

Discharge of Electricity through Gases. 333 



place not towards the negative pole, but in the opposite direction. 

 I have repeated these experiments with electrodes which were 

 rather further apart. The behaviour of the tube under different 

 circumstances can be shortly expressed by saying that the discharge 

 always passes to the nearest point of the inner boundary of the dark 

 space. When the exhaustion is not sufficient, so that the width of 

 the dark space is less than the distance between the electrodes, the 

 positive discharge takes place towards the negative pole as in the 

 ordinary tubes, but as the dark space gradually expands, the positive 

 discharge contracts, and becomes invisible when the dark space comes 

 into contact with the positive wire. On further reduction of pressure 

 the dark space reaches beyond the positive pole, and the discharge 

 passes from that pole to the nearest point of the negative glow. In 

 other words, the tube behaves as if the glow, and not the negative 

 wire, formed the electrode. But this is exactly what should happen 

 according to our theory. 



The negative particles which are projected from the wire have first 

 to be brought to rest by molecular encounters before their motion is 

 regulated by the electrical forces in the ordinary sense. 



The experiment is conclusive to my mind, because in the neighbour- 

 hood of the positive discharge, as it turns away from the negative 

 pole, we have the current flowing in two opposite directions at closely 

 adjoining places. This could not be possible unless the current in 

 one direction was carried by particles moving against the lines of 

 force by their inertia. The positive discharge at the lowest pressures 

 which I am able to obtain shows some curious phenomena, indicating 

 perhaps that to some extent the phenomena of the negative pole are 

 repeated to a much smaller degree at the positive pole. A dark line 

 is noticed parallel to the positive wire at a distance varying with the 

 p'ressure, and at the best exhaustion which I could obtain about 

 1 millim. distant from it. From the wire to the dark line the 

 discharge is very narrow, but from the dark line it spreads out fan- 

 like towards the negative glow. 



Fig. 6, Plate 1, is taken from a photograph, and shows the phenomena 

 which I have just described. As far as the negative glow in these 

 tubes is concerned, the repulsive forces from the positive pole make 

 themselves very perceptible, so that the glow becomes stronger away 

 from the positive wire, and the tube presents the curious appearance 

 of two discharges from the two poles tending away from each other 

 and towards the glass vessel. The current completes itself on the 

 side of the vessel. This is clearly shown in a photograph (fig. 7), 

 which represents a projection in a plane at right angles to the wire 

 poles. These poles appear therefore as points, and the two discharges 

 passing away from each other and joining over the glass are clearly 

 distinguished. 



z 2 



