﻿258 
  Hood 
  — 
  Color-vision 
  and 
  the 
  Flicker 
  Photometer. 
  

  

  Akt. 
  XXYIII. 
  — 
  On 
  Color-vision 
  and 
  the 
  Flicker 
  Photometer 
  ; 
  

   by 
  Ogden 
  N. 
  Eood, 
  Professor 
  of 
  Physics 
  in 
  Columbia 
  

   University. 
  Part 
  I. 
  

  

  In 
  the 
  matter 
  of 
  color-vision, 
  there 
  seems 
  to 
  have 
  been 
  a 
  

   tacit 
  assumption 
  that 
  all 
  persons 
  could 
  be 
  divided 
  into 
  two 
  

   classes, 
  those 
  with 
  normal 
  vision, 
  and 
  the 
  color-blind. 
  Holm- 
  

   siren's 
  test 
  with 
  colored 
  worsted 
  classifies 
  them 
  in 
  this 
  way, 
  

   and 
  analogous 
  tests 
  give 
  a 
  like 
  result. 
  According 
  to 
  this 
  view, 
  

   the 
  col 
  or- 
  vision 
  of 
  persons 
  free 
  from 
  color 
  blindness 
  has 
  gen- 
  

   erally 
  been 
  considered 
  to 
  be 
  alike. 
  Some 
  time 
  ago, 
  for 
  the 
  

   purpose 
  of 
  comparing 
  my 
  own 
  color-vision 
  with 
  that 
  of 
  others, 
  

   an 
  extensive 
  set 
  of 
  experiments 
  were 
  made 
  with 
  the 
  flicker 
  

   photometer,"^ 
  and 
  while 
  it 
  turned 
  out 
  that 
  not 
  a 
  single 
  person 
  

   agreed 
  with 
  me^ 
  it 
  also 
  was 
  found 
  that 
  no 
  two 
  persons 
  agreed 
  

   with 
  eacli 
  other. 
  These 
  divergences 
  were 
  so 
  large 
  that 
  it 
  was 
  

   impossible 
  to 
  attribute 
  them 
  to 
  errors 
  of 
  observation, 
  and 
  the 
  

   application 
  to 
  them 
  of 
  a 
  control 
  method 
  showed 
  them 
  to 
  

   have 
  a 
  real 
  existence. 
  

  

  In 
  making 
  these 
  determinations 
  eleven 
  persons 
  were 
  finally 
  

   selected, 
  most 
  of 
  them 
  being 
  young 
  men, 
  and 
  all 
  of 
  them 
  

   having 
  claims 
  to 
  the 
  possession 
  of 
  normal 
  vision 
  or 
  varieties 
  of 
  

   it. 
  Two 
  were 
  yonng 
  women, 
  and 
  two, 
  men 
  in 
  middle 
  life. 
  I 
  

   started 
  originally 
  with 
  fourteen 
  persons, 
  but 
  was 
  quickly 
  

   obliged 
  to 
  reject 
  three 
  for 
  previously 
  unsuspected 
  abnormality 
  : 
  

   two 
  of 
  these 
  cases 
  will 
  be 
  considered 
  at 
  the 
  close 
  of 
  this 
  article; 
  

   the 
  third, 
  which 
  is 
  peculiar, 
  is 
  still 
  nnder 
  investigation. 
  In 
  

   comparing 
  the 
  eleven 
  selected 
  persons 
  with 
  myself, 
  it 
  was 
  soon 
  

   found 
  that 
  they 
  could 
  be 
  divided 
  into 
  two 
  classes 
  with 
  regard 
  

   to 
  their 
  preception 
  of 
  green, 
  five 
  in 
  one, 
  six 
  in 
  the 
  other, 
  but 
  

   as 
  far 
  as 
  I 
  could 
  see, 
  there 
  was 
  no 
  especial 
  reason 
  for 
  giving 
  

   preference 
  to 
  one 
  class 
  above 
  the 
  other. 
  It 
  was 
  accordingly 
  

   decided 
  to 
  adopt 
  the 
  mean 
  color-vision 
  of 
  the 
  eleven, 
  as 
  repre- 
  

   senting, 
  for 
  the 
  time 
  being, 
  standard 
  human 
  vision 
  for 
  color, 
  

   and 
  the 
  divergence 
  of 
  each 
  person 
  from 
  this 
  standard 
  was 
  

   then 
  calculated. 
  

  

  This 
  standard 
  color- 
  vision 
  is 
  conveniently 
  indicated 
  by 
  100, 
  

   in 
  the 
  cases 
  of 
  red, 
  green 
  and 
  violet-blue 
  light. 
  100 
  was 
  also 
  

   taken 
  as 
  the 
  maximum 
  attainable 
  in 
  each 
  case, 
  as 
  these 
  experi- 
  

   ments 
  did 
  not 
  deal 
  with 
  the 
  general 
  sensitiveness 
  of 
  the 
  eye 
  to 
  

   light, 
  but 
  with 
  its 
  relative 
  sensitiveness 
  to 
  light 
  of 
  different 
  

   colors. 
  That 
  is 
  to 
  say. 
  in 
  the 
  case 
  of 
  the 
  color-curve 
  of 
  each 
  

   person, 
  the 
  highest 
  ordinate, 
  whatever 
  it 
  may 
  be, 
  is 
  set 
  equal 
  

   to 
  100, 
  the 
  others 
  falling 
  where 
  the 
  observations 
  indicate 
  on 
  

   this 
  assumption. 
  Indeed 
  there 
  is 
  no 
  other 
  way 
  of 
  making 
  the 
  

  

  *See 
  this 
  Journal, 
  Sept. 
  1899, 
  p. 
  194. 
  

  

  