50 THE LOWER PINE BELT, OR SAVANNA REGION. 



tlio upper strata, became charged with a certain amount of phospluite of 

 lime. That the proportion of the phosphate of lime thus obtained to the 

 whole body of the.superficial layers of the marl was afterwards increased; 

 1st, by the removal of a considerable amount of the carbonate of lime, 

 rendered soluble Iw the percolatic^n through it of rain water containing 

 carbonic acid, derived from the decomposing vegetable matters in the soil 

 overlaying the marl. 2d, by a well known proneness of phosphoric 

 acid, when diffusely distributed, to concentrate and to give rise to concre- 

 tionary processes similar to those observed in the flint nodules and peb- 

 bles of the English chalk. This theory agrees with the diffused occur- 

 rence of phosphate of lime in the superficial layers of the marl, as well as 

 with the fact that the upper la^^ers of the deposits and the outside of the 

 nodules are the richest in phosphate. It substitutes for a local cause a^ 

 general one, commensurate at once with the wide area occupied by the 

 phosphate rocks and by the phosphatic marls of the South Atlantic sea- 

 board. Such a cause also might have been in operation ages ago, when 

 the layers of phosphate rock, found at a depth of 300 feet in artesian 

 borings, were forming ; and it may be in operation now, as the dredging 

 work of the United States Coast Survey shows that the marls accumulat- 

 ing, at the depth of 200 fathoms on the floor of the Gulf Stream, between 

 Florida and Cuba, contain a considerable percentage of phosi)hate of 

 lime. 



No systematic survey, determining the extent of these deposits, has 

 yet been attempted. The only information on this bead comes from 

 prospectors, seeking easily accessible rock in localities convenient for 

 shipment. Widely varying estimates as to the quantity of the rock have 

 been ventured. Some have placed it as high as five hundred millions of 

 tons, and others as low as five millions. The latter is the estimate of 

 Prof Shepard, who has prepared a map of the region. He traced the 

 deposit over 240,000 acres, and roughly estimates the accessible rock as 

 covering only about 10,000 acres. Even this estimated area at 800 tons 

 per acre, Avhich he gives as an average, should yield 8,000,000 tons. But 

 if we examine a single mining region, as that for instance occupied by 

 the Ccoaw company, we must conclude that he has very greatly under- 

 estimated the amount. This company has the exclusive right to a terri- 

 tory of about 6,000 acres in Coosaw river, besides the adjacent marshes, 

 yet unexi)lored. Everywhere the river bottom is covered with rock, 

 which for the most part forms a solid sheet, varying from 8 inches to 1^ 

 feet in thickness. Taking the lesser thickness, we have, with a specific 

 gravity of 2.5, after subtracting 25 per cent, for loss in washing and dry- 

 ing, something over 1,700 tons to the acre, which would give for the 

 river territory alone belonging to this one company something more than 



