﻿Charge 
  of 
  the 
  Ions 
  emitted 
  hy 
  Hot 
  Bodies. 
  

  

  7G1 
  

  

  Both 
  bad 
  therefore 
  been 
  strongly 
  heated 
  at 
  some 
  time 
  during 
  

   their 
  history. 
  

  

  It 
  will 
  be 
  difficult 
  to 
  make 
  experiments 
  on 
  the 
  value 
  of 
  

   e/m 
  for 
  ions 
  produced 
  by 
  different 
  gases, 
  since 
  the 
  low 
  

   pressures 
  which 
  are 
  rendered 
  necessary 
  to 
  eliminate 
  the 
  

   effects 
  of 
  collisions 
  make 
  the 
  proportion 
  of 
  the 
  ionization 
  

   due 
  to 
  the 
  effect 
  of 
  the 
  gas 
  very 
  small. 
  

  

  Method 
  of 
  Checking 
  the 
  Measurements. 
  

  

  It 
  was 
  felt 
  that 
  with 
  previously 
  untried 
  methods 
  like 
  those 
  

   which 
  have 
  been 
  employed 
  it 
  would 
  be 
  a 
  great 
  advantage 
  if 
  

   they 
  could 
  be 
  tested 
  by 
  using 
  ions 
  for 
  which 
  the 
  value 
  of 
  

   e/m 
  is 
  known. 
  This 
  is 
  the 
  case 
  with 
  the 
  negative 
  ions 
  from 
  

   hot 
  substances. 
  These 
  are 
  known 
  to 
  be 
  negative 
  electrons, 
  

   and 
  the 
  value 
  of 
  e/m 
  for 
  them 
  at 
  low 
  speeds 
  has 
  been 
  

   estimated 
  by 
  Kaufmann 
  * 
  to 
  be 
  very 
  near 
  1*88 
  X 
  10 
  7 
  E.M. 
  

   units. 
  The 
  value 
  of 
  e/m 
  for 
  the 
  negative 
  ions 
  from 
  both 
  plati- 
  

   num 
  and 
  carbon 
  was 
  therefore 
  determined 
  with 
  this 
  apparatus, 
  

   by 
  the 
  method 
  of 
  finding 
  the 
  deflexion 
  of 
  the 
  maximum 
  

   point. 
  In 
  order 
  to 
  do 
  this 
  of 
  course 
  much 
  smaller 
  magnetic 
  

   fields 
  had 
  to 
  be 
  employed. 
  This 
  was 
  furnished 
  by 
  a 
  pair 
  of 
  

   coils 
  whose 
  outer 
  diameter 
  was 
  17 
  cms. 
  These 
  were 
  bolted 
  

   together 
  at 
  the 
  distance 
  apart 
  required 
  to 
  give 
  the 
  most 
  

   uniform 
  field 
  and 
  were 
  supported 
  so 
  that 
  this 
  field 
  was 
  

   parallel 
  to 
  the 
  edge 
  of 
  the 
  strip. 
  It 
  was 
  found 
  by 
  calculation 
  

   that 
  1 
  amp. 
  through 
  the 
  coil 
  gave 
  13*5 
  lines 
  per 
  cm. 
  2 
  , 
  and 
  

   this 
  result 
  was 
  confirmed 
  by 
  experiments 
  with 
  the 
  fluxmeter. 
  

  

  The 
  first 
  experiments 
  on 
  the 
  negative 
  ionization 
  were 
  

   made 
  with 
  the 
  carbon 
  filament 
  to 
  test 
  whether 
  the 
  product 
  

  

  Vs^r 
  was 
  constant. 
  The 
  apparatus 
  broke 
  down 
  after 
  two 
  

  

  sets 
  of 
  observations 
  had 
  been 
  made, 
  but 
  these 
  were 
  considered 
  

   satisfactory. 
  The 
  numbers 
  are 
  given 
  in 
  the 
  next 
  table. 
  

  

  (volts.) 
  V 
  N 
  • 
  

  

  H. 
  

  

  (lines 
  per 
  cm. 
  2 
  ) 
  

  

  x. 
  x 
  /w 
  

  

  (1 
  = 
  -0635 
  cm.) 
  H 
  VV 
  ' 
  

  

  129 
  11-30 
  

   366 
  1913 
  

  

  13-5 
  

   243 
  

  

  1-6 
  1-346 
  

  

  1-54 
  1-213 
  

  

  1 
  

  

  It 
  was 
  found 
  to 
  be 
  very 
  difficult 
  to 
  make 
  measurements 
  on 
  

   the 
  negative 
  ionization 
  when 
  potentials 
  greater 
  than 
  about 
  

  

  * 
  Ann. 
  der 
  Phys. 
  (4) 
  vol. 
  xix. 
  p. 
  551 
  (1906). 
  

  

  