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VIII. "On the Heat which is developed at the Poles of a Voltaic 

 Battery during the passage of Luminous Discharges in Air 

 and in Vacuo." By JOHN P. GASSIOT, F.R.S. Received 

 June 12, 1861. 



1 . When the wires attached to the terminal plates of an extended 

 series of a voltaic battery are brought into contact with each other, 

 the circuit of the battery is completed ; and if in this state the ends 

 of the wires are separated from each other, the usual luminous 

 or arc-discharge is produced, the length of the arc depending on 

 the number of the cells of which the battery consists. If this lumi- 

 nous discharge is continued for a few seconds, the metallic positive 

 pole or anode becomes red-hot, and will ultimately be fused, while 

 the negative remains comparatively cool. This experiment was ori- 

 ginally described by me in the ' Philosophical Magazine ' of Decem- 

 ber 1838, p. 436. In the same periodical of June 1840, p. 478, Mr. 

 Grove suggested as an explanation, that this effect " might be due 

 to the interposed medium, and that, were there any analogy between 

 the state assumed by voltaic electrodes in elastic media and that 

 which they assumed in electrolytes, it would follow that the chemical 

 action in the positive electrode in atmospheric air would be more 

 violent than at the negative, and that, if the chemical action were more 

 violent, the heat would necessarily be more intense." 



2. Since that time I am not aware that any other explanation rela- 

 tive to the heating of the positive pole of the voltaic battery has 

 been published. Mr. Grove merely gives it as a suggestion ; but as 

 it is immaterial whether either or both poles are of copper, alumi- 

 nium, platinum, or any other metal, or of coke, as in either case it is 

 ihe positive that is heated, the phenomenon cannot arise from any 

 effect of oxidation, but must be due to some action in the battery 

 circuit hitherto unexplained. 



3. In the Bakerian Lecture for 1858, I have stated that, "when 

 the discharge from an induction coil is taken in air or in vacuo with 

 thin platinum wires, the negative terminal becomes red-hot, and if 

 the discharges are continued the wire will be fused." This heating 

 of the negative terminal, provided the wires are thin, always takes 

 place whatever may be the length of the discharge or the medium 

 through which it passes. 



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