﻿Striations 
  in 
  the 
  Electric 
  Discharge. 
  449 
  

  

  x. 
  

  

  

  

  X. 
  

  

  — 
  

  

  

  

  - 
  9 
  

  

  -f 
  '0 
  

  

  

  

  + 
  (37 
  

  

  -f 
  1-5 
  

  

  

  

  -f33 
  

  

  -3-5 
  

  

  

  

  -{-30 
  

  

  -1- 
  / 
  

  

  

  

  + 
  10 
  

  

  -f-l) 
  

  

  

  

  -10 
  

  

  The 
  last 
  reading 
  was 
  

  

  at 
  

  

  a 
  point 
  just 
  

  

  in 
  front 
  o£ 
  a 
  second 
  

  

  stria 
  tion. 
  

  

  

  

  

  The 
  distance 
  between 
  

  

  the 
  

  

  bri 
  oh 
  t 
  heads 
  

  

  of 
  successive 
  striations 
  

  

  was 
  9 
  mm. 
  and 
  the 
  thickness 
  of 
  the 
  dark 
  space 
  2 
  mm. 
  

  

  From 
  the 
  preceding 
  table 
  we 
  see 
  that 
  in 
  the 
  space 
  of 
  1 
  mm. 
  

   at 
  the 
  head 
  of 
  a 
  striation 
  we 
  have 
  a 
  change 
  in 
  the 
  electric 
  

   force 
  of 
  76 
  volts 
  per 
  cm. 
  By 
  means 
  of 
  the 
  equation 
  

  

  -^ 
  =4:7rp 
  

  

  we 
  see 
  that 
  the 
  density 
  of 
  the 
  negative 
  electricity 
  at 
  the 
  head 
  

   of 
  the 
  striation 
  is 
  about 
  i 
  of 
  an 
  electrostatic 
  unit 
  per 
  c.c. 
  

   The 
  density 
  of 
  the 
  positive 
  electricity 
  in 
  the 
  other 
  portions 
  

   is 
  very 
  much 
  less 
  than 
  this. 
  With 
  Wehnelt 
  electrodes 
  there 
  

   is 
  frequently 
  only 
  a 
  small 
  potential-difference 
  between 
  cor- 
  

   responding 
  points 
  in 
  adjacent 
  striations: 
  in 
  some 
  cases 
  this 
  

   difference 
  was 
  only 
  2*7 
  volts. 
  

  

  The 
  changes 
  in 
  the 
  electric 
  force 
  are 
  much 
  more 
  abrupt 
  

   at 
  low 
  pressures 
  than 
  at 
  high 
  ones; 
  though 
  there 
  is 
  always 
  a 
  

   large 
  increase 
  in 
  the 
  force 
  at 
  the 
  bright 
  head 
  of 
  the 
  striation. 
  

   I 
  have 
  not 
  observed 
  the 
  existence 
  of 
  the 
  negative 
  forces 
  when 
  

   the 
  pressure 
  was 
  more 
  than 
  a 
  fraction 
  of 
  a 
  millimetre 
  of 
  

   mercury. 
  

  

  I 
  have 
  found 
  other 
  cases 
  in 
  which 
  the 
  negative 
  forces 
  are 
  

   even 
  more 
  pronounced 
  than 
  those 
  I 
  have 
  already 
  considered 
  ; 
  

   perhaps 
  the 
  most 
  striking 
  of 
  these 
  is 
  one 
  w^here 
  the 
  anode 
  

   and 
  cathode 
  are 
  connected 
  together 
  and 
  with 
  earth 
  by 
  

   stout 
  metallic 
  connexions, 
  so 
  that 
  the 
  two 
  are 
  at 
  the 
  same 
  

   potential, 
  and 
  therefore 
  the 
  average 
  negative 
  force 
  between 
  

   them 
  is 
  as 
  great 
  as 
  the 
  average 
  positive 
  force. 
  The 
  anode 
  is 
  

   perforated 
  by 
  a 
  very 
  fine 
  hole, 
  and 
  through 
  this 
  hole 
  a 
  stream 
  

   of 
  Canal 
  rays, 
  i. 
  e. 
  positively 
  electrified 
  particles, 
  passes 
  into 
  

   the 
  tube 
  : 
  this 
  produces 
  when 
  the 
  pressure 
  is 
  suitable 
  a 
  fully 
  

   developed 
  discharge, 
  with 
  striations, 
  Faraday 
  dark 
  space, 
  a 
  

   well-developed 
  negative 
  glow 
  and 
  dark 
  space; 
  and 
  in 
  spite 
  of 
  

   the 
  anode 
  and 
  cathode 
  being 
  at 
  the 
  same 
  potential 
  there 
  is 
  in 
  

   this 
  case 
  the 
  normal 
  cathode 
  fall 
  of 
  about 
  300 
  volts 
  at 
  the 
  

   cathode 
  : 
  the 
  negative 
  forces 
  in 
  a 
  tube 
  of 
  this 
  kind 
  must 
  be 
  

   very 
  consideraljle, 
  as 
  they 
  have 
  to 
  balance 
  the 
  cathode 
  fall. 
  

  

  