﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  861 
  

  

  per 
  cent, 
  greater 
  values 
  for 
  the 
  rotation 
  divided 
  by 
  the 
  thick- 
  

   ness 
  than 
  No. 
  41. 
  The 
  magnitudes 
  of 
  both 
  are 
  again, 
  as 
  in 
  

   iron 
  and 
  cobalt, 
  greatly 
  in 
  excess 
  of 
  those 
  obtained 
  by 
  Lobach 
  

   for 
  the 
  corresponding 
  type 
  of 
  films. 
  

  

  The 
  extinction 
  coefficients 
  recorded 
  in 
  Table 
  XVIII. 
  were 
  

   obtained 
  by 
  measuring 
  the 
  transmission 
  and 
  magnetic 
  rotation 
  

   of 
  a 
  thin 
  deposit, 
  then 
  depositing 
  over 
  this 
  and 
  repeating 
  the 
  

   measurements. 
  The 
  thickness 
  was 
  calculated 
  from 
  the 
  mean 
  

   rotatory 
  power 
  of 
  films 
  41 
  and 
  42, 
  hence 
  the 
  values 
  obtained 
  

   for 
  the 
  extinction 
  are 
  consequently 
  of 
  questionable 
  accuracy. 
  

  

  16. 
  Summary 
  and 
  Conclusions. 
  

  

  (a) 
  Three 
  types 
  of 
  both 
  iron 
  and 
  cobalt 
  have 
  been 
  investi- 
  

   gated 
  with 
  respect 
  to 
  their 
  magneto-optical 
  activity, 
  their 
  

   optical 
  extinction, 
  and 
  also 
  in 
  part 
  their 
  refractive 
  indices 
  and 
  

   reflexion. 
  These 
  types 
  are 
  found 
  to 
  differ 
  essentially 
  in 
  the 
  

   period 
  of 
  their 
  optical 
  resonance 
  ; 
  and 
  further 
  also 
  in 
  the 
  

   magnitude 
  of 
  their 
  optical 
  extinction, 
  which 
  appears 
  to 
  be 
  

   largely 
  a 
  friction 
  phenomenon. 
  In 
  the 
  dark 
  type 
  the 
  

   resonance 
  region 
  is 
  in 
  or 
  very 
  near 
  the 
  visible 
  spectrum, 
  so 
  

   that 
  dark 
  iron 
  gives 
  a 
  marked 
  anomaly 
  in 
  both 
  magnetic 
  

   "rotation 
  and 
  ellipticity 
  ; 
  and 
  dark 
  cobalt 
  gives 
  curves 
  for 
  the 
  

   same 
  of 
  such 
  a 
  form 
  as 
  to 
  suggest, 
  when 
  combined 
  with 
  those 
  

   of 
  the 
  dark 
  iron, 
  the 
  typical 
  form 
  of 
  the 
  rotation 
  and 
  ellipticity 
  

   on 
  both 
  sides 
  of 
  the 
  resonance 
  region. 
  These 
  hypothetical 
  

   curves 
  possess 
  positive 
  values 
  for 
  the 
  magnetic 
  rotation 
  out- 
  

   side 
  the 
  resonance 
  region 
  changing 
  through 
  zero 
  to 
  negative 
  

   within 
  it 
  ; 
  and 
  negative 
  ellipticity 
  in 
  the 
  region 
  of 
  periods 
  

   shorter 
  than 
  that 
  of 
  resonance, 
  changing 
  to 
  positive 
  in 
  the 
  

   region 
  of 
  longer 
  periods. 
  The 
  rotation 
  increases 
  toward 
  a 
  

   maximum 
  value 
  on 
  leaving 
  the 
  resonance 
  region 
  in 
  both 
  

   directions 
  ; 
  the 
  ellipticity 
  increases 
  to 
  a 
  maximum 
  magnitude, 
  

   then 
  appears 
  to 
  decrease 
  asymptotically 
  toward 
  zero 
  on 
  both 
  

   sides. 
  The 
  hypothetical 
  rotation 
  curve 
  appears 
  to 
  have 
  the 
  

   general 
  form 
  of 
  that 
  given 
  by 
  Elias 
  * 
  for 
  erbium 
  chloride, 
  

   but 
  with 
  values 
  opposite 
  in 
  sign. 
  

  

  (b) 
  No 
  corresponding 
  anomaly 
  exists 
  in 
  the 
  refractive 
  index 
  

   curves, 
  leading 
  to 
  the 
  conclusion 
  that 
  the 
  ions 
  producing 
  

   magnetic 
  anomaly 
  do 
  not 
  appreciably 
  contribute 
  to 
  the 
  

   refractive 
  index. 
  

  

  (c) 
  In 
  the 
  electrolytic 
  films 
  the 
  magneto-optical 
  effects 
  

   indicate 
  that 
  the 
  resonance 
  region 
  lies 
  in 
  the 
  ultra-violet. 
  

   The 
  magnetic 
  rotatory 
  power, 
  the 
  differential 
  optical 
  

  

  Physik. 
  Zeitschr. 
  ix. 
  p. 
  931 
  (1906). 
  

  

  