RICHLAND COUNTY. 313 



ments on the surface. If erosion by rain-fall excavated the depressions 

 and ravines, the water would have had force sufficient only to carry away 

 the clay, sand, and finer gravels, and the surface would now be covered 

 with bowlders and fragments of rocks; but such a condition of the sur- 

 face is nowhere found. A comparatively few isolated bowlders are scat- 

 tered over the surface as though dropped upon it. In the deeper ravines, 

 which should be filled with a mass of these bowlders, they are very rarely 

 found, and are no more abundant upon the slopes than upon the tops of 

 the hills. 



On the margins of the streams there is frequently at the bottom a de- 

 posit of laminated or finely stratified clay, with rudely stratified gravel 

 and bowlders above. The fragments of the local rocks are here rounded 

 and globular; no striated granitic fragments are found, In places, all 

 the fragments of the local rocks have been ground to powder, and, with 

 all the clay and finer gravels of the Drift, have been washed away, leav- 

 ing only coarse, well rounded, granitic pebbles, with occasional bowlders 

 of the corniferous limestone. In this material, also, cavities are occa» 

 sionally found having no outlets, the character of the underlying rocks 

 and the form of the surface indicating that they are not properly " sink 

 holes," such as are often found in limestone regions. A little east of the 

 railroad station at Lexington, two such cavities are quite conspicuous. 

 They are on a long, billowy, ridge filled with coarse gravel and bowlders, 

 and covered with a forest of hard maple. In the deepest cavity the de- 

 pression is twenty-five feet, in the other fifteen feet. The slopes in each 

 are smooth, without rock fragments, and covered with the native forest 

 trees. In both there is accumulation of humus at the bottom, and the 

 deeper one contains a little water. They afiord a ready explanation of 

 the origin of the small ponds having no outlet, found in other places along 

 this divide, with dead forest trees standing in the water. In the orig- 

 inal cavity the drainage through the porous bottom was free, and the 

 forests occupied the bottom and the slopes. The wash of the slopes and 

 the fine material of the decomposed vegetation gradually accumulated in 

 the gravelly bottom, which, like a filter long used, gradually became im- 

 pervious to the water, which encroached more and more upon the veg- 

 etation, ultimately destroying it, and the dry cavity became a pond. The 

 accumulation of vegetable debris, and the growth of water plants upon 

 the margin, will finally convert the pond into a marsh, which, in the 

 end, will be filled up and obliterated. 



A general section made north and south through the county, elimina- 

 ting the water courses, would be substantially as represented on the sub- 

 joined wood cut : 



