SOURCE OF NITROGEN. 161 



always exist in rain and snow water. It is the simplest of 

 the compounds of nitrogen. Nitrogen has for hydrogen the 

 most powerful affinity. It is capable of being held in solu- 

 tion in water, and readily enters into combination with car- 

 bonic, sulphuric and muriatic acids, and by all these means it 

 becomes fixed in the soil. A certain portion of the ammonia 

 which falls in rain water evaporates, but some of it must en- 

 ter the organs of plants, and by entering into new combina- 

 tions in the different organs, produces albumen, gluten, qui- 

 nine, morphia, cyanogen, and a number of other compounds 

 containing nitrogen. 



(5) Finally, if we add to these considerations the fact, that 

 ammonia is found in the atmosphere, that it is constantly 

 produced in the soil, and must enter the organs of plants, 

 where, owing to its easy decomposition, its nitrogen must be 

 assimilated, it becomes certain that it yields nitrogen in 

 the processes of nutrition. 



The quantity of nitrogen which plants derive from this 

 source cannot be determined. Liebig attempts to prove, that 

 ammonia is the only source of the nitrogen. He also attempts 

 to explain the utility of gypsum, burned clay, powdered char- 

 coal and humus, on the principle that these substances absorb 

 ammonia from the atmosphere, and fix it in the soil. The 

 carbonate of ammonia, which is diffused through the soil and 

 dissolved in water, is decomposed by the gypsum,* and the 

 resulting sulphate of ammonia yields its nitrogen to the plant 

 as its wants demand. As water is necessary to the decom- 

 position of the carbonate by the gypsum, its influence is not 

 observed on dry fields. The other substances mentioned, 

 act by absorption, condensing the ammonia in their pores. 

 The arguments brought in favor of this theory, are not all 

 of them well founded ; and if they were, would not prove it 



* One bushel of plaster, on this theory, would fix a quantity of am- 

 monia, equal to 6*250 pounds of horse urine, and every pound of ni- 

 trogen would produce 100 pounds of hay or grain, 

 14 



