Mr Orange, On certain pheoiomena of the kathode region. 225 



almost impossible. If, then, we consider the beams to be con- 

 stituted of straight rays instead of curved ones, the problems 

 which face us are two much simpler ones. 



(i) To account for the directions of the constituent straight 

 rays, and 



(ii) To account for the occurrence of the luminosity of the 

 rays after, and only after, they have passed through the kathodic 

 interspace. 



With regard to the first question, let us consider the canal 

 beam which arises from the longest side of the triangle and 

 runs towards the left of the picture (Fig. 2, PI. VI). 



Adopting Prof. Thomson's explanation of the mutual inter- 

 dependence of kathode and canal rays, we suppose this beam to 

 have its origin in the region to the right of the kathode. It would 

 be interesting then to know where the kathode rays which, starting 

 from the longest side of the triangle, run to the right, accomplish 

 the ionization which gives rise to the canal rays. 



Reference to Fig. 1, PI. VI, tells us roughly where the kathode 

 rays in question excite phosphorescence on the glass vessel. This 

 has been indicated by the dotted line fg in the diagram, Fig. 3. 

 There is thus at least a rough correspondence between the region 

 where ions are produced by the kathode rays and the backward 

 prolongation of the visible canal rays. The same argument 

 seems to apply to the other two canal ray beams. (It is evident 

 however, that one limit of the phosphorescence, at e, Fig. 3, is 

 rendered uncertain by the occurrence of the anode side tube at 

 that part of the bulb.) 



The second question, that of the luminosity of the canal rays 

 after passing the kathode, remains to be considered. If the canal 

 rays be regarded as positive ions which move up to the kathode 

 with continually increasing velocity and, after passing the kathode, 

 lose their velocity by the reverse process, it is indeed difficult to 

 account for their luminosity occurring only after passing the 

 kathode. It can be shown quite readily, however, that the posi- 

 tive ions are much more likely to be neutralized when moving 

 away from the kathode than when approaching it. For in the 

 former case they encounter negative ions moving in nearly the 

 same direction, while in the latter they encounter them travelling 

 in nearly the opposite one. Thus if recombination is associated 

 with luminosity, as is probable, we can see why the canal rays are 

 visible only after passing the kathode. We may consider the 

 recombination to occur entirely within a short distance of the 

 kathode, in which case the visible length of the rays can be 

 explained by supposing the ions to vibrate for about 5 x 10~^ sec, 

 or we may consider that recombination occurs throughout the 

 whole visible length of the beam. 



