﻿S50 
  Prof. 
  Skinner 
  and 
  Mr. 
  Tool 
  on 
  the 
  Optical 
  

  

  Table 
  IX. 
  — 
  Metallic 
  Iron. 
  

   Thickness 
  : 
  No. 
  11, 
  15'4 
  x 
  10~ 
  7 
  ; 
  No. 
  15, 
  19 
  x 
  10~ 
  7 
  cm. 
  

  

  

  

  Field 
  : 
  

  

  13,200 
  

  

  C.G.S. 
  

  

  

  

  

  

  No. 
  11. 
  

  

  1 
  

  

  

  No. 
  15. 
  

  

  

  Wave- 
  

   length. 
  

  

  

  

  

  

  

  

  Eotat. 
  

  

  Compens. 
  

  

  Ellipt. 
  

  

  Eotat. 
  

  

  Compens. 
  

  

  Ellipt. 
  

  

  

  (deg.). 
  

  

  (deg.). 
  

  

  X10 
  8 
  . 
  

  

  (deg.)- 
  

  

  (deg.). 
  

  

  X103. 
  

  

  406... 
  

  

  ■78 
  

  

  

  

  

  

  

  417... 
  

  

  •83 
  

  

  72 
  

  

  177 
  

  

  •98 
  

  

  ... 
  

  

  

  431 
  ... 
  

  

  •85 
  

  

  

  

  

  

  

  440... 
  

  

  ■87 
  

  

  72 
  

  

  170 
  

  

  107 
  

  

  8*8 
  

  

  20-8 
  

  

  460.., 
  

  

  •92 
  

  

  73 
  

  

  16-7 
  

  

  

  

  

  480... 
  

  

  •95 
  

  

  7-3 
  

  

  160 
  

  

  1-22 
  

  

  8 
  V 
  7 
  

  

  19-0 
  

  

  600... 
  

  

  106 
  

  

  72 
  

  

  15-2 
  

  

  

  

  

  520... 
  

  

  1-08 
  

  

  7*2 
  

  

  146 
  

  

  ISO 
  

  

  8 
  V 
  8 
  

  

  17-9 
  

  

  540... 
  

  

  10(5 
  

  

  73 
  

  

  146 
  

  

  

  

  

  560... 
  

  

  115 
  

  

  71 
  

  

  13-7 
  

  

  1-43 
  

  

  8 
  V 
  8 
  

  

  16-9 
  

  

  580... 
  

  

  117 
  

  

  71 
  

  

  132 
  

  

  

  

  

  600... 
  

  

  1-30 
  

  

  7-0 
  

  

  126 
  

  

  1 
  : 
  50 
  

  

  8 
  V 
  8 
  

  

  15-9 
  

  

  630... 
  

  

  1-20 
  

  

  70 
  

  

  L2-1 
  

  

  

  86 
  

  

  14-8 
  

  

  660... 
  

  

  117 
  

  

  70 
  

  

  11-5 
  

  

  1*59 
  

  

  

  

  680... 
  

  

  1-20 
  

  

  73 
  

  

  US 
  

  

  

  ... 
  

  

  

  rotation 
  and 
  ellipticity 
  to 
  the 
  thickness 
  is 
  considered. 
  Table 
  X. 
  

   gives 
  these 
  £or 
  the 
  two 
  film- 
  represented 
  in 
  Table 
  IX. 
  Both 
  

   possess 
  about 
  the 
  same 
  rotatory 
  power 
  which 
  is 
  three 
  times 
  

   that 
  of 
  the 
  electrolytic 
  films. 
  The 
  ratio 
  of 
  ellipticity 
  to 
  the 
  

   thickness 
  is 
  also 
  two 
  to 
  three 
  times 
  as 
  large 
  in 
  the 
  metallic 
  

   typo 
  as 
  in 
  the 
  electrolytic. 
  

  

  The 
  results 
  in 
  Table 
  X. 
  and 
  corresponding 
  curves 
  in 
  fig. 
  9 
  

   show 
  that 
  the 
  ellipticity 
  is 
  not 
  proportional 
  to 
  the 
  thickness, 
  

   if 
  the 
  two 
  films 
  arc 
  of 
  exactly 
  the 
  same 
  type. 
  This 
  incon- 
  

   >i>tency 
  becomes 
  more 
  marked 
  with 
  thinner 
  films, 
  and 
  leads 
  

   to 
  the 
  suggestion 
  (discussed 
  below) 
  that 
  an 
  observable 
  part 
  

   of 
  the 
  ellipticity 
  of 
  the 
  transmitted 
  light 
  arises 
  from 
  reflexion 
  

   effects, 
  an 
  explanation 
  put 
  forward 
  by 
  Righi 
  * 
  for 
  the 
  existence 
  

   of 
  ellipticity 
  in 
  the 
  transmitted 
  light. 
  

  

  Table 
  X. 
  also 
  gives 
  the 
  transmission 
  measurements 
  on 
  two 
  

   films 
  (Xos. 
  11 
  aud 
  16) 
  from 
  which 
  the 
  extinction 
  coefficients 
  

   in 
  the 
  adjacent 
  column 
  are 
  calculated. 
  The 
  transmission 
  

   curve 
  of 
  film 
  11 
  is 
  plotted 
  in 
  fig. 
  8. 
  It 
  reveals 
  only 
  a 
  

   slightly 
  greater 
  transparency 
  in 
  the 
  red 
  over 
  that 
  in 
  the 
  blue. 
  

   The 
  extinction 
  curve, 
  plotted 
  in 
  fig. 
  9, 
  is 
  practically 
  straight 
  

   and 
  nearly 
  horizontal. 
  Compared 
  with 
  electrolytic 
  films 
  the 
  

   extinction 
  here 
  is 
  about 
  five 
  times 
  the 
  magnitude 
  obtained 
  

   from 
  them. 
  

  

  * 
  Righi, 
  Mem. 
  R. 
  Accad. 
  Sc. 
  d. 
  Bologna, 
  1886, 
  p. 
  443. 
  

  

  