THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS XXXV 



in Kenosha county, Wisconsin. This vallev is so nearly level 

 that at times it is very difficult to tell which way the water flows. 

 It stands 112 feet above Lake Michigan (Leverett) and drains 

 northward into Root River as well as southward into the Des 

 Plaines. The Des Plaines flows nearly parallel with the shore 

 of Lake Michigan to a 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 portion 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,' 1 thus 

 forming 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 Summit 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 Kan- 

 kakee 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 Illinois. These are within the 

 range of backwater from the Kankakee, but are overflowed 

 only in case of floods from that stream, having been built up 



