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III. Some Notes on Brush Discharges in Gases. 

 By W. H. Harvey and F. Hird, B.A* 



WHILE experimenting on high-frequency discharges we 

 came across a remarkable difference in the behaviour 

 of positive and negative electricity, which forms the subject of 

 these notes. 



The apparatus was arranged in the now well-known manner 

 for obtaining oscillatory discharges of high potential and high 

 frequency, from the discharge of a condenser. The accom- 

 panying diagram and description will make clear the exact 

 arrangement. 



Fig. 1. 



IJ 



t_ B t 



■o D o 



c, 





A is a small magneto-machine giving a continuous current 

 at about 8 volts. 



B is an ordinary induction-coil capable of giving about an 

 inch spark. 



G 1 and 2 are equal condensers, consisting of shellacked glass 

 plates coated with tin-foil. The capacity of each was approxi- 

 mately '0038 microfarad. 



D is an adjustable spark-gap. 



P and S are the primary and secondary of a transformer 



without iron core, the elements of which are as follows : — 



P: mean diameter 5*65 centim.; axial length 20*3 centim.; 



wound with 9 turns of copper-strip 20 millim. x *064 



millim.; approximately L = 1123 centim. 



S : mean diameter 9*4 centim. ; axial length 11 centim. ; 



wound with 78 turns of '38 millim. wire silk-covered, 



* Communicated by the Authors. 



