186 
combustion of the same body, or of different bodies, 
affords. The calorific rays of light, therefore, like 
positive electricity, are able to effect in bodies the 
chemical actions of decomposition and combination, 
and these in an order depending on the state in 
which the bodies are presented to their action. 
455. But besides these operations, which the ca- 
lorific rays effect, we have seen, that the decomposi- 
tion of metallic oxides (451.), of different acids 
(439.), and especially of carbonic acid, is produced 
in that part of the prismatic spectrum which is far- 
thest removed from the heating power of light, and, 
consequently, by the chemical rays, which possess no 
heating power. In all these cases, however, we ob- 
serve decomposition only to take place, and no subse- 
quent combination to follow, in the manner in 
which that operation is accomplished by the calorific 
rays ; for the oxygen is only released from its com- 
bination with the metal, with carbon, or with any 
other substance with which it was previously combi- 
ned, but no new product is, at the same time, formed, 
neither are the usual phenomena of combustion ex- 
hibited. Hence, therefore, we may remark a striking 
difference between the action of the chemical and 
calorific rays of light ; for though both species agree 
in the property of effecting decomposition, the calorific 
rays alone give rise to new combinations. Here, then, 
we trace a close analogy between the operations of so- 
lar light and of electricity, not only in the general si- 
milarity of effect which they produce in bodies, but al- 
so in the particular laws of their action ; for nega- 
tive electricity, like the chemical rays, produces only 
