120 CHARCOAL. 



only one that makes it useful in connexion 

 with the subject of manures is, its powers of 

 absorbing various gases in the pores of its 

 structure, and subsequently yielding them to 

 moisture. 



It i« proved beyond all doubt, that pure 

 fresh burnt charcoal possesses the power of 

 absorbing 90 times its volume of ammonial 

 gas, and 35 times its volume of carbonic acid 

 gas. It has the power also of absorbing the 

 other gases, but it is needless to specify them 

 here, as the two above quoted are those only 

 which produce any effect in relation to agri- 

 culture. This property of charcoal is entirely 

 a mechanical effect, and is not due to any che- 

 mical action resulting between the charcoal 

 and the gas, as the gases so absorbed are readily 

 given out when the charcoal is subjected to the 

 heat of boiling water. 



The densest and heaviest kinds of charcoal 

 possess this capacity of absorption in the high- 

 est degree •; and, consequently, charcoal pre- 

 pared from boxwood is the best for this pur- 

 pose : but this power in all cases is much 

 diminished by reducing the charcoal to a state 

 of powder; it should, therefore, when used for 

 agricultural purposes, be just broken, so as to 

 allow of its equal distribution over the surface 

 of the soil. In this state it will absorb any 

 gas with which it may come in contact; and 

 if any manure has been applied containing 

 ammonia in its free state, that is liable to pass 

 off in a gaseous form, the charcoal will absorb 

 it as it rises, and retain it until the first rain, 

 when the gas will be dissolved by the water 



