HEAT TO GIVE GASEOUS STATE. 55 



Although Joule was already engaged with Dr. Scoresby 

 in a further research on the mechanical powers of electro- 

 magnetism by means of Scoresby's great battery, for which 

 he had been staying at Bradford during July, 1842, yet he 

 found time to conduct his now world-famous investigation 

 u On the Heat Evolved During the Electrolysis of Water," 

 which he read before this Society on January 24, 1843. 

 This paper also contains a summary of the results which he 

 has so far obtained, which shows that he was already in the 

 throes of generalization. 



The first part of this research covers much the same 

 ground as the previous. 



This gives him 1-35 DanielPs cells as the electromotive 

 force necessary to overcome the resistance to the separation 

 of water into its gaseous elements alone. He then remarks 

 " 1 '3 5 will very nearly represent the intensity or electro- 

 motive force required for the separation of the elements 

 of water, and the assumption by them of the gaseous 

 state. By these means heat becomes latent and a reaction 

 on the intensity of the battery takes place without the 

 evolution of free heat. It is most interesting to enquire 

 what part of the whole intensity is due to each action." 



He then describes other experiments from which he de- 

 duces that the electromotive force of r Daniell's cell is suffi- 

 cient to separate the elements of water and give hydrogen 

 the gaseous state, while an electromotive force of 1*45 

 Daniell's cells is necessary to separate the elements, and 

 give to the oxygen as well as the hydrogen the gaseous 

 state, whence subtracting he arrives at 0*45 of a Daniell's 

 cell, as necessary alone to give oxygen the gaseous state, 

 upon which he remarks — " 0*45 resistance to electrolysis 

 is equal to 2°76." (Fah. in lib. water). "It would be 



