376 REPORT OF NATIONAL MUSEUM, 1899. 



shore. The richest and largest beds are at Pabellon de Pica, Punta de 

 Lobos, Huanillos, and Chipana. 



Aside from the localities above mentioned, guano is found on the 

 islands Itschabo, Possession, Pamora, and Halifax, off the Namagua 

 coast of Soutn Africa. The material is described as forming a grayish 

 brown powder, free from large lumps, and possessing a faint ammo- 

 niacal odor. It carries from 8 to 14 per cent of nitrogen and 8 to 12 

 per cent of phosphoric acid. 1 



The West India Islands. Phosphates belonging to the class of leached 

 guanos occur in considerable abundance on several of the islands of the 

 West Indies group, the principal localities being Sombrero, Navassa, 

 Turk, St. Martin, Aruba, Curacao, Orchillas, Arenas, Roncador, Swan, 

 Cat or Guanahani, Redonda, the Pedro and Morant Keys, and the reefs 

 of Los Monges and Aves in Maracaibo Gulf. These, as would natu- 

 rally be expected from their mode of origin, vary greatly, not merely 

 in appearances, but in chemical composition as well. That of Sombrero 

 is described 2 as occurring in two forms one a granular, porous, and 

 friable mass of a white, pink, green, blue, or yellow color (Specimen No. 

 44275, U.S.N.M.); the other as a dense, massive, and homogeneous 

 deposit of a white or yellow color. Many bones occur. The phosphate 

 carries from 70 to 75 per cent phosphate of lime. An analysis as given 

 by Davies 3 is as follows: 



Moisture and water of combination 8. 92 



Phosphoric acid 4 31. 73 



Lime 45. 69 



Carbonic acid 5 5. 99 



Oxide of iron and alumina 7. 07 



Insoluble siliceous matter. . . .60 



100. 00 



The Nevassa phosphate is described by D'Invilliers 6 as occurring 

 (1) in the form of a gray phosphate confined to the lower levels of the 

 island, and (2) a red variety occupying the oval flat of the interior. 

 The gray is the better variety, as shown by the analyses below, though 

 both are aluminous, and difficult of manipulation on that account. 

 Both varieties occur in cavities and fissures in the surface of the hard 

 gray, white, or blue limestone, of which the island is mainly composed. 

 These cavities or pockets are rarely more than 4 or 5 yards wide on 

 the surface, and frequently much smaller, and of depths varying from 

 5 to 25 feet. The deposits, so far as explored, are wholly superficial. 



1 Journal of the Society of Chemical Industry, I, 1882, p. 29. 



2 R. F. Penrose, Bulletin No. 46 of the U. S. Geological Society . 

 8 D. C. Davies, Earthy and Other Minerals, p. 178. 



4 Equal to tribasic phosphate of lime, 69.27 per cent. 



5 Equal to carbonate of lime, 13*61 per cent. 



6 Bulletin of the Geological Society of America, II, 1891, p. 75-89. 



