302 EXPERIMENTAL INVESTIGATIONS. 



antagonistic theory asserts that no electrical disturbance can 

 take place without some chemical or physical change. Now, 

 as the facts of thermography prove a radiation of some sort 

 (for this argument, no matter of what sort) to take place on 

 the juxtaposition of different metals, a physical change is 

 produced, electricity ought to be developed on their separation, 

 caused either by their action on each other, or by the different 

 degrees of evaporation from each of their surfaces when sepa- 

 rated ; this physical or chemical change ought to produce, and 

 does produce, a disturbance of electric equilibrium ; and thus 

 recourse to the incomprehensible action of simple contact is 

 unnecessary. An experiment was shown strongly confirmatory 

 of this view : the discs of zinc and copper were juxtaposed, 

 surface to surface, but contact prevented by a rim of paper, 

 and yet when separated the electroscope was affected ; here, 

 then, was no metallic contact, and yet the electrical effects were 

 produced, which should be so by the mutual radiation, but 

 which should not be so by the contact theory.* 



VOLTAIC PHENOMENA. 



Electrical Mag., Sept. 1843. 



IN the 'Philosophical Magazine,' for October 1839, I have 

 noticed the fact that when copper formed the anode of a 

 voltaic pile in nitro-sulphuric acid, it became inactive, and was 

 neither oxidated, nor was oxygen evolved from its surface ; 

 differing in the latter respect from inactive iron, it perfectly 

 arrested electrolytic action, and consequently the passage of 

 the voltaic current. Some facts which I subsequently ob- 

 served will throw some light on this anomaly, and, as far as I 

 am aware, are in themselves new. 



* See Mr. Gassiot's confirmation of this, avoiding the rim of paper. Phil. 

 Mag., Oct. 1844. 



