330 MISCELLANEOUS FARM SUBJECTS 



valley soils of the Appalachian region also show considerable topo- 

 graphic relief, sometimes exhibiting mountainous surface features. 



The limestone soils are residual in origin, being derived from the 

 weathering in place of limestone of differing age and composition. 

 This is accomplished by the removal through solution of the calcium 

 carbonate of the limestone, leaving behind the more resistant siliceous 

 minerals. These soils are remarkable for the fact that they contain 

 but a very small percentage of the original limestone rock, the larger 

 part having gone into solution. It has thus required the solution of 

 many feet of rock to form a single foot of soil. 



Clarksville Series. Light-gray to brown soils with yellow to red 

 subsoils, derived mainly from the St. Louis limestone. While not 

 as strong as the Hagerstown soils, this is a valuable series. Apples 

 and peaches are commercially important. Tobacco is a leading orod- 

 uct. General farming is firmly established in many extensive regions. 



Cumberland Series. Brown surface soils, derived from thin de- 

 posit of sedimentary material overlying residual limestone subsoils. 

 Used for cotton and other general farm crops, truck, and fruit. 



Decatur Series. Reddish-brown to red soils with intensely red 

 subsoils. Intermediate in value between the two series just described. 

 Cotton, corn, wheat, oats, forage crops, bluegrass, and peaches are the 

 .leading crops. 



Hagerstown Series. Brown to yellowish soils with yellow to 

 reddish subsoils, derived from massive limestone. Among the most 

 productive soils of the eastern United States. Fine wheat and gen- 

 eral farming soils, and the seat of important apple orcharding in- 

 terests. Bluegrass is indigenous. 



GLACIAL AND LOESSIAL REGIONS. 



The soils of the glaciated part of the country constitute one of 

 the most important groups in the United States. This group includes 

 all soils derived directly from till or loess. The soils formed from the 

 till are confined to that part of the country lying north of the south- 

 ern limit of glacial action, but the loess soils occur also south of this 

 line, especially along the Mississippi and Ohio rivers and in Kansas 

 and Nebraska. The line of the southern extension of the ice sheet 

 touches the Atlantic coast about New York City, passes through 

 northern New Jersey, southern New York, and nortnwestern Penn- 

 sylvania, swings southwestward through Ohio to Cincinnati, crosses 

 the Mississippi River at St. Louis, and follows the south side of the 

 Missouri River into Montana, where it crosses the Canadian boundary 

 line, then dips southward into Idaho as a long lobe in the mountain- 

 ous nonagricultural region, and crosses the northwestern part of 

 Washington, including the Puget Sound region. 



Practically all of the United States north of this line was cov- 

 ered in recent geological time by a great continental glacier, many 

 hundreds, and even thousands, of feet in thickness. This great ice 

 sheet, moving in a southern direction, filled up valleys, planed off the 

 tops of hills and mountains, ground up the underlying rocks, carried 

 the derived material both within and upon the ice, and finally de- 

 posited the gravel, sand, silt, and clay as a mantle, varying in tnick- 



