398 XIPHER— DISRUPTIVE DISCHARGES [April 21, 



An illustration of this action is shown in Fig. i. A photographic 

 plate had the heads of two pins resting upon the film. They formed 

 the terminals in a gap in a discharge line from the negative terminal 

 of an eight-plate influence machine to ground. Between this gap 

 and the machine was another gap of about i mm., which was at the 

 large knob of the machine. 



In order to produce the effect shown in the figure, the machine 

 was turned very slowly for several minutes. Small discharges 

 occurred at the small gap. When there was danger of a spark be- 

 tween the pin-heads, the machine was stopped for twenty or thirty 

 seconds and then continued. This resulted in draining the negative 

 corpuscles from the air around the grounded pin-head. A progres- 

 sive elongation of these drainage lines was examined in a series of 

 plates in which this operation was continued for an increasing time 

 interval, the plates being then developed. 



In Fig. I after continuing the slow driving of the machine for 

 about three minutes, its speed was then suddenly increased and a 

 disruptive discharge passed over the photographic film between the 

 pin-heads. 



This plate is one of many hundreds that have shown this phe- 

 nomenon of a diffused conduction in the region around the positive 

 end of the disruptive channel. This channel began at the negative 

 pin-head, in the midst of the negative glow. That region was not 

 in a condition of conduction for the negative discharge, and has not 

 been in any case observed. Fig. i is one of a few cases where the 

 discharge wandered considerably from the line joining the pin- 

 heads. In some cases the plate was in the positive line. In some 

 cases the two pin-head terminals were directly connected to the 

 positive terminals of the machine with minute gaps at the machine. 

 In all cases the diffusion area was formed at the positive pin-head 

 terminal. In all cases the appearance shown in Fig. i was observed. 

 The appearance is that which might be caused by a volley of nega- 

 tive corpuscles discharged from the end of the disruptive channel, 

 and aimed at the pin-head forming the positive, in this case the 

 grounded, terminal. The pin-head shielded that portion of the film 

 which was behind it and in line with this discharge from the fog- 



