No. 4.] BARNYARD MANURE. 311 



take place during this process, but not until recently has 

 anything like a satisfactory explanation of them been made. 

 This explanation depends upon the discovery of existence 

 and actions, in the manure, of three classes of very small 

 microscopic organisms called bacteria. They are responsi- 

 ble, not wholly, but chiefly, for the changes mentioned. Let 

 us note here just what chemical materials are in the manure 

 at the beginning, and what they are changed into. 



The fresh manure contains mineral substances like potash 

 and phosphates, and also organic material of two kinds, 

 namely : the nitrogenous, found in the liquid manure and 

 to some extent in the solid ; and the non-nitrogenous, which 

 largely makes up the straw, leaves, sawdust and solid excre- 

 ment. It is just these two kinds of organic constituents, 

 and what they become, which concern us now. 



In those portions of the manure which are accessible to 

 the air one class of bacteria live and breed in enormous 

 numbers. They feed on the oxygen of the air and the nitro- 

 genous portions of the manure, and in their excrements give 

 ofi" large quantities of nitrates, the latter being the direct 

 products of the oxidation of nitrogenous organic matter 

 anywhere, whether in the bodies of these bacteria or not. 

 These nitrates, being very soluble in water, drain down into 

 the interior of the manure heap, just as they drain through 

 the soil ; but, instead of all going off in the drainage water 

 and becoming lost, as they often do in the soil, they are 

 chiefly lost by an entirely difierent process. 



In the interior of the heap, shut away from the air, these 

 nitrates fall prey to another class of bacteria, known as 

 " nitrate destroyers." They completely undo the work of 

 the other bacteria, or "nitrate formers." The "nitrate 

 destroyers" live on the non-nitrogenous constituents of the 

 straw and leaves and the oxygen of the nitrates. This lib- 

 erates the nitrogen in the form of gas, which escapes into 

 the air and is lost to the farmer. The process also consumes 

 the non-nitrogenous portion, which is chiefly the remainder 

 of the litter. It is formed into water and carbonic acid gas, 

 which escape into the air and thus diminish the bulk of the 

 pile. While the " nitrate formers" live near the surface of 

 the manure and require air for their work, the " nitrate de- 



