334 Dr. A. Schuster. Experiments on the 



Effects observed on Reversal of the Current. 



I now pass to a short description of some curious effects observed 

 on sudden reversal of the current. In my large vessels in which the 

 dark area opposite the positive wire appeared, the phenomena seen 

 when the wire was negative and the cylinder positive present little 

 that needs mentioning in detail. The only trace of positive light is 

 confined to two yellowish lines running parallel and symmetrical to 

 the wire. We have here very likely to deal with the reaction to the 

 repulsive effect on the glow. If, when these yellow bands are seen, 

 the current be slightly interrupted for a short time and passed again 

 in the same direction, these bands will appear perfectly steady from 

 the beginning of the passage. If, however, before making contact in 

 the same direction, a single spark be passed in the reverse direction, 

 the two bands will at first appear close together and right opposite 

 the negative wire, then quickly to move outward and to take up their 

 final position. If, after the cylinder has been positive, the current is 

 interrupted for a longer period of time, say five minutes, then the 

 same effects as on reversal will appear. Thus it seems that a 

 certain state has been established which dies away in something like 

 five minutes, but which can also be made to disappear by a single 

 spark in the opposite direction. 



Similar effects, though not so striking, are observed with the wire 



negative. The dark area seems to take time to establish itself. A 



short interruption of the current will make it reappear fully from the 



beginning, but if either five minutes are allowed to lapse, or a spark 



in the opposite direction is passed through the vessel, the dark area 



will not be well developed to begin with, but is filled with a faint 



glow which, however, dies away rapidly. These phenomena are, I 



think, fully in accordance with the theory here suggested, for it is 



clear that the condenser action will take time to establish itself and 



to die away, just as in a liquid. The effects observed when the 



cylinder is positive are not, in my opinion, produced by such a 



condenser action at the positive pole, but are secondary effects 



depending on the changes in the glow. When the current is finally 



established, the glow will be strongest away from the cylinder, and 



the positive discharge will consequently set out from parts of the 



cylinder not directly opposite the negative electrode. Hittorf has 



already noticed that when the negative electrode consisted of a long 



wire, the glow was found on first making contact to start from the 



point and to run backwards, covering gradually the whole of the 



wire. This is perhaps the place to dispose of an objection which 



might be raised against the theory. There are apparently no 



appreciable polarisation currents like those observed in liquids, but I do 



not think that this is a very serious difficulty. We usually represent 



