﻿690 
  Prof. 
  J. 
  J. 
  Thomson 
  on 
  

  

  the 
  side 
  tube 
  at 
  some 
  distance 
  from 
  the 
  gauze 
  ; 
  the 
  ionization 
  

   in 
  the 
  side 
  tube 
  produced 
  a 
  leak 
  of 
  the 
  electroscope. 
  It 
  was 
  

   found 
  that 
  even 
  when 
  the 
  primary 
  cathode 
  particles 
  were 
  

   coiled 
  up 
  by 
  the 
  strong 
  magnetic 
  field 
  into 
  a 
  small 
  bundle 
  at 
  

   the 
  mouth 
  of 
  the 
  tube 
  from 
  which 
  they 
  emerge, 
  there 
  was 
  a 
  

   rapid 
  leak 
  of 
  the 
  electroscope 
  showing 
  that 
  the 
  gas 
  in 
  the 
  

   side 
  tube 
  was 
  ionized. 
  The 
  leak 
  was 
  more 
  rapid 
  when 
  the 
  

   electroscope 
  was 
  positively 
  than 
  when 
  it 
  was 
  negatively 
  

   charged. 
  

  

  A 
  somewhat 
  similar 
  experiment 
  was 
  also 
  tried 
  with 
  the 
  

   apparatus 
  represented 
  in 
  fig. 
  6. 
  A 
  magnetic 
  field 
  of 
  1200 
  

   was 
  established 
  between 
  the 
  pole-pieces, 
  and 
  the 
  plates 
  

   L, 
  M, 
  N 
  connected 
  with 
  the 
  earth, 
  so 
  that 
  there 
  was 
  no 
  

   electric 
  field 
  in 
  the 
  ionizing 
  vessel. 
  Under 
  these 
  circum- 
  

   stances 
  neither 
  the 
  cylinder 
  nor 
  the 
  disk 
  received 
  any 
  

   electric 
  charge 
  when 
  the 
  electric 
  discharge 
  passed 
  through 
  

   the 
  upper 
  tube. 
  The 
  Faraday 
  cylinder 
  was 
  then 
  disconnected 
  

   from 
  the 
  electroscope 
  and 
  charged 
  up 
  positively 
  to 
  about 
  

   40 
  volts 
  ; 
  the 
  disk 
  now 
  acquired 
  a 
  positive 
  charge, 
  when 
  the 
  

   cylinder 
  was 
  charged 
  to 
  —40 
  volts 
  the 
  disk 
  got 
  a 
  negative 
  

   charge. 
  This 
  shows 
  that 
  the 
  gas 
  between 
  the 
  cylinder 
  and 
  

   disk 
  was 
  ionized, 
  though 
  the 
  magnetic 
  field 
  prevented 
  any 
  

   negative 
  corpuscles 
  from 
  entering 
  this 
  region. 
  

  

  Though 
  we 
  have 
  given 
  reasons 
  for 
  thinking 
  that 
  the 
  

   Rontgen 
  rays 
  are 
  not 
  the 
  cause 
  of 
  the 
  ionization 
  in 
  the 
  side 
  

   tube 
  when 
  this 
  is 
  exposed 
  to 
  strong 
  magnetic 
  fields, 
  soft 
  

   Rontgen 
  rays 
  are 
  produced 
  by 
  the 
  impact 
  of 
  the 
  primary 
  

   cathode 
  rays 
  against 
  the 
  molecules 
  of 
  the 
  gas 
  in 
  the 
  tube. 
  

   This 
  was 
  proved 
  by 
  covering 
  the 
  end 
  of 
  the 
  side 
  tube 
  (fig. 
  8) 
  

   with 
  thin 
  aluminium 
  foil 
  and 
  placing 
  in 
  the 
  side 
  tube 
  behind 
  

   the 
  foil 
  an 
  insulated 
  metal 
  plate 
  connected 
  with 
  a 
  charged 
  

   electroscope. 
  The 
  escape 
  of 
  electricity 
  from 
  this 
  plate 
  could 
  

   not 
  be 
  ascribed 
  to 
  ionized 
  gas 
  making 
  its 
  way 
  from 
  the 
  main 
  

   tube 
  into 
  the 
  side 
  one, 
  for 
  the 
  only 
  channel 
  of 
  communication 
  

   w 
  T 
  as 
  through 
  a 
  long 
  stretch 
  of 
  glass 
  tubing 
  from 
  the 
  main 
  tube 
  

   to 
  the 
  pump, 
  and 
  then 
  through 
  another 
  long 
  tube 
  from 
  the 
  

   pump 
  to 
  the 
  side 
  tube; 
  since 
  the 
  opening 
  between 
  the 
  main 
  tube 
  

   and 
  the 
  side 
  tube 
  was 
  closed, 
  it 
  was 
  necessary 
  to 
  exhaust 
  

   them 
  separately. 
  When 
  the 
  primary 
  and 
  secondary 
  cathode 
  

   rays 
  were 
  well 
  developed 
  and 
  the 
  main 
  tube 
  filled 
  with 
  a 
  

   bright 
  glow, 
  the 
  charge 
  from 
  the 
  electroscope 
  rapidly 
  leaked 
  

   away 
  whether 
  it 
  were 
  positive 
  or 
  negative. 
  The 
  gas 
  in 
  the 
  

   side 
  tube 
  is 
  thus 
  ionized 
  by 
  rays 
  which 
  have 
  passed 
  through 
  

   the 
  thin 
  aluminium 
  foil. 
  The 
  leak 
  was, 
  however, 
  completely 
  

   stopped 
  when, 
  by 
  means 
  of 
  a 
  strong 
  magnetic 
  field, 
  the 
  

  

  