CHEMICAL DECOMPOSITION BY HEAT. 99 



body heated so as to be luminous lias the power of 

 causing the combination of the elements of water with 

 explosive violence.* But as this acute experimental 

 philosopher somewhat boldly but still most reasonably 

 inquires : " Is it not probable that, if not light, some 

 other actinic power (like that which accompanies light in 

 the spectrum, and is revealed to us by its chemical 

 effects in the processes of photography) is evolved by the 

 heat, and, though invisible, determines, in conjunction 

 with the affinity, that atomic change which transforms 

 the three volumes of oxygen and hydrogen into two of 

 steam ?f 



This speculation explains, in a very satisfactory manner, 

 some results which were obtained by Count Rumford, in 

 1798. In a series of experiments instituted for the 

 purpose of examining "those chemical properties of 

 light which have been attributed to it," he has shown 

 that many cases of chemical decomposition occur in 

 perfect darkness, under the influence of heat, which are 

 precisely similar to those produced by exposure to the 

 sun's rays.i 



It must, however, be remembered, that both solar 

 light and heat are sometimes found in direct antagonism 

 to actinic power, and that the most decided chemical 

 changes are produced by those rays in which neither 

 heat nor light can be detected. The most remarkable 

 phenomena of this class will be explained under the 

 head of actinism. 



* Davy's Researches on Flame- Works, vol. vi. Philosophica 

 Transactions for 1817. 



f On the Effect of Heat in lessening the affinities of the Elements 

 of Water : by the Rev. Thomas Romney Robinson, D.D. Trans- 

 actions of the Royal Irish Academy, vol. xxi. part 2. 



I An Inquiry concerning the Chemical Properties that have bctn 

 attributed to Light: by ] Benjamin, Count of Rumford. Philoso- 

 phical Transactions, vol. Ixxxviii. p. 440. The results obtained 

 by Count Rumford were probably due to the non-luminous heat- 

 rays parathermic rays which are known to be given off by 

 boiling water. 



