AUXILIARY A2s"D EXCEPTIO^'TAL 3IAXURE3. C9 



of their substance, are a mixed pliospliato and carbonate 

 of lime. 



Althougli there seems to be considerable difference in 

 the results obtained by different experiments, the general 

 conclusion seems to be that the usual difference in the 

 effects produced by soluble and insoluble phosphates is 

 much diminished when the latter are reduced to very fine 

 powder and applied in very large quantities. The pow- 

 dered phosphate is cheaper than the manufactured ma- 

 nure. But there can be no doubt that an increased use 

 of ground coprolites would result in increasing their cost 

 in the market, aud the advantage would thus to some ex- 

 tent be lost. 



After fine grinding, the coprolite powder may be mixed 

 with farm-yard manure, either under the cattle or else in 

 the dung heap, and the carbonic acid formed by the fer- 

 mentation of the dung tends to the solubility of the 

 mineral phosphates by actual superphosphating. Sixteen 

 years ago. Professor Graham pointed out the greater ad- 

 vantage to agriculture of the cheap carbonic acid method 

 of superphosphating than of the dear sulphuric acid 

 method; first, because it was vastly cheaioer, and secondly, 

 because it did not give rise to the production of insoluble 

 phosphates. 



Ground phosphate requires to be used in mucli larger 

 quantities than dissolved phosphate, if it is to produce 

 equal results. As a top-dressing on grass land, however, 

 it should only be applied in showery weather, so that the 

 rains may wash it into the soil. For barley and turnips 

 it is harrowed in or mixed with the soil; and there also 

 it is more effective in a moist season than in a dry one; 

 and its efficacy is in all cases greatly enhanced by com- 

 posting it with the substances mentioned above before 

 applying it to the land. 



Nitrate of Soda and Sulphate of Ammonia. — These are 

 the two chief nitrogenous manures in the market^ and 



