﻿166 
  . 
  Dr. 
  J. 
  Kunz 
  on 
  Cathode 
  and 
  

  

  insulated, 
  the 
  outer 
  coating 
  being 
  free. 
  The 
  negative 
  glow 
  

   now 
  never 
  enters 
  the 
  tube, 
  no 
  blue 
  beams 
  o£ 
  cathode 
  rays 
  

   appear, 
  neither 
  the 
  rings 
  a, 
  b, 
  c 
  of 
  fig. 
  4. 
  At 
  the 
  lowest 
  

   pressure, 
  however, 
  a 
  faint 
  small 
  spot 
  of 
  phosphorescence 
  

   appears 
  at 
  the 
  poles 
  of 
  the 
  bulb, 
  flitting 
  hither 
  and 
  thither 
  

   in 
  a 
  very 
  unsettled 
  fashion. 
  Small 
  sparks 
  move 
  round 
  about 
  

   the 
  edges 
  of 
  the 
  tube, 
  giving 
  rise 
  to 
  irregiar 
  cathode-rays. 
  

   The 
  rings 
  e 
  and 
  d 
  of 
  fig. 
  4 
  are 
  found 
  to 
  be 
  indistinct. 
  At 
  

   the 
  most 
  complete 
  vacuum, 
  a 
  small 
  amount 
  of 
  yellowish-white 
  

   light 
  is 
  to 
  be 
  seen 
  in 
  the 
  centre 
  of 
  the 
  glass 
  tube 
  of 
  the 
  

   cathode. 
  

  

  If 
  two 
  short 
  glass 
  tubes 
  about 
  4 
  mm. 
  long 
  are 
  introduced 
  

   into 
  the 
  metal 
  tube 
  from 
  both 
  ends, 
  so 
  that 
  only 
  the 
  inner 
  

   edges 
  are 
  covered, 
  the 
  phenomena 
  in 
  the 
  beginning 
  of 
  the 
  

   exhaustion 
  are 
  different 
  from 
  those 
  just 
  described 
  in 
  so 
  far 
  as 
  

   the 
  negative 
  glow 
  enters 
  into 
  the 
  tube 
  from 
  both 
  ends 
  without 
  

   going 
  through 
  the 
  whole 
  tube, 
  and 
  as 
  the 
  blue 
  central 
  cathode 
  

   rays 
  just 
  appear 
  at 
  the 
  ends 
  of 
  the 
  tube 
  producing 
  a 
  spot 
  of 
  

   weak 
  phosphorescence 
  at 
  the 
  poles 
  of 
  the 
  glass 
  bulb. 
  As 
  the 
  

   air 
  is 
  pumped 
  out, 
  this 
  blue 
  light 
  disappears 
  again 
  ; 
  but 
  the 
  

   polar 
  spots 
  in 
  front 
  of 
  the 
  openings 
  of 
  the 
  cylinder 
  are 
  much 
  

   brighter 
  and 
  more 
  fixed 
  than 
  in 
  the 
  previous 
  experiment, 
  

   much 
  as 
  in 
  the 
  first 
  experiment. 
  The 
  inner 
  edges 
  of 
  the 
  

   glass 
  tubes 
  exhibit 
  a 
  red 
  glow, 
  as 
  if 
  due 
  to 
  the 
  impact 
  of 
  

   positive 
  rays. 
  As 
  in 
  the 
  case 
  of 
  small 
  glass 
  tubes 
  put 
  at 
  the 
  

   inner 
  ends 
  of 
  the 
  tube, 
  the 
  blue 
  central 
  beam 
  and 
  the 
  rings 
  

   a 
  and 
  b 
  of 
  fig. 
  4 
  do 
  not 
  appear, 
  we 
  see 
  that 
  these 
  phenomena 
  

   take 
  their 
  origin 
  from 
  the 
  inner 
  edges 
  of 
  the 
  metallic 
  tube. 
  

   The 
  bright 
  central 
  spots 
  f 
  of 
  fig. 
  4 
  are 
  due 
  to 
  rays 
  starting 
  

   from 
  the 
  central 
  parts 
  of 
  the 
  tube. 
  The 
  difference 
  in 
  the 
  

   appearance 
  in 
  the 
  case 
  of 
  one 
  glass 
  tube 
  filling 
  the 
  whole 
  

   metallic 
  cylinder, 
  and 
  of 
  two 
  short 
  glass 
  tubes 
  at 
  the 
  ends 
  of 
  

   the 
  cathode 
  for 
  a 
  certain 
  not 
  too 
  low 
  pressure, 
  is 
  illustrated 
  

   in 
  fig. 
  6. 
  If 
  the 
  pressure 
  becomes 
  lower, 
  the 
  central 
  blue 
  

   light 
  of 
  fig. 
  6 
  b 
  disappears, 
  the 
  polar 
  spots 
  p 
  get 
  fainter, 
  and 
  

   the 
  first, 
  second, 
  and 
  third 
  layers 
  in 
  fig. 
  6/; 
  give 
  the 
  same 
  

   aspect 
  as 
  those 
  in 
  fig. 
  6 
  a. 
  The 
  polar 
  spots 
  of 
  phosphorescence 
  

   p 
  in 
  fig. 
  6 
  b 
  become 
  very 
  bright 
  again 
  with 
  still 
  decreasing 
  

   pressure, 
  while 
  the 
  corresponding 
  spots 
  in 
  the 
  case 
  of 
  the 
  

   long 
  glass 
  tube 
  filling 
  the 
  whole 
  cathode 
  are 
  found 
  to 
  be 
  very 
  

   dim 
  and 
  unsettled. 
  

  

  If 
  a 
  short 
  glass 
  tube 
  is 
  introduced 
  into 
  the 
  cathode 
  so 
  that 
  

   at 
  either 
  end 
  about 
  2 
  nun. 
  of 
  the 
  inner 
  surface 
  of 
  the 
  metal 
  

   cylinder 
  is 
  free, 
  we 
  should 
  expect 
  from 
  the 
  last 
  experiment 
  

  

  tlie 
  same 
  succession 
  of 
  phenomena 
  as 
  those 
  observed 
  in 
  the 
  

  

  firsl 
  experiment, 
  and 
  that 
  is 
  indeed 
  what 
  happens. 
  \\ 
  ith 
  

  

  