ElylSHA MlTCHEr.1. SCIENTIFIC SOCIETY. 17 



three-fourths of the atmosphere around us consists of 

 nitrog'en, and it enters as an essential constituent into 

 all forms of animal and plant life. The complex nitro- 

 g^enous organic compounds found in nature are not as- 

 similated as such, but are in some wa\^ formed within 

 the plant from simpler nitroo-en compounds taken in 

 through the roots. 



When these complex compounds are exposed to the 

 decomposing- agfencies of the air and soil the}^ readily 

 return to the simpler and most stable forms which can 

 exist in nature. The nitrates, as the last and highest 

 state of oxidation of nitrogen, are known to be the most 

 stable compovmds. As an evidence of this, vast deposits 

 of sodium nitrate have been stored up and preserved in 

 the rainless regions of Chili, Peru and other countries. 

 Minute amounts of nitrates are almost universal!}^ pres- 

 ent in soils and waters. They have been found b}" 

 many experiments and practical field tests to be the 

 form of nitrogen most acceptable as a plant food and 

 to an application of which the\^ most readily respond. 

 Nitrates would seem to have been indicated b}^ nature 

 as the most convenient starting point for the forma- 

 tion of all nitrog'en compounds 



A knowledge of their wide-spread existence in tiature 

 and the very important relation which they bear to ag- 

 riculture has long* been known. Chemists have per- 

 formed many experiments and adv^anced numerous the- 

 ories as to the manner of their formation. This natur- 

 al phenomenon was evidently a process of oxidation 

 brought about by means of atmospheric and soil agen- 

 cies. Simple oxidation was not sufficient to explain the 

 notable nitrate formation in compost heaps and nitre 

 beds. The process was known to be much more active 

 and to take place near the earth's surface. Calcium 

 3 



