﻿Positive 
  Rays. 
  681 
  

  

  give 
  exactly 
  the 
  same 
  value 
  for 
  e/m 
  as 
  when 
  the 
  apparatus 
  

   had 
  been 
  filled 
  with 
  hydrogen, 
  as 
  in 
  the 
  experiments 
  discussed 
  

   on 
  pages 
  678, 
  679. 
  

  

  By 
  measuring 
  the 
  relative 
  numbers 
  o£ 
  ions 
  carried 
  to 
  the 
  

   cylinder 
  and 
  the 
  disk 
  by 
  different 
  voltages 
  against 
  a 
  constant 
  

   magnetic 
  field 
  we 
  can 
  readily 
  estimate 
  the 
  relative 
  amounts 
  

   of 
  heavy 
  and 
  light 
  ions 
  in 
  the 
  gas. 
  Indeed 
  I 
  think 
  that 
  by 
  

   using 
  a 
  very 
  small 
  hole 
  in 
  the 
  plate 
  N 
  a 
  very 
  fair 
  analysis 
  of 
  

   the 
  gas 
  in 
  the 
  ionizing 
  chamber 
  might 
  be 
  made. 
  Thus 
  

   suppose 
  the 
  magnetic 
  field 
  were 
  that 
  due 
  to 
  3 
  amperes 
  

   through 
  the 
  coils 
  of 
  the 
  electromagnet; 
  then 
  with 
  apparatus 
  

   of 
  the 
  dimensions 
  used 
  in 
  one 
  of 
  the 
  experiments 
  the 
  ions 
  

   for 
  which 
  <?/m 
  = 
  10 
  4 
  would 
  not 
  reach 
  the 
  disk 
  until 
  V 
  = 
  900, 
  

   while 
  those 
  for 
  which 
  6/?n 
  — 
  jrlO 
  4 
  would 
  reach 
  it 
  when 
  

   V 
  = 
  450, 
  those 
  for 
  which 
  ^/m 
  = 
  1 
  1 
  gl0 
  4 
  when 
  V=56, 
  those 
  for 
  

   which 
  V=3 
  1 
  2 
  10 
  4 
  when 
  Y 
  = 
  28. 
  Thus 
  for 
  ions 
  of 
  different 
  

   atomic 
  weights 
  the 
  stages 
  are 
  well 
  separated, 
  and 
  the 
  relative 
  

   numbers 
  of 
  the 
  ions 
  of 
  the 
  different 
  kinds 
  could 
  be 
  determined. 
  

   With 
  the 
  comparatively 
  large 
  hole 
  used 
  in 
  the 
  experiments 
  

   described 
  above 
  it 
  was 
  quite 
  easy 
  to 
  observe 
  the 
  gradual 
  

   diminution 
  in 
  the 
  number 
  of 
  the 
  lighter 
  ions, 
  as 
  each 
  dose 
  of 
  

   oxygen 
  was 
  supplied 
  to 
  the 
  tube 
  and 
  then 
  pumped 
  out. 
  This 
  

   method 
  of 
  analysis 
  is 
  applicable 
  at 
  pressures 
  far 
  below 
  those 
  

   at 
  which 
  even 
  spectrum 
  analysis 
  is 
  available. 
  

  

  By 
  reversing 
  the 
  potentials 
  in 
  the 
  ionization 
  chamber 
  we 
  

   can 
  collect 
  and 
  send 
  through 
  the 
  opening 
  in 
  the 
  plate 
  nega- 
  

   tive 
  ions 
  and 
  corpuscles 
  which 
  are 
  present 
  in 
  large 
  numbers 
  

   in 
  the 
  gas. 
  The 
  corpuscles, 
  on 
  account 
  of 
  their 
  small 
  mass, 
  

   are 
  prevented 
  from 
  reaching 
  either 
  the 
  Faraday 
  cylinder 
  or 
  

   the 
  disk 
  by 
  a 
  comparatively 
  small 
  magnetic 
  force, 
  and 
  then 
  

   only 
  negative 
  ions 
  get 
  through 
  to 
  the 
  conductor. 
  The 
  pro- 
  

   portion 
  of 
  these 
  reaching 
  the 
  disk 
  and 
  cylinder 
  with 
  changes 
  

   in 
  the 
  electric 
  and 
  magnetic 
  fields 
  show 
  variations 
  of 
  a 
  similar 
  

   character 
  to 
  those 
  observed 
  for 
  the 
  positive 
  ions. 
  

  

  The 
  relative 
  rates 
  at 
  which 
  the 
  cylinder 
  or 
  disk 
  charged 
  up 
  

   according 
  as 
  positive 
  or 
  negative 
  ions 
  were 
  supplied 
  to 
  them 
  

   from 
  the 
  ionization 
  chamber 
  was 
  determined. 
  When 
  the 
  

   magnetic 
  field 
  was 
  weak 
  the 
  rate 
  of 
  charging 
  was 
  much 
  

   more 
  rapid 
  with 
  negative 
  than 
  with 
  positive 
  ions 
  ; 
  this 
  was 
  

   due 
  to 
  the 
  excess 
  of 
  corpuscles 
  in 
  the 
  ionization 
  chamber; 
  

   when, 
  however, 
  the 
  magnetic 
  field 
  was 
  strong 
  enough 
  to 
  stop 
  

   the 
  corpuscles, 
  the 
  rate 
  of 
  charging 
  under 
  potential-differences 
  

   of 
  the 
  order 
  of 
  about 
  200 
  volts 
  was 
  about 
  the 
  same 
  for 
  the 
  

   negative 
  as 
  for 
  the 
  positive 
  ions, 
  while 
  with 
  smaller 
  differences 
  

   of 
  potential, 
  say 
  25 
  volts, 
  the 
  rate 
  of 
  charging 
  with 
  negative 
  

   ions 
  was 
  only 
  about 
  1/6 
  of 
  that 
  with 
  positive. 
  The 
  positive 
  

  

  