40 Some Astronomical Problems. [Sess. 



But the immense dissipation of energy must reduce the ex- 

 pansive power of these highly heated gases, and the body of 

 the sun must shrink. It can readily be shown that a body 

 of gas shrinking under these conditions produces a large 

 amount of heat, and it is suggested that a supply of heat will 

 be maintained through continual shrinkage without much 

 alteration until the physical condition of the interior of the 

 sun undergoes alteration, — in other words, till it begins to 

 solidify. 



It is a captivating theory, and has held the ground for a, 

 long time. It is probably true in a measure, but many have 

 felt that it would break down under the stress of the enor- 

 mously long periods of time demanded by the insatiable evol- 

 utionist. It is difficult to get away from the fact that a 

 shrinking sun must be a continually cooling sun. 



Within the last few years the unexpected has happened, 

 and in the discovery of that remarkable element, radium, the 

 scientific mind has found a sedative for its perplexities, and 

 a kind of elixir of life for our apparently fast-dying sun. 

 He can go on now for untold ages, and we can heave a sigh 

 of relief at the thought that the calamity of extinction will 

 not happen in our day. 



The element radium is undergoing a process peculiar (at least 

 in any measure) to itself, but which is acquiring a prominent 

 place in modern politics, namely, devolution. Eadium has 

 a very high atomic weight ; its atom, or molecule, appears to 

 be unstable ; and it is slowly breaking down, and producing 

 in the process elements of a less atomic weight than its own. 

 This wonderful process is attended by the liberation of an 

 enormous amount of energy, — enormous when compared with 

 the exceedingly small amount of matter transformed in a 

 given period of time. It is estimated that radium will give 

 out in one hour sufficient heat to raise its own weight of 

 water from the freezing- to the boiling-point. This emission 

 of energy by the radium atom is very fixed and persistent in 

 amount, and does not appear to vary in the smallest degree 

 even under the most extreme conditions. The presence of 

 radium, then, in the sun is now the great factor in the main- 

 tenance of his supply of energy. I do not know that the 

 spectroscope has revealed the presence of radium in the sun, 



