142 GEOLOGICAL SURVEY 
Occasionally a level spot occurs where the impervious sub-soil of porcelain clay retains the rain- 
water, producing a verdant spot, interspersed with plants that love wet places, which contrasts plea- 
santly with the surrounding parched and scanty herbage. Beds of pure quartzose sand are also 
found here among these hills, that would answer well for the manufacture of glass. 
On Horse Creek I examined a very remarkable sand stone, which is not uncommon among the 
strata under consideration. It consists entirely of the ruins of granite, consolidated into a pretty 
hard rock. The quartz, feldspar, and mica are there, and it requires a close examination to satisfy 
one that it is neither granite nor gneiss, in which the feldspar has barely lost its lustre. It is soon 
seen, however, that the latter mineral is not disposed, throughout the mass, in crystalline grains, as 
is the case in granitic rocks, but that it is the cement, keeping the whole together. It is not, in fact, 
feldspar, but that mineral deprived of nearly all its potash. 
This rock varies much in its structure, and is coarse or fine grained, as quartz or porcelain clay 
abounds in it. In some beds the quartz and mica are disposed in lamin, and it then resem- 
bles gneiss. In almost every case round pieces of the kaolin will be found scattered through it, 
which will always be sufficient to distinguish it from the older rocks, in the absence of organic 
remains. 
OF the beds of loose sand of this formation fine sections are seen on the “Inclined Plane,” at 
Aikin: they are composed of sand, colored clays, kaolin, with water-worn fragments of the latter 
interspersed. 
The next stratum, superimposed on these, is uncovered on a little stream about one half mile 
west of Aiken. It is a yellowish white, silicious rock, comparatively light. It yields readily to any 
cutting implement when first taken from the quarry, but becomes much harder by exposure. It is 
disposed in very regular beds, evidently deposited from still water, and indicating a period of 
repose that succeeded the deposition of the preceding beds, which present, in the manner m which 
they are thrown up, evidence of strong currents, and otherwise agitated waters. ‘This bed, which 
is not more than four feet thick at this place, is very variable in its structure and appearance: some- 
times appearing as a laminated silicious clay, at other localities it is quite hard, breaks with a con- 
- choidal fracture, and resembles menilite. Another variety is light and porous, and so closely résem- 
bling the infusorial earth of Virginia, that I incautiously referred it to that substance, and thus 
misled Mr. Ruffin. This curious stratum I traced, at distant localities, nearly encircling the boun- 
dary of the calcareous beds of the Charleston Basin. 
On the hill side, and overlying this, the northern edge of a bed composed of silicified shells, 
cemented together, and resembling buhr millstone, is found. The fossils at this locality are neither 
numerous nor well preserved, but I recognised, among them, Fusus papillatus, Ostrea longirostris, 
and O. Alabamiensis—well known Eocene fossils. 
A few miles south of Aiken, on Cedar Creek, one of the branches of Upper Three Runs, this 
rock is again exposed in beds of considerable thickness. On each side of the little valley, on the 
farm of M. Caradeaux, thick ledges of silicified shells are seen outcropping, and as they are under- 
laid by sandy beds, which are often washed away, the rocks tumble down and strew the surface. 
The shells having left their hollow casts only, which gives the rock a cellular structure that fits it 
admirably for mill-stones. The casts are sometimes filled with silica, in the form of curiously inter- 
