402 



NIPHER— DISRUPTIVE DISCHARGES 



[April 21, 



is not in the rarefied condition which exists within' the disruptive 

 spark channel. This part of the discharge must be practically noise- 

 less. The sound produced by the spark is caused by the collapse of 

 the spark channel in a manner similar to that caused by the crack 

 produced by the end of a whip-lash, which also cuts a hole in the 

 air. When an electrical discharge occurs between clouds or between 



Fig. 4. 



a region containing an excess and one having a deficiency of elec- 

 trical corpuscles, the latter region must be in a condition like that 

 surrounding the grounded anode in Fig. i. The disruptive channel 

 will dififuse into it. This region is one which is properly called a 

 region of conduction. 



The other end of the discharge channel must penetrate regions 

 where the air is super-charged with corpuscles. It is not in the 



