﻿Properties 
  of 
  Films 
  of 
  Magnetic 
  Metals. 
  835 
  

  

  In 
  those 
  cases 
  where 
  the 
  current 
  was 
  adjusted 
  to 
  a 
  

   magnitude 
  such 
  that 
  a 
  film 
  of 
  the 
  desired 
  opacity 
  was 
  

   produced 
  in 
  two 
  to 
  four 
  hours, 
  the 
  appearance 
  of 
  the 
  film, 
  

   as 
  also 
  its 
  optical 
  characteristics, 
  was 
  very 
  different 
  from 
  

   those 
  produced 
  in 
  a 
  few 
  seconds 
  on 
  raising 
  the 
  cathode 
  to 
  a 
  

   white 
  heat 
  by 
  cutting 
  resistance 
  out 
  of 
  the 
  circuit. 
  These 
  

   latter 
  films 
  appear 
  by 
  reflected 
  light 
  as 
  perfect 
  metallic 
  

   mirrors, 
  while 
  the 
  former 
  are 
  much 
  like 
  polished 
  dark 
  glass. 
  

   The 
  latter 
  are 
  very 
  hard, 
  and 
  seem 
  to 
  be 
  fused 
  on 
  to 
  the 
  

   glass 
  ; 
  while 
  the 
  former 
  are 
  soft 
  and 
  brittle, 
  lacking 
  the 
  

   coherence 
  of 
  fused 
  iron. 
  For 
  the 
  same 
  opacity 
  the 
  metallic 
  

   films 
  are 
  strikingly 
  thinner 
  than 
  the 
  dark 
  ones, 
  being 
  too 
  

   thin 
  to 
  show 
  the 
  least 
  trace 
  of 
  interference-fringes, 
  while 
  

   with 
  the 
  dark 
  these 
  may 
  be 
  very 
  distinct. 
  The 
  metallic 
  

   films 
  impart 
  no 
  tint 
  to 
  transmitted 
  light 
  ; 
  the 
  dark 
  appear 
  a 
  

   yellow-brown 
  arising 
  from 
  a 
  marked 
  relative 
  absorption 
  of 
  

   the 
  shorter 
  waves. 
  When 
  deposited 
  in 
  hydrogen 
  the 
  metallic 
  

   type 
  absorb 
  the 
  gas 
  at 
  a 
  remarkable 
  rate 
  even 
  for 
  some 
  time 
  

   after 
  the 
  current 
  is 
  broken 
  *; 
  but 
  the 
  dark, 
  which 
  exhibit 
  like 
  

   properties 
  whether 
  deposited 
  in 
  hydrogen 
  or 
  helium, 
  take 
  up 
  

   no 
  observable 
  quantity 
  of 
  the 
  gas 
  either 
  during 
  or 
  after 
  the 
  

   process 
  of 
  deposition. 
  For 
  this 
  reason 
  the 
  exceptional 
  

   properties 
  of 
  the 
  dark 
  films 
  must 
  be 
  ascribed 
  to 
  the 
  form 
  

   in 
  which 
  the 
  metal 
  is 
  deposited, 
  and 
  not 
  to 
  a 
  chemical 
  

   combination 
  of 
  the 
  metal 
  with 
  the 
  gas. 
  

  

  In 
  a 
  few 
  cases 
  films 
  were 
  obtained 
  which 
  exhibited 
  optical 
  

   properties 
  intermediate 
  between 
  those 
  of 
  the 
  two 
  types 
  

   described 
  ; 
  but 
  since 
  these 
  appeared 
  to 
  be 
  made 
  up 
  of 
  layers 
  

   of 
  different 
  hardness, 
  and 
  the 
  conditions 
  of 
  deposit 
  were 
  

   such 
  as 
  made 
  it 
  likely, 
  we 
  conclude 
  that 
  they 
  were 
  simply 
  a 
  

   mixture 
  of 
  the 
  two 
  already 
  described 
  f 
  . 
  

  

  Films 
  were 
  also 
  deposited 
  electrolytically 
  from 
  a 
  solution 
  of 
  

   ferrous 
  ammonium 
  sulphate 
  on 
  glass 
  platinized 
  according 
  to 
  

   the 
  method 
  of 
  Kundt. 
  The 
  appearance 
  of 
  these 
  is 
  like 
  that 
  

   of 
  the 
  metallic 
  type 
  of 
  cathode 
  film. 
  

  

  Cobalt. 
  — 
  Three 
  types 
  of 
  cobalt 
  films 
  were 
  readily 
  produced 
  

   in 
  the 
  same 
  way 
  as 
  the 
  corresponding 
  ones 
  of 
  iron. 
  They 
  are 
  

   similar 
  in 
  appearance 
  to 
  the 
  iron. 
  They 
  differ 
  greatly 
  in 
  their 
  

  

  * 
  See 
  W. 
  Heald, 
  Phys. 
  Eev. 
  xxiv. 
  p. 
  269. 
  

  

  t 
  To 
  this 
  mixed 
  type 
  belong, 
  to 
  all 
  appearances, 
  those 
  obtained 
  by 
  

   Harris 
  (I. 
  c.) 
  in 
  hydrogen 
  : 
  while 
  those 
  he 
  deposited 
  in 
  nitrogen 
  belong- 
  

   to 
  that 
  designated 
  here 
  as 
  dark 
  (arising 
  probably 
  from 
  less 
  heating 
  of 
  the 
  

   cathode 
  in 
  nitrogen). 
  Hence 
  the 
  variation 
  which 
  Harris 
  ascribes 
  to 
  a 
  

   change 
  in 
  the 
  kind 
  of 
  gas 
  was 
  caused 
  in 
  fact 
  by 
  the 
  consequent 
  change 
  

   in 
  the 
  temperature 
  of 
  the 
  cathode. 
  This, 
  however, 
  does 
  not 
  explain 
  the 
  

   characteristics 
  exhibited 
  by 
  the 
  films 
  which 
  he 
  deposited 
  in 
  oxysren. 
  

   These 
  were 
  probablv 
  largely 
  oxidized 
  in 
  the 
  process 
  of 
  deposition. 
  

  

  312 
  

  

  