296 EGYPTIAN AGRICULTURE. 



mineral superphosphates are manufactured and in view 

 of the fact that phosphatic deposits have bean discovered 

 in various parts of the country, notably at-Keneh, in the 

 neighbourhood of the Dakhla Oasis, and in the Sinai 

 Peninsula. 



Apart from raw phosphate mineral superphosphate is 

 the only phosphatic artificial at present employed in any 

 quantity in the country and its use is steadily increasing. 

 Its nature and manufacture must therefore be considered 

 at some length. 



Basic slag may come into more general use in time ; 

 so far its application has been practically confined to 

 small experimental areas. 



RAW PHOSPHATES. 



In various parts of the world rocky masses exist which 

 on analysis prove to be largely made up of tricalcic ortho- 

 phosphate Ca 3 (P0 4 ) 2 . The best known deposits are 

 those of the United States (South Carolina and Florida) 

 Canada, France, Belgium, Algeria, etc. etc. These deposits, 

 either in a finely divided state or after conversion into 

 the manure " superphosphate," to be described later, are 

 now employed in immense quantity in agriculture to 

 replace the phosphoric acid removed from the land in 

 crops and ?o keep up the percentage of this valuable plant 

 fo xl in the soil. The different deposits, some of which 

 sliow di tinct signs of animal origin, vary very much 

 amongst them>elves both as regards physical c-haractjr an 1 

 chemical composition. Some are of a hard crystalline nature 

 making them difficult to grind, others are soft and amor- 



