234 GEOLOGICAL SURVEY 
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The animal matter is, of course, dissipated, but the phosphate remains unchanged.* A few 
miles inland, the Post Pliocene Marls are found, that contain an amount of carbonate, varying, 
where shells are at all abundant, between 12 and 69 per cent. of carbonate of lime. 
A specimen from Wadmalaw gave, 
@arbonatesof lime; = 2" i223 e. 2 eee 57.0 
Silictous sand) soe socenin eee ae Se cee ene 40.0 
‘Aluminasand: Oxideiof iron\>-- --2--=seeee ees 3.0 
100.0 
Another specimen from St. Thomas’s parish, near the coast, of a white marl, with the shells very 
much decomposed, and quite accessible, gave, 
Garbonateroiplimesteenaha. See Sloe s ee ee 60.0 
Silicioustsand.=* So" 2623 aa eee eee 36.0 
Aluminaand Oxade\of irons — 2 a soe en 4.0 
100.0 
Mr. Ruffin analysed three specimens from Edisto island, which contained respectively 18, 27, and 
58 per cent. of carbonate of lime; and another from Distant island, near Beaufort, which gave 47 
per cent. Some of the beds in Horry are unmixed heaps of shells, and of course rich in carbonate 
of lime. 'The shells in these beds are generally in as perfect a state of preservation as the recent 
shells on the coast; still, when mixed with the soil, they are soon atiacked and decomposed, with 
the exception of the oyster family, which resist all ordinary agencies with surprising effect. 
Besides these there are other sources of calcareous manures in this part of the State. In many 
places the refuse of old indigo works has been discovered, which is sometimes rich enough in cal- 
careous matter to render it a profitable application to the land. 
It is so long since indigo was manufactured in this region, that it has been entirely forgotten, and 
it is only by the accidental discovery of the old lime that was used in the preparation, that it is 
brought to mind.t These deposits of lime, mixed with earthy matters and the refuse of the 
vats, are often extensive, and so equivocal in appearance, that it becomes really difficult to decide 
on their real character. In general, however, the absence of fossils, and the peculiar appearance of 
hydrated lime, although converted again into a carbonate, are suflicient to distinguish them from the 
calcareous deposits that have resulted from the natural decomposition of shells. Ata landing on 
the left bank of the Combahee, above the ferry, I saw a low bluff in which were numerous concre- 
tionary nodules of lime, very different from the indigo lime, that must belong to the beds in which 
they are found. It should not excite surprise, that strata which were deposited when the marls of 
the Ashley, Cooper, and Santee, formed the coast, should contain lime. I have already shown that 
these marls were washed by water, which transported their ruins to a distance. 
In the point of view in which we are now considering these deposits, it makes but little difference 
*It may be worth while to remark, that when bones are burned for the purpose of facilitating the grinding before they are 
applied to the soil, that the phosphate of lime, of which they are composed, remains undecomposed, the bones barely losing the 
fatty matter they contain, which, according to Payne, is an advantage; for the grease, it seems, prevents, to a certain extent, the 
decomposition of the bone dust. 
+ The manufacture of Indigo still lingers in Orangeburg district. T. W. Glover, Esq., was kind enough to prepare for me an 
account of the ::anufacture as practiced there, which is presented. Appendix. 
