﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  849 
  

  

  tested 
  for 
  both 
  rotation 
  and 
  ellipticity 
  in 
  a 
  field 
  of 
  about 
  

   13,000 
  lines. 
  The 
  results 
  are 
  given 
  in 
  the 
  following 
  table: 
  — 
  

  

  

  Table 
  VIII. 
  

  

  

  

  

  

  Wave-length 
  ....'. 
  

  

  440 
  480 
  520 
  ' 
  

  

  560 
  

  

  600 
  

  

  630 
  

  

  660 
  

  

  

  Rotation 
  (deg.) 
  

  

  -•16 
  -'17 
  --I9, 
  

  

  -•19 
  

  

  -•18 
  

  

  -•14 
  

  

  -•18 
  

  

  Ellipticity 
  xlO 
  8 
  "' 
  ... 
  

  

  -•06 
  -"23 
  --42 
  

  

  -•45 
  

  

  -•50 
  

  

  -•90 
  

  

  -•70 
  

  

  These 
  results 
  show 
  that 
  the 
  rotation 
  of 
  reflected 
  light 
  is 
  

   about 
  the 
  same 
  for 
  all 
  colours, 
  but 
  the 
  ellipticity 
  — 
  on 
  the 
  

   whole 
  small— 
  increases 
  slightly 
  with 
  the 
  wave-length. 
  We 
  

   find 
  here 
  that 
  the 
  negative 
  rotation 
  is 
  also 
  accompanied 
  by 
  a 
  

   negative 
  ellipticity, 
  both 
  being 
  positive 
  in 
  the 
  case 
  of 
  trans- 
  

   mitted 
  light. 
  

  

  8. 
  Metallic 
  Iron. 
  

  

  The 
  type 
  of 
  films 
  designated 
  as 
  metallic, 
  to 
  distinguish 
  

   them 
  from 
  the 
  other 
  type 
  obtained 
  from 
  cathode 
  deposit 
  

   in 
  vacuo, 
  seem 
  to 
  be 
  produced 
  by 
  sublimation 
  of 
  the 
  cathode. 
  

   They 
  are 
  probably 
  nearer 
  normal 
  iron 
  in 
  their 
  structure 
  than 
  

   either 
  of 
  the 
  other 
  types. 
  This 
  is 
  indicated 
  by 
  their 
  

   appearance, 
  and 
  also 
  suggested 
  by 
  their 
  magnetic 
  charac- 
  

   teristics. 
  

  

  The 
  reflexion 
  coefficients 
  as 
  measured 
  are 
  practically 
  con- 
  

   stant 
  throughout 
  the 
  spectrum, 
  an 
  average 
  of 
  37 
  per 
  cent, 
  

   of 
  the 
  light 
  being 
  reflected. 
  Their 
  absorption 
  is 
  so 
  great 
  

   that 
  only 
  very 
  thin 
  specimens 
  could 
  be 
  investigated, 
  the 
  

   thickest 
  being 
  19 
  x 
  10 
  -7 
  cm., 
  from 
  which 
  the 
  thickness 
  

   of 
  the 
  others 
  was 
  obtained 
  by 
  measuring 
  their 
  magnetic 
  

   rotation. 
  This 
  film 
  (No. 
  15) 
  was 
  very 
  carefully 
  measured, 
  

   following 
  the 
  method 
  described 
  in 
  § 
  2, 
  by 
  two 
  observers 
  

   independently, 
  whose 
  mean 
  results 
  differed 
  by 
  only 
  three 
  

   per 
  cent. 
  

  

  In 
  Table 
  IX. 
  are 
  found 
  the 
  magnetic 
  rotation 
  and 
  ellip- 
  

   ticity 
  produced 
  by 
  two 
  different 
  films 
  of 
  this 
  type 
  in 
  a 
  field 
  

   of 
  13,200 
  units. 
  The 
  results 
  from 
  film 
  15 
  are 
  plotted 
  in 
  fig. 
  8 
  

   (PL 
  XXIV.). 
  The 
  form 
  of 
  the 
  rotation 
  curve 
  is 
  very 
  similar 
  

   to 
  that 
  from 
  electrolytic 
  iron, 
  but 
  the 
  ellipticity 
  curve 
  is 
  

   distinctly 
  different, 
  the 
  ellipticity, 
  decreasing 
  instead 
  of 
  in- 
  

   creasing, 
  with 
  the 
  wave-length. 
  The 
  form 
  of 
  the 
  latter 
  indi- 
  

   cates 
  the 
  resonance 
  region 
  as 
  being 
  farther 
  out 
  in 
  the 
  ultra- 
  

   violet 
  than 
  that 
  of 
  the 
  electrolytic 
  iron 
  type. 
  A 
  more 
  marked 
  

   difference 
  in 
  the 
  two 
  types 
  becomes 
  evident 
  when 
  the 
  ratio 
  of 
  

   Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  No. 
  96. 
  Dec. 
  1908. 
  3 
  K 
  

  

  