﻿International 
  Unit 
  of 
  Candle 
  Power, 
  265», 
  

  

  of 
  the 
  flame 
  *. 
  Two 
  standards 
  will 
  not 
  necessarily 
  diminish 
  

   in 
  Candle 
  Power 
  at 
  the 
  same 
  rate, 
  and 
  it 
  is 
  therefore 
  neces- 
  

   sary 
  to 
  take 
  readings 
  after 
  the 
  air 
  of 
  the 
  room 
  has 
  been 
  

   changed 
  and 
  before 
  the 
  C.P. 
  of 
  the 
  lamps 
  has 
  had 
  time 
  

   to 
  be 
  affected. 
  The 
  method 
  of 
  measuring 
  humidity 
  must 
  

   therefore 
  be 
  a 
  rapid 
  one, 
  and 
  it 
  is 
  now 
  generally 
  agreed 
  that 
  

   from 
  considerations 
  of 
  accuracy 
  and 
  quickness 
  of 
  reading 
  

   the 
  ventilated 
  hygrometer 
  is 
  the 
  best 
  instrument 
  to 
  use 
  f. 
  

   In 
  the 
  German 
  and 
  French 
  comparisons 
  this 
  has 
  been 
  

   used, 
  but 
  in 
  the 
  English 
  comparisons 
  (as 
  reported 
  to 
  the 
  

   Photometric 
  Commission 
  meeting 
  in 
  Zurich 
  in 
  1907) 
  the 
  

   unventilated 
  hygrometer 
  was 
  employed 
  {, 
  and 
  in 
  the 
  tables 
  

   published 
  in 
  the 
  proceeding's 
  of 
  the 
  Commission 
  the 
  author's 
  

   results 
  are 
  given 
  in 
  terms 
  of 
  humidity 
  measured 
  by 
  this 
  

   instrument. 
  The 
  ratios 
  tabulated 
  in 
  the 
  present 
  paper 
  are 
  

   corrected 
  so 
  as 
  to 
  be 
  in 
  terms 
  of 
  the 
  ventilated 
  hygrometer. 
  

   In 
  each 
  case 
  values 
  are 
  taken 
  for 
  tbe 
  humidity 
  at 
  which 
  each 
  

   lamp, 
  in 
  the 
  country 
  where 
  it 
  forms 
  the 
  standard, 
  is 
  con- 
  

   sidered 
  to 
  give 
  its 
  nominal 
  Candle 
  Power. 
  

  

  The 
  Unit 
  of 
  the 
  United 
  States 
  of 
  America. 
  — 
  In 
  the 
  initial 
  

   adoption 
  of 
  a 
  unit 
  of 
  Candle 
  Power 
  the 
  United 
  States 
  of 
  

   America 
  endeavoured 
  to 
  make 
  its 
  value 
  as 
  nearly 
  as 
  possible 
  

   the 
  same 
  as 
  that 
  accepted 
  at 
  the 
  time 
  in 
  this 
  country 
  §. 
  

   This 
  was 
  before 
  Prof. 
  Vernon 
  Harcourt 
  and 
  the 
  Metropolitan 
  

   Gas 
  Referees 
  (London) 
  had 
  established 
  the 
  10 
  Candle 
  Pentane 
  

   Lamp 
  on 
  the 
  present 
  definite 
  basis. 
  

  

  The 
  American 
  Inst, 
  of 
  Electrical 
  Engineers 
  recommended 
  

   the 
  derivation 
  of 
  their 
  unit 
  from 
  the 
  Hefner 
  Lamp 
  by 
  in- 
  

   creasing 
  its 
  value 
  in 
  the 
  ratio 
  of 
  0' 
  88 
  to 
  1. 
  This 
  seemed 
  at 
  

   the 
  time, 
  from 
  different 
  observers' 
  work, 
  to 
  be 
  the 
  most 
  

   probable 
  ratio 
  between 
  the 
  Hefner 
  and 
  British 
  units. 
  The 
  

   gas 
  industry 
  in 
  America, 
  however, 
  did 
  not 
  follow 
  this 
  course 
  

   but 
  developed 
  their 
  unit 
  along 
  the 
  lines 
  of 
  the 
  10 
  Candle 
  

   Pentane 
  Lamp 
  || 
  . 
  The 
  result 
  is 
  that 
  there 
  has 
  been, 
  up 
  

   to 
  now, 
  an 
  appreciable 
  difference 
  between 
  the 
  units 
  adopted 
  

   in 
  the 
  two 
  industries 
  in 
  that 
  country. 
  The 
  Illuminating 
  

  

  * 
  Eeport 
  Arner. 
  Gas 
  Inst., 
  " 
  Methods 
  of 
  taking 
  C.P. 
  of 
  Gas," 
  Ilium. 
  

   Eng. 
  1909, 
  p. 
  203. 
  

  

  t 
  Proc. 
  Roy. 
  Soc. 
  Edinburgh, 
  vol. 
  xliii., 
  1905 
  ; 
  also 
  " 
  Zur 
  kenntniss 
  des 
  

   Ventilierten 
  Psychrometers," 
  Akademische 
  Abhandlung 
  der 
  Fakultat 
  

   der 
  Universitat 
  zu 
  Upsala, 
  by 
  Aron 
  Svensson, 
  1898. 
  

  

  X 
  See 
  B.A. 
  Pteport, 
  Dublin, 
  1908. 
  

  

  § 
  Bulletin 
  of 
  the 
  Bureau 
  of 
  Standards, 
  vol. 
  iii., 
  no. 
  1, 
  p. 
  65 
  ; 
  Report 
  to 
  

   the 
  American 
  Gas 
  Institute 
  on 
  "A 
  Unit 
  of 
  Light," 
  Journal 
  of 
  Gas 
  

   Lighting, 
  vol. 
  104, 
  1908, 
  p. 
  426. 
  

  

  ll 
  " 
  The 
  VVorking 
  Standards 
  of 
  Light 
  and 
  their 
  Use 
  in 
  the 
  Photometry 
  

   of 
  Gas," 
  Ch. 
  O. 
  Bond, 
  Franklin 
  Inst. 
  1908. 
  

  

  