Mr. J. Prideaux on the Theory of Voltaic Action. 215 



rous and unequivocal experiments, amongst which the following 

 may be cited as well suited to contrast it with the chemical 

 source of electricity. 



9. Professor Berzelius took 12 glasses, each 3 inches deep 

 and | inch wide, half filled them with alkalescent muriate of 

 lime, the other half with dilute nitric acid. Into each he 

 put a copper wire with a zinc foot, the zinc lying in the alka- 

 lescent liquid, the copper bending over into the acid of the 

 succeeding glass. This formed what is commonly called the 

 circle of cups. 



So long as the poles were unconnected, the copper dissolved 

 in the acid, and the zinc remained unacted on ; but as soon as 

 the connexion was made (through solution of salt), the solu- 

 tion of copper ceased, and the zinc began to oxidate, the zinc 

 becoming positive (in the liquid) and the copper negative, as 

 usual in voltaic arrangements. 



Here the chemical action, which was in full play on the 

 copper, before the electrical circulation was opened, instead 

 of directing that circulation, was checked, and even reversed 

 by it. 



A simpler variation of this experiment will be described 

 (14-). And.it will also be seen (13), that placing the zinc in 

 an alkaline, the copper in an acid solution, is more efficacious 

 than the contrary arrangement, although the acid acts much 

 more freely on the zinc than on the copper. 



It is also generally known, that of neutral salts, none (ex- 

 cept sal-ammoniac) makes a more efficacious charge than sul- 

 phate of zinc, which is very unlikely to undergo decompo- 

 sition. 



10. Sir Humphry Davy's theory assumes that* "chemical 

 and electrical attractions are produced by the same cause; 

 acting in one case on particles, in the other on masses : and 

 the same property, under different modifications, is the cause 

 of all the phsenomena exhibited by different voltaic combina^- 

 tions." A view so comprehensive, embracing every modifi- 

 cation of chemical as well as electrical action, seems to include 

 the other two, and every one that has been, or can be, at- 

 tempted on the subject. But what it gains in extent it wants 

 in distinctness. 



11. It may, however, be limited by the word "attraction," 

 and by the statements that a plate of platinum in solution of 

 potass is positive to a plate of the same metal in acid, in con- 

 sequence of the attraction of the oxygen of the acid for the 

 one plate, and of that of the metal of the potass for the other ; 

 — a consequence not very evident. Also, that the cause of a 



* Philosophical Transactions, 1826, Fart IV. 



