BY THE DECOMPOSITION OF WATER. 65 



set at liberty, cannot be insignificant, for the 

 atmosphere must receive 989 cubic feet of oxygen 

 for every pound of hydrogen assimilated. 



It has already been stated, that a plant, in the 

 formation of woody fibre, must always yield to the at- 

 mosphere the same proportional quantity of oxygen ; 

 that the volume of this gas set free would be the 

 same whether it were due to the decomposition 

 of carbonic acid or of water. It was considered 

 most probable that the latter was the case. 



From their generating caoutchouc, wax, fats, and 

 volatile oils containing hydrogen in large quantity, 

 and no oxygen, we may be certain that plants 

 possess the property of decomposing water, because 

 from no other body could they obtain the hydro- 

 gen of those matters. It has also been proved 

 by the observations of Humboldt on the fungi, that 

 water may be decomposed without the assimilation 

 of hydrogen. Water is a remarkable combination 

 of two elements, which have the power to separate 

 themselves from one another, in innumerable pro- 

 cesses, in a manner imperceptible to our senses ; 

 while carbonic acid, on the contrary, is only decom- 

 posable by violent chemical action. 



Most vegetable structures contain hydrogen in 

 the form of water, which can be separated as such, 

 and replaced by other bodies ; but the hydrogen 

 which is essential to their constitution cannot pos- 

 sibly exist in the state of water. 



All the hydrogen necessary for the formation of 



F 



