XXIV FISHES OF ILLINOIS 



miles distant, while the southern stream, known as Kickapoo slough, 

 pursues a winding course southward and westward, opening into the 

 Mississippi a few miles south of the mouth of Rock River. 



The upper Rock River is a clear, quiet-flowing stream with sandy 

 bottom. Lower in its course the bed becomes more often rocky 

 and the current quickens. Naturally, the water, unless roiled by 

 freshets, keeps its bright, clear character until well down near the 

 mouth. Its tributaries, however, at times pour in a flood of stained 

 and muddy water, making the lower portion a turbid stream, while, of 

 late, sewage and other contamination have done much to impair the 

 original brilliancy of the water. Yet, as Illinois rivers go, it must 

 even now be considered a clear stream, while the bold bluffs and out- 

 cropping rocks along its banks make it one of the most picturesque 

 rivers in the state. 



The principal branches of Rock River are Pecatonica, Kishwau- 

 kee, and Green rivers. 



PECATONICA RIVER 



Pecatonica River rises in Iowa county, Wisconsin, in the driftless 

 area, and flows south, entering Illinois in the northwest corner of 

 Stephenson county. It then flows in a course a little south of west 

 to Freeport, where it turns westward, entering Winnebago county 

 near the center of its western boundary. Another turn is then made, 

 to the north and east, the stream finally emptying into Rock River 

 at Rockton. The Pecatonica is about 150 miles long, over half of 

 this distance lying in Wisconsin. Its drainage basin covers 2,225 

 square miles. Its discharge in ordinary low water is about 940 cubic 

 feet per second, and the average flow for the year is estimated to be 

 over 2,300 cubic feet per second. Almost all of that portion of the 

 basin lying in Wisconsin is included in the driftless area, the river 

 entering the Illinoisan drift just above the Illinois state-line. It 

 flows through this drift until, at a point 10 miles above its mouth, it 

 inters the Iowan drift. For 10 or 15 miles above this point, how- 

 ever, it follows closely the northern boundary of this drift. The 

 country which the Petaconica drains is rolling, partly timber and 

 partly prairie. 



The Indian name of the river (spelled Peeka-ton-oke on the old 

 maps) is said by some authors to mean "muddy," and by others to 

 mean "crooked." The river, especially in its lower portion, would 

 fit either or both. The fall of the river averages only about half a 

 foot per mile, and throughout its course it curves and winds about, 

 not abruptly but in long undulating turns, through its rich alluvial 



