﻿A. 
  A. 
  Jlichehon 
  — 
  Motion 
  of 
  the 
  Earth 
  and 
  the 
  Ether. 
  475 
  

  

  Art. 
  LI. 
  — 
  The 
  relative 
  Motion 
  of 
  the 
  Earth 
  and 
  the 
  Ether 
  ; 
  

   by 
  Albert 
  A. 
  Michelsox. 
  

  

  To 
  account 
  for 
  the 
  phenomenon 
  of 
  aberration 
  Fresnel 
  sup- 
  

   poses 
  the 
  luminiferons 
  ether 
  at 
  rest, 
  the 
  earth 
  moving 
  through 
  

   this 
  medium 
  without 
  communicating 
  any 
  perceptible 
  part 
  of 
  

   its 
  motion. 
  On 
  this 
  theory 
  it 
  has 
  been 
  shown* 
  that 
  it 
  should 
  

   be 
  possible 
  to 
  detect 
  a 
  difference 
  of 
  the 
  velocity 
  of 
  light 
  in 
  two 
  

   directions 
  at 
  right 
  angles. 
  As 
  no 
  such 
  difference 
  was 
  observed, 
  

   it 
  would 
  seem 
  to 
  follow 
  that 
  Fresnel's 
  hypothesis 
  is 
  incorrect. 
  

  

  Another 
  theory 
  is 
  that 
  of 
  Stokes, 
  in 
  which 
  the 
  aberration 
  is 
  

   accounted 
  for 
  if 
  the 
  relative 
  velocity 
  of 
  the 
  earth 
  and 
  the 
  ether 
  

   have 
  a 
  potential. 
  This 
  requirement, 
  however, 
  is 
  inconsistent 
  

   with 
  the 
  results 
  of 
  the 
  experiment 
  just 
  cited, 
  which 
  indicates 
  

   that 
  at 
  the 
  earth's 
  surface 
  the 
  relative 
  motion 
  is 
  zero. 
  

  

  In 
  the 
  hope 
  of 
  detecting 
  a 
  relative 
  motion 
  corresponding 
  to 
  

   a 
  difference 
  of 
  level, 
  the 
  following 
  experiment 
  was 
  undertaken. 
  

  

  I 
  take 
  this 
  opportunity 
  of 
  gratefully 
  acknowledging 
  the 
  

   faithful 
  and 
  efficient 
  services 
  rendered 
  in 
  the 
  execution 
  of 
  this 
  

   work 
  by 
  Professor 
  S. 
  W. 
  Stratton 
  and 
  Mr. 
  C. 
  E. 
  Mann. 
  

  

  Light 
  from 
  the 
  source 
  s, 
  a 
  calcium 
  light 
  or 
  an 
  electric 
  arc 
  

   lamp, 
  separated 
  into 
  two 
  pencils 
  at 
  a 
  plane-parallel 
  glass 
  plate, 
  

   #, 
  lightly 
  silvered. 
  The 
  two 
  pencils 
  were 
  reflected 
  by 
  double 
  

   mirrors 
  along 
  the 
  paths 
  oabcoe, 
  and 
  ochaoe, 
  respectively. 
  The 
  

   two 
  paths 
  being 
  equal, 
  interference 
  fringes 
  could 
  be 
  observed 
  

   with 
  the 
  aid 
  of 
  the 
  telescope 
  at 
  e. 
  Fig. 
  2 
  shows 
  details 
  of 
  the 
  

   corner 
  at 
  c 
  : 
  ])Q 
  are 
  plane-parallel 
  glass 
  disks, 
  cemented 
  to 
  the 
  

  

  *This 
  Journal, 
  Xovember, 
  18S7. 
  

  

  