RICHLAND COUNTY. 3138 
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, leay- 
' 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 afford 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: | 
