ORIGIN AND AGE OF THE SUNS HEAT. 281 



Now, in proving that the antiquity of our habitable 

 globe must be far greater than 20 or 30 million years, 

 we prove that there must have been some other source 

 in addition to gravity from which the sun derived his 

 store of energy; and this is the point which I have 

 been endeavouring to reach by this somewhat lengthy 

 discussion. 



