﻿the 
  Velocity 
  of 
  Light. 
  333 
  

  

  cannot 
  be 
  far 
  from 
  the 
  truth. 
  The 
  authors 
  conclude 
  as 
  

   follows 
  : 
  

  

  "lis 
  (ces 
  valeurs) 
  sont 
  sensiblements 
  egaux 
  au 
  rapport 
  

   des 
  unites 
  electromagnetique 
  et 
  electrostatique 
  de 
  quantite 
  

   dVleetricite, 
  comme 
  la 
  theorie 
  de 
  Maxwell 
  Pindique, 
  et 
  aussi 
  

   a 
  la 
  vitesse 
  de 
  la 
  lumiere. 
  II 
  y 
  a 
  un 
  inter 
  et 
  capital 
  a 
  rechercher 
  

   si 
  cette 
  egalite 
  des 
  trois 
  nombres 
  est 
  settlement 
  approximative, 
  

   ou 
  si 
  elle 
  ofFre 
  un 
  caractere 
  absolu 
  ; 
  on 
  devra 
  done 
  s'efforcer, 
  

   dans 
  les 
  determinations 
  ulterieures 
  de 
  la 
  vitesse 
  de 
  propaga- 
  

   tion 
  des 
  ondes 
  electromagnetiques, 
  non 
  seulement 
  d'atteindre 
  

   la 
  plus 
  grande 
  exactitude 
  possible, 
  mais 
  aussi 
  de 
  determiner 
  le 
  

   degre 
  d'approximation 
  des 
  nombres 
  obtenus." 
  

  

  It 
  would 
  appear, 
  then, 
  that 
  there 
  is 
  but 
  little 
  doubt 
  that 
  in 
  

   the 
  near 
  future 
  both 
  these 
  determinations 
  will 
  be 
  made 
  with 
  

   at 
  least 
  the 
  same 
  high 
  order 
  of 
  accuracy 
  as 
  obtains 
  in 
  the 
  

   measurement 
  of 
  the 
  velocity 
  of 
  light. 
  In 
  this 
  case, 
  any 
  

   possible 
  difference 
  in 
  the 
  resulting 
  values 
  would 
  not 
  cast 
  any 
  

   doubt 
  upon 
  the 
  electromagnetic 
  theory, 
  but 
  would 
  doubtless 
  

   be 
  traceable 
  to 
  the 
  enormous 
  difference 
  in 
  the 
  conditions 
  

   determined 
  by 
  light-waves 
  on 
  the 
  one 
  hand, 
  and 
  electric 
  

   oscillations 
  or 
  static 
  charges 
  on 
  the 
  other. 
  On 
  the 
  contrary, 
  

   such 
  a 
  difference 
  might 
  almost 
  certainly 
  be 
  predicted, 
  and 
  

   would 
  probably 
  throw 
  much 
  light 
  on 
  the 
  structure 
  and 
  mode 
  

   of 
  action 
  of 
  dielectrics. 
  

  

  Having 
  reviewed 
  in 
  some 
  detail 
  the 
  order 
  of 
  accuracy 
  

   attained 
  in 
  the 
  astronomical 
  elements 
  which 
  are 
  to 
  be 
  com- 
  

   bined 
  with 
  V, 
  and 
  the 
  electromagnetic 
  results 
  which 
  are 
  to 
  

   be 
  compared 
  with 
  Y, 
  let 
  us 
  consider 
  the 
  actual 
  order 
  of 
  

   accuracy 
  obtained 
  in 
  the 
  measurement 
  of 
  Y 
  itself. 
  

  

  Concerning 
  this, 
  as 
  in 
  the 
  cases 
  just 
  reviewed, 
  a 
  con- 
  

   siderable 
  diversity 
  of 
  opinion 
  will 
  prevail 
  concerning 
  the 
  

   relative 
  weight 
  which 
  should 
  be 
  attributed 
  to 
  the 
  various 
  

   determinations. 
  

  

  The 
  following 
  table 
  is 
  taken 
  from 
  Professor 
  Newcomb's 
  

   report 
  : 
  

  

  (1) 
  Foucault, 
  1862 
  298,000 
  

  

  (2) 
  Corau 
  (I), 
  1874 
  298,500 
  

  

  (3) 
  Cornu 
  (2), 
  1878 
  300,100 
  

  

  (4) 
  Cornu 
  (2) 
  as 
  discussed 
  by 
  Listing 
  ... 
  299,990 
  

  

  (5) 
  Young 
  and 
  Forbes, 
  1880-^1 
  301,382 
  

  

  (6) 
  Michelson 
  (1) 
  299,910 
  

  

  (7) 
  Michelson 
  (2)... 
  299,853 
  

  

  (8) 
  Newcomb 
  (selected 
  results) 
  299,860 
  

  

  (9) 
  Newcomb 
  (all 
  observations) 
  299,810 
  

  

  There 
  is 
  no 
  doubt 
  that 
  the 
  weights 
  which 
  should 
  be 
  assigned 
  

  

  