280 CELESTIAL DYNAMICS. 



A correct theory of the origin of the sun's heat must ex- 

 plain the cause of such enormous temperatures. This expla- 

 nation can be deduced from the foregoing statements. Ac- 

 cording to Pouillet, the temperature at which bodies appear 

 intensely white-hot is about 1500 C. The heat generated by 

 the combustion of one kilogramme of hydrogen is, as deter- 

 mined by Dulong, 34,500, and according to the more recent 

 experiments of Grassi, 34,666 units of heat. One part of 

 hydrogen combines with eight parts of oxygen to form water ; 

 hence one kilogramme of these two gases mixed in this ratio 

 would produce 3850. 



Let us now compare this heat with the amount of the 

 same agent generated by the fall of an asteroid into the sun. 

 Without taking into account the low specific heat of such 

 masses when compared with that of water, we find the heat 

 developed by the asteroid to be from 7000 to 15,000 times 

 greater than that of the oxyhydrogen mixture. From data 

 like these, the extraordinary diathermic energy of the sun's 

 rays, the immense radiation from his surface, and the high 

 temperature in the focus of the reflector are easily accounted 

 for. 



The facts above mentioned show that, unless we assume 

 on the sun the existence of matter with unheard of chemical 

 properties as a deus ex machind, no chemical process could 

 maintain the present high radiation of the sun ; it also fol- 

 lows from the above results, that the chemical nature of bo- 

 dies which fall into the sun does not in the least aifect our 

 conclusions; the effect produced by the most inflammable 

 substance would not differ by one-thousandth part from that 

 resulting from the fall of matter possessing but feeble chemi- 

 cal affinities. As the brightest artificial light appears dark in 

 comparison with the sun's light, so the mechanical processes 

 of the heavens throw into the shade the most powerful chem- 

 ical actions. 



The quality of the sun's rays, as dependent on his temper- 



