THE PIEDMONT REGION. 141 



Where the mica slates are underlaid by or alternate with gneiss, as in 

 Abbeville, they give rise to good soils. In most places, however, the slate 

 contains lenticuler quartz grains, coated with mica, which, being inde- 

 structi1)le, occupy the surface as the rock disintegrates and gives rise to 

 poor soils. The sand of the talcose slate is exceedingly fine, and pack 

 very closely. Says Leiber, in speaking of clearing out a spring : " At a 

 depth of six inches below the bed of the stream, the sand was as dry as 

 ashes, showing that the water had never penetrated to that depth." This 

 affords an explanation of the serious effects produced by droughts on such 

 soils. 



II. The clay slates underlie a soil that is characterized as a cold gray 

 soil. In color they vary from gray to yellow and brown. The subsoil is 

 for tlie most part, of yellow clay; but, sometimes it is reddish. These 

 soils are better adapted for small grain, and especially for oats, than for 

 cotton. They cover an extensive area in Edgefield, and reach along the 

 northern border of the tertiary, thence to Chesterfield. The clay slate 

 soils in the last named county contain less silica than those of Edgefield. 

 Instead of being gray, they are reddish, and are altogether better soils. 



The following analyses are given by Tuomey : 



(13) 



Organic matter 2.40 



Silica 80.72 



Alumina 12.00 



Oxide of iron l.GO 



Lime trace. 



Magnesia 0.50 



Potash and soda trace. 



Water and loss 3.33 



100.00 100.00 100.00 



Xo. 13 is from Stevens creek, Edgefield; No. 14 from Richland ; Xo. 15 

 from Lexington. 



III. The Trappean soils overlie the extensive dykes of melaphyre and 

 aphanitic porphyry, traversing York and Chester counties in a north- 

 easterly direction, coinciding very nearly wdth that of the Charlotte and 

 Columbia railroad. They give rise to a distinctly marked body of lands, 

 known as the " rolling blackjack lands " and as " blackjack flats." The 

 latter are the most extensive, and better defined in their characters. The 

 lands are level, the streams slow and tortuous, with low banks, notwith- 

 standing that the general elevation is little less than that of the surround- 



