﻿Canal 
  Rays 
  from 
  Hollow 
  Cathodes* 
  165 
  

  

  to 
  the 
  axis 
  of 
  the 
  tube. 
  The 
  inner 
  edge 
  of 
  both 
  ends 
  of 
  j 
  the 
  

   cathodic 
  cylinder 
  glows 
  also 
  with 
  a 
  dim 
  red 
  light.^ 
  

  

  The 
  question 
  now 
  arises 
  as 
  to 
  what 
  is 
  the 
  origin"of 
  the 
  

   blue 
  polar 
  beam, 
  

   existence. 
  

  

  and 
  how 
  the 
  various 
  rings 
  are 
  brought 
  into 
  

  

  Experiment 
  2. 
  — 
  If 
  the 
  outside 
  of 
  the 
  cylindrical 
  tube 
  and 
  

   the 
  edge 
  at 
  either 
  end 
  are 
  covered 
  with 
  ebonite, 
  so 
  that 
  only 
  

   the 
  inner 
  metal 
  surface 
  is 
  free, 
  the 
  same 
  succession 
  of 
  

   phenomena 
  occurs 
  as 
  in 
  experiment 
  1, 
  except 
  that 
  the 
  two 
  

   faint 
  rings 
  c 
  and 
  d 
  and 
  the 
  three 
  layers 
  round 
  the 
  outer 
  

   surface 
  do 
  not 
  appear. 
  Neither 
  are 
  they 
  to 
  be 
  found 
  when 
  

   only 
  the 
  outer 
  edge 
  of 
  both 
  ends 
  is 
  covered 
  with 
  a 
  ring 
  

   of 
  ebonite. 
  These 
  rings 
  e 
  and 
  d 
  take 
  their 
  origin, 
  therefore, 
  

   at 
  the 
  end 
  of 
  the 
  tube 
  on 
  the 
  outer 
  surface 
  of 
  the 
  cylinder. 
  

   They 
  might 
  be 
  considered 
  as 
  belonging 
  to 
  the 
  meridian 
  band 
  

   of 
  phosphorescence, 
  with 
  which 
  they 
  have 
  the 
  same 
  con- 
  

   nexion 
  as 
  have 
  the 
  two 
  rings 
  a 
  and 
  b 
  with 
  the 
  central 
  spot 
  in 
  

   fig. 
  4. 
  If 
  the 
  whole 
  tube 
  is 
  insulated 
  except 
  for 
  the 
  inner 
  

   surface, 
  the 
  blue 
  polar 
  rays 
  are 
  very 
  bright, 
  spreading 
  out 
  

   wider 
  than 
  in 
  the 
  first 
  experiment 
  and 
  producing 
  rings 
  of 
  

   variable 
  diameter. 
  In 
  this 
  case, 
  at 
  a 
  certain 
  not-too-low 
  

   pressure, 
  beautiful 
  striations 
  of 
  red 
  positive 
  light 
  were 
  found 
  

   to 
  reach 
  the 
  region 
  of 
  the 
  blue 
  cathode 
  light, 
  as 
  a 
  rule 
  only 
  

   in 
  the 
  beginning 
  of 
  a 
  new 
  discharge 
  and 
  going 
  back 
  to 
  the 
  

   anode 
  without 
  change 
  of 
  pressure. 
  This 
  aspect 
  is 
  given 
  in 
  

   fig. 
  5. 
  

  

  Fig. 
  5. 
  

  

  Experiment 
  3. 
  — 
  A 
  glass 
  tube 
  is 
  introduced 
  into 
  the 
  cathodic 
  

   tube 
  so 
  that 
  the 
  inner 
  coating 
  of 
  the 
  cylinder 
  is 
  perfectly 
  

  

  