EGYPTIAN AGRICULTURE. 



view of the price of imported phcsphatic manures it must 

 be regarded as a valuable addition to the list of native 

 manures and there is no reason why the application of the 

 finely ground deposit should not become much more general 

 than it is. From its sparing solubility in soil water ground 

 phosphate is naturally slow of action, and the effect of its 

 application is spread over several years. Fine grinding, 

 by greatly increasing the s mount of surface expoeed to 

 the soil solvents, greatly increases the ava : lability of the 

 manure. The consumption of ihis native mineral phos- 

 phate amounts probably to about 2000 tons per annum. 



MINERAL SUPERPHOSPHATES.- 



The name superphosphate (usually contracted to "su- 

 per") is applied to the mixture resulting from the regulated 

 action of strong sulphuric acid upon some form of tricalcic 

 orthophosphate and consisting essentially of monocalcic 

 orthophosphate and calcium sulphate (gypsum). Supers 

 were originally made by treating spent animal charcoal 

 with acid, but now the phosphate employed is nearly 

 always that of ground mineral phosphate or phosphatic 

 guano. In the manufacture of some high -class supers 

 this is replaced by that of bone-a>h. The "dissolved 

 bones" and " vitriolated bones " of the artificial manure 

 market are simply varieties of super prepared from bones 

 and acid, containing varying quantities of nitrogen derived 

 from the organic part of the bones, and therefore of addi- 

 tional value from the presence in them of this consti- 

 tuent. 



The object in making superphosphate is to produce a 



