Niplier — Nature of the Electric Discharge. 11 



seemed of doubtful value after two years of constant 

 work. The character of the difference in results when 

 the plate was enclosed in a case of hard rubber and when 

 it was wholly exposed to the wire in the positive line 

 seemed unexplainable, until the idea finally suggested 

 itself that the positive brush discharge was a negative 

 inflow, or drainage into the exhaust terminal. 



These results give a clear explanation of the reason 

 why in forked discharges the ends of the branches or 

 forks point towards the negative terminal.^ 



These branches are drainage channels. 



Figs. B and C of Plate V, were made under the same 

 conditions as Fig. A of Plate XXI, in No. 4, Vol. XIX, 

 of these Transactions. They show more clearly how the 

 radial discharge lines from the negative pin head termi- 

 nal or cathode are crossed by the drainage lines from 

 the grounded pin head. They also show how these lines 

 unite when they meet end on, and how the drainage lines 

 are distorted in the region where the opposing " winds'' 

 mingle with each other. Even in air of atmosphere pres- 

 sure, the drainage lines extend beyond the cathode ter- 

 minal. 



These plates had pin-heads resting upon the photo- 

 graphic film. They formed the terminals of a gap in the 

 grounded negative line from the influence machine. A 

 faint disruptive discharge across a minute gap at the 

 machine, was accompanied by a glow across the plate 

 between the pin-heads. A disruptive spark there was 

 avoided. 



The distortion of the drainage lines as they approach 

 the negative glow, shows the effect of the commingling 

 of the super-charged molecules urged outwards from 

 the cathode pin-head, and the molecules of air or metal, 

 from which negative corpuscles have been drained, and 

 which are moving in the opposite direction. Wlien a 

 copper sheet is placed transversely across the middle 



* See Thomson's Recent Researches in Electricity and Magnetism, 

 p. 169, Fig. 73. 



