39 



heat, with that in which the plants might be already 

 growing. 



The admixture of charcoal with the soil, is said to he 

 a means of adding to its nutritive qualities. Charcoal, 

 which is nearly pure carbon, may be supposed conti- 

 nually to give off a portion of this gaseous substance 

 during its decomposition, and this uniting with a por- 

 tion of the oxygen contained in the air, would furnish a 

 supply of carbonic acid gas, to the atmosphere imme- 

 diately about the plants. It should however be borne 

 in mind, that charcoal, is a substance whose decompo- 

 sition except under the influence of heat, proceeds very 

 slowly indeed, and therefore its chemical influence must 

 not be overrated : doubtless however, the small portion 

 which does combine with the oxygen of the air, is di- 

 rectly beneficial to the plants; for it is a function of the 

 vegetable kingdom by the action of their leaves, when 

 under the influence of light, to decompose carbonic acid, 

 the oxygen of which is liberated, and the carbon fixed in 

 the living tissue. It is therefore probable that a supply 

 of carbonic acid, artificially maintained about the leaves 

 and stems of plants, may be beneficial to them, by fur- 

 nishing them directly with a portion of carbon, which 

 they cannot absorb in a seperate state. When the char- 

 coal is made from twigs, and the small branches of trees, 

 its decomposition is often more rapid, than when it is 

 obtained by the usual course of manufactering it : if the 

 latter kind of charcoal is employed, it should be broken 

 into pieces of a small size ; and in ordinary cases, it 

 should not be used in larger proportion than with about 

 twice its bulk of soil, with which it should be intimately 

 blended. , 



Besides its chemical action, which is probably bene- 

 ficial, charcoal has a decidedly advantageous mechanical 

 action in the composition of soils, and this is of a two- 

 fold nature : first, in common with anv similar mate- 



