

Discharges in Elect rodeless Vacuum- T% 



507 



connecting the tinfoil to either of the outside coatings, A or 

 B ; of the jars instead of to earth. This result led the author 

 to try a series of experiments to endeavour to determine 

 the cause of the effect, of which the typical ones are here given. 



Experiment! {vide fig. 2) . A Fig-. 2. 



and B are the outside coatings 

 of a pair of Leyden jars (those 

 employed were about pint size). 

 C and D two vertical and paral- 

 lel metal plates, at a distance of 

 about one foot from the jars. The 

 spark-gap, S, is adjusted by a 

 screw, so that the spark-length 

 can be varied by small amounts 

 when necessary. A single turn 

 of wire, a b, encloses an exhausted 

 bulb, and its ends are connected 

 to A and B, as shown in the 

 figure, so that a the part nearest 

 to C is connected to A, and b to 

 B. Two loose wires, e and/, are 

 also connected to A and B. 



The spark-gap is now shortened until there is just no 

 luminous ring in the bulb. 



The plates C and D are then connected to the outer 

 coatings A and B by means of the two loose wires, with the 

 following results : — 



(1) A to C. Bright ring. 

 B to D. Bright ring. 



A to C and B to D simultaneously. Bright ring. 

 A to D. ) 



B to G. > No luminous ring. 



A to D and B to C. J 



Expt. 2. — The wire turn a b is removed from the bulb, 

 given a half twist, and then replaced ; so that a is now 

 nearest to D, and b to C. Plates not connected, no luminous 

 ring. 



(1) A to C. 



(2) BtoD. 

 A to G and 

 A to D. 

 B toC. 

 A to D and I 



Expt. 3 

 then connected to 

 Expt. 



(3) 



(5) 

 (6) 



(3) 



(5) 

 (6) 



B to 



,} 



No luminous ring. 



Bright ring. 



Arranged as in Expt. 1, case (1) or (2). C is 

 D, and the ring becomes less bright. 

 4. — Arranged as in Expt. 1, case (1). C and D 



2N2 



