﻿218 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  Euler 
  was 
  following 
  in 
  the 
  path 
  of 
  Huyghens 
  when 
  Newton, 
  enter- 
  

   ing 
  the 
  scene, 
  objected 
  that, 
  if 
  light 
  were 
  due 
  to 
  waves, 
  the 
  latter 
  

   would 
  invade 
  the 
  space 
  behind 
  a 
  body, 
  thus 
  making 
  shadows 
  impos- 
  

   sible. 
  This, 
  however, 
  proved 
  to 
  be 
  a 
  double-edged 
  weapon, 
  for, 
  

   while 
  reducing 
  his 
  opponents 
  to 
  silence, 
  Newton 
  himself 
  could 
  not 
  

   escape 
  from 
  the 
  consequences 
  of 
  his 
  own 
  arguments 
  and 
  he 
  had 
  to 
  

   explain 
  very 
  artificially, 
  by 
  added 
  suppositions, 
  the 
  rings 
  shown 
  by 
  

   thin 
  lamina 
  just 
  discovered 
  by 
  him. 
  Newton 
  was 
  not 
  in 
  optics 
  the 
  

   transcendent 
  man 
  that 
  he 
  was 
  in 
  the 
  universal 
  attraction 
  due 
  to 
  

   gravity. 
  He 
  had 
  stated 
  a 
  definite 
  dislike 
  of 
  hypotheses 
  but 
  no 
  man 
  

   was 
  more 
  prone 
  to 
  use 
  them; 
  starting 
  from 
  false 
  premises, 
  he 
  piled 
  

   error 
  upon 
  error. 
  His 
  emission 
  theory 
  has 
  died, 
  never 
  to 
  return. 
  

  

  This 
  state 
  of 
  aifairs 
  continued 
  up 
  to 
  the 
  beginning 
  of 
  the 
  nine- 
  

   teenth 
  century, 
  when 
  Thomas 
  Young, 
  the 
  most 
  gifted 
  of 
  English 
  

   scientists 
  since 
  Newton, 
  in 
  his 
  turn 
  took 
  up 
  the 
  undulatory 
  theory 
  

   of 
  light. 
  After 
  starting 
  his 
  career 
  with 
  the 
  excellent 
  discovery 
  that 
  

   the 
  accommodation 
  of 
  the 
  eye 
  was 
  produced 
  by 
  changes 
  in 
  the 
  curva- 
  

   ture 
  of 
  its 
  crystalline 
  lens, 
  Avith 
  rare 
  sagacity 
  he 
  showed 
  that 
  the 
  

   principle 
  of 
  interference 
  already 
  utilized 
  with 
  sound 
  was 
  applicable 
  

   to 
  light. 
  He 
  thus 
  explained 
  the 
  rainbow 
  tints 
  of 
  thin 
  lamina 
  and 
  

   Newton's 
  rings 
  and 
  subsequently 
  the 
  colors 
  of 
  striated 
  surfaces. 
  He 
  

   studied 
  polarization, 
  determined 
  the 
  lengths 
  of 
  light 
  waves, 
  and 
  

   attributed 
  to 
  the 
  ether 
  the 
  properties 
  of 
  a 
  solid 
  body, 
  but 
  he 
  was 
  

   somewhat 
  frustrated 
  by 
  the 
  phenomenon 
  of 
  diffraction 
  of 
  light, 
  dis- 
  

   covered 
  like 
  interference 
  by 
  the 
  illustrious 
  Italian 
  physicist, 
  Grim- 
  

   aldi 
  of 
  Bologna, 
  who 
  gave 
  to 
  the 
  phenomenon 
  the 
  name 
  by 
  winch 
  

   it 
  is 
  still 
  known. 
  

  

  This 
  period 
  was 
  notable 
  for 
  a 
  succession 
  of 
  discoveries 
  as 
  curious 
  

   as 
  they 
  were 
  unexpected. 
  In 
  1808 
  the 
  French 
  physicist, 
  Malus, 
  

   professor 
  at 
  the 
  Ecole 
  Polytechnique, 
  discovered 
  polarization 
  by 
  

   reflection 
  when 
  from 
  his 
  house 
  he 
  was 
  examining 
  with 
  a 
  prism 
  of 
  

   Iceland 
  spar 
  the 
  image 
  of 
  the 
  sun 
  reflected 
  from 
  the 
  glass 
  w^indows 
  of 
  

   the 
  Luxembourg 
  in 
  Paris; 
  in 
  1811 
  Arago 
  noted 
  the 
  beautiful 
  colors 
  

   of 
  lamina 
  of 
  mica 
  traversed 
  by 
  polarized 
  light, 
  as 
  well 
  as 
  the 
  rotation 
  

   of 
  the 
  plane 
  of 
  polarization 
  by 
  crystals 
  of 
  quartz; 
  in 
  1812 
  Biot 
  

   brought 
  to 
  light 
  new 
  lelationships 
  between 
  the 
  reflection 
  and 
  the 
  

   polarization 
  of 
  light 
  by 
  crystallized 
  bodies; 
  in 
  1813 
  Seebeck 
  called 
  

   attention 
  to 
  the 
  polarization 
  of 
  light 
  rays 
  in 
  passing 
  through 
  tour- 
  

   maline, 
  and 
  Brewster 
  to 
  the 
  colored 
  bands 
  about 
  the 
  axes 
  of 
  a 
  double- 
  

   axis 
  crystal; 
  and 
  finally, 
  in 
  1814, 
  WoUaston 
  showed 
  the 
  rings 
  of 
  

   Iceland 
  spar. 
  

  

  Fresnel, 
  in 
  1814, 
  commenced 
  the 
  researches 
  which 
  led 
  him 
  from 
  

   discovery 
  to 
  discovery 
  with 
  a 
  speed 
  unexampled 
  in 
  the 
  history 
  of 
  

   science. 
  His 
  name 
  is 
  especially 
  known 
  to 
  the 
  public 
  by 
  his 
  invention 
  

   of 
  the 
  lighthouse 
  lens, 
  which 
  bears 
  his 
  name 
  and 
  which 
  replaced 
  very 
  

   advantageously 
  the 
  older 
  reflectors. 
  It 
  not 
  only 
  augments 
  the 
  amount 
  

  

  