ELECTRO-CHEMICAL EFFECTS. 



with this apparatus. If the handles P and N be held in the 

 hands, the arms and body become the conductor through which 

 the current passes from P to if . If x Y be made to revolve, shocks 

 are felt, which become insupportable when the current has a 

 certain intensity. 



If it be desired to give local shocks to certain parts of the 

 body, the hands of the operator, protected by non-conducting 

 gloves, direct the knobs at the ends of the handles to the parts 

 of the body between which it is desired to produce the voltaic 

 shock. 



167. For telegraphic purposes it will be sufficient to place the 

 line wire in connection with one of the handles P or N, while the 

 other handle is in connection with the earth. A current will then 

 be transmitted on the line wire which will be intermitting, but 

 which may be rendered continuous by a combination of magneto- 

 electric machines. 



168. It remains, in fine, to show how the chemical properties 

 of the electric current can be made to supply the means of trans- 

 mitting signals between two distant stations. 



When a current of adequate intensity is made to pass through 

 certain chemical compounds it is found that these are decomposed, 

 one of their constituents being carried away in the direction of 

 the current, and the other in the contrary direction. 



169. One of the most striking examples of the application of 

 this principle is presented in the case of water, which, as is 

 well known, is a compound of the gases called oxygen and 

 hydrogen. 



Let us suppose that a series of cups, oh, fig.6o, containing water are 

 placed so that an electric current shall pass successively through 

 them, commencing at the wire P and passing at o into the first 



Fig. 65. 



cup ; thence through the water to h, and from h along the wire I 

 to o in the second cup ; thence in like manner through the water 

 to h, and then along the wire i', and so on to N, the wire P being 

 supposed to be connected with the positive pole of a battery, and 

 the wire N with its negative pole. The current will therefore 

 flow from P to N passing through the water in each of the cups. 

 Under such circumstances the water will be gradually decomposed 

 in each of the cups the particles of oxygen moving against the 



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