v.] nOXE FERTILISERS 155 



be needful enough if the steamed bone flour were in any 

 way being passed off as bone meal, but provided it is 

 sold on its own basis as a material containing nearly 

 sixty per cent, of tri-calcic phosphate and one per cent, 

 or so of nitroi;en, it is a better manure than bone meal. 

 The fine grinding of the steamed bone flour allows the 

 phosphates to pass into solution, while the extra 

 nitrogen of the raw bone is so slow in its action, that as 

 a rule it would pay the farmer to buy steamed bone 

 flour instead of bone meal and to make up this deficiency 

 by the addition of a more active nitrogenous material. 



Just as the long-standing knowledge of the effect of 

 bones has given rise to a certain prejudice in their 

 favour, which is reflected in the fact that they realise 

 a rather higher price than their content in nitrogen and 

 phosphoric acid would justify, something of the same 

 tradition exists on the side of dissolved bones and bone 

 superphosphate. There is no experimental evidence to 

 lead one to expect that a mixture of superphosphate 

 and sulphate of ammonia will not give as good results 

 as dissolved bones containing the same amount of 

 nitrogen and phosphoric acid ; indeed, the former mixture 

 will probably be more effective, because it is finer and in 

 better mechanical condition. And yet dissolved bones 

 is generally much the dearer fertiliser : for example, at 

 the time of writing, the price of dissolved bones in 

 London is £^, 5s. per ton, and it contains 275 per cent, 

 of nitrogen and 15 per cent, of phosphoric acid. To 

 supply 275 units of nitrogen, 2| cwts. of sulphate of 

 ammonia containing 20 per cent, of nitrogen will be 

 required, and this costs 32s. ; to supply 15 units of phos- 

 phoric acid i\ tons of superphosphate with 12 per cent, 

 of phosphoric acid would be wanted, and this would cost 

 £1, 2s. 6d. For 32 + 62-6 = 94s. 6d., therefore, the same 

 amount of nitrogen and phosphoric acid could be 



