252 APPENDIX TO PART I. 



animal charcoal, although I foresaw the probability that 

 none of them would answer so well as that of pine wood, 

 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 pre- 

 serving the parts of the plants with which it is in contact, 

 — whether they be roots, branches, leaves, or pieces of 

 leaves, — unchanged 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 propaga- 

 tion. There can scarcely be a doubt also that the char- 

 coal undergoes 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 

 necessary for the nutrition of vegetables.| In what other 

 manner, indeed, can we explain the deep green color and 

 great luxuriance 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 favorable influence by decomposing and absorb- 

 ing the matters 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 the power which it possesses of absorbing water 

 with rapidity, and, after its saturation, of allowing all other 

 water to sink through it, are causes also of its favorable 

 effects. These experiments show what a close affinity the 

 component parts of charcoal have to all plants, for every 

 experiment was crowned with success, although plants 



* M Lucas has recently repeated these experiments, and found that 

 the animal charcoal obtained by the calcination of bones possesses a 

 decided advantage over all other kinds of charcoal, which he subjected 

 to expeiiment — Liebig's Mnnalen^ Band xxxix. Heft I. S. 127. 



t As some misconception has arisen regarding this explanation of the 

 action of charcoal upon vegetation, and an idea propagated, that the 

 introduction of these opinions into this work incorporated them with 

 those of Liebig, it is necessary to state that they are merely inserted 

 here as part of the papers of M. Lucas. The true explanation has 

 been given in a former part of the work, viz. that charcoal possesses 

 the power of absorbing carbonic acid and ammonia from the atmo- 

 sphere, which serve for the nourishment of plants — Ed. 



