14 VOLTAIC CIHOLE. CHAP. II. 



and the gas is now evolved on the surface of the 

 platinum rod, hut the chemical action still continues 

 upon the zinc ; in addition to this, we have a 

 current of electricity, as it is called, in the wire, as 

 may he shewn by suspending a magnetic needle 

 parallel to the wire, when the needle will place 

 itself at right angles to it. The explanation of these 

 actions is the following: the oxygen of the water 

 (the electrolyte) combines chemically with the zinc, 

 and the hydrogen, the other element of the electro- 

 lyte, is evolved upon the surface of the platinum ; 

 during these actions electricity is evolved, and the 

 circuit being completed, it is thrown into dynamic 

 force, current force. The water is the decomposing 

 electrolyte ; its anion, the oxygen, combines at the 

 anode with the zinc ; whilst the cation, the hydrogen, 

 is evolved on the surface of the cathode, the platinum. 

 The sulphuric acid, by dissolving the oxide of zinc 

 as it is formed, removes it from the surface of the 

 zinc, and thus assists in continuing the chemical 

 action ■'. 



Now the direction of the current is invariably 

 associated with the direction in which the active 

 chemical forces oblige the anions and cations to 

 move in the circuit. In the circle we have been 

 speaking of, the action was at the anode, at the zinc 



" A different view may be taken in regard to this explanation 

 of the action of the sulphuric acid. See Daniell and Miller, 

 on the nature of Compound Electrolytes. Philosophical Trans- 

 actions, 1839, p. 97. 



