90 MAXURES, 



tlie apple enter tlie nose. The same is true when we 

 smell hartshorn, cologne, etc. 



The intensity of these odors bears no relation to 

 the amount of the substance passing into the air; for 

 instance, a grain of musk will continue to give off 

 a strong odor for many years, while gum camphor, 

 Mith a much less intense odor, wastes away very 

 rapidly. Ammonia escapes rapidly. 



Manures made by animals have an offensive odor, 

 simply because volatile parts of the decomposing 

 manure escape into the air, and are therefore made 

 perceptible. All organic parts in turn may become 

 volatile, assuming a gaseous form as they decom- 

 pose. 



We do not see the gases rising, but there are many 

 ways by which we can detect them. If we wave a 

 feather over a manure heap, from which ammonia is 

 escaping, the feather having been recently dipped in 

 muriatic acid, white fumes will appear around the 

 feather, being the muriate of ammonia formed by the 

 union of the escaping gas with the acid. Xot only 

 ammonia, but also carbonic acid, and other gases 

 which are useful to vegetation escape, and are given 

 to the winds. Indeed it may be stated in few words 

 that all of the organic part oi plants (all that was ob- 

 tained from the air, from water, and from ammonia), 

 constituting more than nine-tenths of their dry weight, 

 may be evaporated by the assistance of decay or 

 combustion. The atmospheric ])arts of manures may 

 be lost in the same manner ; and, if the process of 

 decomposition be continued long enough, nothing 



