WATER PROVINCES OF THE UNITED STATES 63 



The rocks of the Piedmont Plateau proper consist mainly of 

 schists, gneisses, granites and other metamorphic or igneous 

 rocks, all of which are of crystalline texture. The rocks of the 

 Triassic basins consist mainly of sandstones, shales, etc., frequently 

 of a deep red color. 



The waters of the Piedmont Plateau are relatively uncertain 

 in occurrence, depending largely on the existence of joints or 

 other fissures in the rocks, but good supplies have nevertheless 

 been obtained at numerous points. In composition the waters are 

 usually fairly good, although they sometimes contain considerable 

 mineral matter. Relatively few deep wells have been sunk in 

 this region, owing to the uncertainty of supply, dependence being 

 placed largely on. streams or on shallow wells dug in the weathered 

 upper portion of the rocks. The waters are used largely for 

 domestic and farm purposes and in small industrial establish- 

 ments. In a few places public water supplies are obtained from 

 the Piedmont rocks, and some important mineral springs are 

 found in the region. 



Similar to the Piedmont Plateau are the great areas of igneous 

 rocks in Minnesota and Wisconsin and in New York and New 

 England. The topography of the rocks in these regions is, in 

 general, somewhat more rugged than in the Piedmont Plateau 

 proper, and less use is made of the waters, largely because of the 

 abundance of lakes, springs and spring-fed streams, or of waters 

 in the glacial drift which often overlies the crystalline rocks in 

 this portion of the country. 



Appalachian Mountains. - - The Appalachian Mountains may 

 be considered as beginning in eastern Pennsylvania and extending 

 southward to central Alabama. The Berkshire Hills in Con- 

 necticut and Massachusetts and the Green Mountains in Vermont 

 are included in the area by some. The rocks throughout the 

 region are strongly folded and broken by faults, the harder beds 

 giving rise to the great mountain ridges which characterize the 

 belt. The rocks consist of quartzites, sandstones, shales and 

 limestones. The sandstones and certain of the limestones carry 



