﻿610 
  

  

  Prof. 
  K. 
  W. 
  Wood 
  on 
  the 
  Absorpt 
  

  

  ion. 
  

  

  The 
  apparatus 
  as 
  arranged 
  for 
  photographing 
  the 
  fringes 
  and 
  

   measuring 
  the 
  wave-length 
  of 
  the 
  monochromatic 
  light 
  em- 
  

   ployed, 
  is 
  shown 
  in 
  fig. 
  2. 
  The 
  light 
  of 
  an 
  arc-lamp 
  A 
  falls 
  on 
  

  

  FIG. 
  2. 
  

  

  ■S> 
  A 
  

  

  a 
  mirror 
  cemented 
  to 
  the 
  back 
  of 
  a 
  prism 
  which 
  stands 
  on 
  a 
  

   revolving 
  graduated 
  circle. 
  The 
  collimator 
  objective 
  T 
  pro- 
  

   jects 
  a 
  spectrum 
  on 
  the 
  slit 
  S, 
  which 
  can 
  be 
  shifted 
  by 
  turning 
  

   the 
  circle 
  which 
  carries 
  the 
  prism. 
  The 
  monochromatic 
  light 
  

   which 
  leaves 
  the 
  slit, 
  after 
  passage 
  through 
  a 
  collimating-lens 
  

   L, 
  falls 
  on 
  the 
  interferometer. 
  Plane 
  parallel 
  plates 
  carrying 
  

   the 
  selenium 
  films 
  are 
  shown 
  at 
  b. 
  To 
  get 
  rid 
  of 
  the 
  multiple 
  

  

  