PEINCIPAL PHOSPHATE DEPOSITS. 



43 



TABLE XXXIIL— ANALYSIS OF BAKER ISLAND GUANO. 



Tribasic lahosphate of lime . 



Tribasic phosphate of magnesia 



Irou phosphate 



Sulphate of lime . 



Alkalies 



Chlorine 



Ammonia 



Nitric acid . 



Water, sand, etc. . • 



Pe?- cent. 

 78-79 

 6-12 

 0-12 

 0-13 

 0-85 

 0-13 

 0-07 

 0-45 

 13-34 



100-00 



Baker Island was the first island in the Pacific Ocean in which 

 guano was discovered and exploited. It is not, therefore, astonish- 

 ing that the deposit is partially exhausted. 



Other isles in the Pacific Ocean contain vast quantities of 

 phospho guano, absolutely similar in composition to that of Baker 

 Island, But the greater part of these deposits are only of historical 

 value seeing that, if they are not exhausted, their output is insuffici- 

 ent. Thus the deposits of Baker Island, Lacepede, Malton, and 

 Pelsart, w^ould appear to be far from exhausted, and still to contain 

 enormous quantities of guano. But the greater number of the 

 islands are abandoned, because the cost of working and freights 

 are too high for the selling price of the guano, which at the present 

 time cannot compete with mineral phosphate. 



Jarvis Guano is a mixture of powder, hard plates, and some- 

 what friable stratified fragments. The plates have a porcelain char- 

 acter sometimes semi-milky, already found in analogous guanos. 

 Perfectly dried in an oven at 100" C. (212° P.) these fragments pre- 

 serve their appearance. By detaching the stalagmites, which 

 cover the plates, it has been found that they owe their semi-trans- 

 parent appearance to the hydration of the phosphate of lime, 

 evidently precipitated in a very slow manner. The phosphate so 

 hydrated cannot, in fact, lose its water, except at a red heat, and 

 the hard Jarvis plates still contain 11 or 12 per cent, which 

 analysts have often confounded with organic matter, when they 

 have ignited the manure after simple drying in the oven. This 

 physical state of the phosphate of lime may be understood by going 

 iDack to the phenomena which have successively led to the evapora- 

 tion of the nitrogenous substances in the guano. Such phenomena 

 cause the partial solution of the phosphate of lime, then later on, 



been wrought in an intensive manner. Some per cents of carbonate of lime 

 are always found in it, and only 75 per cent of tribasic phosphate of lime. The 

 above analysis may also apply to all analyses of this class, from the point where 

 they do not contain large amounts of gypsum, sand, and analogous mipunties, 

 as certain guanos from Jarvis Island. 



