﻿470 
  MR 
  WILLIAM 
  SWAN 
  ON 
  THE 
  

  

  radiated 
  structure 
  seems 
  therefore 
  to 
  indicate 
  the 
  existence 
  of 
  something 
  tending 
  

   to 
  limit 
  the 
  transmission 
  of 
  the 
  rays 
  to 
  directions 
  normal 
  to 
  the 
  sun's 
  surface, 
  

   and 
  capable 
  of 
  absorbing 
  them 
  more 
  powerfully 
  at 
  certain 
  points 
  than 
  at 
  others. 
  

   The 
  bright 
  beams 
  of 
  light 
  in 
  the 
  corona 
  strongly 
  resembled 
  sunbeams 
  shining 
  

   through 
  narrow 
  apertures 
  in 
  clouds 
  ; 
  and 
  it 
  was 
  indeed 
  that 
  resemblance 
  which 
  

   first 
  led 
  me 
  to 
  entertain 
  the 
  idea 
  that 
  an 
  envelope 
  of 
  cloudy 
  matter 
  surrounds 
  the 
  

   sun. 
  Immediately 
  after 
  witnessing 
  the 
  late 
  eclipse, 
  when 
  I 
  reflected 
  on 
  the 
  strik- 
  

   ing 
  want 
  of 
  continuity 
  I 
  had 
  observed 
  in 
  the 
  illumination 
  of 
  the 
  corona, 
  I 
  was 
  

   strongly 
  impressed 
  with 
  the 
  conviction 
  that 
  something 
  existed 
  near 
  the 
  surface 
  of 
  

   the 
  sun 
  which 
  intercepted 
  his 
  light 
  more 
  at 
  certain 
  points 
  than 
  at 
  others. 
  It 
  then 
  

   occurred 
  to 
  me, 
  that 
  as 
  the 
  red 
  prominences, 
  from 
  their 
  power 
  of 
  reflecting 
  light, 
  

   must 
  also 
  absorb 
  it, 
  the 
  medium 
  which 
  absorbed 
  the 
  sun's 
  light 
  irregularly, 
  and 
  

   caused 
  the 
  unequal 
  illumination 
  of 
  the 
  corona, 
  might 
  be 
  no 
  other 
  than 
  the 
  matter 
  

   composing 
  the 
  red 
  prominences 
  ; 
  that 
  matter 
  being 
  supposed 
  to 
  constitute 
  an 
  

   envelope 
  surrounding 
  the 
  sun, 
  of 
  which 
  the 
  red 
  prominences 
  are 
  only 
  the 
  higher, 
  

   and 
  probably 
  the 
  rarer 
  portions. 
  

  

  If 
  the 
  faculse 
  are 
  apertures 
  in 
  the 
  envelope 
  of 
  cloud, 
  as 
  has 
  been 
  supposed, 
  it 
  

   will 
  follow 
  that 
  faculse 
  near 
  the 
  sun's 
  limb 
  may 
  be 
  connected 
  with 
  the 
  bright 
  

   beams 
  in 
  the 
  corona. 
  If, 
  then, 
  a 
  considerable 
  portion 
  of 
  the 
  sun's 
  surface 
  near 
  

   his 
  limb 
  were 
  intersected 
  by 
  numerous 
  branching 
  faculse, 
  with 
  openings 
  gradually 
  

   increasing 
  in 
  width 
  towards 
  the 
  centre 
  of 
  the 
  group, 
  we 
  should 
  probably 
  have 
  a 
  

   mass 
  of 
  light 
  in 
  the 
  corona 
  like 
  that 
  represented 
  in 
  Plate 
  XII., 
  which 
  was 
  seen 
  at 
  

   the 
  late 
  eclipse 
  about 
  30° 
  to 
  the 
  east 
  of 
  the 
  sun's 
  vertex. 
  On 
  the 
  other 
  hand, 
  

   light 
  proceeding 
  from 
  a 
  single 
  long 
  facula 
  in 
  the 
  sun's 
  limb, 
  presented 
  to 
  the 
  

   eye 
  endwise, 
  might 
  occasion 
  the 
  appearance 
  of 
  the 
  narrow 
  bright 
  beams 
  which 
  

   were 
  seen 
  in 
  the 
  corona 
  ; 
  and 
  a 
  considerable 
  variety 
  of 
  effects 
  might 
  be 
  produced 
  

   by 
  faculse 
  whose 
  positions 
  were 
  differently 
  inclined 
  to 
  the 
  visual 
  direction. 
  

  

  The 
  following 
  queries 
  embody 
  the 
  Irypothesis 
  which 
  I 
  have 
  now 
  ventured 
  to 
  

   propose 
  regarding 
  the 
  red 
  prominences, 
  and 
  the 
  other 
  solar 
  phenomena 
  which 
  I 
  

   have 
  supposed 
  to 
  be 
  connected 
  with 
  them 
  : 
  — 
  

  

  1. 
  May 
  not 
  the 
  sun's 
  luminous 
  atmosphere 
  be 
  surrounded 
  by 
  an 
  envelope 
  of 
  

   cloud 
  capable 
  of 
  absorbing 
  part 
  of 
  his 
  light, 
  and 
  having 
  the 
  property 
  of 
  appearing 
  

   red 
  when 
  seen 
  by 
  reflected 
  light 
  ? 
  

  

  2. 
  As 
  the 
  spots 
  on 
  the 
  sun 
  have 
  been 
  supposed 
  to 
  be 
  formed 
  by 
  upward 
  cur- 
  

   rents 
  in 
  his 
  atmosphere, 
  may 
  not 
  the 
  same, 
  or 
  similar 
  currents, 
  force 
  up 
  portions 
  

  

  of 
  the 
  envelope 
  of 
  cloud, 
  and 
  sometimes 
  actually 
  rupture 
  it 
  ? 
  

  

  3. 
  May 
  not 
  the 
  higher 
  portions 
  of 
  the 
  envelope 
  of 
  cloud 
  be 
  seen 
  projecting 
  

   beyond 
  the 
  moon's 
  limb 
  during 
  the 
  total 
  phase 
  of 
  a 
  solar 
  eclipse, 
  and 
  thus 
  consti- 
  

   tute 
  the 
  red 
  prominences 
  ? 
  

  

  4. 
  May 
  not 
  this 
  envelope 
  be 
  the 
  chief 
  agent 
  in 
  causing 
  the 
  diminished 
  bright- 
  

   ness 
  of 
  the 
  sun's 
  disc 
  towards 
  his 
  edges, 
  owing 
  to 
  the 
  greater 
  thickness 
  of 
  the 
  

  

  