364 POPULAR LECTURES AND ADDRESSES. 



created an as active source of heat at some time 

 of not immeasurable antiquity, by an over-ruling 

 decree ; or the heat which he has already radiated 

 away, and that which he still possesses, must 

 have been acquired by a natural process, follow- 

 ing permanently established laws. Without pro- 

 nouncing the former supposition to be essentially 

 incredible, we may safely say that it is in the 

 highest degree improbable, if we can show 

 the latter to be not contradictory to known 

 physical laws. And we do show this and more, 

 by merely pointing to certain actions, going on 

 before us at present, which, if sufficiently abundant 

 at some past time, must have given the sun heat 

 enough to account for all we know of his past 

 radiation and present temperature. 



It is not necessary at present to enter at length 

 on details regarding the meteoric theory, which 

 appears to have been first proposed in a definite 

 form by Mayer, and afterwards independently 

 by Waterston ; or regarding the modified hypo- 

 thesis of meteoric vortices, which the writer of the 

 present article showed to be necessary, in order that 



