SOUTH CAEOLINA PHOSPHATES. 101 



ure their peculiar celluLar structure, but seem, in many cases, 

 to have materially increased in compactness and weight, by a 

 kind of internal segregation or condensation of phosphate of 

 lime, though no trace of mineral phosphate has ever been 

 found in them. On this account they have been sometimes 

 considered petrifactions, but analysis shows an almost perfect 

 absence of silex, and they contain 85 per cent, of pure bone 

 phosphate of lime. It may be asked if these fossil bones and 

 phosphatic rocks are purely animal in their origin, how does 

 it occur that the bone, retaining its original form, and to some 

 extent its size, contains a greater per cent, of phosphate of 

 lime than it did in its fresh state ? This may be easily ex- 

 plained by analyzing a specimen of fresh bone and comparing 

 it with the analysis of a fossil bone. Dr. Pratt, of Charles- 

 ton, the pioneer in this discovery, and from whom I have re- 

 ceived the greatest assistance in the study of this deposit, 

 gives the following analysis. Take the long, hard bone of 

 an ox, — 



Phosphate of lime, ..... 61.24 

 Carbonate of lime, . . . . .8.60 

 Organic matter and water, . . .30.16 



100.00 



Remove by decomposition, putrefaction or otherwise, from 

 this bone 28 parts of the organic matter and water, and we 

 have, — 



Phosphate of lime, . . . . .61.24 

 Carbonate of lime, . . . . .8.60 

 Organic matter and water, . . . . 2.16 



72.00 



And out of every 72 parts of residue, 61.24 parts, equivalent 

 to 85.05 per cent., will be pure bone phosphate of lime. 

 Again, to test the rock, take the average of mixed bone, such 

 as is ordinarily used in making commercial bone-dust, and 

 we have, — 



