GUANO 197 



this guano is of little economic importance. By 

 far tlie greater bnlk of the material is produced in 

 the great rookeries of sea-birds which here and 

 there dot the surface of the earth. 



Some of these rookeries no longer exist, for the 

 birds changed their breeding-ground perhaps a 

 thousand years ago, but their excreta remain in 

 thick beds many feet deep. Here, after centuries 

 of leaching, the nitrates have gathered in large 

 pockets in the form of crystals, or what is better 

 known as saltpeter. In Chile and Peru there are 

 enormous accumulations of these nitrates, com- 

 mercially termed Chile saltpeter, which are noth- 

 ing more than ancient guano deposits altered by 

 time and the elements. 



Although excrement is the basic element of 

 guano, dead fish, dead birds, rotten seaweed, and 

 all the refuse which accumulates about a rookery 

 are included in its make-up. Together these make 

 an evil-smelling compound, but one highly bene- 

 ficial to plant life when applied to the soil. 



The fresh product is naturally high in soluble 

 minerals. If laid down in a region of moist cli- 

 mate, constant leaching follows, causing it to 

 lose much in valuable fertilizing compounds. The 

 potash and phosphoric acid, being already in a 

 soluble state, are dissolved off by rain-water, and 

 the presence of lime leads to a decomposition of 

 the organic material and a subsequent release of 

 nitrogen in the character of ammonia. Therefore, 



