SOILS OF ILLINOIS. 793 



SANDY SOILS. 



The sandy soils, though apparently much alike in structure, are varied 

 in their methods of deposit. They occur in the beaches along the bor- 

 ders of Lake Michigan, in the valley bottoms of the main streams, on 

 the bluffs and along the borders of the streams which lead away from 

 the newer drift district, in basins within the newer drift district (as the 

 Kankakee and Illinois-Vermilion), and to a limited extent in the moraines. 

 There is also an extensive development of sand in northwestern Illinois, in 

 the Green River Basin and the bordering districts, as far north as northern 

 Whiteside County. Where the sand is of medium to coarse grade it is 

 usually rather barren, but where fine, as in the eastern portion of the sandy 

 belt bordering the Illinois in Tazewell and Mason counties, it is productive. 

 Within the sand-covered districts there are more or less extensive tracts of 

 wet, mucky land between sand ridges. This, where artificially drained, 

 has often proved very productive. There are districts where the loess 

 assumes a sandy phase, but in these places the sand is very fine, so fine 

 that individual grains can scarcely be detected by the eye, and the fertility 

 is about as great as in the typical loess. 



BLUFF LOESS SOILS. 



The very porous phase of the loess within the region under discussion 

 is confined mainly to the borders of the Mississippi, Illinois, Ohio, and 

 Wabash rivers, extending back usually but a few miles from the streams. 

 It may therefore properly be called the "bluff loess." There is, however, 

 a porous loess along the south border of the Green River Basin, and in 

 general the loess between the Mississippi and Illinois rivers is more porous 

 than on uplands to the west or east. In southern Illinois the loess becomes 

 a compact white clay within a few miles back from the Mississippi, Ohio, 

 and Wabash rivers, but in western Illinois it changes to the slowly per- 

 vious silt which is more productive than the white clay. The very porous 

 loess which borders the main streams will permit roots to penetrate readily 

 to a great depth, there being observations of penetration to 25 or 30 feet. 

 It is, however, usually of such a texture that water rises in it by capil- 

 larity in dry seasons and adecpiately supplies the crops. 



The mechanical analyses of specimens of the bluff loess made under 

 the direction of Professor Whitney have been presented in tabular form in 



