CHAP. 11. VOLTAIC CIRCLE. 15 



surface, and the direction of the current was in the 

 direction the cation hydrogen may be supposed to 

 move, viz. from the zinc across the fluid to the 

 platinum, the platinum being the positive electrode. 

 I may just observe, that in the majority of instances 

 the exciting action is at the anode, and the metal 

 acted upon is considered as positive to the other 

 metal ; but when we speak of the positive extremity 

 of the current, this is generally in contact with the 

 metal not acted upon. It is as well to bear this 

 in mind, otherwise it will lead to considerable 

 confusion of ideas, when speaking of the positive 

 electrode and positive metal. 



In the following arrangement, if we take peroxide 

 of manganese, sulphuret of potassium in solution 

 as the electrolyte, and platinum, and form them 

 into a circuit, the platinum will be negative to the 

 peroxide of manganese ; the current will be in the 

 reverse direction to that observed in the former 

 arrangement. Now whether we suppose the cation 

 potassium to abstract the anion oxygen from the 

 peroxide or the latter, the cation potassium from the 

 sulphur, still the current passes in the direction 

 that the cation the potassium may be supposed to 

 move in the circle, and in this case the peroxide 

 will not only be the positive electrode, but will also 

 form the so-called positive metal of the circuit. 



In the following circuit, zinc, muriatic acid, and 

 peroxide of lead, the acting points, are at both 

 extremities, at the anode and cathode. In this in- 



