SOIL OP THE MOUNTAIN. 105 



been shown, of the heavy sand group at the base, and in the 

 lower part of the coal series. These rocks form the barren 

 heights and precipitous gorges of its knobs and gaps. The 

 surface, in many of the ravines, is formed almost exclusively 

 of deposits of coarse fragments, and sometimes ranges of 

 enormous boulders of these sand masses. This occurs on 

 both sides of the mountain, very large extents of the surface 

 being frequently strewed over with these fragments. They 

 are often of great size, exhibiting the dimensions of 40 by 60 

 feet, and sometimes 30 feet in thickness. They are fre- 

 quently found a considerable distance from the summit line, 

 in chains or ranges of smaller fragments of the conglomerate 

 and sand rocks, and generally correspond to the deeper 

 notches in the crest line of the mountain. As these drifts 

 are several miles from the original rocks from which they are 

 derived, the precise history or mode of transportation affords 

 subject-matter for contemplation, interesting to the geologist. 



The argillaceous or slate material is also abundant in the 

 masses of the mountain, giving a clayey character to the soil 

 of many districts, and a general intermixture of clay and 

 sand to almost all the soils of the mountain. The extreme 

 summits of the knobs and ridges are sometimes but slightly 

 covered with a soil of almost pure sand. Proceeding from 

 the southern line of the State to the northeastern termination 

 of the Alleghany, there is a gradual increase of the silicious 

 element, with an accompanying predominance of the same 

 in the soils of the regions through which it ranges. This is 

 shown in the wilderness counties, especially the region of 

 the outcropping masses, forming the terminating ledges or 

 rim of the great Bituminous Coal Basin. 



The limestone material is not found in great abundance 

 in the rocks of the mountain. The layers of this rock are 

 thin ; and those impure, from intermixture with iron, clay, 

 and sand. Proceeding from the northern line of the State 

 towards the southwest, where the valleys between the Alle- 

 ghany and its collateral ridges are deeper, the limestone 

 formations and softer shales and slates thicken, and become 



