﻿12 
  

  

  Dr. 
  W. 
  M. 
  Hicks 
  on 
  the 
  Michel 
  son-Mori 
  ei/ 
  

  

  to 
  be 
  noticed 
  about 
  this 
  wave- 
  diagram 
  is 
  that 
  precisely 
  the 
  

   same 
  diagram 
  will 
  serve 
  for 
  every 
  instant 
  of 
  the 
  motion 
  ; 
  

   only 
  in 
  this 
  case 
  the 
  lines 
  do 
  not 
  represent 
  crests, 
  but 
  all 
  

   belong 
  to 
  the 
  same 
  phase 
  of 
  the 
  respective 
  waves, 
  this 
  common 
  

   phase 
  differing 
  with 
  the 
  instant 
  for 
  which 
  the 
  diagram 
  is 
  

   drawn. 
  This 
  is 
  because 
  the 
  change 
  produced 
  by 
  reflexion 
  so 
  

   modifies 
  the 
  reflected 
  waves 
  (as 
  will 
  be 
  seen 
  shortly) 
  that 
  the 
  

   incident 
  crests 
  and 
  their 
  corresponding 
  reflected 
  crests 
  always 
  

   intersect 
  along 
  the 
  surface 
  as 
  it 
  moves 
  through 
  the 
  aether. 
  

   If 
  the 
  diagram 
  were 
  drawn 
  with 
  angles 
  of 
  reflexion 
  and 
  

   incidence 
  equal 
  at 
  one 
  instant, 
  at 
  the 
  next 
  they 
  would 
  be 
  

   thrown 
  into 
  confusion. 
  This 
  permanence 
  of 
  type 
  is 
  the 
  

   basis 
  of 
  the 
  development 
  of 
  the 
  theory 
  adopted 
  in 
  the 
  follow- 
  

   ing 
  general 
  reasoning. 
  The 
  diagram 
  gives 
  an 
  instantaneous 
  

   view. 
  If 
  an 
  observer 
  is 
  fixed 
  in 
  the 
  aether 
  he 
  sees 
  that 
  in 
  this 
  

   picture 
  the 
  waves 
  have 
  different 
  wave-lengths, 
  but 
  that 
  they 
  

   advance 
  with 
  the 
  same 
  velocity 
  V, 
  and 
  the 
  apparatus 
  moves 
  

   with 
  U. 
  If 
  the 
  observer 
  is 
  fixed 
  to 
  the 
  apparatus 
  he 
  sees 
  

   that 
  in 
  this 
  picture 
  the 
  apparatus 
  is 
  fixed 
  but 
  that 
  each 
  

   system 
  of 
  waves 
  advances 
  with 
  a 
  different 
  velocity, 
  yet 
  in 
  all 
  

   cases 
  such, 
  that 
  as 
  they 
  reach 
  him 
  their 
  frequencies 
  are 
  the 
  

   same 
  — 
  the 
  longer 
  waves 
  have 
  the 
  greater 
  apparent 
  velocity 
  

   of 
  propagation. 
  

  

  2. 
  It 
  will 
  be 
  best 
  to 
  consider 
  first 
  the 
  case 
  of 
  no 
  drift 
  of 
  

   the 
  aether. 
  Here 
  the 
  aether 
  between 
  B 
  and 
  C 
  will 
  be 
  mapped 
  

   out 
  by 
  a 
  network 
  of 
  lines 
  representing 
  crests 
  of 
  two 
  sets 
  of 
  

  

  waves, 
  the 
  meshes 
  of 
  which, 
  in 
  case 
  of 
  no 
  motion, 
  are 
  equal 
  - 
  

   sided 
  parallelograms. 
  The 
  diagonals 
  which 
  lie 
  between 
  the 
  

   advancing 
  sides 
  of 
  the 
  waves 
  are 
  points 
  of 
  maximum 
  dis- 
  

   turbance. 
  They 
  form 
  a 
  system 
  of 
  parallel 
  straight 
  lines 
  

   bisecting 
  the 
  angles 
  between 
  the 
  wave-fronts, 
  and 
  at 
  a 
  

  

  