4 ELECTROLYSIS. 



condense in a few words the definition of energy : it is the capa- 

 bility of effecting work. This definition equally applies to all 

 natural forces, and even to those which are in a state of repose. 



Energy is potential, or actual : potential when, in order 

 to manifest itself, it requires a determinative cause; actual 

 or kinetic when it is in action at the moment of being con- 

 sidered. The steam in a boiler, gunpowder, a coiled spring, 

 a piece of coal, all contain a certain quantity of potential 

 energy. The fall of a body, the steam acting in a cylinder, a 

 current passing through a chemical battery, all develop actual 

 or kinetic energy. There exists, in the universe, a total quan- 

 tity of energy which is susceptible of infinite transformation, 

 but the totality of which is an invariable quantity. It is quite 

 as impossible to annihilate or create a quantity, however small, 

 of energy, as to create or annihilate matter: all the phenomena 

 of nature are in reality nothing but transformations of energy, 

 and if it is sometimes difficult to explain what has become of 

 some mechanical work which, as such, has entirely disappeared, 

 one can be certain that it has been wholly transformed into 

 heat, electricity, chemical work, &c. in other words, into one 

 or more forms of energy. 



This principle, which is named conservation of energy or 

 of motive forces, was explained in all its details, for the first 

 time, by Dr. Helmholtz, in 1847, and it has contributed in a 

 large measure to the progress of the mechanical, chemical, and 

 electrical industries. When the experimenters have become 

 perfectly convinced that energy of whatever kind could not dis- 

 appear without instantaneously reappearing under some other 

 forms, they have searched for the absent energy through all 

 possible transformations without feeling discouraged by the 

 difficulties sometimes considerable of investigation, and they 

 have always succeeded in integrally finding, under the most 

 varied and sometimes the most unsuspected forms, all that 

 energy. We shall see, further on, that electricity, instead of 

 being considered as a form of energy, can be considered as a 

 simple transformator of energy. As M. Eaynaud said with 

 much reason: "Machines of all kinds are nothing more than 

 tools for the distribution and repartition of energy ; they restore, 



