﻿Experiment 
  relating 
  to 
  the 
  Drift 
  of 
  the 
  /Ether. 
  35 
  

  

  If 
  D 
  denote 
  the 
  distance 
  o£ 
  the 
  central 
  band 
  from 
  the 
  

   intersection 
  of 
  the 
  plate 
  and 
  mirrors, 
  when 
  there 
  is 
  no 
  drift 
  — 
  

   or 
  when 
  the 
  drift 
  is 
  parallel 
  to 
  the 
  plate 
  — 
  

  

  b 
  

  

  D 
  

  

  sin(B-A) 
  

  

  Dsin(B-A) 
  

   sin 
  (B-A.) 
  -if 
  2 
  cos 
  2a* 
  

  

  t? 
  2 
  D 
  cos 
  2« 
  

  

  Displacement 
  to 
  \ 
  __ 
  t\_ 
  

  

  left 
  of 
  this 
  position 
  J 
  " 
  sin 
  (B 
  ■— 
  A) 
  — 
  if 
  2 
  cos 
  2a' 
  

  

  In 
  any 
  given 
  case 
  suppose 
  sin(B— 
  A) 
  = 
  J&f 
  2 
  7 
  then 
  

  

  Displacement 
  = 
  7 
  ^-. 
  

  

  r 
  fc 
  — 
  cos 
  la 
  

  

  Fiff. 
  6. 
  

  

  Fig. 
  6 
  shows 
  how 
  the 
  displacement 
  changes 
  with 
  a, 
  for 
  the 
  

  

  D2 
  

  

  