﻿700 
  

  

  Prof. 
  J. 
  Trowbridge 
  on 
  

  

  Fig-. 
  4. 
  

  

  group 
  of 
  positive 
  rays, 
  I 
  resolved 
  to 
  damp 
  all 
  oscillations 
  

   by 
  introducing 
  a 
  large 
  water 
  resistance 
  in 
  the 
  oscillating 
  

   circuit. 
  While 
  the 
  dimensions 
  of 
  the 
  

   discharge-tube 
  between 
  the 
  anode 
  and 
  

   the 
  cathode 
  remained 
  the 
  same 
  as 
  in 
  

   the 
  experiments 
  described 
  above, 
  the 
  

   canal 
  region 
  was 
  changed 
  from 
  a 
  cir- 
  

   cular 
  tube 
  of 
  3 
  cm. 
  diameter 
  to 
  the 
  

   form 
  shown 
  in 
  fig. 
  4 
  in 
  plan 
  P 
  and 
  

   end 
  section 
  E. 
  The 
  width 
  of 
  the 
  cross 
  

   section 
  was 
  3*5 
  cm. 
  It 
  will 
  be 
  noticed 
  

   that 
  it 
  had 
  a 
  flattened 
  egg-shaped 
  sec- 
  

   tion 
  to 
  enable 
  me 
  to 
  place 
  it 
  between 
  

   the 
  poles 
  of 
  an 
  electromagnet. 
  When 
  

   all 
  oscillations 
  were 
  damped 
  and 
  a 
  

   magnetic 
  field 
  of 
  500 
  lines 
  to 
  the 
  centi- 
  

   metre 
  was 
  excited, 
  the 
  positive 
  rays 
  

   produced 
  a 
  narrow 
  sharply 
  defined 
  band 
  

   of 
  fluorescence 
  which 
  is 
  represented 
  /^ 
  A 
  

  

  in 
  the 
  photograph 
  fig. 
  5. 
  The 
  middle 
  ( 
  E 
  J 
  

  

  of 
  the 
  end 
  of 
  the 
  tube 
  is 
  indicated 
  by 
  V 
  _^y 
  

  

  the 
  sharp 
  pointers 
  on 
  the 
  photograph 
  ; 
  

  

  and 
  it 
  will 
  be 
  seen 
  that 
  the 
  phosphorescent 
  band 
  extends 
  to 
  

  

  approximately 
  equal 
  distances 
  on 
  both 
  sides 
  of 
  the 
  middle 
  of 
  

  

  Fiar. 
  5. 
  

  

  the 
  screen. 
  At 
  first 
  I 
  thought 
  that 
  I 
  was 
  dealing 
  with 
  a 
  

   mixture 
  of 
  positive 
  and 
  negative 
  rays, 
  and 
  various 
  theories 
  

  

  