Proceedings of the Farmebs^ Club. 357 



tute phosphate of lime, which consists of definite proportions of tlie 

 acid and lime. In this form the acid is moderately soluble, and may 

 be absorbed by the roots of plants with considerable readiness. It is 

 fomid, howev^er, that if we dissolve the bones in sulphuric acid or oil 

 of vitriol, that the sulphuric acid unites with two-thirds of the lime, 

 driving out the phosphoric acid therefrom into the other third of the 

 lime, which, with this triple portion of the phosphoric acid, consti- 

 tutes superphosphates. By this means the whole of the phosphoric 

 acid is made immediately soluble and consequently acts very quickly 

 upon the plants. Its effects are, indeed, so rapid that in practice it 

 is better not to convert the bones wholly into superphosphate, as 

 otherwise the effect would be too powerful at the beginning 

 of the season when ammonia is most required, but would be 

 almost spent at the end, when the formation or ripening of 

 the seed demands the greatest supply of phosphoric acid. About 

 one pound of sulphuric acid to two pounds of bones will generally 

 be found the most proper' proportions in making superphosphate, 

 but the quantity of sulphuric acid may be' diminished or 

 increased according as the fertilizer is desired to exert a more or less 

 rapid effect upon the plant. The best way for the farmer to obtain 

 superphosphate is to make it himself, inasmuch as the process is sim- 

 ple, and requires but little skill, and when carried out under his own 

 eye yields a manure of the value of which he may be sure ; while, on 

 the other hand, there is no guarantee but the statement of the vender 

 that the purchased article has not been adulterated. Superphosphate 

 has, indeed, like bone dust, so-called, guano and other artificial fertili- 

 zers, been notoriously a subject of common adulteration with com- 

 paratively worthless substances, which even a chemical analysis, 

 unless conducted with the greatest care, will not always fully expose ; 

 for a manure may, by analysis, indicate a large percentage of phos- 

 phate, and yet this latter may be in a condition in which the plant 

 roots are unable to lay hold of it. It has sometimes happened that 

 so termed phosphate has been put in the market which did not con- 

 tain a particle of soluble phosphoric acid. As just explained, the 

 superphosphate is very soluble, and consequently acts with such 

 rapidity that it is expended the first season ; hence when it is desired 

 to secure more permanent effects, bone meal should be used instead, 

 as being less soluble and of course less quickly taken up by the 

 plants. With regard to the quantity to be used per acre, no 

 general rule • can be laid down for this ; to secure the best 



