66 
Navassa phosphates. 
No.1. | No.2. | No.3. | No.4. | No.5. | No.6. | No.7. | No.8 |No.9. 
Moisture, water of compo- 
sition, and loss in heating. 11.37.) 12..65°| 312308 | 12.08 10. 90 13.99 | 12.55 9.35 | 10.53 
Phosphoric TY Ci A 98h ee 31.18 | 2847} 31.15] 30.21) 31.08) 30.04; 31.90} 31.85 | 29.60 
TMB Ha S.Ce ate =o teowae cence 37.70} 34.07 | 38.58 | 35.32] 36.54] 35.99} 36.09 | 37.91 | 31.72 
Magnesia, carbonicacid,oxide) 16.83 | 18.53 | 15.57) 19.65 | 17.78 | 17.04) 16.91 | 17.99 | 25.45 
of iron, alumina, &c. 
Insoluble siliceous matter...! 2. 92 6. 28 2. 62 2.74 3. 70 2. 94 2. 55 2.90 | 2.70 
100. 00 100. 00° 100. 00 | 100. 60 | 100 100. 00° “100. 00 | 100 100. 00 100. 00 |100, 00 
peeapal toeribasio phosphate | 68.07 ~ 62, 15 | 68.01 | 65.94] 67. "85 65.58 | 69. 64 69.53 | 64. 62 
of lime. 
The carbonate of lime in the first three specimens amounts to over five 
per cent. 
Rock-phosphates of quite variable character are also found in St. 
Martin, a small island of the Windward group. They are mingled with 
inferior materials, requiring care and labor to eliminate. The percent- 
age of phosphate of lime in eight analyses ranged from 36.39 to 80.64, 
and of carbonate of lime from 6.57 to.46.81. It is remarkable that the 
latter element was almost in inverse proportion to the former. Those 
specimens of low percentage of phosphate are practically useless and 
unsalable. 
Aruba, one of the Leeward Caribbean islands, belonging to Holland, 
has been occupied for gold-mining since 1824. The mining company 
have recently obtained a concession to work the newly-discovered phos- 
phatic minerals ofthe island. These are compact; hard, stone-like masses 
of rock, of light-brown or yellowish color, streaked with chocolate bands, 
and are frequently interlaced with calc-spar. These phosphates will 
probably prove a better investment than the gold-mining of the island, — 
as they contain from 63 to 76 per cent. of phosphate of lime, with 
variable quantities of the carbonate. 
Redonda, another Caribbean islet, yields a peculiar phosphate, once 
mistaken for phosphate of lime, but now known to consist, principally, 
of the hydrated phosphate of alumina with varying proportions of oxide 
of iron and insoluble siliceous matter. It is utilized for the production 
of alum, and the impure phosphoric acid extracted is incorporated with 
salts of ammonia and other fertilizing materials, to make artificial 
manures. After treatment with sulphuric acid it is also used to precipi- 
tate and clarify town sewage, for which it is a very effective agent. Four 
analyses of this material showed from 42.35 to 84.09 per cent. of phos- 
phate of lime, though in most samples there is little or no lime in com- 
position. 
The phosphate of Alta Vela, an islet near Hayti, is harder and lighter 
colored than that of Redonda; three analyses gave from 43.81 to 67.37 
per cent. of phosphate. 
After giving in detail the specific characters of these different phos- 
phatic deposits, Dr. Voelcker presents some conclusions of general 
interest and value. He says that none of the varieties described are of 
any great value unless treated with sulphuric acid. Some German 
phosphates of low quality have been usefully applied after simple pul- 
verization in the neighborhood of their extraction, like marl, at the rate 
of about a ton per acre; but as a rule phosphates are useful only in the 
manufacture of superphosphates, in which the aim of the process is to 
~ender the phosphate soluble. Soluble phosphate of lime is a specific 
