REPORT ON NITRIFICATION. 313 



III. Such are the different circumstances under which nitrates are 

 produced in nature. An artificial mode of nitrification has been long 

 practiced, and on the continent of Europe a large amount of labor 

 and attention has been bestowed upon it.* 



The general plan has been already alluded to, (page 306, note.) It 

 consists in mixing earth, old mortar, and rubbish of various kinds 

 with animal matters, (stable manure, &c.,) making the whole into 

 heaps called nitre, beds, and keeping these exposed to the air and 

 moderately moist until nitrification is completed. This is practiced, 

 under many variations of detail, in different places. The most per- 

 fect system seems to be the Prussian, according to which the mass is 

 made into walls, which are steep on one side and cut into steps on 

 the other. The tops of these steps are made into gutters, in which 

 water is poured which percolates the wall and evaporates from the 

 opposite or vertical side. On that side, of course, the nitrates accu- 

 mulate and effloresce, and the earth from it being scraped off from 

 time to time, is leached for the purpose of extracting them. While 

 this is done, fresh material is added to the steps, so that the size and 

 shape of the wall is preserved. In many places the materials are 

 piled into heaps and turned over, from time to time, to expose a fresh 

 surface to the air. 



The great objection to all nitre beds I should say to be this: that 

 while nitrates are formed on the surface, where the air has free access, 

 in the interior of the heap the organic matters present tend to recon- 

 vert them into ammonia; and thus, between the influences of two 

 opposing forces, the process of nitrification goes on but slowly. It 

 is found in practice that it requires about three years for an ordinary 

 nitre bed to become fit for extraction, and as, during that time, much 

 labor must be bestowed upon it, and materials used that would be 

 valuable for agricultural purposes, the utility of keeping them up 

 has been much questioned in Europe. 



The large importations of nitre from India, made in recent times, 

 have diminished considerably the cultivation of the saltpetre planta- 

 tions, as they are called, and, in fact, they are found not to be remu- 

 nerative under present circumstances, and are too slow in their 

 operation to serve as a provision against sudden emergencies. If, 

 instead of making these heaps, the ammoniacal exhalations from the 

 organic matters were made to pass, duly mixed with air and moisture, 

 into a porous earth or other nitrifiable mass, the transformation would, 

 in all probability, be much more rapid. 



IV. We may now inquire what better modes of artificial nitrification 

 are suggested by our present knowledge of the nature of the process 

 and by the industrial means at our command. The various possible 

 plans divide themselves into two general classes: first, those which 

 involve the oxidation of ammonia; and second, those which depend 

 upon the fixation of the nitrogen of the air. The first of these more 

 especially demands our attention, as being of more certain feasibility, 



'"' In Sweden every peasant is obliged to maintain a nitre bed, and to furnish a certain 

 amount to the government. 



