Mr. A. Schuster. 



Behaviour of Copper Electrodes. — Let us first consider the case of 

 conductors charged negatively. Clean copper, heated to a full 

 redness in air, is found to discharge negative electricity freely, but, if 

 oxidised carefully all over the surface, it will retain its charge. If on 

 the other hand oxidised copper is heated in hydrogen instead of 

 in air, it will be quickly discharged until all the oxide is reduced ; 

 after that, the charge will be retained. In other words, negative 

 electricity is quickly discharged during the process of oxidation or 

 deoxidation, but not otherwise, as when clean copper is heated in- 

 hydrogen or oxidised copper in air. So far as the experiments could 

 be carried out with iron in place of copper they gave similar results. 

 As regards the behaviour of copper when it is positively electrified, the 

 phenomena are not so sharply defined. Positive copper in an atmo- 

 sphere of hydrogen seems certainly to discharge itself, even when 

 perfectly reduced, so that it retains a negative charge. Copper in air 

 seems to discharge positive electricity less freely when it is oxidised 

 than during the process of oxidation, but whether it ultimately 

 retains its charge in all cases or not has not yet been completely de- 

 termined. Preliminary experiments in nitrogen have given the same 

 results as those observed in hydrogen, leakage taking place when 

 red-hot copper is electrified positively, but not when it is electrified 

 negatively. 



These experiments tend to show that the process of oxidation or 

 deoxidation can powerfully affect the facility of discharge from red- 

 hot iron or copper; so much so that no very extraordinary precau- 

 tions are necessary to destroy all signs of leakage of a negative charge. 

 We are not justified as yet in asserting that jfche discharge of negative 

 electricity is always accompanied by a chemical action even with the 

 metals experimented upon, for the temperature at which the experi- 

 ments were carried on was limited by the danger of melting the 

 copper, and the leakage was only tested by the more or less rapid 

 collapse of two gold leaves connected with the charged body. A 

 higher temperature might have brought out the leakage again, or 

 even at a red heat more delicate methods might have shown that the 

 leakage was only greatly reduced, but not destroyed. As regards 

 positively charged bodies, it is still an open question whether 

 chemical action plays any part in regulating the rate of discharge. 

 The gold leaves collapsed quickly when copper was heated in hydro- 

 gen, but there may have been some action between the two bodies, 

 and Mr. Stanton noticed the fact that the copper became very brittle. 

 It is possible that with pure gases not acting chemically on the 

 electrodes no discharge at all takes place, but this is by no means 

 proved, and on the whole I think the evidence is against the supposi- 

 tion. We must fo^ the present be satisfied with the fact that we can 

 actually trace the effect of chemical action in destroying the leakage 

 of negative electricity. 



