^856.] Stall-Manure and Straw. 553 



faction and decay. For tMs reason, we perceive a visible and spon- 

 taneous evolution of heat, wherever considerable quantities of animal 

 or vegetable matters putrefy, decay, or rot. Hence soil rich in hu- 

 mus (for humus must be considered vegetable fiber, undergoing 

 decay or slow combustion) will always preserve a greater amount of 

 warmth than soil which is poor in this ingredient, and this the more, 

 because on account of its dark color it absorbs a larger proportion 

 of the rays of the sun than a soil of lighter color. The heatino- of 

 stall-manure is thus explained at once ; it will be stronger in propor- 

 tion to the larger masses heaped on each other, and to the abundance 

 of azotized substances they contain, inasmuch as these latter produce 

 a brisker putrefaction ; in the first case, however, the heat is better 

 kept together, and is constantly generated anew, because, with in- 

 creasing temperature, the putrefactive process is more energetically 

 carried on. 



Next to heat, air and water have an essential influence upon the 

 progress of putrid disintegration in organic matter. Substances from 

 which all water has been removed by drying do not suffer this de- 

 composition, as is exemplified in dried fruits, seeds, leaves, etc., 

 which we can preserve for years, whilst in a moist state they soon 

 become corrupt. With a moderate degree of moisture, decomposi- 

 tion proceeds most rapidly and successfully. An excessive quantity 

 of water retards it, because when substances are entirely covered 

 with water their heating, and at the same time the access of air, are 

 prevented. 



The exclusion or non-exclusion of air from fermenting vegetable 

 and animal remains, occasions a great diff"erence in the nature of 

 the decomposition. In the first case, as, for example, in the decompo- 

 sition of animal manure, when piled together in large and compact 

 heaps, and of urine in the drainings' reservoir, in the steeping of 

 flax, in the fermentation of potted cheese, etc., gasses and vapors of 

 highly disagreeable odor are generated, which may be regarded as 

 partially putrefied or partially consumed substances ; they are pro- 

 duced from want of air, or, more accurately speaking, of oxygen. 

 This decomposition is called, ^\m^\j,imtref action. It has the greatest 

 analogy to charring 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, am- 

 moniacal gas-water, pyrolygneous acid, etc., are likewise generated in 

 large quantity. On the contrary, when the air can freely enter, 



