﻿220 
  ANNUAL 
  KErOKT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  the 
  undulatory 
  hypothesis. 
  Tliis 
  generalization 
  was 
  truly 
  impres- 
  

   sive. 
  Hamilton, 
  of 
  Dublin, 
  taking 
  up 
  the 
  theory 
  later 
  Avhere 
  Fresnel 
  

   had 
  left 
  it, 
  found 
  from 
  his 
  calculations 
  that 
  at 
  four 
  points 
  on 
  the 
  

   surface 
  of 
  the 
  wave 
  in 
  a 
  doubly 
  refracting 
  crystal 
  the 
  ray 
  is 
  not 
  

   just 
  doubly 
  separated 
  but 
  rather 
  broken 
  into 
  an 
  infinite 
  number 
  of 
  

   components. 
  This 
  was 
  confirmed 
  experimentally 
  some 
  time 
  later 
  by 
  

   Lloyd. 
  

  

  As 
  much 
  an 
  experimenter 
  as 
  a 
  mathematician, 
  Fresnel 
  submitted 
  

   the 
  results 
  of 
  his 
  calculations 
  to 
  the 
  control 
  of 
  well-conceived 
  and 
  

   well-executed 
  experiments. 
  As 
  he 
  tried 
  to 
  visualize 
  that 
  which 
  he 
  

   suspected 
  in 
  the 
  invisible 
  theoretical 
  domain, 
  he 
  often 
  had 
  recourse 
  to 
  

   imagination 
  — 
  that 
  daring 
  and 
  wonderful 
  faculty 
  which, 
  duly 
  in- 
  

   spired 
  and 
  bridled, 
  becomes 
  the 
  most 
  powerful 
  instrument 
  of 
  

   discovery. 
  

  

  The 
  French 
  Academy 
  of 
  Sciences 
  opened 
  its 
  door 
  to 
  Fresnel 
  in 
  

   1823. 
  Filled 
  with 
  honors 
  in 
  France 
  and 
  elsewhere, 
  he 
  had 
  the 
  un- 
  

   happiness 
  of 
  seeing 
  his 
  health, 
  always 
  delicate, 
  weaken 
  more 
  and 
  

   more. 
  He 
  died 
  in 
  his 
  fortieth 
  year 
  at 
  Ville 
  d'Avray, 
  July 
  14, 
  1827." 
  

  

  Fresnel 
  was 
  Avell 
  judged 
  by 
  Tyndall, 
  among 
  others: 
  

  

  His 
  brain 
  was 
  too 
  vigorous 
  for 
  the 
  body 
  witli 
  \^liieli 
  it 
  was 
  associated; 
  

   that 
  body 
  prematurely 
  became 
  a 
  ruin 
  ; 
  and 
  Fresnel 
  left 
  this 
  world 
  leaving 
  

   behind 
  him 
  a 
  name 
  immortal 
  in 
  the 
  annals 
  of 
  science. 
  

  

  There 
  are 
  tilings 
  which 
  are 
  better 
  than 
  science 
  itself. 
  Character 
  outweighs 
  

   the 
  intellect. 
  It 
  is 
  particularly 
  pleasant 
  to 
  those 
  who 
  love 
  to 
  think 
  well 
  of 
  

   human 
  nature 
  to 
  see 
  united 
  a 
  great 
  mind 
  and 
  an 
  upright 
  character. 
  This 
  

   uniini 
  wjas 
  found 
  in 
  this 
  young 
  Frenchman. 
  In 
  his 
  ardent 
  disciissions 
  of 
  the 
  

   undulatory 
  theory 
  he 
  bore 
  himself 
  with 
  integrity, 
  claiming 
  only 
  his 
  rights, 
  

   and 
  I'eady 
  to 
  accede 
  their 
  rights 
  to 
  others. 
  He 
  early 
  recognized 
  and 
  praised 
  

   the 
  merits 
  of 
  Thomas 
  Young. 
  It 
  was 
  indeed 
  Fresnel 
  and 
  his 
  compatriot 
  Arago 
  

   vvho 
  revealed 
  to 
  England 
  the 
  consciousness 
  of 
  the 
  injustice 
  done 
  to 
  Young 
  

   by 
  the 
  Edinburgh 
  Review. 
  

  

  I 
  wish 
  to 
  read 
  to 
  you 
  a 
  short 
  extract 
  from 
  a 
  letter 
  written 
  in 
  1824 
  by 
  

   Fresnel 
  to 
  Young, 
  for 
  it 
  throws 
  a 
  pleasant 
  light 
  upon 
  the 
  character 
  of 
  Fresnel, 
  

   the 
  French 
  philosopher 
  : 
  

  

  " 
  For 
  a 
  long 
  time," 
  writes 
  Fresnel, 
  " 
  this 
  sensitiveness, 
  or 
  this 
  vanity, 
  

   which 
  we 
  call 
  the 
  love 
  of 
  glory, 
  has 
  been 
  much 
  dulled 
  in 
  me 
  ; 
  I 
  work 
  far 
  less 
  

   to 
  gain 
  public 
  approbation 
  than 
  an 
  approbation 
  within 
  myself 
  which 
  has 
  

   always 
  been 
  the 
  most 
  pleasant 
  recompense 
  for 
  my 
  efforts. 
  Without 
  doubt 
  I 
  

   have 
  often 
  had 
  need 
  of 
  the 
  prick 
  of 
  vanity 
  to 
  arouse 
  me 
  to 
  follow 
  out 
  my 
  

   researches 
  in 
  moments 
  of 
  distaste 
  or 
  discouragement 
  ; 
  but 
  all 
  the 
  compliments 
  

   which 
  I 
  have 
  been 
  enabled 
  to 
  receive 
  from 
  Messieurs 
  Arago, 
  de 
  La 
  Place, 
  or 
  

   Biot 
  have 
  never 
  given 
  me 
  as 
  much 
  pleasure 
  as 
  the 
  discovery 
  of 
  a 
  theoretical 
  

   truth 
  and 
  the 
  confirniiition 
  of 
  my 
  calculations 
  by 
  experiment." 
  * 
  

  

  Tyndall 
  rightly 
  saw 
  in 
  this 
  letter 
  an 
  example 
  to 
  be 
  followed. 
  

   Science 
  should 
  be 
  cultivated 
  for 
  itself, 
  for 
  the 
  pure 
  love 
  of 
  truth, 
  

   and 
  not 
  for 
  the 
  applause 
  or 
  the 
  material 
  advantages 
  which 
  may 
  

   accrue 
  from 
  it. 
  

  

  * 
  Six 
  lectures 
  on 
  light, 
  delivered 
  in 
  the 
  United 
  States 
  of 
  America 
  in 
  1872 
  and 
  1873, 
  

   fifth 
  edition, 
  p. 
  210, 
  211. 
  This 
  letter 
  is 
  dated 
  Nov. 
  26, 
  1824. 
  

  

  