32 Phosphate Rocks of South Carolina, 
HOW THE NODULES WERE CONVERTED 
INTO PHOSPHATE-ROCKS. 
At this stage of the history of the origin of the 
Phosphate-rocks, the reader naturally expects, and it 
seems to us also the proper place to explain the man- 
ner in which these masses of Lime Rock or Carbon- 
ate of Lime have been changed into Phosphate-rocks, 
or Phosphate of Lime, and to give all the evidence in 
support of the hypothesis which science can bring to 
bear on the subject. 
In a former chapter, p. 21, we have endeavored to 
show that the outcrop or exposed edges of the 
upturned Santee beds which are seen near Aiken in 
this State, were originally Marl rocks, rich in Carbon- 
ate of Lime, and undoubtedly belonged to those beds, 
but have lost their Carbonate of Lime, and have been 
changed into a mass of flint rock or ‘“ Buhrstone.” 
We now propose to explain how this change 
occurred, and then to point out the analogy existing 
between the rocks of the lowest bed of the Eocene 
Marl changing from a lime rock into a flint rock, having 
no lime; and the rocks of the youngest beds of the 
same Eocene age changing intoa Phosphate-rock, and 
retaining but a small portion of Carbonate of Lime. 
How, in fact, a Marl or Lime rock may be converted 
into flint, under certain chemical influences, and into 
Phosphate-rock under other influences of a very dif- 
ferent nature. 
The Santee Marl, where it outcrops near Aiken 
and along the strike of the bed in Orangeburg and 
