﻿110 
  Prof. 
  R. 
  W. 
  Wood 
  on 
  th-t 
  Anomalous 
  

  

  each 
  end, 
  and 
  wetting 
  it 
  from 
  time 
  to 
  time. 
  I 
  have 
  had 
  one 
  

   tube 
  made 
  with 
  water-jackets 
  at 
  each 
  end, 
  but 
  it 
  seems 
  to 
  

   have 
  no 
  especial 
  advantage, 
  and 
  is 
  more 
  complicated. 
  Por- 
  

   celain 
  tubes 
  are 
  quite 
  satisfactory, 
  but 
  I 
  prefer 
  the 
  iron 
  on 
  

   the 
  whole. 
  

  

  By 
  employing 
  a 
  tube 
  of 
  about 
  5 
  cm. 
  diameter 
  I 
  have 
  

   succeeded 
  in 
  projecting 
  the 
  anomalous 
  spectrum, 
  but 
  the 
  

   appearance 
  is 
  so 
  very 
  inferior 
  to 
  that 
  of 
  the 
  phenomenon 
  

   when 
  seen 
  subjectively, 
  that 
  I 
  should 
  never 
  think 
  of 
  employing 
  

   the 
  method. 
  

  

  No 
  trace 
  of 
  any 
  influence 
  of 
  the 
  fluted 
  absorption-bands 
  on 
  

   the 
  dispersion 
  has 
  been 
  detected. 
  

  

  It 
  is 
  a 
  matter 
  of 
  some 
  interest 
  to 
  know 
  what 
  becomes 
  of 
  

   the 
  energy 
  absorbed 
  by 
  a 
  sodium 
  flame, 
  or 
  by 
  non-luminous 
  

   sodium 
  vapour. 
  Most 
  of 
  it 
  is 
  undoubtedly 
  spent 
  in 
  raising 
  

   the 
  temperature 
  of 
  the 
  vapour; 
  this 
  rise 
  of 
  temperature 
  I 
  have 
  

   shown 
  experimentally 
  by 
  making 
  the 
  dispersion 
  -tube 
  the 
  

   chamber 
  of 
  a 
  radiophone, 
  and 
  illuminating 
  it 
  with 
  intermittent 
  

   light. 
  It 
  was 
  found 
  that 
  the 
  radiophone 
  sang 
  loudly 
  when 
  

   illuminated 
  by 
  an 
  intense 
  beam 
  of 
  light 
  which 
  contained 
  

   waves 
  of 
  the 
  frequency 
  of 
  the 
  sodium 
  radiations, 
  but 
  became 
  

   almost 
  silent 
  when 
  these 
  frequencies 
  were 
  removed. 
  

  

  Prismatic 
  analysis 
  was 
  found 
  to 
  weaken 
  the 
  light 
  too 
  much 
  : 
  

   consequently 
  a 
  very 
  thin 
  film 
  of 
  cyanine 
  was 
  used 
  which 
  was 
  

   quite 
  opaque 
  to 
  the 
  region 
  of 
  the 
  D 
  lines 
  while 
  transparent 
  

   to 
  the 
  rest 
  of 
  the 
  spectrum. 
  Sunlight 
  concentrated 
  by 
  a 
  large 
  

   mirror 
  was 
  employed 
  for 
  the 
  illumination. 
  

  

  It 
  has 
  always 
  appeared 
  to 
  me 
  thinkable 
  that 
  the 
  absorbing 
  

   sodium 
  ions, 
  when 
  in 
  resonant 
  vibration, 
  might 
  emit 
  a 
  certain 
  

   amount 
  of 
  light 
  laterally. 
  Kayser 
  mentions 
  in 
  his 
  new 
  work 
  

   on 
  spectroscopy 
  an 
  experiment 
  made 
  by 
  Miller, 
  in 
  an 
  attempt 
  

   to 
  detect 
  this 
  phenomenon 
  if 
  it 
  existed. 
  The 
  possibility 
  of 
  

   such 
  a 
  lateral 
  radiation 
  is 
  discussed 
  by 
  Drude 
  in 
  his 
  Lehrbuch 
  

   der 
  Optik 
  (p. 
  4i>3), 
  and 
  is 
  shown 
  to 
  depend 
  on 
  a 
  small 
  value 
  

   of 
  the 
  constant 
  r 
  in 
  the 
  equation 
  of 
  motion 
  of 
  an 
  ion 
  vibrating 
  

   under 
  the 
  influence 
  of 
  a 
  periodic 
  electric 
  force. 
  For 
  sodium 
  

   vapour, 
  r 
  is 
  calculated 
  to 
  be 
  something 
  between 
  10 
  and 
  100. 
  

   If 
  it 
  were 
  equal 
  to 
  one 
  we 
  should 
  expect 
  a 
  lateral 
  radiation 
  

   of 
  light, 
  w 
  r 
  hich, 
  says 
  Drude, 
  has 
  never 
  been 
  observed. 
  

  

  While 
  experimenting 
  with 
  the 
  very 
  intense 
  beam 
  of 
  sun- 
  

   light 
  in 
  the 
  radiophone 
  experiment, 
  1 
  observed 
  what 
  appeared 
  

   to 
  be 
  a 
  lateral 
  radiation 
  of 
  a 
  clear 
  green 
  light 
  by 
  the 
  vapour. 
  

  

  My 
  first 
  thought 
  was 
  that 
  it 
  was 
  light 
  scattered 
  by 
  the 
  

   small 
  particles 
  of 
  oxide 
  which 
  are 
  always 
  floating 
  about. 
  If 
  

   this 
  were 
  the 
  case, 
  the 
  spectrum 
  of 
  the 
  light 
  should 
  be 
  that 
  of 
  

   white 
  light 
  after 
  transmission 
  through 
  sodium 
  vapour. 
  An 
  

  

  