210 APPENDIX. 



" The charcoal employed in these experiments was the 

 dust-like powder of charcoal from firs and pines, such as is 

 used in the forges of blacksmiths, and may be easily pro- 

 cured in any quantity. It was found to have most effect 

 when allowed to lie during the winter exposed to the action 

 of the air. In order to ascertain the effects of different 

 kinds of charcoal, experiments were also made upon that 

 obtained from the hard woods and peat, and also upon 

 animal charcoal, although I foresaw the probability that 

 none of them would answer so well as that of pinewood, 

 both on account of its porosity and the ease with which it 

 is decomposed. 



'* It is superfluous to remark, that in treating plants in the 

 manner here described, they must be plentifully supplied 

 with water, since the air having such free access penetrates 

 and dries the roots, so that unless this precaution is taken, 

 the failure of all such experiments is unavoidable. 



" The action of charcoal consists primarily in its preserving 

 the parts of the plants with which it is in contact ; whether 

 they be roots, branches, leaves, or pieces of leaves, un- 

 changed in their vital power for a long space of time, so 

 that the plant obtains time to develop the organs which 

 are necessary for its further support and propagation. 

 There can scarcely be a doubt also that the charcoal under- 

 goes decomposition ; for after being used five to six years 

 it becomes a coaly earth ; and if this is the case, it must 

 yield carbon, or carbonic oxide, abundantly to the plants 

 growing in it, and thus afford the principal substance ne- 

 cessary for the nutrition of vegetables. In what other manner 

 indeed can we explain the deep green colour and great luxu- 

 riance of the leaves and every part of the plants, which can 

 be obtained in no other kind of soil, according to the opinion 

 of men well qualified to judge? It exercises likewise a 

 favourable influence by decomposing and absorbing the 

 matters absorbed [query, excreted] by the roots, so as to keep 

 the soil free from the putrefying substances which are often 

 the cause of the death of the spongiolce. Its porosity as well as 



