FIXATION OF NITROGEN IN NATURE. 217 



and liberate + 2791 Cal. ; + 139'5 Cal. per equivalent of 

 nitrogen. 



All these numbers exceed that corresponding to the oxidation 

 of ammonia alone (-f 109), there is therefore ground for sup- 

 posing that nitrification is facilitated by the simultaneous 

 oxidation of the carbon contained in the organic principle. 



3. ON THE TRANSFORMATION OF FREE NITROGEN INTO 

 NITROGENOUS COMPOUNDS. 



First Section. Problem of ike Fixation of Nitrogen in Nature. 



1. The problem of the fixation of the nitrogen of the air 

 and its transformation into nitrogenous compounds, such as the 

 nitrates or aminoniaeal salts in the mineral kingdom, the 

 alkalis, amides, and albumenoid compounds in the vegetable 

 and animal kingdom, has long formed a subject of controversy. 

 A nitrogenous compound of any class being formed, it is easier 

 afterwards to change it into a compound of another class, and 

 it is precisely of this transformation that we have been treating 

 in the foregoing paragraphs. But there still remains the 

 problem of the formation of this initial compound, for nitrogen 

 does not combine directly with any body at the ordinary 

 temperature and in the absence of the conditions which will 

 presently be indicated. On the other hand, the natural nitro- 

 genous compounds tend constantly to be destroyed, under the 

 diverse influences of slow or rapid combustion, fermentation, 

 putrefaction, and even of the normal nutrition of animals, 

 influences which all tend to set free nitrogen. Hence it follows 

 that natural nitrogenous compounds being constantly destroyed 

 and never reproduced, the actual supply of them should con- 

 tinually diminish. Thus it is that the methodical researches 

 made on the use of manures in agriculture have not done much 

 more than reveal causes of destruction, without establishing 

 with certainty any general cause of regeneration, that is to say, 

 any cause sufficiently powerful to explain the reproduction of 

 the nitrogenous compounds. Nevertheless, vegetation is in- 

 definitely prolonged, and without languishing, on the same spot 

 of ground, whenever it is not over stimulated and rendered 

 exhaustive by human industry, a fact which seems to show 

 that there exist slowly acting causes of reproduction of nitro- 

 genous compounds, sufficiently efficacious to support spontaneous 

 vegetation. It is these causes which we are about to consider. 



2. Slow oxidations. From the purely chemical point of view, 

 and under natural conditions, free nitrogen may be united to 

 oxygen in certain slow oxidations. It is beyond question, for 

 instance, that air kept for some time in contact with phosphorus 

 contains several thousandth parts of oxynitric compounds, it 

 being sufficient to agitate this air with lime or baryta water, and 



