﻿

  9-10 
  Prof. 
  R. 
  W. 
  Wood 
  on 
  a 
  Method 
  of 
  Showing 
  

  

  Referring 
  to 
  my 
  first 
  paper 
  on 
  the 
  subject 
  in 
  this 
  Magazine, 
  

   I 
  had 
  from 
  the 
  first 
  recognized 
  that 
  the 
  question, 
  which 
  of 
  

   the 
  various 
  theories 
  represented 
  the 
  law 
  of 
  nature, 
  was 
  one 
  

   Eor 
  experiment 
  to 
  decide. 
  1 
  have 
  completed 
  the 
  experiments 
  

   Eoreshadowed*, 
  and 
  in 
  contradiction 
  to 
  Kaufmann 
  have 
  

   verified 
  the 
  substantial 
  accuracy 
  of 
  the 
  Lorentz 
  formula 
  for 
  

   the 
  electromagnetic 
  ma—, 
  and 
  therefore 
  also 
  of 
  the 
  Lorentz- 
  

   Einstein 
  principle 
  of 
  relativity, 
  since 
  the 
  only 
  serious 
  objection 
  

   to 
  it- 
  complete 
  acceptance 
  has 
  been 
  removed. 
  

  

  B 
  .mi 
  University, 
  Oct. 
  5 
  L9 
  18. 
  

  

  I, 
  XXX. 
  On 
  a 
  Method 
  <>/' 
  Sliowng 
  Fluorescent 
  Absorption 
  

   directly 
  if 
  it 
  exists. 
  By 
  R. 
  W. 
  WOOD, 
  Professor 
  of 
  Expe- 
  

   rimental 
  Physics, 
  Johns 
  Hopkins 
  University], 
  

  

  THE 
  question 
  as 
  to 
  whether 
  the 
  fluorescence 
  of 
  an 
  

   absorbing 
  medium 
  modifies 
  in 
  any 
  way 
  its 
  absorption 
  

   appears 
  to 
  be 
  -till 
  unsettled. 
  Burkes 
  experiments 
  with 
  

   uranium 
  glass! 
  appeared 
  to 
  show 
  that 
  a 
  block 
  of 
  the 
  glass, 
  

   when 
  excited 
  to 
  fluorescence 
  by 
  a 
  transverse 
  beam 
  of 
  light, 
  

   absorbed 
  the 
  fluorescent 
  light 
  of 
  a 
  second 
  block 
  of 
  the 
  Mime 
  

   glass 
  more 
  strongly 
  than 
  when 
  unilluminated. 
  More 
  recent 
  

   work 
  by 
  Nichols 
  and 
  Merritl 
  § 
  showed 
  the 
  same 
  effect 
  in 
  the 
  

   case 
  of 
  solutions 
  of 
  fluorescein, 
  and 
  apparently 
  confirmed 
  the 
  

   discovery 
  of 
  Burke. 
  They 
  made 
  use 
  of 
  the 
  spectrophoto- 
  

   meter, 
  measuring 
  the 
  intensity 
  of 
  the 
  Light 
  of 
  the 
  fluorescing 
  

   solution 
  alone 
  (r), 
  the 
  intensity 
  of 
  a 
  source 
  of 
  light 
  seen 
  

   through 
  this 
  solution 
  when 
  not 
  stimulated 
  to 
  fluorescence 
  (T), 
  

   and 
  the 
  intensity 
  of 
  the 
  fluorescence 
  plus 
  that 
  of 
  the 
  source 
  

   when 
  seen 
  through 
  the 
  fluorescing 
  solution 
  (C). 
  It 
  is 
  

   obvious 
  that 
  if 
  the 
  absorption 
  is 
  not 
  modified 
  by 
  the 
  fluor- 
  

   escence, 
  we 
  shall 
  have 
  F 
  + 
  T=C. 
  They 
  found, 
  however, 
  

   that 
  in 
  practically 
  every 
  case 
  < 
  ' 
  was 
  less 
  than 
  F 
  + 
  T. 
  Similar 
  

   results 
  wereobtained 
  by 
  Miss 
  Wick 
  !| 
  , 
  with 
  resorufin, 
  working 
  

   in 
  the 
  same 
  laboratory. 
  Camichel^f 
  has, 
  however, 
  been 
  

   unable 
  to 
  find 
  any 
  trace 
  whatever 
  of 
  the 
  effect, 
  using 
  similar 
  

   methods. 
  

  

  * 
  Phil. 
  Mag-, 
  ser. 
  6, 
  vol. 
  xiii. 
  p. 
  419 
  (April 
  1907). 
  

  

  + 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  Phil. 
  Trans, 
  exci. 
  p. 
  87 
  (1898). 
  

  

  § 
  Plm. 
  Rev. 
  xviii. 
  p. 
  447 
  (1904). 
  

  

  |] 
  Phys. 
  Rev. 
  xxiv. 
  p. 
  407 
  (1907). 
  

  

  If 
  Compt. 
  Bend. 
  cxl. 
  p. 
  139 
  (1904). 
  

  

  