﻿THE 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  — 
  .♦ 
  — 
  

  

  

  [SIXTH 
  SERIES.] 
  

  

  M 
  A 
  Y 
  1918. 
  

  

  XL1I. 
  On 
  the 
  Scattering 
  of 
  Light 
  by 
  a 
  Cloud 
  of 
  similar 
  

   small 
  Particles 
  of 
  any 
  Shape 
  and 
  oriented 
  at 
  random. 
  

   By 
  Lord 
  Rayleigh, 
  Q.M., 
  F.R.S.* 
  

  

  FOR 
  distinctness 
  of 
  conception 
  the 
  material 
  of 
  the 
  par- 
  

   ticles 
  may 
  be 
  supposed 
  to 
  be 
  uniform 
  and 
  non-magnetic, 
  

   but 
  of 
  dielectric 
  capacity 
  different 
  from 
  that 
  of 
  the 
  sur- 
  

   rounding 
  medium 
  ; 
  at 
  the 
  same 
  time 
  the 
  results 
  at 
  which 
  we 
  

   shall 
  arrive 
  are 
  doubtless 
  more 
  general. 
  The 
  smallness 
  is, 
  of 
  

   course, 
  to 
  be 
  understood 
  as 
  relative 
  to 
  the 
  wave-length 
  of 
  the 
  

   vibrations. 
  

  

  When 
  the 
  particles 
  are 
  spherical, 
  the 
  problem 
  is 
  simple, 
  as 
  

   their 
  orientation 
  does 
  not 
  then 
  enter 
  t- 
  If 
  the 
  incident 
  light 
  

   be 
  polarized, 
  there 
  is 
  no 
  scattered 
  ray 
  in 
  the 
  direction 
  of 
  

   primary 
  electric 
  vibration, 
  or 
  if 
  the 
  incident 
  light 
  be 
  un- 
  

   polarized 
  there 
  is 
  complete 
  polarization 
  of 
  the 
  light 
  scattered 
  

   at 
  right 
  angles 
  to 
  the 
  direction 
  of 
  primary 
  propagation. 
  The 
  

   consideration 
  of 
  elongated 
  particles 
  shows 
  at 
  once 
  that 
  a 
  want 
  

   of 
  symmetry 
  must 
  usually 
  entail 
  a 
  departure 
  from 
  the 
  above 
  

   law 
  of 
  polarization 
  and 
  may 
  be 
  one 
  of 
  the 
  causes, 
  though 
  

   probably 
  not 
  the 
  most 
  important, 
  of 
  the 
  incomplete 
  polariza- 
  

   tion 
  of 
  sky-light 
  at 
  90° 
  from 
  the 
  sun. 
  My 
  son's 
  recent 
  

   experiments 
  upon 
  light 
  scattered 
  by 
  carefully 
  filtered 
  gases 
  J 
  

   reveal 
  a 
  decided 
  deficiency 
  of 
  polarization 
  in 
  the 
  light 
  emitted 
  

  

  * 
  Communicated 
  bv 
  the 
  Author. 
  

  

  t 
  Phil. 
  Mag. 
  vol. 
  kli. 
  pp. 
  107, 
  274, 
  447 
  (1871), 
  vol. 
  xii. 
  p. 
  81 
  (1881), 
  

   vol. 
  xlvii. 
  p. 
  375 
  (1899); 
  Scientific 
  Papers, 
  vol. 
  i. 
  pp. 
  87, 
  104, 
  518 
  

   vol. 
  iv. 
  p. 
  397. 
  

  

  X 
  Rov. 
  Soc. 
  Proc. 
  Feb. 
  28, 
  1918. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  35. 
  No. 
  209. 
  May 
  1918. 
  2 
  D 
  

  

  