32 CHEMICAL MANURES. 



the rivers Apalachicola in the west and north, and Caloosabatchee 

 in the south. Throughout all these districts, representing a length 

 of 400 miles, the exploitation has been followed up with feverish 

 enterprise, and the quantities marketed, not only in the United 

 States but in Europe, have rapidly increased. So as to be able to 

 give some details of the nature of the phosphates collected in this 

 region, the geology of Florida will not be discussed. 



Description of the Deposits. — Four kinds of phosphates are 

 differentiated by the following names, viz. Hard Rock, Soft Phos- 

 phate, Land Pebbles, River Pebbles. 



Hard Bock. — Rock phosphate as a type is hard, compact, with 

 a fine homogeneous grain, usually a pale yellow with irregular 

 cavities often coated with mamillary concretions of phosphate of 

 lime. These cavities are sometimes filled with amorphous phos- 

 phate of argillaceous aspect, due to the transport by water of 

 particles of phosphate in suspension. The hard rock deposits of 

 the Eocene are concentrated in a narrow belt of about 144: miles 

 long, almost parallel with the West Coast of Florida, and at a dis- 

 tance from the sea varying between 25 to 50 miles. Taken as a 

 whole, hard rock occurs as a conglomerate of boulders, cemented 

 by a gangue, consisting of phosphatic sand, clay, or other detritus 

 from the disintegration of the hard rock, and which constitutes the 

 soft phosphate. The magnitude of these deposits of hard rock 

 vary considerably. Near Dunellon they are often 40 to 50 feet 

 thick, elsewhere only 5 to 10 feet. On certain points phosphate 

 is found on the outcrops, especially in Levy County, but more often 

 it is covered by a layer of sand 10 feet thick. There are two kinds 

 of rock phosphate, solid rock and laminated rock. The solid 

 rock is more or less homogeneous, of a white, grey, or yellow colour, 

 sometimes deep blue or black, but more often it is marbled. The 

 hard rock of good quality contains 77 to 82 per cent of phosphate 

 of lime, and 3 per cent of oxides of iron and alumina. The analysis 

 of a fine sample of hard rock gave the following figures : — 



TABLE XXIII.— ANALYSIS OF A FINE SAMPLE OF HARD HOCK 



PHOSPHATE. 



Per cenf.'^ 

 Water 0-92 



Calcium fluoride . 

 Phosphate of lime 

 Carbonate of lime 

 Oxide of alumina . 

 Oxide of iron 

 Silica . 



4-4 

 83-14 

 8-63 

 1-52 

 8 -40 

 4-l:-5 



The analysis of two cargoes of 800 tons each, from the Bhie 

 River Phosphate Co., gave : — 



^ Totals to 106-19 ; the error is evidently in the oxide of iron. — Tr.. 



