﻿158 
  

  

  On 
  the 
  Spectrum 
  of 
  Cog 
  girts 
  Comet. 
  

  

  [Jan. 
  7> 
  

  

  comet 
  of 
  1862 
  : 
  — 
  " 
  Die 
  Farbe 
  des 
  Strahls 
  erscheint 
  mir 
  gelbrdthlich 
  ; 
  die 
  

   des" 
  uingebenden 
  Nebels 
  (vielleicht 
  aus 
  Contrast) 
  mattblaulich. 
  . 
  . 
  . 
  Die 
  

   Farbe 
  der 
  Ausstromung 
  erscheint 
  mir 
  gelblich; 
  die 
  Coma 
  hat 
  blau- 
  

   liches 
  Licht." 
  

  

  3. 
  The 
  Continuous 
  Spectrum 
  ivhich 
  accompanies 
  the 
  Gaseous 
  Spectrum. 
  

  

  This 
  spectrum 
  was 
  observed 
  in 
  every 
  part 
  of 
  the 
  coma; 
  near 
  its 
  

   boundary, 
  and 
  in 
  the 
  dark 
  space 
  behind 
  the 
  nucleus, 
  the 
  continuous 
  

   spectrum 
  became 
  so 
  faint 
  as 
  to 
  be 
  detected 
  with 
  difficulty, 
  at 
  the 
  same 
  time 
  

   that 
  the 
  bright 
  bands 
  were 
  distinctly 
  visible. 
  

  

  The 
  greater 
  brightness 
  of 
  some 
  parts 
  of 
  the 
  envelopes 
  and 
  of 
  the 
  coma 
  

   appeared 
  to 
  be 
  due 
  for 
  the 
  most 
  part 
  to 
  the 
  presence 
  of 
  a 
  larger 
  quantity 
  

   of 
  the 
  matter 
  which 
  gives 
  a 
  continuous 
  spectrum. 
  When 
  the 
  slit 
  was 
  

   placed 
  on 
  these 
  brighter 
  parts 
  of 
  the 
  comet, 
  the 
  gaseous 
  spectrum 
  did 
  not 
  

   become 
  brighter 
  in 
  the 
  same 
  degree, 
  but 
  there 
  was 
  an 
  increase 
  in 
  the 
  

   brightness 
  of 
  the 
  continuous 
  spectrum. 
  

  

  Behind 
  the 
  nucleus, 
  the 
  bright 
  bands 
  became 
  fainter 
  relatively 
  to 
  the 
  

   accompanying 
  continuous 
  spectrum, 
  until 
  the 
  brightest 
  band 
  only 
  could 
  

   be 
  detected. 
  The 
  more 
  distant 
  parts 
  of 
  the 
  tail 
  give 
  probably 
  a 
  con- 
  

   tinuous 
  spectrum 
  only. 
  

  

  In 
  the 
  coma 
  there 
  was 
  seen 
  occasionally 
  a 
  remarkable 
  inequality 
  in 
  the 
  

   brightness 
  of 
  the 
  continuous 
  spectrum 
  between 
  the 
  bands. 
  On 
  some 
  

   occasions 
  the 
  light 
  between 
  the 
  first 
  and 
  second 
  band 
  was 
  bright, 
  while 
  

   in 
  the 
  other 
  parts 
  of 
  the 
  spectrum 
  the 
  light 
  was 
  faint. 
  

  

  On 
  several 
  evenings 
  I 
  satisfied 
  myself 
  that 
  polarized 
  light 
  was 
  present 
  

   in 
  every 
  part 
  of 
  the 
  comet. 
  I 
  do 
  not 
  think 
  that 
  the 
  proportion 
  of 
  

   polarized 
  light 
  exceeded 
  -J- 
  of 
  the 
  total 
  light. 
  The 
  polarization, 
  as 
  exhi- 
  

   bited 
  by 
  the 
  partial 
  extinction 
  of 
  one 
  of 
  the 
  images 
  formed 
  by 
  a 
  double- 
  

   image 
  prism, 
  appeared 
  to 
  be 
  more 
  marked 
  in 
  the 
  tail. 
  It 
  must 
  be 
  remem- 
  

   bered 
  that 
  such 
  would 
  appear 
  to 
  be 
  the 
  case 
  to 
  some 
  extent 
  even 
  if 
  the 
  

   proportion 
  were 
  not 
  really 
  greater, 
  because 
  the 
  same 
  proportional 
  dimi- 
  

   nution 
  in 
  a 
  faint 
  object 
  is 
  more 
  appreciated 
  by 
  the 
  eye. 
  Still 
  there 
  was 
  

   probably 
  a 
  relatively 
  large 
  proportion 
  of 
  polarized 
  light 
  in 
  the 
  tail. 
  

  

  The 
  reflected 
  solar 
  light 
  would 
  account 
  for 
  a 
  large 
  part 
  of 
  the 
  continuous 
  

   spectrum. 
  To 
  what 
  source 
  are 
  we 
  to 
  ascribe 
  the 
  remaining 
  light 
  which 
  

   the 
  prism 
  resolves 
  into 
  a 
  continuous 
  spectrum 
  ? 
  Is 
  it 
  due 
  to 
  reflection 
  

   from 
  discrete 
  particles, 
  too 
  large 
  relatively 
  to 
  the 
  wave-lengths 
  of 
  the 
  

   light 
  for 
  polarization 
  to 
  take 
  place 
  ? 
  or 
  is 
  it 
  due 
  to 
  incandescent 
  solid 
  

   particles 
  ? 
  From 
  the 
  coexistence 
  of 
  the 
  band-spectrum, 
  we 
  can 
  scarcely 
  

   think 
  of 
  distinct 
  masses 
  of 
  gas 
  dense 
  enough 
  to 
  give 
  a 
  continuous 
  

   spectrum. 
  

  

  The 
  difficulty 
  which 
  presents 
  itself 
  in 
  accounting 
  for 
  sufficient 
  heat 
  

   to 
  maintain 
  this 
  matter 
  and 
  the 
  nucleus 
  in 
  a 
  state 
  of 
  incandescence 
  has 
  

   also 
  to 
  be 
  encountered 
  in 
  respect 
  of 
  the 
  gaseous 
  matter 
  which 
  emits 
  the 
  

   light 
  which 
  is 
  resolved 
  into 
  the 
  bright 
  bands. 
  

  

  