﻿AECHITECTUEE 
  OF 
  ATOMS 
  ABBOT. 
  161 
  

  

  all 
  chemical 
  compounds 
  into 
  atoms, 
  then 
  the 
  metallic 
  spectrum 
  lines 
  

   grow 
  faint, 
  with 
  hydrogen 
  lines 
  becoming 
  strong, 
  and 
  at 
  length 
  in 
  

   the 
  blue- 
  white 
  giant 
  stage 
  of 
  Rigel 
  and 
  Spica, 
  where 
  maximum 
  

   temperature 
  is 
  reached, 
  only 
  hydrogen 
  and 
  helium 
  lines 
  remain. 
  

   This 
  is 
  the 
  turning 
  point. 
  The 
  star 
  cools 
  and 
  grows 
  denser 
  as 
  it 
  goes 
  

   on 
  into 
  the 
  dwarf 
  stage. 
  Metallic 
  lines 
  reappear, 
  and 
  at 
  last 
  the 
  

   star 
  fades 
  out 
  as 
  a 
  dwarf 
  of 
  type 
  M, 
  now 
  indistinguishable 
  in 
  spec- 
  

   trum, 
  except 
  for 
  certain 
  details 
  visible 
  only 
  to 
  experts 
  (which, 
  never- 
  

   theless, 
  are 
  highly 
  characteristic 
  of 
  the 
  altered 
  density), 
  from 
  its 
  

   original 
  type 
  as 
  a 
  class 
  M 
  giant. 
  This 
  progress 
  is 
  summarized 
  in 
  the 
  

   following 
  table: 
  

  

  