SECOND CHAPTER. 



OF THE DIFFERENT DENSITY OF THE PLANETS 

 AND THE RELATION OF THEIR MASSES. 



have shown that the particles of the primitive ele- 

 mentary matter having been uniformly distributed by 

 themselves in space would, by falling towards the sun, 

 remain moving in the places where the velocity acquired 

 by them in falling just attained equality with the attraction 

 exerted upon them, and that their direction would be 

 bent aside till it became perpendicular to the radius of 

 their orbit, as ought to hold in circular movements. 



But if we now consider particles of different specific 

 density at the same distance from the sun, those of greater 

 specific gravity press farther down through the resistance 

 of the other particles towards the sun, and are not so 

 soon bent aside from their paths as the lighter particles ; 

 and hence their movement becomes circular only when 

 they approach nearer the sun. On the other hand, the 

 elements of a lighter kind are sooner bent from the 

 straight line of their fall, and turn into circular move- 

 ments before they have penetrated so far towards the 

 centre, and therefore will remain revolving at greater 

 distances. They can neither penetrate so far through 



