﻿820 
  Mr. 
  H. 
  L. 
  P. 
  Jolly 
  on 
  the 
  

  

  contained 
  in 
  the 
  red 
  line 
  (X 
  6563) 
  as 
  recorded 
  when 
  the 
  

   receiving 
  slit 
  of 
  the 
  thermopile 
  coincided 
  in 
  breadth 
  with 
  the 
  

   sharp 
  outline 
  o£ 
  the 
  said 
  line. 
  Each 
  group 
  o£ 
  three 
  numbers 
  

   consists 
  of 
  a 
  zero 
  observation 
  at 
  the 
  beginning 
  and 
  end, 
  with 
  

   the 
  deflexion 
  observation 
  between. 
  

  

  In 
  Table 
  III. 
  are 
  summarized 
  the 
  results 
  of 
  three 
  such 
  sets 
  

   of 
  observations 
  at 
  different 
  pressures. 
  

  

  Table 
  III. 
  

  

  

  Current 
  B. 
  

  

  Ci 
  

  

  JRRENT 
  C. 
  

  

  1 
  

  

  Pressure. 
  

   1-86 
  cm. 
  

  

  Total 
  

   radiation. 
  

  

  H 
  a 
  . 
  

  

  B 
  Ha 
  

  

  Total 
  

   radiation. 
  

  

  H 
  a 
  . 
  

  

  v 
  -Total 
  

   6*08 
  

  

  i 
  N 
  B 
  ' 
  

  

  3-37 
  

  

  0-53 
  

  

  6-36 
  

  

  456 
  

  

  0-75 
  

  

  0-93 
  

  

  3-60 
  „ 
  

  

  232 
  

  

  036 
  

  

  645 
  

  

  302 
  

  

  0-52 
  

  

  5-81 
  

  

  1 
  090 
  

  

  5-03 
  „ 
  

  

  3-73 
  

  

  0-55 
  

  

  6'80 
  

  

  5-67 
  

  

  0-97 
  

  

  5*85 
  

  

  0-86 
  

  

  In 
  considering 
  this 
  table 
  the 
  only 
  vertical 
  columns 
  which 
  

   should 
  be 
  compared 
  are 
  that 
  containing 
  pressure 
  and 
  that 
  

  

  . 
  JST 
  C 
  

   containing 
  the 
  quantity^—, 
  for 
  the 
  other 
  vertical 
  columns 
  

  

  are 
  not 
  u 
  comparable/' 
  [For 
  a 
  rigorous 
  definition 
  of 
  ' 
  c 
  com- 
  

   parable 
  "" 
  spectra 
  see 
  Vegard, 
  Ann. 
  der 
  Phys. 
  vol. 
  xxxix. 
  

   p.lU(l»l2).] 
  _ 
  Nc 
  

  

  The 
  fact 
  that 
  the 
  quantity 
  ^ 
  

  

  is 
  in 
  all 
  cases 
  less 
  than 
  

  

  unity 
  indicates 
  a 
  shift 
  of 
  energy 
  of 
  such 
  a 
  kind 
  as 
  to 
  make 
  

   H 
  a 
  relatively 
  stronger 
  at 
  higher 
  current-density, 
  and 
  the 
  

  

  N 
  c 
  

   greater 
  and 
  greater 
  divergence 
  of 
  -^ 
  from 
  unity 
  as 
  the 
  

  

  pressure 
  rises 
  confirms 
  the 
  conclusion. 
  

  

  The 
  quantities 
  Nc 
  and 
  N 
  B 
  given 
  in 
  the 
  4th 
  and 
  7th 
  

  

  columns 
  have 
  no 
  value 
  when 
  considered 
  alone. 
  That 
  is 
  to 
  

  

  say, 
  the 
  2nd 
  and 
  3rd 
  columns 
  are 
  not 
  comparable. 
  This 
  

  

  results 
  naturally 
  from 
  the 
  interposition 
  of 
  a 
  prism 
  in 
  order 
  

  

  to 
  obtain 
  the 
  radiation 
  from 
  H 
  a 
  , 
  which 
  operation 
  introduces 
  

  

  an 
  unknown 
  factor 
  of 
  loss. 
  It 
  is 
  only 
  when 
  we 
  form 
  the 
  

  

  Nc 
  

   quotient 
  ^- 
  that 
  the 
  number 
  obtained 
  has 
  significance, 
  and, 
  

  

  far 
  from 
  being 
  about 
  \ 
  of 
  the 
  total 
  visible 
  radiation, 
  

  

  