﻿152 
  

  

  Mr. 
  J. 
  N. 
  Lockyer 
  on 
  a 
  

  

  [Jan. 
  7 
  ', 
  

  

  January 
  7, 
  1875. 
  

  

  JOSEPH 
  D 
  ALTON 
  HOOKER, 
  C.B., 
  President, 
  in 
  the 
  Chair. 
  

  

  The 
  Presents 
  receive! 
  were 
  laid 
  on 
  the 
  table, 
  and 
  thanks 
  ordered 
  for 
  

   them. 
  

  

  The 
  following 
  Papers 
  were 
  read 
  : 
  — 
  

  

  I. 
  " 
  Remarks 
  on 
  a 
  New 
  Map 
  of 
  the 
  Solar 
  Spectrum." 
  By 
  

   J. 
  Norman 
  Lockyer, 
  E.R.S. 
  Received 
  November 
  13, 
  

   1874. 
  

  

  I 
  beg 
  permission 
  to 
  lay 
  before 
  the 
  Royal 
  Society 
  a 
  portion 
  of 
  the 
  new 
  

   map 
  of 
  the 
  solar 
  spectrum 
  referred 
  to 
  in 
  one 
  of 
  my 
  former 
  communi- 
  

   cations. 
  

  

  It 
  consists 
  of 
  the 
  portion 
  between 
  w. 
  1. 
  39 
  and 
  41. 
  

   I 
  have 
  found 
  it 
  necessary, 
  in 
  order 
  to 
  include 
  all 
  the 
  lines 
  visible 
  in 
  

   my 
  photographs 
  in 
  such 
  a 
  manner 
  that 
  coincidences 
  may 
  be 
  clearly 
  

  

  o 
  

  

  shown, 
  to 
  construct 
  it 
  on 
  four 
  times 
  the 
  scale 
  of 
  Angstrom's 
  " 
  Spectre 
  

   Normal." 
  

  

  The 
  spectra 
  of 
  the 
  following 
  elements 
  have 
  been 
  photographed 
  side 
  by 
  

   side 
  with 
  the 
  solar 
  spectrum 
  and 
  the 
  coincidences 
  shown 
  : 
  — 
  

  

  Ee, 
  Co, 
  Ni, 
  Mn, 
  Ce, 
  IT, 
  Cr, 
  Ba, 
  Sr, 
  Ca, 
  K, 
  Al. 
  

  

  The 
  wave-lengths 
  of 
  new 
  lines 
  in 
  the 
  portion 
  of 
  this 
  spectrum 
  at 
  pre- 
  

   sent 
  completed 
  have 
  been 
  obtained 
  from 
  curves 
  of 
  graphical 
  interpolation. 
  

   Instead 
  of 
  the 
  reading 
  of 
  a 
  micrometer-scale, 
  a 
  photographic 
  print 
  of 
  the 
  

   spectrum 
  has 
  been 
  employed 
  in 
  the 
  construction 
  of 
  these 
  curves, 
  the 
  

   wave-lengths 
  of 
  the 
  principal 
  lines 
  being 
  taken 
  from 
  an 
  unpublished 
  map 
  

   of 
  the 
  ultra-violet 
  region 
  of 
  the 
  solar 
  spectrum, 
  a 
  copy 
  of 
  which 
  has 
  been 
  

   kindly 
  placed 
  at 
  my 
  disposal 
  by 
  M. 
  Cornu. 
  The 
  photograph 
  of 
  the 
  solar 
  

   spectrum 
  from 
  the 
  ultra-violet 
  to 
  beyond 
  E, 
  kindly 
  given 
  to 
  me 
  by 
  Mr. 
  

   Rutherfurd, 
  has 
  also 
  proved 
  of 
  great 
  service 
  in 
  the 
  present 
  work. 
  I 
  have, 
  

   in 
  fact, 
  up 
  to 
  the 
  present 
  time, 
  only 
  been 
  able 
  to 
  excel 
  this 
  photograph 
  in 
  

   the 
  region 
  about 
  H. 
  

  

  From 
  the 
  extreme 
  difficulty 
  of 
  carrying 
  on 
  eye-observations 
  upon 
  the 
  

   portion 
  of 
  the 
  spectrum 
  now 
  completed, 
  Angstrom's 
  map 
  is, 
  of 
  course, 
  

   very 
  incomplete 
  about 
  this 
  region. 
  The 
  few 
  lines 
  mapped 
  differ 
  slightly 
  

   in 
  some 
  cases 
  from 
  the 
  positions 
  assigned 
  by 
  Cornu 
  ; 
  but 
  the 
  wave-lengths 
  

   given 
  by 
  the 
  latter 
  observer 
  generally 
  fall 
  into 
  the 
  curve 
  without 
  breaking 
  

   its 
  symmetry, 
  and 
  these 
  positions 
  have 
  therefore 
  been 
  adopted. 
  The 
  

   advantage 
  possessed 
  by 
  the 
  photographic 
  method 
  over 
  eye-observation 
  

   may 
  be 
  estimated 
  from 
  the 
  following 
  numerical 
  comparisons 
  : 
  — 
  

  

  