﻿Colour* 
  by 
  Differential 
  Visual 
  Difusivky. 
  415 
  

  

  resistances 
  b. 
  The 
  light 
  from 
  these 
  lamps 
  passes 
  through 
  

   diaphragms 
  c 
  and 
  coloured 
  glasses 
  d 
  to 
  the 
  matte 
  white 
  

   screen 
  <?, 
  which 
  is 
  viewed 
  through 
  the 
  slit 
  /by 
  the 
  eye 
  at 
  h 
  y 
  

   after 
  being 
  reflected 
  from 
  the 
  mirror 
  g, 
  arranged 
  to 
  rotate 
  

  

  Fig. 
  1. 
  

  

  la 
  

  

  lb 
  

  

  1 
  a. 
  Stationary 
  slit 
  coloured 
  red 
  (r) 
  at 
  one 
  end, 
  blue 
  (b) 
  at 
  the 
  other, 
  

  

  and 
  the 
  purple 
  formed 
  by 
  their 
  mixture 
  {p) 
  in 
  the 
  middle. 
  

   1 
  b. 
  Appearance 
  of 
  slit 
  when 
  in 
  motion 
  in 
  the 
  direction 
  of 
  the 
  arrow. 
  

  

  about 
  a 
  vertical 
  axis. 
  At 
  j 
  are 
  movable 
  screens 
  of 
  short 
  

   vertical 
  length, 
  which 
  can 
  be 
  so 
  placed 
  that 
  either 
  top 
  or 
  

   bottom 
  of 
  the 
  screen 
  e 
  is 
  illuminated 
  by 
  one 
  colour 
  of 
  light 
  

   alone. 
  With 
  this 
  arrangement 
  it 
  is 
  possible 
  to 
  have 
  the 
  

   slit/ 
  appear 
  of 
  either 
  colour 
  given 
  by 
  the 
  glasses 
  at 
  d, 
  half 
  of 
  

   one 
  colour 
  and 
  half 
  of 
  ihe 
  other, 
  or 
  else 
  part 
  one 
  colour, 
  part 
  

   the 
  other 
  colour, 
  and 
  part 
  the 
  mixture 
  of 
  the 
  two 
  as 
  in 
  

   fig. 
  la. 
  

  

  3. 
  Jiesults 
  with 
  purple 
  light. 
  

  

  Four 
  possible 
  behaviours 
  of 
  the 
  purple 
  mixture 
  region 
  of 
  

   the 
  strip 
  shown 
  in 
  fig. 
  1 
  a 
  may 
  be 
  imagined. 
  On 
  lateral 
  

   movement 
  either 
  (1) 
  the 
  purple 
  may 
  move 
  bodily 
  as 
  the 
  red 
  

   constituent, 
  or 
  (2) 
  as 
  the 
  blue 
  constituent, 
  or 
  (3) 
  it 
  may 
  

   exhibit 
  an 
  intermediate 
  shift, 
  or 
  (4) 
  it 
  may 
  spread 
  out 
  into 
  

   red 
  and 
  blue. 
  Either 
  (1), 
  (2), 
  or 
  (3) 
  would 
  be 
  possible 
  

   interpretations 
  of 
  the 
  previous 
  trial. 
  

  

  