54 



DETERMINATION OF SPEED 



[CH. V. 



Direct Determination of the Speed of Cathode 



Rays. 



Figs. 6 and 7 illustrate sufficiently the ingenious 

 device applied by Wiechert, in accordance with a 

 method of Des Coudres, for directly measuring the 

 velocity of cathode rays during the time of their 



J3/ 



FIG. 6. Connexions of the circuits in Wiechert's experiment for 

 measuring directly the speed of cathode rays as they travel down a tube. 



transit down the axis of an exhausted glass tube of 

 moderate length. 



Keferring to either of the figures, the tube has a 

 curved cathode C at one end, whereby the rays are 

 focussed through an aperture in a screen B ; they 

 then travel down the tube to another perforated 

 screen B', whence the central portion of them reaches 

 a phosphorescent screen at S. 



The tube is excited by a kind of Tesla induction 



