﻿a 
  Spherical 
  Gaseous 
  Nebula, 
  

   F&. 
  1. 
  

  

  o 
  R 
  5 
  R* 
  R 
  3 
  R 
  2 
  Ri 
  

  

  T^, 
  T 
  2 
  R 
  2 
  , 
  T3R3, 
  T 
  4 
  R 
  4 
  , 
  T 
  5 
  R 
  5 
  , 
  are 
  temperature 
  curves 
  for 
  a 
  constant 
  

   mass 
  of 
  monatomic 
  gas 
  in 
  equilibrium, 
  at 
  five 
  stages 
  of 
  its 
  history, 
  

   numbered 
  1, 
  2, 
  3, 
  4, 
  5, 
  in 
  order 
  of 
  time, 
  while 
  it 
  is 
  losing 
  heat 
  by- 
  

   radiation 
  into 
  space. 
  

  

  B2 
  

  

  