190 



discharges at South Chicago in Illinois. The old discharge was in Lake 

 County on the southeast border of the lake. Near the source the river 

 fiOws in an almost straight line and has the appearance of an artificial 

 ditch rather than a natural stream. After flowing across the counties 

 of Porter and Lake it crosses the State line but three miles south of 

 its entry into Porter County and almost due west of its source. From 

 the State line it flows in a northwesterly direction, for about seven miles 

 and then at Blue Island, Illinois, it makes a sharp curve, then flows north- 

 east then southeast and again crosses into Lake County about three miles 

 north of its first line then continuing eastward for fourteen miles to 

 its old point of discharge, but two and a half miles from the ixiint where 

 it first entered Lake County. The area Inchided in this meander con- 

 sists of sliglitly elevated morainie tracts, sandy beaches and marshes. 



LAKES. 

 In the nortliern part of the State are hundreds of lakes varying much 

 in size. These lakes are chiefly confined to the four northern tiers of 

 counties. These lakes are .ill due to the irregular deposition of glacial 

 drift. They occupy basins within the morainie area. They may be di- 

 vided into three classes. (1) Kettle Hole Lakes, those which have been 

 formed by tlie melting of detached blocks of ice. (2) Channel Lakes, in 

 which the basins are the abandoned channels of glacial streams. (3) 

 Irregular lakes, those with no general form of outline but are due to the 

 irregular depressions formed in the accumulated drift. 



The abundant vegetation has pnidnced considerable deposits of ])eat 

 about the margins of many of the lakes, and many of the smaller ones 

 have been completely filled. Good marl deposits also occur in many of 

 the lakes and is being utilized for the manufacture of cement, brick and 

 tile. 



No lakes occur outside the limits of the Wisconsin drift, although 

 many basins of extinct lakes occur over the southwestern border of 

 the Illinoian. Some small ponded areas are found which take consid- 

 erable proportions in wet .seasons but are not permanent. In the drift- 

 less area numerous small ponds are found, which owe their origin chiefly 

 to sink hole depressions in which the outlet has become clogged. 



For (loscrlption of Indiana Stroams, see U. S. G. S. Monographs XXXVII and 

 XLI.— Leverett. 



