﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  

  

  839 
  

  

  o. 
  

  

  Magnetic 
  Rotation 
  and 
  Ellipticity. 
  

  

  The 
  rotation 
  of 
  plane-polarized 
  light 
  by 
  the 
  films, 
  when 
  

   subjected 
  to 
  a 
  magnetizing 
  force 
  in 
  the 
  direction 
  o£ 
  the 
  ray, 
  

   was 
  measured 
  for 
  both 
  transmission 
  and 
  reflexion. 
  The 
  

   corresponding 
  ellipticity 
  produced 
  in 
  the 
  originally 
  plane 
  

   vibration 
  was 
  also 
  measured. 
  Finally, 
  plane-polarized 
  light 
  

   sent 
  through 
  the 
  films 
  in 
  a 
  direction 
  normal 
  to 
  the 
  field, 
  and 
  

   with 
  its 
  azimuth 
  of 
  vibration 
  at 
  45° 
  to 
  it, 
  was 
  tested 
  in 
  the 
  

   most 
  promising 
  films 
  for 
  ellipticity, 
  but 
  none 
  detected. 
  

  

  Rotation. 
  — 
  Figure 
  3 
  presents 
  a 
  diagram 
  of 
  the 
  system 
  used 
  

   for 
  measuring 
  rotation. 
  A 
  very 
  clear 
  sun 
  as 
  source 
  was 
  

   necessary 
  for 
  all 
  observations 
  where 
  transmitted 
  light 
  was 
  

   studied. 
  This 
  was 
  concentrated 
  by 
  a 
  long-focus 
  lens 
  L 
  x 
  on 
  

  

  Fig. 
  3. 
  

  

  & 
  

  

  the 
  collimator 
  slit 
  S 
  x 
  of 
  a 
  Fuess 
  spectral 
  instrument 
  so 
  

  

  adjusted 
  as 
  to 
  furnish 
  at 
  the 
  emergent 
  slit 
  S< 
  

  

  ;tically 
  

  

  monochromatic 
  bundle 
  of 
  rays 
  of 
  any 
  desired 
  colour. 
  The 
  

   extremes 
  of 
  the 
  bundle 
  differed 
  in 
  wave-length 
  usually 
  by 
  

   about 
  10 
  [if!. 
  These 
  rays 
  passed 
  successively 
  through 
  an 
  

   achromatic 
  lens 
  L 
  2 
  , 
  a 
  polarizing 
  prism 
  P, 
  the 
  film 
  F 
  (placed 
  

   between 
  the 
  magnet-poles), 
  and 
  the 
  Lippich 
  half-shade 
  

   analysing 
  pair 
  A 
  1 
  and 
  A, 
  which 
  were 
  mounted 
  in 
  the 
  axis 
  of 
  

   a 
  graduated 
  circle. 
  A 
  viewing 
  telescope 
  focussed 
  on 
  the 
  

   edge 
  of 
  the 
  half 
  nicol 
  Ai 
  completed 
  the 
  optical 
  system. 
  

   Settings 
  were 
  made 
  by 
  rotating 
  the 
  analysing 
  pair 
  (fixed 
  

   relative 
  to 
  each 
  other) 
  until 
  the 
  customary 
  match 
  w 
  T 
  as 
  

   obtained. 
  

  

  