﻿F. 
  W. 
  Very— 
  Solar 
  Radiation. 
  613 
  

  

  where 
  \ 
  = 
  wave-lengths, 
  a 
  = 
  ordinates 
  in 
  the 
  spectral 
  energy- 
  

   curve 
  for 
  the 
  center 
  of 
  the 
  solar 
  disk 
  (Abbot), 
  b 
  — 
  transmission 
  

   by 
  the 
  solar 
  " 
  atmosphere 
  " 
  (Very), 
  c 
  — 
  a/b, 
  or 
  the 
  photo- 
  

   spheric 
  ordinates 
  which 
  would 
  be 
  observed 
  if 
  the 
  sun's 
  " 
  atmos- 
  

   phere 
  " 
  * 
  above 
  the 
  photosphere 
  could 
  be 
  removed. 
  

  

  The 
  wave-length 
  of 
  the 
  photospheric 
  maximum 
  differs 
  very 
  

   little 
  from 
  a 
  similar, 
  unpublished 
  reduction 
  of 
  these 
  measures 
  

   made 
  in 
  the 
  summer 
  of 
  1882 
  at 
  the 
  Allegheny 
  Observatory 
  

   during 
  Director 
  Langley's 
  absence 
  in 
  England, 
  where 
  he 
  an- 
  

   nounced 
  at 
  the 
  Royal 
  Institution 
  his 
  theory 
  of 
  the 
  " 
  blue 
  sun." 
  

   If 
  my 
  measures 
  had 
  been 
  made 
  sooner, 
  the 
  form 
  of 
  this 
  

   announcement 
  would 
  have 
  been 
  a 
  little 
  different, 
  for 
  upon 
  re- 
  

   combining 
  the 
  spectrum 
  colors 
  in 
  the 
  proportions 
  required 
  to 
  

   reconstitute 
  a 
  light 
  equivalent 
  to 
  unabsorbed 
  sunlight, 
  I 
  actu- 
  

   ally 
  obtained 
  a 
  delicate 
  tint 
  of 
  lavender, 
  instead 
  of 
  blue. 
  These 
  

   provisional 
  values 
  of 
  absorption 
  by 
  a 
  species 
  of 
  solar 
  atmos- 
  

   phere 
  were 
  accepted 
  by 
  Langley 
  at 
  that 
  time, 
  although 
  some 
  

   singular 
  relations 
  between 
  the 
  apparent 
  absorption 
  at 
  different 
  

   radial 
  distances 
  remained 
  outstanding, 
  whicli 
  are 
  now 
  partially 
  

   explained 
  in 
  several 
  papers 
  by 
  Professor 
  Schuster 
  and 
  myself, 
  

   even 
  if 
  it 
  is 
  not 
  possible 
  to 
  assign 
  definite 
  limits 
  to 
  several 
  dis- 
  

   tinct 
  yet 
  probably 
  simultaneously 
  commingled 
  processes. 
  f 
  

  

  Since 
  Mr. 
  Abbot 
  has 
  recently 
  obtained 
  similar 
  curves 
  show- 
  

   ing 
  a 
  great 
  diminution 
  in 
  the 
  radiation 
  of 
  short 
  wave-length 
  

   between 
  the 
  center 
  and 
  limb 
  of 
  the 
  solar 
  disk,;f 
  perhaps 
  the 
  

   reason 
  why 
  he 
  has 
  not 
  applied 
  this 
  knowledge 
  in 
  reproducing 
  

   the 
  energy-curve 
  of 
  the 
  photospheric 
  radiation 
  may 
  be 
  his 
  un- 
  

   belief 
  in 
  the 
  reality 
  of 
  the 
  photosphere. 
  My 
  result 
  is 
  given 
  for 
  

   whatever 
  it 
  may 
  be 
  worth 
  and 
  indicates 
  a 
  photospheric 
  tem- 
  

   perature. 
  

  

  T 
  = 
  2930/0-41 
  =r 
  7146° 
  Abs. 
  C.§ 
  

  

  Owing 
  to 
  the 
  total 
  absorption 
  of 
  the 
  shorter 
  ultra-violet 
  

   waves 
  by 
  the 
  atmospheres 
  of 
  either 
  sun 
  or 
  earth, 
  the 
  losses 
  of 
  

   these 
  radiations 
  are 
  somewhat 
  problematical, 
  and 
  both 
  the 
  

   restoration 
  and 
  the 
  resulting 
  temperature 
  are 
  liable 
  to 
  be 
  

   underrated. 
  Assuming 
  that 
  the 
  photosphere 
  is 
  composed 
  of 
  

   nascent 
  molecules, 
  or 
  molecular 
  aggregates 
  forming 
  minute 
  

   mist 
  particles, 
  this 
  temperature 
  is 
  that 
  of 
  the 
  complete 
  ioniza- 
  

  

  * 
  The 
  solar 
  envelopes 
  include, 
  besides 
  gaseous 
  material 
  (mainly 
  dissociated 
  

   by 
  reason 
  of 
  the 
  excessive 
  heat), 
  the 
  dust 
  of 
  the 
  coronal 
  filaments 
  and 
  'some 
  

   material 
  (either 
  molecules 
  or 
  mist 
  particles) 
  in 
  close 
  contact 
  with, 
  or 
  perhaps 
  

   in 
  its 
  denser 
  distribution 
  constituting, 
  the 
  photosphere. 
  This 
  comminuted 
  

   material 
  scatters 
  the 
  shorter 
  waves 
  powerfully. 
  

  

  f 
  See 
  the 
  AstrophysicalJournal, 
  vol. 
  xvi, 
  p. 
  73 
  and 
  p. 
  320 
  ; 
  vol, 
  xix, 
  p, 
  139; 
  

   vol. 
  xxi, 
  p. 
  1 
  and 
  p. 
  258. 
  

  

  JThe 
  Sun, 
  figure 
  25, 
  p. 
  106. 
  

  

  § 
  This 
  approximate 
  formula 
  requires 
  slight 
  modifications 
  to 
  adapt 
  it 
  to 
  the 
  

   refinements 
  of 
  the 
  Wien-Planck 
  law. 
  

  

  