88 



Mr. A. A. C. Swinton. 



Experiments were next tried with the aluminium obstacle, moved 

 so that its point just entered the converging cone of cathode rays, 

 when a small portion of the ring was cut out, but on the opposite 

 side, as shown in fig. 14, this confirming the previous experi- 

 ments, which showed that the rays cross one another's paths at the 

 focus without rotation. Upon moving the aluminium obstacle a 

 little nearer to the cathode, so that its point entered still further into 

 the convergent cathode beam, one half of the ring disappeared, as in 

 fig. ] 5, while when the obstacle — which, it should be remembered, 

 blocked only one quarter of the circular area of the tube— was 

 brought close up to the cathode, only about one quarter of the ring 

 remained, as in fig. 16. 



Further experiments were tried with the aluminium obstacle both 

 in the divergent and convergent cones, but with the tube exhausted 

 to different degrees of vacuum, the result being as shown in 

 figs. 17 and 18, in which in each case B shows the highest vacuum 

 and B" the lowest, from which it will be observed that when the 

 obstacle was in the divergent cone, a portion of the ring was cut off 

 exactly proportional to the angle subtended by the sides of the 

 obstacle ; while when the obstacle was placed in the convergent 



