18 AV STARR* REALMS. 



constant rate. We are aware that ingenious machinery 

 is often applied for the purpose of stoking the fires under 

 steam boilers. It is claimed for these machines that they 

 administer the coal to the fire so regularly that the pro- 

 duction of steam is carried on with all desired uniformity. 

 If there were sufficient fuel in the sun for the mainte- 

 nance of its radiation, and if there were gas or other mate- 

 rial suitable for union with that fuel in sufficient quantity 

 to generate the necessary heat, it seems difficult to ima- 

 gine by what arrangements the combustion of the two 

 elements eager for union could be so controlled that the 

 supply of heat produced should remain practically con- 

 stant. How are we to suppose that the gas and the fuel 

 can be continuously brought together in the duly regulated 

 quantities ? These considerations alone suffice to render 

 it highly improbable that chemical union could afford an 

 effective explanation of sun heat. 



There is a still more insuperable objection. Careful 

 experiments have taught us the precise quantity of heat 

 that can be extracted from a ton of coal when combined 

 with the requisite quantity of oxygen for combustion at 

 the best possible advantage. We are, therefore, able to 

 compute how much coal would have to be consumed every 

 day to generate enough heat for the maintenance of solar 

 radiation. We can show that the sun's daily expenditure 

 is so enormous that the supply of fuel that would be neces- 

 sary places this view of the origin of the sun's heat alto- 

 gether out of the question. Suppose that the whole sun 

 from its surface to its centre were a solid globe of coal 

 Suppose that from some source or other a supply of oxygen 

 were available which was adequate for the combustion of 



