Some Experiments with Cathode Bays. 



83 



condition of affairs exists in the converging beam of rays between 

 the cathode and the focns. Owing to the well-known difficulty of 

 getting any discharge to pass when the distance between the elec- 

 trodes is less than the thickness of the dark space, and to the dis- 

 turbing effect which the anti-cathode screen is found to have when 

 brought within the focus of the cathode, especially with high vacua, 

 this question was found much more difficult to decide than that of 

 the hollo wness of the divergent cone. However, that the conver- 

 gent cone also acts under certain circumstances as though it were 

 almost completely hollow, and acts generally as if it had a consider- 

 able tendency towards hollowness at low vacua, was also finally fully 

 determined. The lower portions of figs. 5, 6, and 7 show the bright 



T T J 



+ + 



ring appearance upon the carbon anti-cathode at two different 

 degrees of exhanstion, B being higher vacua than B', and with the 

 anti-cathode at the three different distances from the cathode within 

 the focus of the latter, as shown in the upper part of each figure. 

 As will be observed in this case, the degree of vacuum is found not 

 to appreciably affect the dimensions of the figure, though it should 



VOL. LXI. Q 



