1898.] on Some New Studies in Cathode and Bontgen Badiations. 595 



from the cathode, and moving it gradually towards the latter, it will 

 be observed that at first there is a slight gradual increase in the 

 length of the alternative spark. Then for the next small movement 



Fig. 



19. — Dingram showing liow the resistance of a tube is altered 

 by varying the position of tlie anode. 



there is a very sudden increase, and after that again a gradual increase 

 till we get to the point marked in dotted lines, which denotes the 

 limit of travel that the anti-cathode was allowed. 



Now let us come to Fig. 20, which represents the effect of moving 

 the cathode in the same tubs, the anti-cathode being stationary in the 

 position shown. Here, as will be seen, the less the distance between 

 cathode and anti-cathode the less is the length of the alternative 

 spark. 



This distance in this case doe? not appear, however, to be the 

 determining factor, as it is more than counterbalanced by the more 

 important factor of the position of the cathode relatively to the glass 

 walls of the tube. We have a gradual decrease in the length of the 

 alternative spark as the cathode is moved a little towards the anti- 

 cathode, then a further much more rapid decrease as the cathode 

 emerges from the annex, and a still further slight decrease as it is 

 moved away from the glass walls out into the bulb. 



Now as to the effect upon the Eontgen rays, as it has been before 

 remarked, the greater the resistance of the tube and the greater the 

 E.M.F. ncccss.iry to cause a discharge to pass, the greater is the 



