1857.] StuU Manure and Straw. 181 



or dry distillation, where, as, for example, in the manufacture of 

 common illuminating-gas, or in charcoal piles, from deficiency of 

 air, half-burnt, strong-smelling combinations, tar, ammoniacal gas- 

 water, pyroligneous acid, etc., are likewise generated in large quan- 

 tity. On the contrary, when the air can freely enter, these offens- 

 ive gases and vapors combine with more oxygen, and now undergo 

 complete putrefaction or combustion; and the products so eliminated 

 are destitute of smell. This kind of decomposition, which is most 

 analagous to complete combustion, and, like this, takes j)lace with 

 abundant air and a proper draught, is called decay. 



Why putrid drainings and putrid manures, when applied to mead- 

 ows or fields, diffuse at first a powerful odor but lose this smell a 

 short time afterwards, is therefore very simply explained; they lose 

 their odor, because they can now absorb oxygen in any quantity 

 from the air, and from the process of putrefaction can make a fur- 

 ther transition into that of decay. 



If moist vegetable or animal tissues lie in a room from which the 

 air is entirely or partially excluded — for instance, in a cellar which 

 has no ventilation, or in a chest, etc. — then in the undisturbed, 

 damp air a decomposition takes place, consisting partly of putrefac- 

 tion, partly of decay — the well-known process of moldering., recog- 

 nized mainly by its close smell and simultaneous production of 

 mold, fungi, and spongy excrescences. By the addition of water, 

 this kind of decomposition may be converted into putrefaction ; by 

 the introduction of a current of air, into decay; or, lastly, it may 

 be brought entirely to a close, if by means of ventilation all moist- 

 ure is evaporated, and the decaying body becomes completely dry. 

 In common conversation, the words " putrefaction," "moldering," 

 " decay," are deemed synonymous in meaning, and the one or the 

 other of these words is used at the pleasure of the speaker to desig- 

 nate the changes under our consideration. In the majority of cases, 

 it is indeed a matter of indifference, and in a strict sense not at all 

 incorrect, inasmuch as in most decomposing bodies all three process- 

 es are of simultaneous occurrence ; externally, with free access of air, 

 decay ; in the midst, between both, moldering. Here, however, 

 reference must be made to a distinction in these processes, the 

 knowledge of which is important in a practical respect ; we mean, 

 the fact that we have to consider putrefying and moldering sub- 

 stances only as a half-prepared or half-finished nutriment for the 

 plants in cultivation; decaying siibstances, on the contrary, as a fully 



