﻿Positive 
  Rays. 
  689 
  

  

  while 
  the 
  effect 
  is 
  what 
  we 
  should 
  expect 
  if 
  the 
  ionization 
  

   were 
  due 
  to 
  uncharged 
  systems. 
  

  

  In 
  the 
  preceding 
  experiments 
  there 
  is 
  the 
  possibility 
  that 
  

   the 
  ionization 
  might 
  arise 
  in 
  some 
  such 
  way 
  as 
  the 
  following. 
  

   The 
  secondary 
  cathode 
  rays 
  would 
  have 
  to 
  penetrate 
  some 
  

   way 
  between 
  the 
  two 
  pieces 
  of 
  gauze 
  before 
  they 
  were 
  

   stopped, 
  and 
  if 
  they 
  collided 
  against 
  the 
  molecules 
  of 
  the 
  gas 
  

   they 
  might 
  ionize 
  it 
  : 
  the 
  positive 
  ions 
  so 
  produced 
  would, 
  

   under 
  the 
  action 
  of 
  the 
  electric 
  field 
  between 
  the 
  pieces 
  of 
  

   gauze, 
  acquire 
  considerable 
  kinetic 
  energy 
  when 
  they 
  reached 
  

   the 
  lower 
  gauze, 
  they 
  would 
  travel 
  some 
  distance 
  after 
  

   passing 
  through 
  before 
  they 
  were 
  stopped 
  and 
  brought 
  back 
  

   to 
  the 
  gauze, 
  and 
  would 
  thus 
  have 
  an 
  opportunity 
  of 
  ionizing 
  

   the 
  gas 
  below 
  the 
  gauze 
  by 
  collision. 
  The 
  negative 
  cor- 
  

   puscles 
  produced 
  in 
  this 
  way 
  would 
  be 
  repelled 
  from 
  the 
  

   lower 
  gauze 
  and 
  might 
  acquire 
  sufficient 
  energy 
  to 
  produce 
  

   fresh 
  ions 
  by 
  collisions, 
  and 
  thus 
  give 
  rise 
  to 
  the 
  luminosity 
  

   observed 
  below 
  the 
  gauze. 
  To 
  eliminate 
  this 
  source 
  of 
  

   ionization, 
  a 
  strong 
  magnetic 
  field 
  was 
  used 
  to 
  prevent 
  any 
  

   of 
  the 
  secondary 
  cathode 
  rays 
  from 
  straying 
  into 
  a 
  region 
  

   where 
  they 
  could 
  affect 
  the 
  ionization 
  in 
  the 
  region 
  under 
  

   observation. 
  Two 
  arrangements 
  were 
  used 
  for 
  this 
  purpose. 
  

   In 
  the 
  first, 
  the 
  tube 
  with 
  the 
  hot 
  lime 
  cathode 
  (fig. 
  8) 
  was 
  

   used. 
  The 
  primary 
  cathode 
  rays 
  were 
  coiled 
  up 
  into 
  a 
  small 
  

   bunch 
  by 
  means 
  of 
  a 
  strong 
  electromagnet 
  placed 
  just 
  under 
  

   the 
  tube, 
  from 
  which 
  the 
  cathode 
  rays 
  emerge, 
  the 
  cathode 
  

   rays 
  in 
  the 
  early 
  part 
  of 
  their 
  path 
  were 
  screened 
  from 
  the 
  

   effect 
  of 
  the 
  magnetic 
  force 
  by 
  thick 
  iron 
  plates. 
  The 
  

   magnetic 
  force 
  was 
  strong 
  enough 
  to 
  prevent 
  the 
  primary 
  

   cathode 
  rays, 
  which 
  were 
  produced 
  under 
  a 
  potential 
  

   difference 
  of 
  about 
  250 
  volts, 
  from 
  travelling 
  more 
  than 
  

   2 
  or 
  3 
  millimetres 
  across 
  the 
  lines 
  of 
  force. 
  The 
  path 
  of 
  

   the 
  rays 
  when 
  not 
  under 
  the 
  influence 
  of 
  magnetic 
  force 
  

   never 
  approached 
  within 
  this 
  distance 
  of 
  the 
  two 
  pieces 
  of 
  

   gauze, 
  and 
  the 
  deflexion 
  of 
  these 
  rays 
  by 
  the 
  magnet 
  was 
  

   away 
  from 
  the 
  gauze. 
  No 
  luminosity 
  could 
  be 
  seen 
  close 
  to 
  

   the 
  gauze 
  next 
  to 
  the 
  discharge-tube. 
  Nevertheless, 
  when 
  

   the 
  lower 
  gauze 
  N 
  was 
  at 
  a 
  potential 
  of 
  about 
  200 
  volts, 
  the 
  

   upper 
  gauze 
  being 
  earthed, 
  there 
  was 
  a 
  perceptible 
  luminous 
  

   discharge 
  in 
  the 
  side 
  tube, 
  showing 
  that 
  in 
  spite 
  of 
  the 
  strong 
  

   magnetic 
  field 
  something 
  must 
  have 
  passed 
  across 
  the 
  gauze 
  

   and 
  ionized 
  the 
  gas 
  in 
  the 
  side 
  tube. 
  A 
  modification 
  of 
  this 
  

   experiment 
  was 
  tried, 
  in 
  which 
  the 
  two 
  pieces 
  of 
  gauze 
  were 
  

   connected 
  together 
  and 
  with 
  the 
  earth, 
  and 
  an 
  insulated 
  

   plate 
  connected 
  with 
  a 
  charged 
  electroscope 
  was 
  placed 
  in 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  No. 
  94. 
  Oct. 
  1908. 
  2 
  Z 
  

  

  