upon Electrical Discharge Phenomena in Rarefied Gases. 175 



generally very sensitive to variations in the charge upon the glass walls, 

 and that touching the bulb at various places with the fingers produces 

 vigorous movements of the glow within. 



In a bulb, the diameter of which was about 3 inches, the ring 

 threaded itself on to either of the electrodes E x or E 9 , when the centre of 

 the bulb was electrically connected to the cups C 2 and C l respectively. 



When only one electrode was magnetised, after the bulb had been 

 stimulated, the rotation of the glow was more easily seen owing to the 

 formation around the magnetised electrode of a wide, spiral-shaped, 

 luminous cloud which was apparently rotating as it became more and 

 more dim, and it was then noticed that the direction of rotation 

 could be reversed by reversing the polarity of the magnetised electrode. 

 No change in the effect was observed when the connections to the 

 bulb were reversed. 



The form of the electrodes was next varied, but the effects pro- 

 duced were mainly the same. With a pointed cathode and a concave 

 anode the ring formed as usual, but it was observed that, whenever 

 these relations were reversed, no ring could be obtained. Indeed, 

 having first of all stimulated the bulb with the concave electrode 

 negative, it was not only impossible to obtain a ring on magnetising 

 the electrodes, but even when the connections were reversed still no 

 ring would form until after repeated or prolonged stimulation of the 

 bulb. Neither did a ring form when the electrodes were magnetised 

 so that like poles faced each other a similar result to that already 

 observed with pointed electrodes. 



It may be worth recording that when pointed electrodes were em- 

 ployed, the ring formed equally well, whether the bulb was stimulated 

 by means of a Tesla oscillator, an induction coil, or a Wimshurst 

 influence machine. 



FIG. 2. 



Finally, experiments were made with external magnetised electrodes, 

 the exhausted bulb being shaped as shown in fig. 2. In this case of 

 course, the discharge was oscillatory, and consequently the effects 

 were not very directly comparable to those already described. 



At a low pressure, however, and when the bulb was filled with a 



