MEMOIR X.] THE DECOMPOSITION OF CARBONIC- ACID GAS. ^73 



For these reasons I conclude that the decomposition 

 of carbonic acid by the leaves of plants is brought about 

 by the rays of light, and that the calorific and so-called 

 chemical rays do not participate in the phenomenon. 

 The rays of light are therefore as much entitled to the 

 appellation of chemical rays as those which have here- 

 tofore passed under that name. 



Next I examined the constitution of the gaseous mixt- 

 ure given off during these decompositions. It proved to 

 be not pure oxygen, but a variable mixture of oxygen, 

 nitrogen, and carbonic acid. Omitting the carbonic acid, 

 which diffused from the solution in variable quantities, 

 the following table represents the composition of the 

 gaseous mixture: 



Analyses of Gas evolved from Carbonated Water. 



This table contains a few out of a great number of 

 experiments, all of which might have been quoted as ex- 

 amples of the conclusions which I wish to deduce. 1st. 

 They all coincide in this, that the oxygen is never 

 evolved without the simultaneous appearance of nitro- 

 gen ; 2d. That when certain leaves are employed, as those 

 of the Pinus tseda, there seems to be a very simple rela- 

 tion between the volumes of oxygen and nitrogen. In 

 the first and second of these experiments, the volume of 

 oxygen is to that of nitrogen as two to one; in the third, 

 as one to one. In certain cases this apparent simplicity 

 of proportion is departed from ; but from its frequent oc- 

 currence in many analyses I have made it seems to de- 



