102 



THE ILLINOIS RIVER SYSTEM. 



The length of the Illinois from its mouth to the place of its 

 formation by the junction of the Des Plaines and the Kankakee 

 is about 270 miles,* and if to this be added the length of the 

 Kankakee, the longest tributary, the total amounts to 505 miles. 

 This is about the length of the Seine, of the Rhone, and of the 

 Oder ; of the Des Moines and of the Sacramento ; it is about one 

 half the length of the Rhine and of the Yellowstone, one third 

 that of the Danube, and over twice that of the Thames and the 

 Tiber. The distance, in a direct line, from the junction of the 

 Des Plaines and the Kankakee to the mouth of the Illinois is 

 214 miles. The increase in length due to the windings of the 

 stream is thus 61 miles or 28%, and the ratio of the development 

 of the stream is 1 : 1.28. From the mouth of the main stream to 

 the head waters of the Kankakee, in a direct line, is 315 miles. 

 Upon this basis the increase due to windings is 190 miles or 

 60%, and the ratio of development is 1 : 1.6. The ratio of de- 

 velopment of the Connecticut River is 1 : 1.2, and that of the 

 Mississippi, as a whole, is 1 : 1.5, while from the mouth of the 

 Ohio to the Gulf it is 1 : 2.0. It is evident that the main stream 

 of the Illinois has an exceptionally direct course, though the 

 channel of the Kankakee is not of this character. 



The area of the basin drained by the Illinois is approxi- 

 mately 29,000 square miles. This is more than twice the area 

 of the Hudson, and also • of the Connecticut, and is comparable 

 with that of the Susquehanna, of the Potomac, of the Po, of the 

 Duero, of the Rhone, and of the Loire. It constitutes less than 

 one forty-third of the entire Mississippi basin. According to 

 Grreenleaf ('85) the drainage basin of the Illinois comprises an 

 area of 29,013 square miles, 24,726 of which lie within the state, 

 1,080 in Wisconsin; and 3,207 in Indiana. About three sevenths 

 of the area of the whole state belong to the drainage basin of 

 the Illinois. The following list of tributaries with their respect- 

 ive areas is taken, with slight modification, from Cooley ('89). 



*The statement of the Standard Dictionary (p. 2172) that the length of the Illi- 

 nois River is 350 miles is manifestly incorrect. 



