﻿$26 
  Mr. 
  H. 
  L. 
  P. 
  Jolly 
  on 
  the 
  

  

  absence 
  of: 
  any 
  particulars, 
  it 
  is 
  impossible 
  to 
  institute 
  a 
  

   general 
  investigation. 
  Many 
  are 
  the 
  theories, 
  no 
  doubt, 
  

   which 
  different 
  physicists 
  conceive 
  when 
  they 
  think 
  of 
  the 
  

   luminosity 
  of 
  gases 
  in 
  discharge-tubes. 
  One 
  view 
  is 
  that 
  it 
  

   is 
  simply 
  the 
  energy 
  of 
  a 
  collision 
  between 
  a 
  corpuscle 
  and 
  

   a 
  molecule 
  which 
  gives 
  rise 
  to 
  radiation. 
  Berndt 
  {Ann. 
  

   tier 
  Phys. 
  vol. 
  xii. 
  p, 
  1101, 
  1903) 
  has 
  developed 
  a 
  particular 
  

   theory 
  a 
  little 
  more 
  in 
  detail. 
  He 
  supposes 
  that 
  the 
  fraction 
  

   of 
  the 
  energy 
  of 
  a 
  moving 
  corpuscle 
  converted 
  into 
  radiant 
  

   energy 
  is 
  proportional 
  to 
  \/v 
  } 
  v 
  being 
  its 
  velocity. 
  The 
  

   result 
  of 
  his 
  calculation 
  is 
  that 
  we 
  should 
  have 
  

  

  Intensity 
  /potential 
  gradientYS 
  

  

  t 
  X 
  ( 
  ) 
  cc 
  pressure. 
  

  

  current 
  \ 
  pressure 
  / 
  r 
  

  

  Curves 
  obtained 
  by 
  plotting 
  this 
  magnitude 
  against 
  p 
  were 
  

   linear 
  at 
  low 
  pressure 
  in 
  the 
  cases 
  of 
  H« 
  and 
  the 
  nitrogen 
  

   bands 
  X5214 
  and 
  X 
  60 
  69, 
  the 
  curves 
  passing 
  through 
  the 
  origin 
  

   of 
  coordinates, 
  but 
  bending 
  away 
  later. 
  

  

  Another 
  view 
  is 
  that 
  the 
  process 
  of 
  ionization 
  is 
  always 
  

   accompanied 
  by 
  radiation, 
  and 
  that 
  a 
  certain 
  amount 
  of 
  

   energy 
  is 
  liberated 
  each 
  time 
  an 
  ion 
  is 
  formed, 
  or 
  a 
  recom- 
  

   bination 
  takes 
  place. 
  There 
  seems 
  much 
  evidence 
  con- 
  

   firmatory 
  of 
  this 
  theory. 
  In 
  the 
  first 
  place, 
  as 
  Pfliiger 
  and 
  

   Ladenburg 
  have 
  shown, 
  absorption 
  of 
  the 
  light 
  emitted 
  by 
  

   gases 
  depends 
  on 
  the 
  absorbing 
  gas 
  being 
  in 
  the 
  same 
  

   electrical 
  state, 
  i.e. 
  it 
  is 
  only 
  when 
  a 
  current 
  is 
  passing- 
  

   through 
  the 
  gas 
  that 
  its 
  atoms 
  are 
  possessed 
  of 
  the 
  natural 
  

   frequency 
  which 
  gives 
  rise 
  to 
  its 
  absorbing 
  power. 
  This 
  is 
  

   very 
  nearly 
  equivalent 
  to 
  saying 
  that 
  a 
  necessary 
  concomitant 
  

   of 
  radiation 
  is 
  ionization. 
  Recently 
  (Phil. 
  Mag. 
  1912) 
  

   Andrade 
  has 
  shown 
  that 
  the 
  radiation 
  from 
  a 
  Bunsen 
  flame 
  

   rendered 
  luminous 
  by 
  metallic 
  vapour 
  is 
  proportional 
  to 
  its 
  

   conductivity 
  when 
  the 
  saturation-current 
  is 
  employed, 
  which 
  

   fact 
  is 
  in 
  direct 
  agreement 
  with 
  the 
  theory 
  in 
  question. 
  

   Radiation 
  from 
  such 
  a 
  flame 
  is 
  subject 
  to 
  the 
  same 
  laws 
  as 
  

   to 
  absorption 
  as 
  gases 
  in 
  discharge-tubes, 
  and 
  there 
  is 
  no 
  

   reason 
  to 
  suppose 
  that 
  the 
  centres 
  of 
  emission 
  are 
  radically 
  

   different 
  in 
  the 
  two 
  cases. 
  

  

  Ladenburg, 
  in 
  a 
  recent 
  paper 
  ( 
  Ann. 
  der 
  Phys. 
  May 
  1912), 
  

   has 
  shown 
  the 
  existence 
  of 
  "anomalous" 
  dispersion 
  and 
  

   magnetic 
  rotation 
  in 
  hydrogen 
  when 
  carrying 
  a 
  discharge, 
  

   and 
  he 
  has 
  come 
  to 
  the 
  conclusion 
  that 
  all 
  the 
  phenomena 
  in 
  

   luminous 
  hydrogen 
  can 
  be 
  explained 
  by 
  supposing 
  a 
  certain 
  

   number 
  N 
  of 
  singular 
  particles 
  to 
  exist 
  in 
  every 
  c.c. 
  of 
  the 
  

   medium, 
  just 
  as 
  in 
  the 
  Drude 
  theory 
  of 
  dispersion. 
  In 
  

  

  