Phosphorescent Glow in Gases. 347 



unimpeded as before. This effect was obtained whether the 

 electrodes were ail connected to the positive or to the negative 

 terminal of the electrical machine, or put to earth. The glow 

 was in each case unaffected both in velocity and in intensity. 

 The distance between the electrodes was about 50 cms. When 

 a discharge passed between one pair of electrodes, each one 

 being separately connected with a different terminal of the 

 Wimshurst, a discharge was easily produced between them, but 

 it did not give rise to an after-glow when the current ceased. 

 It was impossible, however, to say in this instance whether 

 the current also diminished or destroyed the after-glow from 

 the ring discharge, since the current from the second 

 Wimshurst, which gave the continuous current, was not 

 stopped abruptly, and the continuous discharge was too 

 bright to admit of any comparison or distinction between it 

 and the glow. A similar experiment was made with the 

 electrodes close together, and an electromotive force from 180 

 storage-cells was put between them ; the distance being suffi- 

 ciently great to prevent sparking between the electrodes; but 

 no effect whatsoever was produced upon the glow any more 

 than in the previous experiment. Thus it is evident that the 

 glow cannot be the result of the recombination of ions due to 

 the spark as they move down the tube. It is quite possible, 

 however, that recombination does take place in the bulb 

 immediately after the passage of the ring-discharge, and that 

 phosphorescent molecules are there formed which travel down 

 the tube but do not behave as electrified particles. Upon 

 this point the experiment does not of course throw any light ; 

 and all that can be said is that the positive and negative ions 

 which travel down the tube, on recombining — as doubtless 

 they will do — do not emit luminous radiation of sufficient 

 intensity to explain the phosphorescence in question, since 

 the wire-gauze electrodes will act as nets for one set of ions 

 and thereby prevent recombination, so that the glow would be 

 stopped, or at any rate greatly diminished in intensity, at each 

 successive electrode. Such, however, has not been found to 

 be the case. And it may be inferred that the phosphorescence 

 consists of glowing particles or molecules which do not carry 

 a charge of electricity ; which are not destroyed or broken 

 up by an electromotive force sufficiently small not to produce 

 a discharge in the gas ; and which are not created by the 

 recombination of ions along the tube ; but are particles or 

 molecules that are produced in the bulb by the passage of the 

 ring-discharge, and make their way down quite independently 

 of the electrical condition of the tube. 



(5) This view is confirmed by the following experiment, 



2 A2 



