6 SOILS OF THE EASTERN UNITED STATES. 



gulleys cuts deeper into the loess material and removes more and 

 more soft earth from the upland areas. As a result the originally 

 level plateau has been carved into rough and hilly topography along 

 the bluffs and throughout the region where this material and this 

 topography have been developed. From the mouth of the Ohio 

 southward this section is commonly known as the " Cane Hills." 



The surface of the Memphis silt loam attains to elevations of 500 

 feet or more in eastern Missouri and in southern Illinois, where it 

 mantles the uplands as well as follows the bluffs of the Mississippi 

 and its major tributaries. The surface of the type gradually de- 

 scends southward ; it occurs at altitudes of 300 to 350 feet above tide 

 in western Kentucky and western Tennessee and the extreme north- 

 ern portion of Mississippi; thence it gradually slopes southward to 

 an altitude of about 100 feet above sea level at the Mississippi-Louisi- 

 ana line and descends to an altitude of less than 50 feet between 

 Baton Rouge and Xew Orleans. 



Similarly, the bluffs separating the upland from the great alluvial 

 bottoms are higher and more eroded in the more northern portion, 

 rising not infrequently 250 feet above the adjoining alluvial bottoms 

 in western Tennessee and northern Mississippi. Farther south these 

 bluffs rise from 15 to 50 feet above the river, and south of New Or- 

 leans constitute only a low, bounding ridge to the east of the alluvial 

 delta lands. The smaller ridges to the west of the Mississippi River, 

 particularly in Arkansas and in northern Louisiana, rise to alti- 

 tudes of only 15 to 35 feet above the bottom lands by which they are 

 usually surrounded. Thus there is a considerable difference both in 

 absolute elevation above tide level and in the relative elevation above 

 adjoining low lands through the wide extent of territory covered 

 chiefly by the Memphis silt loam. 



The natural drainage of the type is quite complete along the bluff 

 lines and in close proximity to the larger drainage ways and there is 

 practically no difficulty encountered through excess of moisture. In 

 the smoother country somewhat remote from the streams, and par- 

 ticularly in the "Flat Hills" region, latterly mapped as the Rich- 

 land silt loam, there are considerable level areas and even minor 

 depressions where the natural drainage of the Memphis silt loam 

 is deficient. Such areas are always marked by a light-gray to ashy- 

 white surface soil, except where the drainage is so obstructed that 

 local swampy areas have been formed and the shallow mucky accumu- 

 lation over the silty material gives a darker color to the surface soil. 



In practically all instances of this kind there is a further pro- 

 nounced indication of deficient drainage through the presence of 

 small iron concretions, locally known as " iron buckshot " or " iron 

 gravel," to be found both in the surface soil and at a slight depth 

 below it, where the gravel is not infrequently accumulated as a layer 



