Proceedings of the P olttecenic Association. 947 



intermixed with other mineral or organic matters. On many islands 

 in the CarrilDean sea and South Atlantic ocean, as also in the 

 Pacific ocean, large deposits of from fifteen to fifty feet in depth have 

 been discovered, composed of the rock guano. Nevassa, an island 

 which every traveler to California passes, has produced over 100,000 

 tons of guano ; Sombrero, a coral island, lying in 18° 36' N. latitude, 

 and 63° 27' W. longitude comprising about 100 acres, contains the guano 

 disseminated in veins through beds of limestone in inexhaustible sup- 

 ply. The Swan and Baker islands have furnished large amounts of 

 guano, brought into market under the name of Columbian rock 

 guano. These all contain phosphoric acid combined mostly with 

 lime, but also with other bases, such as alumnia or iron. The Som- 

 brero contains forty per cent of phosphoric acid and thirty per cent of 

 lime, with a small amount of ammonical salts. The Peruvian guano 

 contains less phosphoric acid (only ten to eleven per cent), but fifty 

 per cent organic matter, and sixteen per cent of ammonia. Some of 

 the Baker island guano contains even eighty-three per cent of phos- 

 phate of lime. 



All the guano from the Carribean sea, and coming from Mexico or 

 the Atlantic coast, is frequently called Mexican guano, although 

 Columbian guano is more proper. They all vary from twenty-five to 

 fifty -five per cent in their amount of phosphate of lime. The South 

 Carolina phosphate, discovered in 1866 by Dr. Eavenel, is found in 

 two layers, one underlying the other from two to three feet, the 

 upper layer is quite near the surface. Bones and teeth of large 

 marine animals have been found in the strata, and the guano gives 

 by analysis sixty-five per cent of phosphate of lime and nine per 

 cent of carbonate of lime, and some organic matter. 



The Nevassa guano contains not only phosphate but also carbonate 

 of lime, according to Dr. Liebig of Baltimore, who is manufacturing a 

 phosphatic manure from the Nevassa guano, and contains 6.27 j^er cent 

 carbonate of lime, with 63.55 per cent bone and phosphate of lime. 



The Bolivian guano contains 63.61 per cent of phosphates and 

 11.36 organic matter and ammonical salts. 



The Cuban guano is in caves in the island of Cuba, and contains 

 68.11 per cent phosphate of lime, and nearly ten per cent organic 

 matter. 



The Alta Yela guano, situated north latitude seventeen degrees 

 and seventy-two degrees west longitude, eighteen miles from St. 

 Domingo, contains sixty per cent phosphate of lime. 



