﻿446 
  ME 
  WILLIAM 
  SWAN 
  ON 
  THE 
  

  

  minence 
  " 
  distinctly," 
  " 
  with 
  its 
  marked 
  colour;"* 
  and 
  it 
  was 
  seen 
  by 
  so 
  many 
  

   persons 
  at 
  Gpteborg, 
  that 
  its 
  visibility 
  to 
  the 
  naked 
  eye 
  was 
  a 
  common 
  subject 
  of 
  

   conversation 
  for 
  some 
  days 
  after 
  the 
  eclipse. 
  

  

  Mr 
  Williams 
  observes, 
  that 
  " 
  the 
  largest 
  red 
  prominence 
  was 
  visible 
  by 
  the 
  

   unaided 
  eye;"f 
  and 
  Mr 
  Airy 
  states, 
  in 
  his 
  Account 
  of 
  the 
  Total 
  Eclipse 
  of 
  1842, 
  

   that 
  an 
  observer 
  who 
  accompanied 
  him 
  saw 
  these 
  objects 
  with 
  the 
  naked 
  eye4 
  

   The 
  only 
  observer 
  of 
  the 
  late 
  eclipse 
  who 
  formally 
  states 
  that 
  he 
  could 
  not 
  see 
  

   the 
  prominences 
  without 
  using 
  a 
  telescope, 
  is 
  Lieutenant 
  Krag 
  ; 
  § 
  but 
  such 
  nega- 
  

   tive 
  evidence 
  cannot 
  affect 
  the 
  concurring 
  testimony 
  of 
  so 
  many 
  observers 
  who 
  saw 
  

   them 
  distinctly 
  by 
  unaided 
  vision 
  ; 
  and 
  we 
  must 
  therefore 
  reject 
  the 
  idea 
  that 
  

   they 
  are 
  caused 
  by 
  the 
  telescopes 
  used 
  in 
  observing 
  the 
  eclipse. 
  || 
  

  

  2. 
  On 
  the 
  Hypothesis 
  that 
  the 
  Red 
  Prominences 
  are 
  Phenomena 
  arising 
  from 
  the 
  Action 
  of 
  

   unequally 
  heated 
  Strata 
  of 
  Air 
  on 
  the 
  Sun's 
  rays. 
  

  

  Another 
  opinion 
  regarding 
  the 
  red 
  prominences 
  is 
  that 
  advanced 
  by 
  M. 
  Faye, 
  

   who 
  conceives 
  them 
  to 
  arise 
  from 
  a 
  species 
  of 
  mirage, 
  occasioned 
  by 
  the 
  unequally 
  

   heated 
  state 
  of 
  the 
  atmosphere 
  during 
  a 
  total 
  eclipse. 
  The 
  air 
  all 
  round 
  the 
  

   moon's 
  shadow 
  is 
  heated 
  by 
  the 
  sun, 
  while 
  that 
  within 
  the 
  shadow 
  is 
  sheltered 
  

   from 
  his 
  rays. 
  This 
  he 
  conceives 
  occasions 
  a 
  reduction 
  of 
  temperature 
  in 
  the 
  air 
  

   within 
  the 
  shadow 
  ; 
  and 
  the 
  warm 
  air 
  without, 
  communicating 
  its 
  heat 
  to 
  that 
  

   within, 
  gives 
  rise 
  to 
  a 
  succession 
  of 
  concentric 
  layers 
  gradually 
  decreasing 
  in 
  tem- 
  

   perature, 
  from 
  the 
  surface 
  of 
  the 
  shadow 
  inwards. 
  These 
  layers 
  of 
  unequal 
  den- 
  

   sity, 
  acting 
  on 
  the 
  rays 
  proceeding 
  from 
  the 
  edge 
  of 
  the 
  moon 
  to 
  the 
  observer's 
  

   eye, 
  will, 
  it 
  is 
  assumed, 
  — 
  like 
  the 
  unequally 
  heated 
  strata 
  of 
  air 
  which 
  sometimes 
  

   exist 
  near 
  the 
  horizon, 
  — 
  produce 
  the 
  well 
  known 
  phenomena 
  of 
  mirage. 
  The 
  red 
  

   prominences, 
  he 
  supposes, 
  are 
  then 
  merely 
  the 
  magnified 
  and 
  distorted 
  images 
  of 
  

   lunar 
  mountains, 
  illuminated 
  obliquely 
  by 
  the 
  sun.^f 
  

  

  * 
  Edinburgh 
  New 
  Philosophical 
  Journal, 
  Oct. 
  1851, 
  p. 
  375. 
  

