236 SOILS AND MANUKES 



of dicalcic phosphate, by the addition of an appropriate 

 amount of lime. This product was called precipitated 

 phosphate, and would probably have become a useful 

 and popular manure had it not been discovered that 

 better results could be obtained by simply grinding 

 the slag to a fine powder and spreading it on the land 

 direct. Any process of solution is not only more ex- 

 pensive to carry out, but it also removes the free lime 

 and destroys the basic character which is one of the most 

 valuable qualities of slag. Moreover, any treatment of 

 the kind is superfluous. The total amount o,f injurious 

 substances in an ordinary dressing of basic slag is small 

 compared with the mass of the soil, and when the slag is 

 finely ground, these are rapidly oxidised. At all events 

 no appreciable injury to the crops has ever been traced 

 to them. 



