﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  841 
  

  

  ellipticity 
  were 
  obtained 
  by 
  reversing 
  the 
  magnetizing 
  

   current 
  in 
  the 
  electromagnet, 
  which 
  doubled 
  the 
  magnitude 
  

   of 
  the 
  quantity 
  sought. 
  

  

  The 
  direction 
  o£ 
  vibration 
  in 
  the 
  ellipse 
  was 
  determined 
  by 
  

   comparing 
  the 
  compensator 
  with 
  a 
  quarter-wave 
  plate, 
  the 
  

   slow 
  and 
  fast 
  azimuths 
  o£ 
  which 
  had 
  been 
  determined 
  by 
  

   means 
  of 
  the 
  interferometer. 
  

  

  Experimental 
  Kesults. 
  

   0. 
  Dark 
  Iron. 
  

  

  In 
  Table 
  I. 
  (p. 
  842) 
  are 
  incorporated 
  the 
  values 
  of 
  the 
  mag- 
  

   netic 
  rotation 
  and 
  ellipticity 
  imparted 
  by 
  three 
  different 
  films 
  

   of 
  dark 
  iron 
  to 
  light 
  transmitted 
  through 
  them 
  along 
  the 
  lines 
  

   of 
  force, 
  and 
  with 
  field-strengths 
  giving 
  maximum 
  effects. 
  

   Two 
  of 
  these 
  films 
  (Nos. 
  3 
  and 
  4) 
  were 
  deposited 
  in 
  an 
  

   atmosphere 
  of 
  hydrogen, 
  the 
  third 
  (No. 
  2) 
  in 
  helium. 
  The 
  

   rotation 
  and 
  compensator 
  values 
  are 
  half 
  the 
  observed, 
  which 
  

   were, 
  as 
  already 
  stated, 
  obtained 
  by 
  reversing 
  the 
  magnetizing 
  

   current. 
  The 
  ellipticity 
  (ratio 
  of 
  minor 
  to 
  major 
  axis) 
  was 
  

   obtained 
  from 
  the 
  compensator 
  values 
  by 
  use 
  of 
  the 
  formula 
  

   given 
  on 
  page 
  840. 
  Positive 
  values 
  represent 
  rotation 
  (or 
  

   vibration) 
  in 
  the 
  direction 
  of 
  the 
  magnetizing 
  current 
  ; 
  

   negative, 
  the 
  opposite 
  direction. 
  By 
  all 
  three 
  films 
  the 
  

   rotation 
  is 
  reversed 
  in 
  direction 
  at 
  a 
  wave-length 
  of 
  about 
  

   540 
  yttyu,, 
  and 
  the 
  ellipticity 
  at 
  about 
  460 
  [Xfju. 
  This 
  similarity 
  

   in 
  the 
  results 
  from 
  films 
  deposited 
  in 
  hydrogen 
  and 
  in 
  helium 
  

   indicates 
  that 
  their 
  peculiar 
  properties 
  are 
  to 
  be 
  ascribed 
  to 
  

   the 
  form 
  in 
  which 
  the 
  iron 
  is 
  deposited 
  rather 
  than 
  to 
  the 
  

   existence 
  of 
  any 
  chemical 
  combination 
  with, 
  the 
  gas. 
  This 
  

   conclusion 
  is 
  strengthened 
  by 
  the 
  fact 
  that 
  iron 
  deposited 
  by 
  

   Harris 
  in 
  nitrogen 
  (I. 
  c.) 
  gives 
  also 
  zero 
  rotation 
  and 
  ellip- 
  

   ticity 
  at 
  the 
  same 
  positions 
  in 
  the 
  spectrum. 
  

  

  Fig. 
  4 
  (PI. 
  XXIV.) 
  represents 
  graphically 
  the 
  results 
  from 
  

   film 
  3. 
  The 
  abscissas 
  represent 
  wave-lengths 
  ; 
  the 
  ordinates 
  

   in 
  the 
  rotation 
  curve 
  give 
  the 
  rotation 
  in 
  degrees 
  multiplied 
  by 
  

   ten, 
  and 
  in 
  the 
  ellipticity 
  curve 
  the 
  ratio 
  of 
  minor 
  to 
  major 
  axis 
  

   multiplied 
  by 
  one 
  thousand. 
  In 
  the 
  same 
  figure 
  is 
  plotted 
  

   the 
  transmission 
  curve 
  of 
  the 
  film, 
  the 
  ordinates 
  representing 
  

   the 
  per 
  cent, 
  transmission 
  divided 
  by 
  five. 
  The 
  values 
  for 
  

   this 
  latter 
  curve 
  are 
  taken 
  from 
  Table 
  II. 
  The 
  relatively 
  

   large 
  transmission 
  of 
  the 
  longer 
  waves 
  causes 
  the 
  film 
  to 
  

   impart 
  a 
  rich 
  golden 
  tint 
  to 
  white 
  light. 
  

  

  In 
  Table 
  II. 
  (p. 
  843) 
  are 
  given 
  for 
  the 
  same 
  films 
  the 
  values 
  

   of 
  rotation 
  and 
  ellipticity 
  divided 
  by 
  the 
  thickness 
  of 
  the 
  

  

  