496 Prof, Skinner on Conditions controlling the Drop of 



reduced ionization in the negative glow, which in turn 

 necessitates (for the same current passing) an increased 



Fig. 3. 

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velocity of the ions moving up to the cathode, and hence an 

 increased cathode drop. 



Fig. 4. 



To study this a tube of form shown in fig. 4 was first 

 tried. The cathode was inlaid in guttapercha, its stem 



