﻿54 
  Mr, 
  F. 
  Twyman 
  on 
  Interferometers 
  for 
  

  

  Fig. 
  7. 
  

  

  A 
  B 
  

  

  DE 
  

  

  Lens 
  Interferometer. 
  

   Fig. 
  8. 
  

  

  Lens 
  Interferometer. 
  

  

  