S04 AMMONIA AND NITRIC ACID. 



If, then, in Schattenmann's experiments, and those at 

 Bogenhausen, there were no results from the salts of am- 

 monia, tliis did not arise from the fact of these salts being 

 in themselves ineffective ; but they were inactive, because 

 the conditions of their activity were wanting. Lawes 

 and Gilbert supphed these conditions to their field, and 

 hence ensured activity to the ammoniacal salts they used. 

 The results obtained by Kuhlmann respecting the effect 

 of salts of ammonia upon meadows are precisely similar. 

 He manm-ed a piece of meadow land with sulphate of 

 ammonia, and obtained a crop of hay larger than the 

 yield of the unmanured plot, because a certain quantity 

 of phosphoric acid, potash, &c. was rendered active, 

 which without the cooperation of salts of ammonia would 

 not have been the case. On adding phosphate of lime to 

 the salts of ammonia, the activity of the latter was 

 enhanced m an extraordinary degree ; he obtained, — 



Return of hay ^ per hectare, 1844. 



Excess above the 

 unmanured plot 

 kilo. kilo. kilo. 



(1) By maniiring with 250 sulphate of ammonia . . 5564 1744 



(2) „ „ 333 sal ammoniac, with phosphate 



of lime 9906 6086 



(3) Unmanured plot 3820 — 



Thus, by sulphate of ammonia alojie, Kuhlmann ob- 

 tained rather more than half as much hay again as the 

 yield of the unmanured plot ; and by adding phosphate 

 of hme he gained almost three times as much. 



Those who maintained the theory of the special im- 

 portance to agriculture of nitrogen in manure, formed a 

 similar notion about the cause of fertility in land. 



If, in fact, the efficacy of any manure depended on the 

 enrichment of the soil with nitrogen, exhaustion could be 

 explained only by the diminution of the store of nitrogen ; 

 and the manure would restore fertihty when the nitrogen 



