﻿168 
  Dr. 
  J. 
  Kunz 
  on 
  Cathode 
  and 
  

  

  In 
  the 
  last 
  two 
  cases 
  the 
  glass 
  tube 
  glows 
  at 
  low 
  pressure 
  

   with 
  an 
  intense 
  orange 
  light, 
  which 
  might 
  be 
  brought 
  about 
  

   by 
  the 
  impact 
  of 
  positive 
  particles. 
  After 
  the 
  experiment 
  

   a 
  brown 
  deposit 
  was 
  found 
  on 
  the 
  inner 
  surface 
  of 
  this 
  glass 
  

   tube. 
  This 
  experiment 
  tells 
  us 
  again 
  that 
  the 
  rays 
  producing 
  

   the 
  ring 
  a 
  of 
  fig. 
  4 
  start 
  from 
  the 
  inner 
  edge 
  of 
  the 
  cathodic 
  

   cylinder, 
  the 
  ring 
  b 
  from 
  a 
  part 
  nearer 
  to 
  the 
  centre, 
  and 
  the 
  

   central 
  spot 
  /from 
  the 
  middle 
  of 
  the 
  hollow 
  cathode. 
  

  

  The 
  blue 
  cathode 
  rays 
  propagating 
  in 
  the 
  direction 
  of 
  the 
  

   axis 
  arise 
  from 
  the 
  edges 
  of 
  the 
  cathode, 
  as 
  will 
  be 
  seen 
  

   directly 
  from 
  fig. 
  3. 
  

  

  The 
  phenomena 
  observed 
  on 
  each 
  side 
  of 
  the 
  cathodic 
  

   cylinder 
  seem 
  to 
  be 
  independent 
  of 
  one 
  another. 
  If, 
  for 
  

   instance, 
  a 
  short 
  glass 
  tube 
  is 
  introduced 
  covering 
  the 
  inner 
  

   end 
  of 
  the 
  metallic 
  tube, 
  or 
  if 
  this 
  end 
  is 
  closed 
  by 
  a 
  short 
  

   metal 
  bar, 
  the 
  phenomena 
  observed 
  on 
  the 
  other 
  side 
  of 
  the 
  

   tube 
  coincide 
  with 
  those 
  observed 
  in 
  experiment 
  1. 
  

  

  If 
  at 
  one 
  end 
  of 
  the 
  cathode 
  a 
  metal 
  wire 
  or 
  a 
  small 
  piece 
  

   of 
  ebonite 
  is 
  pushed 
  over 
  the 
  inner 
  and 
  outer 
  edge 
  of 
  the 
  tube, 
  

   the 
  disturbance 
  of 
  the 
  picture 
  produced 
  by 
  the 
  cathode 
  rays 
  

   will 
  be 
  found 
  to 
  be 
  at 
  a 
  place 
  opposite 
  to 
  the 
  obstacle 
  in 
  the 
  

   tube, 
  showing 
  that 
  the 
  rays 
  giving 
  rise 
  to 
  the 
  ring 
  a 
  of 
  fig. 
  4 
  

   cross 
  one 
  another. 
  With 
  decreasing 
  pressure, 
  the 
  rings 
  of 
  

   phosphorescence 
  illustrated 
  in 
  fig. 
  4 
  appear 
  in 
  the 
  order 
  

   a, 
  b, 
  e, 
  f. 
  It 
  is 
  also 
  worth 
  mentioning 
  tbat 
  the 
  diameters 
  of 
  

   the 
  rings 
  depend 
  on 
  the 
  pressure. 
  With 
  decreasing 
  pressure 
  

   the 
  diameters 
  of 
  the 
  rings 
  become 
  smaller. 
  A 
  reduction 
  of 
  

   5*4 
  cm. 
  to 
  5'0 
  cm. 
  was 
  observed 
  in 
  the 
  diameter 
  of 
  the 
  ring 
  a, 
  

   and 
  of 
  3'8 
  cm. 
  to 
  2'9 
  cm. 
  in 
  ring 
  b. 
  

  

  We 
  shall 
  now 
  proceed 
  to 
  explain 
  the 
  appearance 
  of 
  the 
  

   rings 
  quite 
  distinctly 
  separated 
  from 
  one 
  another, 
  as 
  indicated 
  

   in 
  fig. 
  4. 
  The 
  cathode 
  rays 
  are 
  deflected 
  in 
  an 
  electric 
  field, 
  

   which 
  is 
  very 
  intense 
  in 
  the 
  Crookes's 
  dark 
  space. 
  When 
  the 
  

   pressure 
  is 
  not 
  very 
  low, 
  the 
  field 
  close 
  to 
  the 
  cathode 
  is 
  

   more 
  intense 
  than 
  that 
  at 
  some 
  distance 
  away 
  from 
  it. 
  The 
  

   corpuscles 
  being 
  still 
  close 
  to 
  the 
  cathode, 
  will 
  acquire 
  so 
  

   much 
  kinetic 
  energy 
  that 
  they 
  will 
  not 
  be 
  much 
  deflected 
  

   from 
  the 
  path 
  along 
  the 
  normals 
  of 
  the 
  surface 
  ; 
  they 
  will, 
  

   however, 
  soon 
  be 
  absorbed 
  and 
  ionize 
  the 
  air 
  in 
  the 
  opening 
  

   of 
  the 
  tube 
  of 
  the 
  cathode 
  to 
  a 
  very 
  great 
  extent. 
  This 
  

   ionization 
  is 
  accompanied 
  by 
  a 
  very 
  bright 
  luminosity 
  of 
  the 
  

   gas 
  column 
  inside 
  the 
  tube. 
  The 
  component 
  of 
  the 
  electric 
  

   force 
  acting 
  parallel 
  to 
  the 
  axis 
  of 
  the 
  tube, 
  will 
  move 
  the 
  

   ions 
  parallel 
  to 
  this 
  axis. 
  Tim- 
  the 
  rays 
  shown 
  in 
  fig. 
  2 
  may 
  

   be 
  produced. 
  If 
  now 
  the 
  pressure 
  1 
  decreases, 
  the 
  dark 
  space 
  

   gets 
  bigger 
  and 
  tills 
  the 
  whole 
  metallic 
  tube. 
  The 
  ionization 
  

  

  