoc river. 



3. Bark river. 



a) Scuppernong river and creek. 



2. Illinois river tributaries: 



4. Fox river. 



a) Muckwonago river. 



b) Pewaukee river. 



3. Lake Michigan tributaries: 



5. Menomonee river. 



An examination of the map will show that a vast majority of the larger 

 lakes are arranged in two chains, the component lakes being connected 



