193 



The liue between the residual types and the loess covered tracts is 

 well defined as to differences of plant growth and crop production, but 

 the line between the pale silt and the black soils of the Wisconsin drift 

 is very conspicuous. 



The loess soils are easily cultivated, much of the surface of a well 

 tilled ilekl is frequently a loose tioiu'y dust, and when small clods occur 

 they are easily broken. The soil may be plowed when wet and yet 

 easily be worked to a loose pliable condition. There is a marked deficiency 

 of organic matter in the virgin soil .and as this amount becomes less the 

 soils get in a poor physical con.ditioi' and are sometimes difficult to man- 

 age. A systematic rotation of crops and good application of stable ma- 

 nure are necessary to keep the soils in good condition for cultivation. 

 Much of the land is used for pasture, but when left uncultivated for a 

 few years the gi'ouiid becomes covered with a browth of briars. 



The principal alluvial soils of the State are those of the White 

 niver, Wabash and Ohio Valleys. The valleys of these streams and 

 their tributaries are the results of stream erosion, and chiefly by the 

 streams w'hlch now occupy them. During the glacial period they were 

 largely choked with drift, only a small part of which has been removed ; 

 gorges and ravines exist in great numbers along the White Water, White 

 and Ohio rivers and their tributaries. The eastern ti*ibutaries of tlie Wa- 

 bash in Fountain and Parke comities flow through deep gorges cut in 

 the sandstone. The streams flow'ing from the glacial area had their 

 valleys flooded with glacial waters and choked with glacial debris. The 

 effett of this is shown by the extensive terraces of sand and gravel which 

 border their present channels. Between these terraces are the bottom 

 lands, large areas of which contain very productive soils. 



A larger percentage of the drift so/Is are suited for cultivation than 

 those of the driftless area, but there are, however, large areas of the 

 former which are either too rough for agricultural purposes, as in the 

 boulder morainic belts, or too wet, as in the lake and marsh districts of 

 the northern part of the State. 



ROCK OUTCROPS. 



In the northern part of the State rock outcrops are few. At Mo- 

 mence, Illinois, occurs the first limestone outcrop along the Kankakee, 

 and from that point to its junction with the Iroquois there is a solid 



[13—29034] 