  

  f 
  Royal 
  Ast. 
  Soc. 
  Notice, 
  Jan. 
  1852, 
  p. 
  54. 
  

  

  + 
  Royal 
  Ast. 
  Soc. 
  Notice, 
  for 
  Nov. 
  1842, 
  p. 
  220. 
  § 
  Royal 
  Ast. 
  Soc. 
  Notice, 
  Jan. 
  1852, 
  p. 
  47. 
  

  

  || 
  M. 
  Arago's 
  highly 
  interesting 
  Account 
  of 
  the 
  Total 
  Eclipse 
  of 
  July 
  1842, 
  in 
  the 
  AnniCaire 
  

   for 
  1846, 
  contains 
  ample 
  evidence 
  of 
  the 
  visibility 
  of 
  the 
  red 
  prominences 
  to 
  the 
  naked 
  eye. 
  The 
  

   following 
  are 
  some 
  of 
  the 
  testimonies 
  to 
  that 
  fact. 
  M. 
  Abago 
  says, 
  " 
  A 
  Perpignan, 
  plusieurs 
  per- 
  

   sonnes 
  virent 
  les 
  protuberances 
  a 
  Voeil 
  nu. 
  Le 
  fait 
  n'est 
  pas 
  douteux." 
  (p. 
  412.) 
  M. 
  Flauguergues, 
  

   who 
  observed 
  at 
  Toulon, 
  remarks, 
  " 
  Je 
  n'avais 
  point 
  encore 
  repris 
  le 
  telescope, 
  lorsque 
  je 
  fus 
  surpris 
  

   par 
  l'apparition 
  d'un 
  point 
  lumineux 
  rouge; 
  puis, 
  oVun 
  second 
  point 
  semblable.'''' 
  (p. 
  418.) 
  M. 
  Santini, 
  

   who 
  observed 
  the 
  eclipse 
  at 
  Padua, 
  relates 
  that 
  several 
  persons 
  saw 
  the 
  prominences 
  with 
  the 
  naked 
  

   eye, 
  (p. 
  427.) 
  

  

  I 
  did 
  not 
  obtain 
  access 
  to 
  M. 
  Arago's 
  admirable 
  Memoir 
  until 
  after 
  this 
  paper 
  had 
  been 
  read 
  ; 
  

   otherwise 
  I 
  should 
  have 
  gladly 
  availed 
  myself 
  more 
  fully 
  of 
  its 
  valuable 
  contents 
  than 
  is 
  now 
  possible. 
  

  

  % 
  " 
  Cette 
  atmosphere 
  conique 
  [' 
  le 
  cone 
  d' 
  ombre'] 
  doit 
  produire, 
  dans 
  ses 
  couches 
  succes- 
  

  

  sives, 
  concentriques 
  et 
  deplus 
  en 
  plus 
  froides, 
  les 
  phenomenes 
  analogues 
  aux 
  refractions 
  qui 
  s'operent 
  

   pres 
  de 
  l'horizon, 
  en 
  un 
  mot, 
  des 
  phenomenes 
  de 
  mirage." 
  " 
  Les 
  montagnes 
  roses 
  qui 
  apparurent 
  alors 
  

   [8 
  Juillet 
  1842], 
  ne 
  seraient 
  autre 
  chose 
  que 
  les 
  images 
  demesurement 
  agrandies 
  et 
  deformees 
  de 
  

   quelques 
  parties 
  des 
  montagnes 
  lunaires, 
  eclairees 
  obliquement 
  par 
  le 
  Soleil, 
  et 
  visibles 
  a 
  travers 
  des 
  

   vallees 
  qui 
  se 
  trouvent 
  ca 
  et 
  la, 
  dans 
  une 
  direction 
  favorable, 
  sur 
  le 
  bord 
  apparent 
  de 
  la 
  Lune." 
  — 
  

   Comptes 
  Rendus 
  de 
  V 
  Academie, 
  4 
  Nov. 
  1850, 
  p. 
  643. 
  

  

  