APPLICATION OF CHARCOAL IN PLANT CULTURE. 147 
its influence, by regulating the combination of substances which 
are capable of supplying nutriment ; and in the other case, that 
is, mechanically, its influence seems to consist in regulating the 
conditions and bearing of certain matters, which are liable to 
become ill adapted to the purpose for which they are designed. 
But wherever charcoal is applied to the soil in which plants are 
cultivated, these distinct and separate influences go on together 
and simultaneously, and therefore we may reasonably infer that 
its beneficial character may be in part ascribed to both. 
The chemical composition of charcoal would seem to suggest, 
that it may be the means of supplying plants directly with a 
portion of matter which they can appropriate to their nutrition. 
It consists of impure carbon (the diamond being composed of 
carbon in a pure state), and carbon entering into combination 
with a portion of oxygen, is then capable of ministering to the 
growth of plants, though, whilst in a free and uncombined form, 
they cannot absorb it. When it is combined with a portion of 
oxygen, which it derives from the atmosphere, it becomes car¬ 
bonic acid gas, and in this state it is absorbed and decomposed 
by the leaves of plants, the oxygen being again liberated, and 
returned to the atmosphere, thus rendering it more capable of 
supporting animal life, whilst the carbon is fixed, and serves to 
increase the vegetable fabric. So say the chemists, and we 
gardeners, for the present at least, must be content to follow 
them, although, as the science of chemistry, without doubt, is 
regulated by simple and unvarying natural laws, there is no 
reason why an attentive study of the science should not enable 
gardeners to speak on these matters from personal conviction, 
and not, as at present, on the authority of others. But the 
chemists tell us more ; they tell us, that except under the in¬ 
fluence of a considerable degree of heat, charcoal is a substance 
which decomposes so slowly, that, under ordinary circumstances 
of vicissitude and exposure, it is almost imperishable ; we must 
not, therefore, overrate its chemical influence ; but as these 
gaseous bodies do exert a very powerful influence, when they 
exist even in such infinitely small proportions as to be altogether 
unappreciable to the senses, we may believe that even the small 
degree of chemical action which can be supposed to take place 
between charcoal and the elements of the atmosphere by which 
it is surrounded, is directly beneficial to plants. 
