through Exhausted Tubes without Electrodei 



327 



It will be useful to consider here the disposition and 

 motion of the tubes of electrostatic induction in the arrange- 

 ment used to produce these electrodeless discharges. We shall 

 take the case where two jars are used, as in /3, fig. 1, as being 

 the more symmetrical. 



Just before the discharge of the jar, the tubes of electro- 

 static induction will be arranged somewhat as follows : — 

 There will be some tubes stretching from one terminal of the 

 electric machine to the other; others will go from the ter- 

 minals to neighbouring conductors, the table on which the 

 machine is placed, the floor and walls of the room, &c. The 

 great majority of the tubes will, however, be short tubes 

 passing through the glass between the coatings of the jars. 

 Let us now consider the behaviour of two of these tubes, one 

 from the jar A, the other from B, when a spark passes between 

 the terminals of the machine. Whilst the spark is passing 

 these may be regarded as connected by a conductor; the tubes 

 which originally stretched between them now contract, the 

 repulsion they exerted on the surrounding tubes is destroyed 

 so that these now crowd into the space between the terminals, 

 the two short tubes under consideration now taking somewhat 

 the form shown in fig. 2. These tubes being of opposite sign 



Fijr. 3. 



Fi-r. 4. 



Fk-. 5. 



tend to run together; they do so until they meet as in fig. 3, 

 when the tubes break up as in fig. 4, the upper portion run- 

 ning into the spark-gap, where it contracts, while the lower 



