Discharge in Rarefied Gases. 377 



II. 



I consider two processes to be necessary for the production 

 of the discharge: — (1) A change in the condition of the aether, 

 preceding the discharge, which produces a certain condition 

 of unstable equilibrium in the arrangement of its parts : this 

 condition may be called, for shortness, tension of the aether. 

 (2) The restoration of equilibrium : this constitutes the dis- 

 charge itself. 



The tension which precedes the discharge is not equally 

 great in all cross sections of a discharge-tube, even when the 

 tube is of equal section throughout; it may even equal zero 

 in certain parts of the tube. The tension has either finite or 

 maximum values at the surface of the metallic poles and at 

 those points which appear as points of issue of the separate 

 positive layers or of the secondary negative pencils. The 

 resultant of the opposing force produced by the tension on 

 each element of the kathode is directed away from it ; at the 

 other points of issue also, it is directed at each point towards 

 the side turned away from the kathode. When the restoration 

 of equilibrium commences, a motion results in consequence 

 of the finite or maximal tension on the surfaces, which ad- 

 vances to the side of each surface of issue remote from the 

 kathode, and, originally excited in free aether, transforms itself 

 secondarily on its way into transversal vibrations of the ma- 

 terial atoms. The distances in which the tension before the 

 discharge was zero, and in which the. motion excited at the 

 surfaces of issue does not propagate itself, remain dark; such 

 places are the distances between the positive light, on the one 

 hand, and the kathode-light or secondary negative light, on the 

 other hand. 



The greater the exhaustion becomes, the more do the dis- 

 tances between the surfaces of origin increase, and at the same 

 time also the distances to which the motion excited at the sur- 

 faces of issue extend. This latter increase, however, is com- 

 pleted more rapidly than the increase in the distances between 

 the surfaces of origin; hence it comes that one and the same 

 section of the space occupied by the discharge may be affected 

 by motions which radiate from two or more surfaces of origin. 

 (Penetration of the kathode-light into the positive light or of 

 the stratified pencils into each other.) Experience shows that 

 such motions penetrating each other do not sensibly alter each 

 other when their directions are the same; but when their 

 original directions are inclined to each other at a considerable 

 angle, they show marked phenomena of deviation *. 

 * Goldstein, Wien. Ber. 1876, 23 Nov. 



Phil Mag. S. 5. Vol. 14. No. 89. Nov. 1882. 2 C 



