﻿THE 
  CENTENAKY 
  OF 
  AUGUSTIN 
  FRESNEL^ 
  

  

  By 
  E.-M. 
  Antoniaui 
  

  

  [AVilh 
  1 
  i)l!ito] 
  

  

  This 
  illusfcrious 
  man 
  is 
  the 
  dominant 
  figure 
  in 
  optics. 
  Tlie 
  success 
  

   of 
  his 
  attacks 
  upon 
  the 
  problems 
  connected 
  with 
  light 
  has 
  been 
  with- 
  

   out 
  equal. 
  He 
  succeeded 
  where 
  Newton 
  failed 
  and 
  made 
  clear 
  the 
  

   mysterious 
  nature 
  of 
  light. 
  

  

  Augustin-Jean 
  Fresnel 
  w'as 
  born 
  at 
  Broglie, 
  in 
  the 
  Province 
  of 
  

   Normandy 
  (Eure), 
  on 
  May 
  10, 
  1788. 
  As 
  a 
  child 
  he 
  gave 
  signs 
  of 
  

   his 
  predilection 
  for 
  the 
  sciences, 
  and 
  at 
  the 
  age 
  of 
  16 
  he 
  entered 
  the 
  

   Ecole 
  Polytechnique, 
  in 
  Paris, 
  later 
  finishing 
  his 
  training 
  as 
  an 
  engi- 
  

   neer 
  at 
  the 
  Ponts 
  et 
  Chaussees. 
  In 
  1815, 
  upon 
  the 
  return 
  of 
  the 
  

   Emperor 
  from 
  the 
  island 
  of 
  Elba, 
  he 
  declared 
  his 
  allegiance 
  to 
  the 
  

   Bourbons, 
  passing 
  the 
  "one 
  hundred 
  days" 
  in 
  a 
  quiet 
  retreat 
  in 
  

   scientific 
  meditation. 
  

  

  Before 
  considering 
  the 
  scientific 
  work 
  of 
  Fresnel 
  we 
  should 
  exam- 
  

   ine 
  the 
  optical 
  theories 
  prevalent 
  when 
  he 
  entered 
  the 
  field. 
  Empe- 
  

   docles 
  in 
  ancient 
  times 
  was 
  the 
  first 
  to 
  conceive 
  the 
  idea 
  that 
  the 
  

   propagation 
  of 
  light 
  was 
  not 
  instantiineous, 
  a 
  fact 
  which 
  Roemer 
  

   demonstrated 
  in 
  masterly 
  fashion 
  at 
  the 
  Observatory 
  of 
  Paris 
  in 
  

   1675. 
  Twenty-four 
  centuries 
  ago 
  Democritus, 
  the 
  founder 
  of 
  the 
  

   atomic 
  theory, 
  considering 
  the 
  very 
  essence 
  of 
  light, 
  attributed 
  it 
  to 
  

   very 
  tenuous 
  particles 
  shot 
  out 
  from 
  the 
  luminous 
  body. 
  This 
  was 
  

   the 
  origin 
  of 
  the 
  emission 
  theory 
  adopted 
  by 
  Newton 
  in 
  the 
  seven- 
  

   teenth 
  centur}', 
  following 
  his 
  celebrated 
  experiment 
  upon 
  the 
  decom- 
  

   position 
  of 
  light 
  in 
  passing 
  through 
  a 
  prism. 
  Already, 
  however, 
  

   Leonardo 
  da 
  Vinci, 
  in 
  the 
  fifteenth 
  century, 
  and 
  subsequently 
  Male- 
  

   branche 
  and 
  Hooke, 
  of 
  the 
  time 
  of 
  Newton, 
  had 
  had 
  a 
  glimpse 
  of 
  the 
  

   undulatory 
  nature 
  of 
  light. 
  Huyghens 
  further 
  developed 
  this 
  idea 
  

   and 
  studied 
  the 
  course 
  of 
  light 
  rays 
  through 
  birefringent 
  crys- 
  

   tals. 
  He 
  developed 
  his 
  famous 
  law, 
  and 
  as 
  a 
  medium 
  in 
  which 
  the 
  

   rays 
  of 
  light 
  might 
  be 
  propagated 
  brought 
  out 
  the 
  idea 
  of 
  the 
  ether, 
  

   an 
  ideal 
  substance, 
  so 
  to 
  speak, 
  of 
  extreme 
  rarefaction 
  and 
  with 
  

   which 
  the 
  ancients 
  believed 
  the 
  whole 
  universe 
  to 
  be 
  filled.- 
  

  

  ' 
  Translated 
  by 
  permission 
  from 
  L'Astronomie, 
  Paris, 
  June. 
  1927. 
  

  

  = 
  That 
  is 
  tbe 
  a-rctpm 
  ai!),)p, 
  the 
  iufmite 
  ether 
  of 
  Ileraclides 
  of 
  I'ontus 
  and 
  of 
  the 
  Pythago- 
  

   reans, 
  the 
  real 
  discoverers 
  of 
  the 
  heliocentric 
  system 
  of 
  the 
  universe 
  2,000 
  years 
  before 
  

   Copernicus 
  (Stob^e, 
  Physics 
  I, 
  24). 
  

  

  217 
  

  

  