ORIGIN OF THE DEPOSIT. 57 



deposit is wholly of animal origin. Though insoluble in 

 water, so much so that if ground fine in the form of bone- 

 meal and applied to growing crops, it will appear to have no 

 perceptible effect, yet it is readily soluble in dilute acids, so 

 that as it is nearly free from phosphate of iron and alumina, 

 and contains but a very low percentage of carbonate of lime, 

 it offers one of the best materials in the world for the manu- 

 facture of superphosphates, inexhaustible in quantity, supe- 

 rior in quality even to fresh bones, and easily and cheaply 

 accessible. 



Various theories have been formed to account for the origin 

 of this vast deposit, which bids fair to be so important, not 

 ouly to the agriculture, but also to the commerce of the 

 country. Some maintain, as I have already intimated, that 

 the phosphate "rock" is of bone or animal origin, and that 

 the presence of large numbers of fossil-bones of marine and 

 of terrestrial animals found imbedded in and intermingled 

 with these deposits, is conclusive evidence of this. They 

 assert, that under a microscope of a high p©wer, the cellular 

 structure of the bones becomes apparent, increased somewhat 

 in compactness and weight by some kind of internal aggrega- 

 tion or condensation of phosphate of lime, and that no trace 

 of mineral phosphate of lime has ever been discovered in 

 them. It can hardly be maintained that they are petrifac- 

 tions, since they are almost entirely free from silex, and 

 actually contain often as much as 85 per cent, of pure bone 

 phosphate of lime, which seems to give color to this. theory. 

 Those who take this view say that, prepared in a thin section 

 on a slide of the microscope, they can be distinguished from 

 fresh bone only by their darker color, and by the compression 

 or compacting of the cellular structure already alluded to. 



To account for the presence of such vast and incredible 

 quantities of bone, stored up and preserved for so many ages 

 for the use of man in these later stages of civilization, they 

 assert, what is undoubtedly true, that there was a time in 

 comparatively recent geological ages, when the whole of the 

 peninsula of Florida was submerged, as well as the whole 

 low coast-line of Georgia and South Carolina, when the Gulf 

 Stream, instead of circling, as it does now, around the great, 

 sharp curve of the Florida reefs, poured its warm and majestic 



