﻿Radiation- 
  P 
  lie 
  no 
  mcna 
  in 
  the 
  Magnetic 
  Field. 
  199 
  

  

  The 
  lines 
  on 
  the 
  plates 
  were 
  identified 
  by 
  comparison 
  with 
  

   the 
  solar 
  spectrum. 
  The 
  negatives 
  were 
  measured 
  on 
  an 
  

   ordinary 
  dividing-engine, 
  with 
  a 
  microscope 
  reading 
  directly 
  

   to 
  yJo 
  of 
  a 
  millimetre, 
  or 
  by 
  estimating 
  the 
  tenths 
  of 
  divisions 
  

   on 
  the 
  head 
  to 
  i^oo 
  °f 
  a 
  millimetre. 
  The 
  accuracy 
  of 
  the 
  

   measurement 
  of 
  the 
  interval 
  between 
  the 
  components 
  of 
  

   course 
  largely 
  varies 
  with 
  the 
  metal 
  used 
  as 
  electrode. 
  In 
  a 
  

   spectrum 
  with 
  sharp 
  lines, 
  for 
  instance 
  that 
  of 
  zinc 
  or 
  cad- 
  

   mium, 
  this 
  interval 
  can 
  be 
  measured 
  with 
  an 
  accuracy 
  

   exceeding 
  that 
  of 
  the 
  magnetic 
  measurements 
  in 
  our 
  case. 
  

   In 
  the 
  case 
  of 
  other 
  substances, 
  for 
  instance 
  copper 
  or 
  tin, 
  the 
  

   lines 
  are 
  so 
  hazy, 
  or 
  of 
  so 
  small 
  intensity, 
  that 
  it 
  is 
  only 
  

   possible 
  to 
  make 
  an 
  estimation. 
  

  

  As 
  an 
  example 
  of 
  the 
  accuracy 
  obtained 
  when 
  magnetic 
  

   triplets 
  resulting 
  from 
  bright 
  sharp 
  lines 
  are 
  measured 
  by 
  

   means 
  of 
  the 
  microscope 
  of 
  the 
  dividing-engine, 
  I 
  will 
  give 
  

   some 
  measurements 
  concerning 
  the 
  line 
  4722 
  of 
  the 
  spectrum 
  

   of 
  zinc. 
  The 
  numbers 
  in 
  the 
  following 
  table 
  are 
  the 
  readings 
  

   (1 
  o~d 
  °f 
  a 
  millimetre) 
  on 
  the 
  head 
  of 
  a 
  micrometer-screw 
  when 
  

   the 
  first 
  and 
  the 
  second 
  component 
  respectively 
  was 
  under 
  the 
  

   wire. 
  

  

  Determination 
  of 
  Distance 
  between 
  the 
  Outer 
  Components 
  of 
  

   the 
  Triplet. 
  (Zinc, 
  A 
  = 
  4722.) 
  

   Component 
  I. 
  Component 
  II. 
  

  

  28-8 
  49-8 
  

  

  28-8 
  48-7 
  

  

  28-9 
  49-9 
  

  

  282 
  49-5 
  

  

  28-8 
  48-7 
  

  

  28-2 
  48-9 
  

  

  Mean 
  28'6 
  49"3 
  

  

  Difference 
  =20'7x 
  x 
  -Jo 
  millim. 
  

  

  The 
  negative 
  was 
  taken 
  in 
  the 
  second 
  spectrum, 
  On 
  the 
  

   negative 
  1 
  millim. 
  corresponded 
  to 
  about 
  4*41 
  Angstrom- 
  

   units. 
  

  

  The 
  following 
  results 
  were 
  obtained 
  concerning 
  lines 
  in 
  the 
  

   blue, 
  violet, 
  and 
  ultra-violet 
  part 
  of 
  the 
  spectrum. 
  

  

  4. 
  Zinc. 
  — 
  The 
  following 
  tables 
  contain 
  under 
  \ 
  the 
  wave- 
  

   lengths 
  of 
  the 
  spectral 
  lines. 
  The 
  meaning 
  of 
  the 
  different 
  

   columns 
  will 
  be 
  clear 
  from 
  the 
  headings. 
  The 
  intensity 
  H 
  of 
  

   the 
  magnetic 
  field 
  was 
  measured 
  by 
  means 
  of 
  a 
  bismuth 
  spiral. 
  

   There 
  is 
  a 
  slight 
  uncertainty 
  in 
  the 
  value 
  of 
  H, 
  the 
  tempe- 
  

   rature-coefficient 
  of 
  the 
  bismuth 
  wire 
  not 
  being 
  accurately 
  

   known. 
  

  

  