XXXll FISHES OF ILLINOIS 



point about 10 miles southwest of Chicago. It then turns southwest 

 for 40 miles, to its junction with the Kankakee. The course of the 

 upper Des Plaines is governed by the moraines along the banks of 

 Lake Michigan, following these more or less in their curves. At 

 Summit it enters into the "Chicago outlet." At flood stages the 

 upper Des Plaines still discharges into Lake Michigan through a por- 

 tion of this old outlet which is known as "Mud Lake" and South 

 Chicago River. Probably the entire discharge, until recent years, has 

 been into the lake instead of down the "Chicago outlet," thus form- 

 ing a system entirely distinct from the lower Des Plaines. In the 

 upper portion of the river the fall averages only a little over 1 foot 

 per mile, and its branches are almost all short and small on account 

 of the moraines. The banks, especially on the west, are quite high, 

 in some places reaching a height of 50 feet, but they are not abrupt. 



In the 40 miles from Summit to the mouth of the river, the valley 

 averages about 1 mile in width and consists of a rather shallow 

 trough cut out of limestone. This is covered with a thin bed of drift, 

 and the banks of the river are consequently low. Just below Sum- 

 mit there are 12 miles which are almost level, so that the land on each 

 side of the river is poorly drained and swampy. Below this the river 

 widens into Goose Lake, three and a half miles long and one third of 

 a mile wide, through which it makes a descent of about 10 feet. The 

 bed of the river narrows again, and just above Lockport it begins to 

 descend very rapidly, dropping about 70 feet in 8 miles. Below this 

 are two lakes, — one, known as Lake Joliet, 2^ miles below Joliet, and 

 the other. Lake Dupage, near the mouth of the Dupage River, the 

 two being three miles apart, and the river falling about 13 feet in 

 the interval (Leverett). In the half mile from Lake Dupage to the 

 junction of the Des Plaines with the Kankakee another descent of 

 two and a half feet is made. The only true flood-plain bottoms lie 

 within the seven miles between Lake Joliet and the head of the Illi- 

 nois. These are within the range of baclcwater from the Kanka- 

 kee, but are overflowed only in case of floods from that stream, 

 having been built up to about the average high-water level. A 

 canal, 100 miles long, called the Illinois and Michigan canal, starts 

 from Lake Michigan at Chicago, and, cutting through the low sum- 

 mit, enters the Des Plaines valley. It crosses the river at Joliet, 

 and then follows along the right bank of this river and of the Illinois 

 to Peru, where it enters the latter river. 



The principal branch of the Des Plaines is the Dupage River, which 

 rises in southern Lake county, and, flowing southward, empties into 

 the Des Plaines only 4 miles above its junction with the Kankakee. 



