CHAPTER IV 



Phosphates in General 



Of all the chemical manures to which we have 

 recourse we find the greatest variety is derived from 

 phosphates. There is a great diversity of matter, 

 distributed practically all over the surface of the 

 globe, which can furnish them. Mineral layers, 

 more or less important and under different forms, 

 are found in the greater part of Europe ; America 

 possesses them in large quantities, and Africa 

 supplies them also. After mineral products come 

 phospho-guanos which exist in many foreign 

 countries. 



Then there are phosphates of bones of many kinds, 

 guano of fish bones, and lastly slags. 



The sources of phosphates therefore are obviously 

 plentiful ; so much so, and in such diverse qualities, 

 that it is not astonishing that sometimes one con- 

 fuses them, and that it seems difficult to distinguish 

 their value as fertilising materials in the great number 

 of preparations that are recommended. Each pro- 

 ducer preaches his own and finds it the best. 



It should be said, however, that many of these 

 phosphates cannot be regarded as manures in many 

 soils, and it is absolutely necessary, therefore, that 



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