Discharge of Electricity through Gases. 329 



I may for the sake of clearness once more mention shortly the 

 principal points of the argument. 



The rapid fall of potential in the neighbourhood of the negative 

 electrode renders the presence of positively electrified particles in its 

 neighbourhood necessary. 



If the distance through which the condenser action takes place is 

 sensible, the positively electrified particles will be acted upon by a 

 neighbouring positive electrode. 



A steady state will be established in which the fall of potential 

 along the normal from the surface will be everywhere the same. 



As however the flow is stronger away from the positive electrode, we 

 must conclude that other forces besides electrical forces determine the 

 flow. 



It is natural to assume that these are chemical forces : that in other 

 words the positively electrified particles are the decomposed molecules, 

 which by their presence assist the decomposition of others, and there- 

 fore the formation of the current. 



Unless a flaw is detected in this line of argument, I think that the 

 conclusion must be granted, namely, that the decomposition of the 

 molecules at the negative electrode is essential to the formation of 

 the glow discharge. This is really all that I endeavour to support in 

 this paper. The rest can only be settled by further experiments. 

 And amongst the rest I count also the primary cause which originally 

 produces the decomposition of molecules at one pole rather than at 

 another. It is possibly due to an electromotive force of contact 

 between the gas and the electrodes which tends to make the gas 

 electronegative. 



It does not seem difficult to explain by our theory the phenomena 

 which happen at the negative electrode on exhaustion. When the 

 pressure is high the discharge passes in a series of distinct sparks, 

 separated by a sufficiently long interval of time to make each spark 

 independent of the one preceding it. Here, of course, the spark will 

 set out from that part of the negative electrode at which the tension 

 is strongest. As the vessel is gradually exhausted the sparks suc- 

 ceed each other more rapidly, and the molecules decomposed during 

 one discharge assist the next discharge. If the decomposition of the 

 molecules goes on at a sufficiently rapid rate the tangential action of 

 which I have spoken comes into play, and the negative glow will 

 cover a greater part cf the negative electrode. The discharge at the 

 same time can become continuous, for the state of polarisation near 

 the electrode can keep up a continuous stress. The stronger the 

 current becomes, the more easily will the negative electrode become 

 covered with the glow. 





