﻿380 
  

  

  Dr. 
  H. 
  Stansfield 
  on 
  

  

  to 
  make 
  6 
  negative, 
  is 
  represented 
  in 
  figs. 
  3 
  and 
  4 
  ; 
  lu^ 
  is 
  

   also 
  plotted 
  in 
  fig. 
  4, 
  to 
  indicate 
  the 
  falling 
  off 
  in 
  the 
  intensity 
  

   of 
  the 
  lioht 
  on 
  this 
  account. 
  

  

  Fig. 
  4. 
  

  

  f^-t 
  

  

  - 
  

  

  

  

  

  

  

  

  

  Q. 
  

  

  ^mm 
  

  

  i\ 
  

  

  

  

  

  

  

  

  

  

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  \ 
  

  

  

  

  

  

  

  

  

  

  lA 
  

  

  

  

  ReUfdat 
  

  

  ion 
  R 
  

  

  

  

  

  / 
  

  

  

  

  

  in 
  wave. 
  

  

  Ltn^fchs 
  

  

  

  

  V 
  

  

  y 
  

  

  Xo 
  

  

  ! 
  ^ 
  

  

  

  

  

  

  

  

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  \ 
  

  

  

  m 
  ij 
  an 
  

   aboofc 
  

  

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   (0,070 
  

  

  

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  1 
  

  

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  /mio 
  

  

  

  

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  /, 
  

  

  

  

  

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  ^ 
  

  

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  ></ 
  

  

  / 
  m>'^ 
  

  

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  / 
  

  

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  r 
  

  

  

  

  

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  / 
  

  

  

  

  

  

  

  ^T 
  

  

  •6 
  

  

  •4 
  

  

  ; 
  

  

  / 
  

  

  / 
  

  

  •m-t 
  

  

  

  

  

  

  

  : 
  '^/ 
  

  

  j^ 
  

  

  

  

  

  

  

  

  i 
  

  

  -3' 
  -r 
  

  

  -r 
  i-r 
  +r 
  

  

  An(jle 
  of 
  rotation 
  9 
  

  

  fkW- 
  

  

  IS 
  

  

  1-6 
  

  

  1-^ 
  

  

  rz. 
  

  

  •^ 
  

  

  +3° 
  *V 
  +5' 
  

  

  T^'iW^/i 
  o/ 
  ^7i^ 
  difr 
  action-hands. 
  — 
  It 
  will 
  be 
  seen 
  from 
  fig. 
  4 
  

   that 
  both 
  e 
  and 
  / 
  are 
  greater 
  than 
  w^ 
  except 
  when 
  ^ 
  = 
  0. 
  

  

  Hence, 
  the 
  angular 
  interval,-, 
  between 
  the 
  equally 
  spaced 
  

  

  diffraction 
  minima 
  is 
  in 
  general 
  greater 
  than 
  - 
  or 
  ^, 
  the 
  

  

  J 
  

   angular 
  intervals, 
  in 
  the 
  direct 
  and 
  reversed 
  cases, 
  between 
  

   successive 
  orders. 
  

  

  Liglit 
  reflected 
  from 
  the 
  ends 
  of 
  the 
  plates. 
  — 
  The 
  step 
  ends 
  

   of 
  the 
  echelon 
  plates, 
  which 
  are 
  finely 
  ground, 
  scatter 
  some 
  of 
  

   the 
  light 
  falling 
  upon 
  them 
  and 
  also 
  give 
  regularly 
  reflected 
  

   beams, 
  represented 
  in 
  fig. 
  3. 
  The 
  reflected 
  beams 
  produce 
  

   echelon 
  spectra 
  ; 
  but 
  as 
  the 
  ends 
  are 
  not 
  polished^ 
  the 
  spectra 
  

  

  