Phosphorescent Glow in Gases. 401 



sufficiently high potential : and the bluish glow described on 

 p. 352 indicates that something of the kind was taking place. 



On one or two occasions I have detected and felt a very 

 feeble discharge from the wire connecting the brass ping to 

 earth. These experiments were therefore repeated with a long 

 brass tube between the bulb and the plug. The plug was 

 soldered to the brass tube and the whole was put to earth, the 

 wires in every case being soldered. The glow did not go 

 beyond the plug, showing that the stoppage when the plug 

 was present and soldered to the long brass tube was doubtless 

 due to the increased capacity of the tube ; with the brass 

 tube alone without the plug the glow travelled along quite 

 unimpeded. 



This proved conclusively that the apparent passage of the 

 glow through metals is purely a secondary effect. 



When a hole was made in the brass plate and a narrow 

 tube about 2 mm. in diameter soldered to it, as in fig. 6, the 



Fi<?. 6. 



glow simply diffused rapidly in all directions, but took longer 

 to rise to its full brilliancy in the immediate neighbourhood 

 of the brass plate, as though it took some time to curve round 

 the orifice, thereby indicating that the phosphorescent par- 

 ticles escaped through the orifice under a slight pressure. 



When the orifice was narrowed down to less than 1 mm. 

 the gkyw was seen distinctly to start some distance from the 

 orifice at the end of the tube, which, in this particular case, 

 was not more than 50 cms. This may once more be attri- 

 buted to the explosive nature of the spark. 



A magnet such as would deviate cathode-rays has no sensible 

 effect upon the path of the particles thus shot out through 

 the orifice ; but as the boundary was so ill-defined, it was 

 impossible, under the circumstances, to decide upon this 

 question with certainty. 



A series of experiments have also been made upon the 

 effect of a magnetic field upon the conductivity produced 

 by the glow, but although they have caused the expenditure 

 of a considerable amount of time and trouble it is felt that as 

 the results so far obtained are not sufficiently conclusive it is 



