

TO THE QUANTITY OF NITROGEN APPLIED. 203 



Each of these columns represents the effect of a hundred 

 pounds of nitrogen upon the grass of a different field, and there 

 is no more approach to equality among the numbers they re- 

 spectively contain, than among those by which the effects upon 

 the oat crops were represented above. One might infer from 

 them, however, that the nitrates possess some special virtue 

 independent of the nitrogen they contain. 



4. In Mr Kuhlmann's two experiments upon old meadow 

 grass, 100 kilogrammes of nitrogen, in the form of 



Increase for 100 kilogrammes of 

 nitrogen. 



Sulphate of ammonia, gave . . 6094 kilogrammes. 



Nitrate of soda, .... 9232 



Nitrate of lime, .... 5143 



And, in his second experiment, 



Muriate of ammonia gave . . 7061 



Nitrate of soda, .... 8453 



Nor, from these experiments, can we venture to say either 

 that like quantities of nitrogen produce like effects in like chv 

 cumstances, or that the comparative effects which two substances 

 may be expected to produce are to be measured by the propor- 

 tions of nitrogen they respectively contain. 



We may safely admit, I think, that each of the salts of am- 

 monia, and each of the nitrates, exercises a special and peculiar 

 action upon vegetation that this action is generally a favour- 

 able, often a profitable one and that the action of each of these 

 compounds is probably different in the case of different plants, 

 and is modified, also, by climate, season, soil, locality, and other 

 circumstances. To make out the several special actions of these 

 compounds, and the modifying influence of circumstances, will 

 require many carefully conducted and skilfully contrived ex- 

 periments. 



2. Influence of the state of chemical combination in which the 

 nitrogen exists in a substance on its efficacy as a manure. 

 Comparative experiments with gelatine, rape-cake, and sul- 

 phate of ammonia, on the weight of the crop. 



The comparative experiments with the salts of ammonia and 



