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Nodular Phosphates of South Carolina. 355 
ten to twenty miles from Charleston ; farther up stream, the 
nodules are found in a sandy soil, and become permeated with 
sand to the amount of thirty per cent and over, when the phos- 
hates do not reach fifty per cent. On some plantations the 
d of phosphatic nodules is over two feet in thickness; and 
the amount of marketable material produced from mining an 
acre may exceed twelve hundred tons. Qn the Stono and 
Edisto rivers there have been found but few rich deposits,—the 
stratum exhibiting continuity in but occasional spots. As a 
ance of an immense pavement, extending over hundreds of 
acres at a depth of three to six feet. It is with difficulty that 
the large masses (often several hundred weight each) can be 
pried apart, so closely are they wedged together,—having a 
smooth, glazed, upper surface, but irregular beneath. The 
masses moreover are often penetrated to considerable depth, 
Sometimes perforated by round _ holes, which extend generally 
in a perpendicular direction. These cavities have a diameter 
of one-half to one inch. The phosphatic masses forming this 
floor are nine to twelve inches in thickness, and overlie a of 
nodular phosphates of smaller size, which extends down to the 
depth of twelve to fifteen inches below the continuous stratum. 
The whole deposit is imbedded in a tenacious clay, underneath 
which occurs a yellow-red marl, This marl is rich in shells 
and the bones of marine and land animals. It is composed, 
when air-dry, of nearly 70 per cent sand, 18 per cent carbonate 
of lime, and 5 to 7 per cent phosphates of lime, alumina and 
iron. It is reported that the nodules form in some limited 
localities a second layer, and as continuous as the top stratum, 
—underlying it at the depth of about one foot. _ : 
_ The phosphatic nodules and masses generally give on fric- 
tion of their fresh surfaces, a peculiar naphthous odor. This 
property is, as a rule, the more decided, the denser the nodules ; 
and is in direct proportion to the amount of organic matter 
contained in them. The impressions of numerous fossil shells 
of the Eocene period occur throughout the various phosphatic 
asses 
es, dhioi ea 
Composition.—The analyses given below are of hand speci- 
mens, taken at random from large quantities of the material of 
the different localities mentioned. They are not supposed to 
