118 Proceedings of Royal Society of Edinburgh, [fee. 21 , 
One interesting result which I can give at present, derived from 
the first and last numbers of the several columns of the preceding 
table, is, that the central density of a globular gaseous star is 22 J 
times its average density. 
Monday , 7th March 1887. 
Sir WILLIAM THOMSON, President, in the Chair. 
The following Communications were read : — 
1. On the Equilibrium of a Gas under its own Gravitation 
only. Part III. By Sir W. Thomson. 
2. History of the Theory of Determinants. Part I. Deter- 
minants in General: Hindenburg (1784) to Eeiss 
(1829). By Dr Muir. 
[This Paper is printed at the end of the Proceedings of the Session.] 
3. Note on Solar Radiation. By Mr John Aitken. 
In the many theories that have been advanced to explain the 
comparative constancy of solar radiation in long past ages as evi- 
denced by geological history, it has been generally assumed that the 
temperature of the sun has not varied much, and to account for 
its not falling in temperature a number of theories have been 
advanced, all suggesting different sources from which it may have 
received the energy which it radiates as heat. Since the chemical 
theory was shown to be insufficient to account for the vast amount 
of heat radiated, other theories, such as the meteoric theory and 
the conservation of energy theory, have been advanced. 
In all these theories it is generally assumed that in order that the 
radiation from the sun may be constant its temperature must also he 
constant, that, in fact, radiation from the sun is in proportion to its 
temperature ; and that if the temperature of the sun falls, its radia- 
tion effect at the earth’s surface will fall in direct proportion to 
