MODERN HIGH FARMING. 



63 



The dredging apparatus ordinarily employed is fitted with 

 washers which effect the separation of the phosphate from the sand 

 and other extraneous bodies, while being raised through the water. 



Both qualities of these phosphates, when finely ground, afford an 

 excellent material for superphosphate manufacture, despite their 

 somewhat heavy percentage in iron and alumina, and their large pro 

 portion of insoluble matter. 



As they contain very little carbonate of lime, their treatment 

 entails no waste of sulphuric acid, and they possess the superiority 

 over many other phosphates, when properly decomposed, of yield- 

 ing up all their phosphoric acid in a soluble form. 



CANADIAN PHOSPHATE occurs in the form of bottle-green crystal- 

 line masses, more or less associated with portions of the gneissic 

 rocks or mica slates which surround it in its native fissures. It is 

 in all respects a mineral, and is found in clearly defined veins and 

 cavities, extending sometimes to a very considerable depth, and be- 

 coming richer in their yield as they go down. 



The following analyses are fairly representative of its general com- 

 position, and have been selected from many hundreds made by our- 

 selves and differing only in trifling details: 



1 



Moisture and Water of combination 0.09 



*Phospboric Acid 41.13 



Lime 53.70 



Carbonic Acid 1.37 



Sulphuric Acid traces 



Oxide of Iron 0.06 



Alumina 0.54 



Magnesia traces 



Fluorine 2.14 



Insoluble Siliceous matters. . . . . 0.97 



100.00 100.00 100.00 



*Equal to Tribasic Phosphates of Lime 89.65 82.05 76.90 



When pure it is a fluor-apatite, composed of phosphate of lime 

 and fluoride of calcium, and is generally presented to commerce in 

 the rough, in. blocks varying in weight, from one to several 

 hundred pounds, of a beautiful green color and brittle texture. 



