80 SCIKXCE IX SHOUT CHAPTERS. 



tion of these conditions -viz. that the vessel containing the 

 dissociated gases, at the temperature of dissociation, shall be 

 surrounded with bodies cooler than itself i.e. capable of 

 receiving more heat from it than they radiate toward it ; there 

 would then take place just so much combustion as would set 

 free the amount of heat required to maintain the temperature 

 of the vessel at the dissociation-point ; or, in other words, 

 combustion would go on to the extent of setting free just so 

 much heat as the gaseous mass was capable of radiating, or 

 otherwise transmitting to surrounding bodies ; and this amount 

 of combustion would continue till all the gases lu.d combined. 



We have only to give this hypothetical vessel a spherical 

 form and an internal diameter of 853,380 miles to construct 

 its enveloping sides of a thick shell of aqueous vapor, etc., and 

 then, by placing in the midst of the contained dissociated gases 

 a nucleus of some kind, we are hypothetically supplied with 

 the main conditions which I suppose to exist in the sun. 



A little reflection upon the application of the above- stated 

 laws to these conditions will show that the stupendous ocean 

 of explosive gases would constitute an enormous stock of fuel 

 capable, by its combustion, of setting free exactly the same 

 quantity of heat as had previously been con v cited into decom- 

 posing or separating force ; the amount of combustion would 

 always be limited by the possible amount of radiation, and the 

 radiation would again be limited by the resisting envelope of 

 aqueous vapor produced by this combustion. 



If these conditions existed in a perfectly calm and undisturb- 

 ed solar atmosphere, there would be a continually increasing 

 external envelope of aqueous vapor, and a continually diminish- 

 ing inner atmosphere of combustible gases ; there would be a 

 gradual diminution of the amount of solar radiation, and a slow 

 and perpetually retarding progress toward solar extinction. 



It should be noted that, according to this explanation, the 

 supply of heat is originally derived from atmospheric condensa- 

 tion due to gravitation, that the storage of surplus heat is 

 effected by dissociation, and its evolution mainly by recombina- 

 tion or combustion. 



The great difficulty, that of the perpetual renewal of the 

 solar fuel, still remains unsolved ; the fact that during the 

 millions of years of geological history we find no indications of 

 any declining average of solar energy is so far still unexplained 

 by this, as by every other, attempt to account for the origin 

 of solar and stellar linht and heat. 



