92 MODERN HIGH FARMING. 



When compound manures .are in question, however, this heading 

 will comprehend the potash and any nitrates that may have been 

 added to them, and will then be of considerable importance. It is 

 the common practice when estimating the nitrates, to add the quan- 

 tity of nitrogen they contain to that found in the organic matter, 

 and calculate the equivalent of the whole as ammonia. 



Even in cases where no organic matter exists, the same mode of 

 estimation can be applied, as, supposing the manure to contain 7^ 

 per cent, of nitrate of soda, it will be equivalent to 1^ per cent, of 

 ammonia, or 1% per cent of nitrogen. The potash salts are chiefly 

 found in manures, either as muriate or nitrate, and their value is de- 

 termined by reducing them to their equivalent in pure potash. 



INSOLUBLE SILICEOUS MATTER means the earthy and sandy 

 bodies forming the gangue by which all mineral phosphates are sur- 

 rounded, and from which it is impossible to entirely free them. In 

 supei phosphates or compound manures, the very maximum quantity 

 of these useless substances should be 6^ to 7 per cent., and anything 

 above these figures would suggest to our minds the addition of some 

 worthless rubbish, with a fraudulent intention. 



As complementary to this explanation of the various constituents, 

 shown by chemical analysis to make up the composition of a 

 manure, it will be wise to give a practical illustration, and we there- 

 fore append the analysis of a "phospho-guano," or artificially pre- 

 pared guano, dissolved in sulphuric acid. 



Moisture 9.12 



*Nitrogenous Organic Matter 38.57 



Phosphoric Acid Soluble in Water 13.20 



Insoluble Phosphate of Lime 5.01 



Sulphate of Lime 19.26 



tAlkaline Salts 9.97 



Insoluble Matters . 4.87 



100.00 



*Containing Nitrogen 9.00 



Equal to Fixed Ammonia 10.92 



tContaining Potash... . 2.75 



