Inaugural Address by the President 23 



metals and pointing to the Volta condenser experiment as 

 precluding the possibility of chemical action. They pointed 

 out that this condenser experiment gave the same result in 

 vacuo where they said no atmospheric action could take place. 

 They omitted to consider, however, that there was no such 

 thing as a vacuum attainable. After the best means of exhaustion 

 known there is always amply sufficient gas left to cause the 

 minute amount of chemical action required for this particular 

 electric effect. 



Since it seemed hopeless to attempt to nullify the electric 

 effect by removing the atmosphere, it occurred to me to try if 

 varying the chemical nature of the atmosphere would cause a 

 corresponding variation of the electric effect.^ In fact I con- 

 sidered that if with a Volta condenser we could arrange a 

 change of the chemical activities of the atmosphere surrounding 

 the plates analogous to the change of the chemical activities of 

 the Hquid in the cell which I have just described, we should find 

 a reversal of the electric charges analogous to the reversal of 

 current in the cell. 



I chose the same metals as Faraday, copper and iron, and of 

 these this small condenser Fig. i was made so as to be enclosed 

 under a glass bell on insulating supports. When tested in 

 ordinary atmosphere the chemical action of which is chiefly 

 directed towards the oxidation of the iron, the usual Volta effect 

 was produced. The iron plate communicated a positive charge to 

 the electrometer. Then, without changing any of the metallic 

 contacts, I passed into the glass bell a stream of hydrogen 

 sulphide gas. The copper was actively attacked and tarnished by 

 the gas and at once took, electrically speaking, the place of the 

 iron in the first case, and a positive electrification was now 

 obtained from it. 



My satisfaction and indeed elation at finding my hypothesis 

 so clearly verified was very great. Indeed I believed that this 

 experiment would end the dispute between the contact and 



9. Phil. Mag. VI., p. 142, 1878. 



