J he Discharge of Electricity from Glowing Metals. 561 



In this case, the copper wire must be heated for a longer time in 

 air before it ceases to effect the discharge, and there is not the same 

 sharpness of definition between the two states. The phenomena 

 observed on heating the now oxidised wire in hydrogen differ also in 

 this case ; the hot wire not only effects discharge dnring the 

 reduction of its oxide coat, but continues to possess this power 

 certainly for a long time to the same degree. Hence, a red-hot 

 copper wire in hydrogen exhibits the curious property of retaining 

 perfectly a charge of negative electricity, and discharging instantly 

 a positive electrification. The hydrogen used was fairly dry, and 

 free from any sensible taste or smell. 



In dry nitrogen, the results were similar to those obtained with 

 hydrogen. The gas was carefully dried, and passed for eight or nine 

 hours over the copper before the electrical tests were made ; the red- 

 hot copper wire retained a negative charge, but not a positive one. 



The above experiments were all made in Dr. Schuster's laboratory, 

 and, in fact, under his immediate supervision. Dr. Schuster has 

 suggested that they are of sufficient interest to publish in their present 

 state, because they show more clearly than the experiments with 

 platinum the nature of the chemical action. In the case of platinum, 

 there is, of course, the advantage that the metal remains generally in 

 the same state, but it is much lessened by the very marked and 

 complex effects of surface condensation and occlusion . 



The potential of the bodies used was observed by means of an 

 ordinary gold leaf electroscope, and was such as to cause a large 

 divergence of the leaves. In all cases where discharge took place, it 

 was found easy to cause complete collapse of the leaves. 



It is proposed to supplement this paper with one dealing with the 

 phenomena in pure and perfectly dry gas. 



