﻿464 
  G. 
  E. 
  Hale— 
  The 
  Ultra- 
  Violet 
  Spectrum 
  

  

  with 
  a 
  radial 
  slit 
  both 
  lines 
  gradually 
  become 
  narrower 
  as 
  the 
  

   distance 
  from 
  the 
  limb 
  increases/and 
  have 
  a 
  pointed 
  appear- 
  

   ance. 
  This 
  might 
  be 
  due 
  to 
  an 
  actual 
  decrease 
  in 
  the 
  width 
  of 
  

   the 
  lines, 
  but, 
  as 
  there 
  is 
  usually 
  a 
  certain 
  increase 
  of 
  intensity 
  

   toward 
  the 
  limb, 
  the 
  effect 
  may 
  be 
  purely 
  photographic. 
  In 
  

   several 
  plates, 
  however, 
  there 
  is 
  so 
  little 
  change 
  of 
  intensity 
  

   that 
  the 
  widening 
  can 
  hardly 
  be 
  due 
  to 
  this 
  cause. 
  The 
  arrow- 
  

   head 
  appearance 
  so 
  frequently 
  seen 
  with 
  the 
  C 
  and 
  F 
  lines, 
  is 
  

   often 
  shown 
  when 
  the 
  slit 
  is 
  radial. 
  A 
  rather 
  curious 
  appear- 
  

   ance 
  has 
  been 
  found 
  on 
  three 
  plates 
  made 
  with 
  radial 
  slit, 
  and 
  

   in 
  the 
  two 
  which 
  best 
  show 
  the 
  effect 
  there 
  is 
  a 
  very 
  sudden 
  

   decrease 
  of 
  intensity 
  in 
  the 
  upper 
  part 
  of 
  the 
  lines. 
  Instead 
  of 
  

   becoming 
  narrower 
  toward 
  the 
  top, 
  the 
  lines 
  seem 
  to 
  expand 
  

   symmetrically 
  on 
  either 
  side, 
  and 
  the 
  edges 
  become 
  hazy 
  and 
  

   indistinct. 
  As 
  in 
  the 
  case 
  of 
  the 
  pointed 
  lines, 
  there 
  is 
  also 
  an 
  

   expansion 
  toward 
  the 
  Jimb, 
  but 
  here 
  the 
  edges 
  are 
  clearly 
  

   defined. 
  The 
  arrow-head 
  appearance 
  is 
  shown 
  in 
  two 
  of 
  these 
  

   plates. 
  With 
  a 
  tangential 
  slit 
  two 
  plates 
  show 
  the 
  lines 
  

   expanded 
  at 
  the 
  ends, 
  and 
  in 
  one 
  plate 
  they 
  are 
  pointed. 
  

   Though 
  in 
  most 
  cases 
  the 
  forms 
  of 
  H 
  and 
  K 
  are 
  very 
  similar, 
  

   there 
  is 
  a 
  single 
  instance 
  where 
  K 
  is 
  shown 
  sharply 
  double 
  in 
  

   the 
  fainter 
  portions 
  at 
  each 
  end 
  of 
  the 
  line, 
  and 
  at 
  one 
  end 
  the 
  

   components 
  seem 
  to 
  diverge 
  slightly. 
  That 
  this 
  is 
  not 
  the 
  

   result 
  of 
  poor 
  focusing 
  is 
  attested 
  by 
  the 
  sharpness 
  of 
  the 
  lines 
  

   in 
  the 
  background 
  of 
  solar 
  spectrum 
  ; 
  at 
  the 
  same 
  time 
  the 
  

   appearance 
  is 
  hardly 
  that 
  of 
  an 
  ordinary 
  reversal. 
  One 
  further 
  

   peculiarity 
  will 
  show 
  that 
  it 
  is 
  safest, 
  for 
  the 
  present 
  at 
  least, 
  

   not 
  to 
  draw 
  any 
  conclusions 
  from 
  such 
  appearances 
  as 
  have 
  

   been 
  noted. 
  In 
  a 
  certain 
  position 
  of 
  the 
  mirror 
  of 
  the 
  measuring 
  

   machine 
  the 
  illumination 
  was 
  such 
  that 
  the 
  edges 
  of 
  the 
  radial 
  

   black 
  lines 
  appeared 
  bright, 
  while 
  the 
  Fraunhofer 
  lines 
  of 
  the 
  

   solar 
  spectrum 
  were 
  also 
  bright, 
  as 
  with 
  ordinary 
  illumination. 
  

   One 
  of 
  the 
  negatives, 
  in 
  which 
  H 
  and 
  K 
  were 
  broader 
  and 
  

   fainter 
  at 
  the 
  top, 
  brought 
  out 
  the 
  effect 
  particularly 
  well. 
  The 
  

   central 
  dark 
  line 
  extended 
  two-thirds 
  of 
  the 
  distance 
  to 
  the 
  top 
  

   of 
  the 
  prominence, 
  and 
  in 
  the 
  upper 
  part 
  it 
  was 
  excessively 
  

   narrow 
  and 
  delicate. 
  Lower 
  down 
  it 
  gradually 
  widened, 
  until 
  

   at 
  a 
  point 
  very 
  near 
  the 
  limb 
  the 
  widening 
  became 
  much 
  more 
  

   rapid, 
  and 
  at 
  the 
  limb 
  itself 
  the 
  line 
  was 
  nearly 
  as 
  wide 
  as 
  

   when 
  seen 
  under 
  ordinary 
  conditions. 
  

  

  A 
  paragraph 
  from 
  Dr. 
  Schuster's 
  report 
  on 
  the 
  results 
  

   obtained 
  with 
  the 
  spectroscopic 
  cameras 
  at 
  the 
  total 
  eclipse 
  of 
  

   August 
  29, 
  1886, 
  seems 
  to 
  refer 
  to 
  a 
  somewhat 
  similar 
  appear- 
  

   ance. 
  Speaking 
  of 
  the 
  photographs 
  of 
  the 
  coronal 
  spectrum, 
  

   Dr. 
  Schuster 
  remarks 
  :* 
  " 
  A 
  bright 
  line 
  shows 
  black 
  on 
  the 
  neg- 
  

   ative, 
  and 
  is 
  bounded 
  on 
  both 
  sides 
  by 
  an 
  apparently 
  lighter 
  

  

  *Phil. 
  Trans., 
  vol. 
  dxxx, 
  (1889), 
  (A.), 
  p. 
  328. 
  

  

  