MEMOIR XI.] THE FORCE INCLUDED IN PLANTS. 



183 



chemical or deoxidizing radiations. In common with all 

 other chemists I accepted this view, and proposed to my- 

 self to determine to which of these principles the decom- 

 position of carbonic acid and the greening of plant leaves 

 are due. 



And first, to ascertain if it were the heat radiation, I 

 converged, by the aid of a large metallic mirror, the dark 

 or invisible radiations emitted by an iron stove on some 

 leaves placed in water. The gas which was set free was 

 nothing more than the water-gas; there was no decom- 

 position of carbonic acid. 



In Fig. 22, a is the concave mirror, b an inverted flask 

 containing the leaves and 

 water; it dips into a glass, 

 c, also containing water, 

 and receives the reflected 

 radiations of the stove, dd. 



Then I tried a similar 

 experiment, using the radi- 

 ations emitted by a bright- 

 ly burning wood fire. The 

 result was the same as the 

 preceding, and I even push- 

 ed the experiment so far 

 that the water became very 

 hot, a portion of its carbonic acid effervesced from it, and 

 the leaves lost their bright green color. Still no decom- 

 position of the carbonic acid could be detected. 



At this time it was generally received that the essen- 

 tial characteristic of the more refrangible the violet 

 rays is that they produce deoxidation. In accordance 

 with this opinion a name deoxidizing had been given 

 them. Now since the decomposition of carbonic acid is 

 an effect of deoxidation, I was not surprised at the issue 

 of the foregoing experiments, and expected to find that 



