﻿Mr. 
  S. 
  K. 
  Mitra 
  on 
  the 
  Asymmetry 
  of 
  

  

  of 
  the 
  spectrometer 
  by 
  a 
  camera 
  with 
  a 
  lens 
  of 
  long 
  focus 
  

   (176 
  cm.). 
  Figs. 
  II, 
  III, 
  and 
  IV 
  reproduce 
  three 
  photographs 
  

   taken 
  at 
  three 
  different 
  angles 
  of 
  incidence, 
  the 
  reflecting 
  

   strips 
  in 
  this 
  case 
  being 
  0*754 
  cm. 
  wide 
  and 
  1*446 
  cm. 
  

   apart. 
  In 
  all 
  the 
  figures, 
  the 
  central 
  fringe 
  of 
  the 
  pattern 
  

   is 
  indicated 
  by 
  a 
  small 
  cross 
  x 
  . 
  The 
  asymmetry 
  of 
  the 
  

   luminosity 
  curve 
  will 
  be 
  evident 
  on 
  comparing 
  the 
  brightness 
  

   of 
  the 
  corresponding 
  bands 
  on 
  either 
  side 
  of 
  the 
  central 
  

   fringe 
  ; 
  for 
  instance, 
  the 
  second 
  band 
  on 
  the 
  right 
  and 
  the 
  

   second 
  band 
  on 
  the 
  left 
  in 
  figs. 
  II 
  and 
  III, 
  or 
  the 
  first 
  band 
  

   on 
  the 
  right 
  and 
  the 
  first 
  band 
  on 
  the 
  left 
  in 
  fig. 
  IV. 
  

  

  The 
  positions 
  of 
  the 
  interference 
  minima 
  in 
  the 
  pattern 
  

   are 
  given 
  by 
  the 
  formula 
  of 
  the 
  usual 
  type 
  

  

  S-4- 
  73 
  " 
  + 
  37r 
  

  

  ± 
  -£ 
  9 
  &c. 
  

  

  2 
  

  

  where 
  8 
  = 
  7r(a 
  + 
  b) 
  (sin 
  i 
  — 
  sin 
  0)/\, 
  a 
  being 
  the 
  width 
  of 
  

   each 
  of 
  the 
  apertures, 
  b 
  their 
  distance 
  apart, 
  and 
  t, 
  6, 
  \ 
  

   having 
  their 
  usual 
  significance. 
  To 
  test 
  whether 
  the 
  formula 
  

   holds 
  good 
  at 
  the 
  oblique 
  incidences 
  used, 
  the 
  negatives 
  

   were 
  measured 
  under 
  a 
  travelling 
  microscope. 
  In 
  photo- 
  

   graph 
  I, 
  the 
  distances 
  between 
  the 
  successive 
  interference 
  

   minima 
  were 
  determined 
  to 
  find 
  whether 
  the 
  relations 
  

  

  sin 
  #i 
  — 
  sin 
  2 
  — 
  si 
  n 
  #2~~ 
  sm 
  &3 
  = 
  sin 
  3 
  - 
  sin 
  # 
  4 
  , 
  &c, 
  

  

  indicated 
  by 
  the 
  formula 
  were 
  valid. 
  The 
  results 
  are 
  shown 
  

   in 
  Table 
  I. 
  

  

  Table 
  I. 
  

  

  

  a 
  — 
  0*48 
  cm. 
  

  

  b 
  = 
  3-60 
  cm. 
  

  

  

  Minima 
  on 
  the 
  

   ; 
  right 
  of 
  the 
  

   centra 
  

  

  Observed 
  value 
  of 
  

  

  sin 
  9 
  n+1 
  — 
  sin 
  9 
  n 
  

  

  X 
  constant. 
  

  

  Minima 
  on 
  the 
  

  

  left 
  of 
  the 
  

   central 
  fringe. 
  

  

  Observed 
  value 
  of 
  

  

  sin 
  n 
  — 
  sin 
  9 
  n 
  +i 
  

  

  X 
  constant. 
  

  

  sin 
  5 
  — 
  sin 
  4 
  

  

  0-712 
  

  

  sin 
  9 
  X 
  — 
  sin 
  9 
  2 
  

  

  0-705 
  

  

  sin 
  4 
  — 
  sin 
  3 
  

  

  0-703 
  

  

  sin 
  9 
  2 
  — 
  sin 
  9 
  3 
  

  

  0-710 
  

  

  sin 
  3 
  — 
  sin 
  2 
  

  

  0711 
  

  

  sin 
  9 
  3 
  — 
  sin 
  9 
  i 
  

  

  0-711 
  

  

  sin 
  2 
  — 
  sin 
  Q 
  x 
  

  

  0-711 
  

  

  sin 
  4 
  — 
  sin 
  9 
  5 
  

  

  0-710 
  

  

  

  

  sin 
  9 
  S 
  — 
  sin 
  6 
  

  

  0-713 
  

  

  