18 BULLETIN 180, U. S. DEPARTMENT OF AGRICULTURE. 
Carolina, northern Georgia, and central Alabama. It is in this 
Piedmont Plateau that the greatest difficulty is experienced in deal- 
ing with soil erosion. 
GEOLOGY OF APPALACHIAN AND PIEDMONT REGIONS. 
The soils are mainly residual, i. e., derived from the underlying 
consolidated rocks. The rocks are of three classes: Old igneous, as 
diorite, diabase, and granite; old metamorphic igneous and sedi- 
mentary, or gneiss, schist, phylhte, and slate ; or young sedimentary 
as Triassic sandstone, conglomerates, and shales. 
SOILS. 
Since the soils of these provinces are mainly residual, they are 
comparatively uniform. The subsoils are nearly always heavy clay, 
and the surface soils are often lighter in texture. Sandy loams, clay 
loams, and clays occupy by far the greater part of the province. 
Where the subsoil is heavy clay, erosion is not so rapid as in the 
soils with lighter subsoils. This is noticeable in portions of western 
Virginia, western North Carolina, and eastern Tennessee, in the Appa- 
lachian Mountain province. The erosion begins in little depressions 
which gradually deepen, forming gullies with sloping banks and 
rounded edges, as shown in Plate V, figure 1 . This is entirely a sur- 
face erosion and easily controlled if properly handled. In the 
mountainous regions terracing is not generally practiced, although 
without a doubt such a system would prove beneficial. 
The Piedmont province of these States and of South Carolina, 
Georgia, and Alabama suffers more from erosion than the regions 
of higher altitudes. Especially is this true near the "Fall Line." 
And in this province also the subsoil is often sandy and less tenacious, 
so that when a gully forms the sides cave in. The erosion then often 
proceeds by the caving in of the walls at the head of the gully, so 
that, in advanced cases, there are formed extensive gulches with 
almost perpendicular sides. This form of erosion is illustrated in 
Plate V, figure 2. 
The most important soils throughout the Piedmont country belong 
to the Cecil series, the Louisa soils probably ranking next in impor- 
tance. These soils are mainly red and gray and have clay subsoils. 
The main differences in the series are that the Louisa soils are less 
productive and have more micaceous subsoils than the Cecil. This 
micaceous character increases their susceptibility to erosion. 
The erosion in the Piedmont province is apparently more pro- 
nounced in the more southerly States. This is probably due largely 
to the climatic conditions. During the winter the temperature is 
not low enough to cause deep freezing, and cold periods are of short 
duration. The formation of ice crystals at the surface of the soil 
raises a thin layer, and when the ice melts there remains an inch or 
