﻿450 
  

  

  Prof. 
  W. 
  Cassie 
  on 
  Multiple 
  

  

  reflexions 
  of 
  the 
  beam. 
  The 
  Joss 
  of 
  light 
  can 
  be 
  reduced 
  to 
  a 
  

   minimum 
  by 
  choosing 
  the 
  angles 
  of 
  the 
  prisms 
  so 
  that 
  the 
  

   light 
  is 
  incident 
  at 
  the 
  angle 
  of 
  polarization. 
  

  

  PQ 
  

  

  TTT 
  

  

  ; 
  'i 
  n 
  » 
  t 
  

  

  '! 
  II 
  l' 
  »' 
  

  

  ( 
  i 
  »i 
  i 
  1 
  " 
  

  

  ', 
  'i 
  i 
  1 
  'i 
  

  

  i 
  '■ 
  \ 
  i' 
  'i 
  

  

  . 
  'i 
  » 
  ij 
  »■ 
  

  

  i 
  ii». 
  1 
  1 
  1 
  1 
  

  

  AI/fyAiA 
  A 
  

  

  L'''i' 
  ' 
  

  

  H 
  l 
  i' 
  if 
  

  

  1 
  1, 
  1 
  

   ' 
  I 
  ' 
  

  

  •^ 
  

  

  11 
  

  

  The! 
  adjustment 
  for 
  light 
  of 
  different 
  refrangibilities 
  is 
  

   secured 
  by 
  turning 
  the 
  prisms 
  in 
  opposite 
  directions 
  so 
  that 
  

   they 
  are 
  always 
  inclined 
  to 
  the 
  beam 
  of 
  light 
  at 
  equal 
  angles. 
  

  

  