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 



