68 ruE SOIL. 



decomposition of organic matter il the soil, certain 

 compounds are formed, known under the general 

 names of humus and hwrnxG acid^ which maj, in a 

 slight degree, affect the growth of plants, hut their 

 practical importance is of too doubtful a character 

 to justify us in considering them. The application 

 of manures, containing organic matter, such as peat, 

 muck, animal manure, etc., supplies the soil with 

 carbon on tlie same principle, and the decomposing 

 matters also generate * carbonic acid gas while being 

 decomposed. The agricultural value of carbon in 

 the soil depends (as we have stated), not on the fact 

 that it enters into the composition of plants, but on 

 certain other important offices which it performs, as 

 follows : — 



1. It makes the soil more retentive of maniu'es. 



2. It causes it to appropriate larger quantities of 

 the fertilizing gases of the atmosphere. 



3. It gives it greater power to absorb moisture. 



4. It renders it warmer. 



1. Carbon (or charcoal) makes the soil retentive 

 of manures, because it has in itself a strong power 

 to absorb, and retain fertilizing matters. There is 

 a simple experiment by which this power can bo 

 shown. 



Ex. — Take two barrels of pure beach sand, and 

 mix with the sand in one barrel a few handfuls of 

 charcoal dust, leaving that in the other pure. Pour 

 a pailful of the brown liquor of the barn-yard 

 through the pure sand, and it M'ill pass out at the 

 • Produce. 



