﻿654 
  Dr. 
  F. 
  C. 
  Brown 
  on 
  the 
  Kinetic 
  Energy 
  of 
  the 
  

  

  was 
  varied 
  by 
  inserting 
  in 
  parallel 
  a 
  standard 
  condenser. 
  

   This 
  was 
  carried 
  out 
  by 
  a 
  key 
  manipulated 
  from 
  outside 
  the 
  

   air-tight 
  box. 
  

  

  Fig. 
  2. 
  

  

  __VWVWAVWVV 
  

  

  The 
  thermionic 
  radiator 
  was 
  heated, 
  indirectly 
  most 
  often, 
  

   by 
  an 
  electric 
  current. 
  The 
  heater 
  was 
  merely 
  a 
  single 
  loop 
  

   of 
  platinum 
  wire 
  or 
  a 
  loop 
  of 
  metal 
  foil, 
  a 
  rough 
  cross- 
  

   sectional 
  view 
  of 
  which 
  is 
  shown 
  in 
  the 
  diagrams. 
  The 
  loop 
  

   supported 
  the 
  radiator 
  and 
  the 
  heat 
  produced 
  by 
  the 
  electric 
  

   current 
  flowed 
  into 
  the 
  radiator 
  by 
  conduction. 
  This 
  device 
  

   enabled 
  the 
  emitting 
  surface 
  to 
  be 
  kept 
  at 
  the 
  same 
  potential. 
  

   It 
  was 
  quite 
  essential 
  that 
  this 
  potential 
  should 
  be 
  zero. 
  

   This 
  was 
  accomplished 
  by 
  shunting 
  the 
  heater 
  with 
  the 
  

   resistance 
  A, 
  of 
  about 
  20 
  ohms. 
  The 
  shunt 
  resistance 
  was 
  

   earthed 
  at 
  such 
  a 
  point 
  that 
  the 
  magnitude 
  of 
  the 
  thermionic 
  

  

  