JSI3 ILLINOIS ACADEMY OF SCIENCE 



The thickness of this loess layer varies remarkably, due 

 in large part to the factor of later erosive extent, but is at 

 its maximum depth along the western margin of the 

 county, where a depth of thirty to forty feet has been re- 

 corded. At Warren, near the eastern border of the county, 

 a depth of ten to fifteen feet is by no means a rare occur- 

 rence. 



Among the physical characters of this loess or silt, there 

 are several features that stand out very prominently, 

 namely, the extreme degree of comminution as evidenced 

 by the fineness of the soil particles, the lack of any pro- 

 nounced, "grit", the yellowish tint, the ability to with- 

 stand long jjeriods of weathering and yet continue to 

 assume almost vertical forms, the clay-like unctuousness 

 and tenacity when wet and the angular and multitudinous 

 lines of fracture when dried, — all these characters are 

 more or less evident in all samples. Porosity is also 

 marked in most varieties, giving, therefore, excellent soil 

 drainage and at the same time retaining moisture, making 

 this, in general, a superior crop soil. 



Chemically it contains, as one would expect from its 

 origin, practically all of the elements found in the lower 

 stratified and igneous rocks. Largely composed of silicate 

 of alumina, it contains also appreciable amounts of iron, 

 lime, magnesia, potash, soda, and traces of many other 

 minerals. It ver}' commonly effervesces with acid, indicat- 

 ing an abundance of lime carbonate, and this presence of 

 lime is further shown b}' the great luxuriance upon it of 

 red clover, which thrives so well in a calcareous soil. An 

 item of interest in connection with its chemical composi- 

 tion and the consequent relation to soil fertility is the 

 experience of those farmers living in the lead-producing 

 area. Abandoned, filled-up mine-shafts, which are always 

 surrounded by an area more or less loaded with the deeper 

 soil laj^ers, invariably become veritable oases of crop lux- 

 uriance once the deep soil has become mixed with the 

 original surface earth, which acts in fact better than 

 manure because the effects are more lasting. 



Soil Varieties. 



From the standpoint of forest distribution, as well as 

 that of agriculture, the soils that are of especial impor- 

 tance are few in number, by far the larger part of the area 



