﻿TH 
  B 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [FOURTH 
  SERIES.] 
  

  

  Sub- 
  

  

  Art. 
  YIII. 
  — 
  Rotatory 
  Polarization 
  of 
  Light 
  iii 
  Media 
  

   jectedto 
  Torsion; 
  bj 
  Arthur 
  W. 
  Ewell. 
  

  

  It 
  is 
  stated 
  in 
  Yerdet's 
  Legons 
  d'Optique 
  Physique* 
  that 
  F. 
  

   E. 
  I^eoraaDii 
  demonstrated 
  mathematically 
  that 
  the 
  plane 
  of 
  

   polarization 
  of 
  a 
  linear 
  polarized 
  ray, 
  propagated 
  parallel 
  to 
  

   the 
  axis 
  of 
  a 
  twisted 
  cylinder, 
  is 
  rotated 
  proportionally 
  to 
  the 
  

   length 
  of 
  the 
  cylinder 
  and 
  the 
  angle 
  of 
  torsion. 
  Yerdet 
  

   remarks 
  that 
  although 
  this 
  result 
  is 
  probably 
  correct, 
  experi- 
  

   mental 
  verification 
  is 
  very 
  difficult 
  and 
  had 
  been 
  sought 
  in 
  

   vain 
  by 
  Neumann 
  and 
  Drion. 
  In 
  the 
  bibliography 
  at 
  the 
  

   close 
  of 
  the 
  chapter 
  in 
  which 
  these 
  statements 
  occur, 
  three 
  

   references 
  are 
  given 
  for 
  ^Neumann's 
  paper. 
  Onef 
  relates 
  to 
  the 
  

   original 
  memoir, 
  the 
  other 
  two 
  to 
  abstracts 
  containing 
  noth- 
  

   ing 
  additional. 
  

  

  In 
  this 
  memoir, 
  from 
  the 
  strains 
  when 
  the 
  torsion 
  is 
  small 
  

   (and 
  when 
  consequently 
  the 
  cross 
  sections 
  remain 
  sensibly 
  

   plane), 
  Neumann 
  obtains 
  an 
  equation 
  which 
  gives 
  a 
  rotation 
  of 
  

   the 
  axes 
  of 
  double 
  refraction 
  proportional 
  to 
  the 
  length 
  of 
  the 
  

   cylinder 
  and 
  in 
  the 
  same 
  direction 
  as 
  the 
  twist 
  but 
  independent 
  

   of 
  the 
  magnitude 
  of 
  the 
  twist, 
  for 
  rays 
  at 
  an 
  angle 
  with 
  the 
  

   axis 
  and 
  whose 
  plane 
  of 
  incidence 
  does 
  not 
  include 
  the 
  axis. 
  

   If 
  the 
  plane 
  of 
  incidence 
  includes 
  the 
  axis 
  or 
  if 
  the 
  ray 
  is 
  

   parallel 
  to 
  the 
  axis, 
  his 
  equation 
  gives 
  no 
  rotation 
  of 
  the 
  axes 
  

   of 
  double 
  refraction. 
  JSTeumann 
  does 
  not 
  state 
  clearly 
  whether 
  

   he 
  considers 
  that 
  a 
  rotation 
  of 
  the 
  axes 
  of 
  double 
  refraction 
  

   implies 
  a 
  rotation 
  of 
  the 
  plane 
  of 
  polarization. 
  A 
  careful 
  

   search 
  failed 
  to 
  bring 
  to 
  light 
  any 
  memoir 
  by 
  Drion 
  on 
  this 
  

   subject 
  or 
  any 
  other 
  memoir 
  by 
  Neumann. 
  

  

  * 
  Vol. 
  li, 
  p. 
  389. 
  

  

  f 
  Abhand. 
  d. 
  koaigl. 
  Akad. 
  d. 
  Wissen. 
  zu 
  Berlin, 
  1841, 
  Part 
  IT. 
  

  

  Am. 
  Jour. 
  Sol 
  — 
  Fourth 
  Series, 
  Vol. 
  VIII, 
  No. 
  44. 
  — 
  August, 
  1899. 
  

   T 
  

  

  