MEASURE OF THE SUN S HEAT. 269 



The same law holds good for celestial bodies. 



The movements of celestial bodies in an absolute vacuum 

 would be as uniform as those of a mathematical pendulum, 

 whereas a resisting medium pervading all space would cause 

 the planets to move in shorter and shorter orbits, and at last 

 to fall into the sun. 



Assuming such a resisting medium, these wandering ce 

 lestial bodies must have on the periphery of the solar system 

 their cradle, and in its centre their grave ; and however long 

 the duration, and however great the number of their revolu 

 tions may be, as many masses will on the average in a cer 

 tain time arrive at the sun as formerly in a like period of 

 time came within his sphere of attraction. 



All these bodies plunge with a violent impetus into their 

 common grave. Since no cause exists without an effect, each 

 of these cosmical masses will, like a weight falling to the 

 earth, produce by its percussion an amount of heat propor 

 tional to its vis viva. 



From the idea of a sun whose attraction acts throughout 

 space, of ponderable bodies scattered throughout the universe, 

 and of a resisting aether, another idea necessarily follows 

 that, namely, of a continual and inexhaustible generation of 

 heat on the central body of this cosmical system. 



Whether such a conception be realized in our solar system 

 whether, in other words, the wonderful and permanent evo 

 lution of light and heat be caused by the uninterrupted fall 

 of cosmical matter into the sun will now be more closely 

 examined. 



The existence of matter in a primordial condition ( Urma- 

 terie), moving about in the universe, and assumed to follow 

 the attraction of the nearest stellar system, will scarcely be 

 denied by astronomers and physicists ; for the richness of 

 surrounding nature, as well as the aspect of the starry heav 

 ens, prevents the belief that the wide space which separates 

 our solar system from the regions governed by the other fixed 



