on the Direct Current Corona. 



299 



glow similar to that of the positive discharge but has a 

 greater thickness. The brushes or negative beads soon 

 formed by a slight potential increase bear a similarity to 

 the arc, and in addition from the position of the negative 

 characteristic curves and the influence which the surface 

 condition and the material of the wires have on them 3 



Fig. 12. 



lead us to the belief that an electron emission is present 

 in addition to ionization by collision in the gas. _ 



The case is somewhat different when a series spark 

 gap is used. We may consider the corona tube as a 

 leaky condenser connected in series with a spark gap and 

 a constant source of high potential. A charge will build 



3 "Direct Current Corona from Different Surfaces and Metals," Phys. 

 Bev., October 1916. 



