CONDITIONS OF FERMENTATION. 33 



that the effect of exposing the manure to the action of 

 the air is to induce the development of the aerobic 

 type of organism, and thus to promote more rapid 

 fermentation. If, on the other hand, the manure be 

 impacted, the slower but more regular fermentation, 

 due to the anaerobic type of organism, will be chiefly 

 promoted. It must be remembered that in the proper 

 rotting of farmyard manure, both kinds of fermenta- 

 tion should be fostered. It is, in fact, on the careful 

 regulation of the two classes of fermentation that the 

 successful rotting of the manure depends. It must 

 further be remembered that, even with a certain amount 

 of openness in a manure-heap, anaerobic fermentation 

 may take place. This is due to the fact that the 

 evolution of carbonic acid gas, in such a case, is so 

 great as to exclude the access of the atmospheric 

 oxygen into the pores of the heap. 



3. The dampness of the manure-heap is another 

 important influence. This, of course, will act in two 

 ways : first, by lowering the temperature. Where 

 the manure-heap is found to be suffering from " fire- 

 fang," the common method in practice is to lower 

 the temperature by moistening the heap with water. 

 Secondly, it acts as a retarder of fermentation by 

 limiting the supply of atmospheric oxygen, and thus 

 preventing, as we have just seen, aerobic fermentation. 



4. The fourth chief influence in regulating fermenta- 

 tion of the manure-heap is its composition, and more 

 especially the amount of nitrogen it contains in a solu- 



c 



