GALVANIC ACTION 



grows warm, and Hydrogen gas is freely evolved from 

 the Zinc surface, causing the effervescence. If the 

 Zinc plate be connected by wire, in or outside of the 

 liquid, to a Copper plate immersed in the same solu- 

 tion, but the plates not in contact, it will be found that 

 the gas will no longer be evolved from the Zinc plate, 

 but will be from the Copper one. The Zinc plate 

 nevertheless, will dissolve more rapidly ; the Copper 

 plate will suffer no loss or change; but will be found 

 charged with positive electricity. If the wire be cut 

 in the middle and the ends kept apart, the prior exist- 

 ing conditions will return. On bringing again the 

 freshly cut ends together, when nearly in contact a 

 spark may be seen to pass from one to the other. The 

 condition will be again reversed, and the charac- 

 teristics of the Electric current are manifested. This 

 constitutes the simplest form of the voltaic battery. 

 By examination it is found that for every molecule of 

 Zinc dissolved a constant quantity of Electricity is 

 produced, which in its turn can be converted into 

 equally constant degrees or quantities of heat, of light, 

 of mechanical motion, or be made use of to effect the 

 decomposition of metallic salts in solution that will 

 be alike constant in the amount thus decomposed. If 

 the process be reversed and a current of electricity, 

 however produced, be transmitted to metal lie plates or 

 objects connected as described, and immersed in a solu- 

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