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



seems to confirm the observations of Schuster* on the relation 

 between the thickness of the dark space and the strength of the 

 current. 



As regards the sheets of rays, the appearances in these experi- 

 ments agree fairly well with the explanations advanced above. 

 In Fig. 1, PI. IX, the kathode rays from the lower plate strike the 

 upper one violently. Some of the rays graze the edge of the 

 plate and produce the sharp, nearly vertical shadow which may be 

 noticed. The upper plate emits secondary kathode rays, which 

 are not sufficiently powerful to travel far towards the lower plate, 

 but are very soon thrown out sideways as three highly luminous, 

 but ill-defined sheets, corresponding to the three sides of the 

 triangle. 



In Figs. 2 and 4, PI. IX, the form of the lower ray sheet is clear 

 and it will be noticed that in these cases it is much further away 

 from the kathode than in any of the examples on Pis. VII and VIII. 

 This is probably due to the fact that rays from the upper (low 

 potential) plate will not have sufficient energy to approach near to 

 the lower kathode and hence when they finally start moving side- 

 ways they are at a considerable distance from it. No such feature 

 is associated with the upper plate. The rays starting from near 

 the latter form two distinct beams (two on each side that is) 

 in most of these examples, (e.g. Figs. 2 and 4, PI. IX.) 



These two beams might be explained as being due to 



(i) the primary rays from the upper plate which have 

 travelled back after visiting the neighbourhood of the lower 

 one, and 



(ii) the secondary rays from the upper plate due to the 

 impact of the primary rays from the lower one. 



The change which has occurred in the position and direction 

 of the " median " beams, owing to the alteration of the potential 

 of the upper plate, is quite what one would anticipate. (Fig. 2, 

 PI. IX.) 



In conclusion, I wish to thank Prof. Sir J. J, Thomson for his 

 valuable suggestions and kindly interest in these investigations. 



My gratitude is due also to Mr E. Everett for his ready 

 assistance at various times. 



* Schuster, loc. cit. p. 556. 



