﻿International 
  Unit 
  of 
  Candle 
  Power, 
  269" 
  

  

  electric 
  lamps 
  which 
  have 
  been 
  measured 
  at 
  some 
  or 
  all 
  

   of 
  the 
  laboratories. 
  These 
  have 
  been 
  chiefly 
  initiated 
  by 
  the 
  

   Americans, 
  who 
  have 
  from 
  time 
  to 
  time 
  sent 
  sets 
  of 
  lamps 
  

   to 
  Europe 
  to 
  have 
  values 
  assigned 
  in 
  London, 
  Paris, 
  and 
  

   Berlin. 
  It 
  is 
  not 
  suggested 
  that 
  all 
  the 
  results 
  given 
  in 
  the 
  

   Table 
  should 
  receive 
  equal 
  weight. 
  In 
  some 
  of 
  the 
  electric 
  

   comparisons 
  the 
  conditions 
  allowed 
  of 
  a 
  greater 
  accuracy 
  

   than 
  in 
  others, 
  when 
  fewer 
  lamps 
  were 
  employed 
  and 
  

   time 
  only 
  allowed 
  a 
  single 
  set 
  of 
  measurements 
  to 
  be 
  

   made. 
  

  

  Columns 
  10^ 
  11, 
  and 
  12 
  contain 
  the 
  values 
  which 
  resulted 
  

   from 
  the 
  intercomparison 
  of 
  flame-standards 
  undertaken 
  at 
  

   each 
  of 
  the 
  laboratories. 
  These 
  were 
  initiated 
  by 
  the 
  Inter- 
  

   national 
  Commission 
  on 
  Photometry 
  and 
  gave 
  a 
  set 
  of 
  ratios 
  

   which 
  brouoht 
  the 
  knowledoe 
  of 
  the 
  relative 
  values 
  of 
  the 
  

   candle 
  power 
  units 
  to 
  within 
  an 
  accuracy 
  of 
  about 
  + 
  or 
  ~1 
  

   per 
  cent. 
  As 
  in 
  the 
  case 
  of 
  the 
  electric 
  comparisons, 
  the 
  

   conditions 
  in 
  some 
  cases 
  probably 
  allowed 
  of 
  a 
  higher 
  

   accuracy 
  than 
  in 
  others 
  — 
  but 
  the 
  results 
  of 
  all 
  the 
  measure- 
  

   ments 
  have 
  been 
  tabulated 
  in 
  order 
  that 
  the 
  bearing 
  may 
  be 
  

   seen 
  of 
  each 
  on 
  the 
  agreement 
  which 
  has 
  been 
  established. 
  

  

  The 
  first 
  series 
  of 
  ratios 
  (columns 
  1 
  to 
  9) 
  may 
  therefore 
  

   be 
  regarded 
  as 
  representing 
  the 
  ratios 
  of 
  the 
  standards 
  as 
  

   they 
  are 
  interpreted 
  in 
  the 
  countries 
  to 
  which 
  they 
  belong, 
  

   whilst 
  in 
  the 
  second 
  series 
  we 
  have 
  the 
  interpretation 
  of 
  the 
  

   values 
  of 
  the 
  standard 
  lamps 
  by 
  experimenters 
  who 
  are 
  not 
  

   so 
  accustomed 
  to 
  their 
  manipulation. 
  

  

  Lines 
  marked 
  A 
  B, 
  C, 
  give 
  the 
  values 
  of 
  the 
  standards 
  in 
  

   terms 
  of 
  the 
  Pentane 
  unit. 
  D, 
  E, 
  F, 
  give 
  them 
  in 
  terms 
  

   of 
  the 
  Hefner 
  and 
  similarly 
  other 
  sets 
  are 
  in 
  terms 
  of 
  the 
  

   Bougie 
  Decimale 
  and 
  the 
  Bureau 
  of 
  Standards 
  Candle. 
  

  

  Without 
  going 
  into 
  detailed 
  comments 
  upon 
  the 
  experi- 
  

   ments 
  from 
  which 
  each 
  ratio 
  in 
  the 
  table 
  is 
  derived 
  it 
  will 
  

   suffice 
  to 
  say 
  that 
  as 
  far 
  as 
  the 
  electric 
  lamp 
  comparisons 
  are 
  

   concerned, 
  greatest 
  stress 
  should 
  be 
  laid 
  on 
  the 
  results 
  in 
  

   columns 
  4 
  and 
  7. 
  This 
  is 
  partly 
  on 
  account 
  of 
  the 
  large 
  

   number 
  of 
  lamps 
  employed, 
  and 
  also 
  because 
  of 
  the 
  more 
  

   prolonged 
  measurements 
  made. 
  Line 
  J 
  illustrates 
  the 
  high 
  

   accuracy 
  it 
  is 
  possible 
  to 
  secure 
  in 
  comparisons 
  of 
  this 
  

   nature. 
  

  

  In 
  the 
  certification 
  of 
  glow-lamps 
  in 
  terms 
  of 
  the 
  Hefner 
  

   Unit 
  the 
  Peichsanstalt 
  only 
  give 
  candle-power 
  values 
  to 
  the 
  

   nearest 
  one 
  per 
  cent. 
  If 
  the 
  average 
  of 
  10 
  or 
  12 
  lamps 
  is 
  

   taken 
  the 
  error 
  thus 
  introduced 
  is 
  probably 
  not 
  great, 
  but 
  

   w^hen 
  the 
  number 
  in 
  small, 
  appreciable 
  inaccuracies 
  may 
  be 
  

   introduced 
  into 
  the 
  mean, 
  and 
  the 
  rather 
  low 
  value 
  obtained 
  

  

  