OF CARBON* 41 



or lesser quantity of this substance, seemed to 

 afford incontestable proof of its correctness."* 



Yet this position is found to be untenable, 

 and conclusive proofs will be offered to show 

 that humus of itself does not enter into the 

 composition of any plant, or afford them the 

 smallest nourishment. 



It has been already noticed, in considering 

 the structureand functions of vegetables, that 

 the roots, the only source by which humus or 

 humic acid could be introduced into plants, 

 can only absorb nourishaient in the shape of a 

 liquid, and if it can be proved that the sub- 

 stance now under consideration, humus, is in- 

 soluble in water, it must be at once admitted 

 that it cannot perform the ofHce hitherto as- 

 cribed to it, and that search must be made 

 elsewhere for the pabulum of plants. 



It has been demonstrated by Sprugel, a Ger- 

 man chemist, that humic acid is only soluble 

 in 2500 times its weight of water, and even to 

 possess this degree of solubility it must be 

 acted on by the water as soon as it is formed 

 from the humus, and that it forms compounds 

 with potash, soda, lime and magnesia, but none 

 of which possess a greater degree of solubility 

 than the humus itself And it has been farther 

 demonstrated that if by any chance it should 

 become dry by exposure to the atmosphere, or 

 be subjected to a temperature lower than 32° 



* Almost all the arguments in favour of the theory here 

 promulgated are taken from Professor Liebig's work before 

 noticed, and in some cases the exact words of the translation 

 are quoted. 

 6 



