442 The Fuel of the Sun % . [October, 



amount of heat required to maintain the temperature of the 

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

 bustion 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 had 

 combined. 



We have only to give this hypothetical vessel a spherical 

 form and an internal diameter of 853,380 miles, — to con- 

 struct its enveloping sides of a thick shell of aqueous 

 vapour, <&c, and then, by placing in the midst of the con- 

 tained 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 

 converted into decomposing 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 vapour pro- 

 duced by this combustion. 



If these conditions existed in a perfectly calm and undis- 

 turbed solar atmosphere, there would be a continually-in- 

 creasing external envelope of aqueous vapour, and a con- 

 tinually-diminishing inner atmosphere of combustible gases; 

 there would be a gradual diminution of the amount of solar 

 radiation, and a slow and perpetually-retarding progress 

 towards solar extinction. 



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

 supply of heat is originally derived from atmospheric con- 

 densation due to gravitation, that the storage of surplus heat 

 is effected by dissociation, and its evolution mainly by re- 

 combination 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 unex- 

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

 origin of solar and stellar light and heat. 



In his inaugural' address to the British Association 

 Meeting of 1866, Mr. Grove put the following very sugges- 

 tive question : — " Our sun, our earth, and planets are con- 

 stantly radiating heat into space ; so, in all probability, are 



