Mr Orange, On certain phenomena of the kathode region. 223 



further, the rays extend through a smaller distance from the 

 kathode ; the boundaries of the beams also change gradually, so 

 that at some distance from the kathode the beams become more 

 constricted. 



In previous work, kathodes of symmetrical or nearly sym- 

 metrical outline have been used, and consequently w^hat one might 

 call the roots of the beams of canal rays have been hidden by the 

 kathode. The shape of these has however been inferred from 

 markings which are found on the inner surfaces of the kathode, 

 after the discharge has been running for some time *. [ Vide Fig. 4, 

 taken from Goldstein's paper.] The case described above indicates 

 that the boundaries of the beams are similar in character whether 

 they fall within the outline of the kathode or not. 



Fig. 4. 



But, arguing from the cases of more regular kathodes, Gold- 

 stein, loG. cit., and Kunz-j- have advanced an explanation of the 

 curved boundaries which only holds when the curvature occurs 

 within the kathodic interspace. 



Goldstein says, " From the concave boundary of the traces and 

 of the pencils themselves, it may be inferred that the rays pro- 

 ceeding from any side are subject to an attraction due to the 

 neighbouring sides. We may, for example, imagine that in the 

 case of the square the rays are originally convergent along straight 

 lines, somewhat after the fashion indicated by the dotted lines in 

 Fig. 7 [Fig. 4 of the present paper], and that it is in consequence 

 of the attraction exerted on them by the adjacent sides that they 

 assume the actually observed form (shown by the full lines)." 



* E. Goldstein, loc. cit. p. 377. 



+ J. Kunz, Phil. Mag. July 1908, p. 180. 



