160 Phosphate Rocks of South Carolina, 
Marl, and which seldom exceeds eight inches in thick- 
ness.* From the number of fish teeth and bones 
found in this sand, Professor Tuomey called it the 
“ Ashley fish-bed.” Above, and in a manner mixed 
with it, is another of irregular and partly rolled frag- 
ments of what is commonly called MMJar/-rock—the 
interstices between each being filled with blue mud. 
These rocks contain the same forms of fossils as are 
found in the Marl below; but the lime which they 
must have contained has been extracted, leaving a 
silicious mass much water-worn and boulder-like in 
appearance, and emitting a foetid odor when broken. 
The Marl of the Ashley contains about 70 per cent. 
of Carbonate of Lime—these only a small quantity, 
say 2 or 3 per cent. 
“That they belong to and were broken off the Marl 
bed below, there can be no doubt, but at what period 
they were washed up and deposited where we now 
find them, is still undetermined. They extend over 
many miles of the surrounding country ; increase in 
size towards the northwest, and decrease in the oppo- 
site course, southwest, where we find them under the 
City of Charleston. 
“For the most part, they are enveloped, as I said, 
in a matrix of blue mud or clay, though often a peaty 
substance (marsh roots?) takes the place of the 
clay, and again the clay and peat are missing, and 
they are found in the sand. 
“Next in the order of super-position are the red 
* In boring the Artesian Well in Charleston, this stratum was reached 
at about sixty feet below the surface, and from it a supply of good water was 
obtained ; the water rises within four feet of the surface. 
