574 Journal of Agricultural Research voi. v. no. 13 



An average of five samples of soil of the Porters series, including 

 types of different texture, shows that 52 per cent of the minerals in the 

 very fine sand separates comprises other minerals than quartz. The 

 potash-bearing minerals are decidedly the predominating ones. Biotite 

 and muscovite mica have been found among the predominating minerals 

 in all five samples, having an average of 20 per cent of all the minerals 

 except quartz. Orthoclase is very abundant in the soils of this province; 

 it, too, has been found among the abundant minerals in all five samples. 

 Microcline is often encountered, especially among the sand particles; 

 however, it is not found as abundantly as orthoclase. A study of the 

 optical properties of biotite and orthoclase often shows them to be under- 

 going well-marked chemical alteration, the former being metamorphosed 

 to chlorite and epidote and the latter wearing down, leaving a somewhat 

 skeleton-shaped residue. Plagioclase ^ feldspars are encountered often in 

 the soils of this locality; in many instances they are found as well- 

 preser\'ed fragments, which show clean faces and sharp edges, as though 

 little decomposition had taken place. 



Another point that may be worthy of note is the accumulation of micas 

 in the silt separates. Not only is this true for the soils of the Appalachian 

 Mountains, but it is most frequently the case with other soils of the United 

 States. If these minerals are found in a soil to any appreciable extent, 

 they usually occur in the largest quantities among the finer particles. 

 This is readily accounted for from their cleavage and other physical 

 properties, which cause them to be quite susceptible to the forces of 

 weathering. As these minerals are carriers of the element potassium, 

 practical significance may be attached to this fact. As they occur 

 among the finer particles, more surface is exposed to the forces which 

 make the soil solution, thereby causing more of this element to be of 

 service to plant life than when found among particles of coarser texture. 



Pyroxene and serpentine are found in more abundance in the Moun- 

 tain soils than is usually the case with those of the Piedmont and Coastal 

 Plain provinces. 



Apatite, the mineral carrying the element phosphorus, is somewhat 

 more common in these soils. It is found both as prismatic apatite and 

 as tiny needles inclosed in other minerals. Fry ^ has called attention to 

 the persistence of included apatite in soils, which may have some bearing 

 on the availability of this element when so found. 



The mineral epidote is often found among the predominating minerals 

 of the soils in all parts of the State. Its persistence is readily explained, 

 as it is a product of the metamorphism of the lesser resistant minerals, 

 biotite and hornblende. 



iThe writer has not attempted to differentiate between the members of the plagioclase group. 

 2 Fry, W. H. The condition of phosphoric acid insoluble in hydrochloric acid. In Jour. Indus, and 

 Engin. Chem., v. s, no. 8, p. 664-665. 1913. 



