4 SOILS OF THE EASTERN UNITED STATES. 



The Knox silt loam differs from the soils of the Marshall series in 

 two essential respects. In the first instance its surface soil is a much 

 lighter brown or even a pale gray, sharply contrasted with the deep 

 brown or black surface soil of the members of the Marshall series, 

 particularly the silt loam. In the second case, the Knox silt loam is 

 distinctly a timbered region soil throughout the entire extent of its 

 occurrence, as contrasted with the Marshall silt loam, which occupies 

 only the prairie areas in the same general region. It differs de- 

 cidedly from the soils of the Marion series, particularly the silt loam, 

 in the darker color of the surface soil and in the timbered nature of 

 the type, as contrasted with the prairie condition of the latter. It is 

 not liable to be confused with any of the other soils of the glacial 

 and loessial region. 



SURFACE FEATURES AND DRAINAGE. 



The Knox silt loam is developed in two distinctive topographic 

 phases. Throughout northern and central Illinois and the north- 

 central portion of Indiana it occupies the rolling to broken areas 

 and the bluffs along the courses of the principal streams. The crests 

 of these hills and bluffs rise from 50 to 150 feet above the bottom 

 lands which they adjoin, and the general belt of the Knox silt loam 

 frequently borders both banks of the stream for long stretches and 

 extends back toward the rolling upland for a distance of 2 to 5 or 6 

 miles. Such areas are most frequently cut by deep V-shaped tribu- 

 tary valleys, giving a very sloping and somewhat eroded surface for 

 the type in such locations. Practically all such areas have been 

 allowed to remain in timber since the first occupation of the country 

 for agricultural purposes, and in many counties in central Indiana 

 and Illinois the principal woodlots and timbered areas still remain 

 upon this type. All such areas are also grown up to native pasture 

 grasses, among which the Canada bluegrass dominates. 



In southern Indiana and in the Ohio River counties of Kentucky 

 where the type occurs, as well as in southwestern Wisconsin and 

 eastern Iowa, the Knox silt loam most frequently occupies undulating 

 to gently rolling upland areas, bordered only by the steeper slopes 

 and eroded portions such as dominate the type in the localities men- 

 tioned in the preceding paragraph. In these areas it is extensively 

 used for agricultural purposes and not infrequently dominates the 

 agriculture of the counties where it is found. 



In Missouri and eastern Nebraska both types of development are 

 found, and it is not infrequently the case that the cultivated fields of 

 the gently rolling upland are bordered by the steep slopes of eroded 

 and dissected margins along the stream courses and the major rivers. 

 In Missouri the hilly portions are timbered. In Nebraska they are 



