THE ELECTRIC CURRENT. 5 



which is developed by an electric motor through which the electric 

 current is forced. 



An electric current flowing through a wire produces an influ- 

 ence which extends throughout the region surrounding the wire, 

 as is evident from the fact that a compass needle is deflected when 

 it is brought near an electric wire. There is, however, no influ- 

 ence exerted in the region surrounding a pipe through which 

 water is flowing. Therefore the hydraulic analogue of the electric 

 current is of no help in giving one a conception of the magnetic 

 effect of the electric current. In the study of those phenomena 

 of the electric current which depend upon its magnetic effect, the 

 hydraulic analogue must be used with caution. 



2. The chemical effect of the electric current.* When a solution 

 of a chemical compound forms a portion of an electric circuit, the 

 compound is, in general, decomposed by the current, as stated 

 above. Thus, melted salts, and acids and salts in solution are 

 decomposed by the electric current. This chemical decomposi- 

 tion is called electrolysis, and the liquid in which electrolysis takes 

 place is called an electrolyte. Electrolysis is usually carried 

 1 out in a vessel provided with two flat plates of metal or carbon 

 which serve to lead the current into and out of the electrolyte. 

 Such an arrangement is called an electrolytic cell, and the plates 

 of metal or carbon are called the electrodes. The electrode upon 

 which the metallic constituent of the solution is deposited is called 



* The chemical effect of the electric current is exemplified by many electrochemical 

 processes which are now used on a large scale in various industrial establishments. 

 See The Electrochemical Manufactures at Niagara, Electrochemical Industry, Vol. I, 

 pages 11-23; The Electrolytic Refining of Copper, Engineering and Mining 

 Journal, September 19, 1896, and Electrochemical Industry, Vol. I, page 416, 

 August, 1903, and The Manufacture of Aluminum by Electrolysis, Electrochemical 

 Industry, Vol. I, page 158, June, 1903. 



Perhaps the best modern treatises on the phenomena of electrolysis are the 

 following : 



A Text-book of Electro-chemistry by LeBlanc, translated by W. R. Whitney and 

 J. W. Brown, The Macmillan Company. 



Electro-chemistry by Danneel, translated by Merriam, John Wiley & Sons. 



The Theory of Electrolytic Dissociation by H. C. Jones, The Macmillan Company. 



