AGRICULTURE AND RURAL ECONOMY. 367 



Exposed to weather in various climates, bird-dung undergoes 

 change, and guanos of various qualities are produced. The 

 ultimate effect of rain is to destroy the organic matter; the 

 guano then remaining is said to be phosphatic, and contains 

 very little nitrogen. These phosphatic guanos are of great 

 value as materials for high-grade superphosphates. In many 

 cases the bases present are insufficient to form tribasic salts 

 with phosphoric acid, and the phosphoric acid is hence in 

 more readily available forms. The principal supplies are 

 from South America, South Africa, a number of islands in 

 the Caribbean Sea, several uninhabited islands in the South 

 Pacific, and Raza and other islands in the Gulf of California. 

 The richest samples analyzed were those from Raza Island, 

 in the Gulf of California; and Shaw's, Enderbury, Starbuck, 

 and other coral islands in the Pacific. These yielded from 

 32 to 40 per cent, of phosphoric acid. The latter are, how- 

 ever, apt to be contaminated with coral rock. The Baker, 

 Howland, and Jarvis islands are nearly exhausted. Mejil- 

 lones guano, a deposit near the coast of Bolivia, is estimat- 

 ed at several million tons. Considering the fact that phos- 

 phoric acid is the ingredient most apt to be deficient in our 

 soils and most largely needed in commercial fertilizers, the 

 reports of Dr. Voelcker, which show that immense supplies 

 of this material are accessible in various parts of the world, 

 are very cheering {Journal Royal Ag. Soc.,x'u., 440-459). 



Nitrogenous Fertilizers. 



Dr. Voelcker reports also a number of unweathered or 

 partially weathered guanos from new deposits on the South 

 American coasts, which indicate that the supply of these is 

 fiir from being exhausted. A number of analvses are given 

 in Vol. XIII., pp. 194 sg., of the journal just referred to. 



Analyses of eleven samples of Peruvian guano are given 

 in the "Report of the Connecticut Agricultural Experiment 

 Station for 1876." They averaged better than was claimed 

 by the sellers: "Of over two hundred samples of fertilizers 

 analyzed at the station, leaving out a few articles of at pres- 

 ent mere local importance, like crude fish-scrap, no others 

 have been found which, as a class, taking into account both 

 quality and price, furnish the valuable ingredients of plant- 

 food so cheaply as Peruvian guano." A great step in ad- 



