222 Mr Orange, On certain 'phenomena of the kathode region. 



Fig. 2, PI. V, but hydrogen was used instead of air in order to 

 obtain canal rays of a more reddish colour than those in air; 

 further, a yellow glass screen, which cut out the blue end of the 

 spectrum, was used in conjunction with orthochromatic plates. 

 It should be remembered that the kathode rays are still just 

 visible at this stage, as shown in Fig. 2, PI. V, but are suppressed 

 in the present example owing to the photographic method used. 

 [An exposure of 40 minutes was necessary and this gave rise to 



Fig. 3. 



difficulties at first owing to the strong tendency of the vacuum to 

 'harden' with continued running of the discharge. By judiciously 

 fixing the initial pressure of the gas, however, it is possible to 

 obtain steady conditions if the discharge is given a preliminary 

 run.] 



The configuration of the canal rays can be made clearer by 

 means of a diagram. Fig. 3*. As the pressure is reduced still 



* It may be stated here that subsequent experiments have shown that the three 

 connecting pins do not affect the boundaries of these beams. 



