HISTORY OF GALVANISM. 71 



ratus, had the power of counteracting, or even 

 changing, the effects of chemical affinity. The General 

 general principle was thus completely established, pn ' 

 that hydrogen, alkalies, and metals, are attracted 

 by the negative, and repelled by the positive end 

 of the pile ; while acids and oxygen are attracted 

 by the positive, and repelled by the negative end. 

 For the production of this effect, it is necessary 

 that there be a conducting chain of particles 

 through the transmitting fluids ; the transfer can- 

 not take place where insoluble compounds are 

 formed, because in this case the new compound is 

 carried out of the sphere of action. 



The establishment of the general principle Effect of 

 mentioned above, suggested some views of the 

 nature of the change produced by electricity, 

 which led to a new train of experiments. Sir 

 H. Davy observes, that many bodies, after being 

 brought into contact, exhibit opposite states when 

 they are separated. When a galvanic combina- 

 tion is formed from an acid, an alkali, and a 

 metal, the alkali appears to acquire, and the acid 

 to part with, a quantity of electricity ; the alkali 

 is therefore rendered positive, and the acid nega- 

 tive, and they will of course have an attraction for 

 each other. He found that when such acids as 

 were capable of being employed in the dry state 

 were touched by metals, and then separated, the 

 acids were rendered negative, and the metals 

 positive; but when the metals were touched by 

 the alkaline earths, the metals became negative. 



