﻿AUGUSTIN" 
  FEESNEL 
  ANTONIADI 
  219 
  

  

  of 
  light 
  but 
  allows 
  the 
  economical 
  construction 
  of 
  a 
  lens 
  of 
  2:reat 
  

   size 
  from 
  glass 
  segments 
  of 
  relativel}^ 
  small 
  size 
  in 
  juxtaposition. 
  

   The 
  lamps 
  constructed 
  with 
  Fresnel 
  concentric 
  wicks 
  were 
  twenty- 
  

   five 
  times 
  more 
  brilliant 
  than 
  those 
  then 
  in 
  use. 
  These 
  inventions, 
  

   however, 
  were 
  only 
  incidents 
  in 
  his 
  career. 
  

  

  He 
  independently 
  rediscovered 
  the 
  phenomenon 
  of 
  interference 
  

   and 
  at 
  once 
  tried 
  to 
  apply 
  it 
  to 
  the 
  explanation 
  of 
  phenomena 
  of 
  

   refraction 
  in 
  the 
  wave 
  theory. 
  His 
  success 
  was 
  complete; 
  but 
  learn- 
  

   ing 
  that 
  Young 
  preceded 
  him, 
  Fresnel, 
  a 
  scientific 
  hero, 
  retracted 
  

   any 
  claim 
  to 
  the 
  discovery.^ 
  Later 
  he 
  was 
  to 
  come 
  in 
  ahead 
  of 
  

   Young. 
  Let 
  us 
  note 
  here 
  that 
  there 
  is 
  no 
  parallel 
  to 
  be 
  drawn 
  

   between 
  the 
  case 
  of 
  Young 
  and 
  Fresnel 
  on 
  the 
  one 
  hand, 
  and 
  that 
  of 
  

   Adams 
  and 
  Le 
  Verrier 
  on 
  the 
  other. 
  For 
  Young, 
  self-taught, 
  was 
  a 
  

   A''ery 
  great 
  man, 
  who 
  had 
  distinguished 
  himself 
  by 
  the 
  publication 
  

   of 
  original 
  and 
  splendid 
  researches; 
  whereas 
  the 
  remarkable 
  mathe- 
  

   matical 
  discovery 
  of 
  Neptune 
  was 
  wholly 
  due 
  to 
  the 
  genius 
  of 
  Le 
  

   Verrier, 
  who 
  shares 
  the 
  glory 
  with 
  no 
  one. 
  

  

  Differently 
  from 
  Young, 
  who 
  considered 
  luminous 
  waves 
  to 
  be 
  

   longitudinal 
  like 
  those 
  of 
  sound, 
  Fresnel 
  introduced 
  for 
  the 
  first 
  time 
  

   the 
  fundamental 
  conception 
  of 
  transverse 
  vibrations 
  of 
  the 
  ether, 
  that 
  

   corner 
  stone 
  of 
  the 
  undulatory 
  theory 
  of 
  light. 
  

  

  He 
  proved 
  that 
  certain 
  biref 
  ringent 
  crystals 
  did 
  not 
  follow 
  the 
  law 
  

   of 
  refraction 
  of 
  Snell 
  and 
  Descartes 
  and 
  formulated 
  the 
  true 
  law. 
  

   He 
  showed 
  the 
  possibility 
  of 
  producing 
  double 
  refraction 
  by 
  pressure 
  

   in 
  glass 
  prisms 
  which 
  ordinarily 
  do 
  not 
  show 
  it. 
  The 
  knowledge 
  

   of 
  that 
  time 
  was 
  greatly 
  extended 
  and 
  developed 
  by 
  his 
  researches 
  

   upon 
  the 
  phenomena 
  of 
  interference. 
  With 
  Arago, 
  he 
  brought 
  to 
  

   light 
  the 
  modification 
  in 
  interference 
  in 
  the 
  case 
  of 
  two 
  rays 
  polarized 
  

   in 
  different 
  azimuths. 
  Then 
  he 
  found 
  the 
  lav/ 
  of 
  the 
  phenomenon 
  

   shown 
  by 
  the 
  colors 
  of 
  thin 
  plates 
  of 
  doubly 
  refracting 
  crystals. 
  

   The 
  discovery 
  of 
  chromatic 
  polarization 
  by 
  Arago 
  was 
  completed 
  by 
  

   Fresnel 
  by 
  that 
  of 
  circular 
  polarization. 
  Finally, 
  his 
  experiment 
  

   with 
  two 
  mirrors 
  giving 
  interference 
  fringes, 
  alternately 
  dark 
  and 
  

   bright, 
  is 
  classic. 
  

  

  Young, 
  like 
  Huyghens 
  and 
  Euler, 
  could 
  not 
  reply 
  to 
  the 
  crucial 
  

   criticism 
  of 
  Newton 
  regarding 
  shadows. 
  It 
  needed 
  Fresnel's 
  genius. 
  

   Through 
  the 
  latter's 
  superior 
  mathematical 
  insight, 
  it 
  was 
  shown 
  that 
  

   the 
  inflection 
  which 
  Newton 
  supposed 
  should 
  exist 
  did 
  occur 
  behind 
  

   opaque 
  bodies, 
  but 
  that 
  the 
  divergent 
  waves 
  effaced 
  each 
  other, 
  

   giving 
  rise 
  to 
  shadows. 
  His 
  great 
  generalization 
  embraced 
  in 
  its 
  

   first 
  onslaught 
  all 
  the 
  phenomena 
  then 
  known; 
  further, 
  the 
  facts 
  

   discovered 
  by 
  Malus, 
  Arago, 
  Biot, 
  and 
  others 
  were 
  not 
  only 
  thor- 
  

   oughly 
  explained, 
  but 
  were 
  shown 
  to 
  be 
  a 
  necessary 
  consequence 
  of 
  

  

  ^ 
  In 
  1823 
  Young 
  wrote 
  that 
  Fresnel 
  had 
  recognized 
  " 
  with 
  the 
  most 
  scrupulous 
  justice 
  

   and 
  most 
  generous 
  candor 
  " 
  the 
  priority 
  of 
  his 
  colleague 
  upon 
  this 
  particular 
  point. 
  

  

  