of the Galvanic Battery. 459 



different manner. Each cell contains two platinum plates, one 

 of which is quite clean, while the other is coated with the brown 

 binoxide of lead. We may consider this plate as consisting of 

 binoxide of lead, for the platinum beneath it only serves to con- 

 nect the particles of that substance with the conducting wire. 

 The bright platinum plate is immersed in nitrous acid contained 

 inside a porous cell, and the peroxide of lead is immersed in 

 nitric acid outside that porous cell. When the battery is at 

 work, the nitrous acid becomes oxidized and converted into 

 nitric acid on the surface of the positive plate, and the peroxide 

 of lead dissolves off from the surface of the negative plate by 

 losing oxygen. You can see the facility with which this trans- 

 fer of oxygen takes place from the one body to the other, by the 

 decolorization of the brown peroxide which takes place when I 

 mix it in this foot glass with a solution of nitrous acid. You 

 perceive by the testimony of this little battery that the oxidation 

 of nitrous acid replaces the chlorination of the zinc in our first 

 cell, and that disoxidation of peroxide of lead here occurs where 

 dechlorination of copper took place in that cell. In all galvanic 

 cells the plates communicate not only by the liquids in which 

 they are immersed, but also by the metallic connecting wires ; 

 and while the cell is at work a galvanic current passes, not 

 only through the connecting wire, but also through the con- 

 necting liquid. 



Now there is this important difference between metals and 

 liquid conductors. Wires are very good conductors, whilst 

 liquids are very bad ones in comparison; and if we put the 

 two plates into the liquid of a cell without connecting them by 

 a wire, there is no current, nor is there that chemical process 

 which we know to be its necessary accompaniment. The use 

 of the connecting wire does supply what is still wanted for the 

 occurrence of the combining process at the one plate, and the 

 decomposing process at the negative plate, and we are unavoid- 

 ably driven to consider that the electrical current is the process 

 by which motion or vibration of atoms is transmitted through 

 that wire from the combustion plate to the separation plate. 

 The evidence in favour of this conclusion is strengthened, and at 

 the same time rendered more precise, by a study of the process 

 which takes place in liquid conductors. It so happens that, 

 inasmuch as the liquids are composed of several elements, and 

 as they undergo a permanent change during the process of con- 

 duction, we are able to gain a most valuable insight into the 

 very behaviour of the component atoms while they are conduct- 

 ing the current. This is so very important a part of my argu- 

 ment, that I must beg leave to state it to you, although I must 

 confess that it deals with questions respecting the position and 



2 H 2 



