344 THE POPULAR SCIENCE MONTHLY. 



will show how plauets and satellites are formed from rotating nebulous 

 masses : 



As radiation still continued, the repulsive force between the par- 

 ticles diminished, which allowed them to approach nearer to each other ; 

 and this tendency to agglomeration resulted in the formation of small 

 centres of local attraction near the surface of the ring, where radiation 

 was most rapid. 



As condensation continued, new centres of local attraction were 

 formed within, while the outer and older nodules continued to increase 

 in size, and to coalesce into larger masses ; till, finally, the outer edge of 

 this ring had changed from an homogeneous and continuous nebulous 

 disk to a multitude of nebulous planetoids of great volume, but of 

 small mass ; while the succeeding interior particles, as fast as they were 

 left out by the contracting spheroid, were preparing to undergo a like 

 change. 



Now, as these planetoids have various periods of revolution, they 

 will occasionally come into conjunction, and then, on account of the 

 great volume and small mass of each, they should coalesce without 

 crash ; till, finally, some preponderating mass should collect all the little 

 ones exterior to its orbit into itself, together with as many of those 

 within its orbit as its gravitating force could control. 



In like manner will all succeeding rings be collected into nebulous 

 planets ; and, if the masses of these planets be sufficiently large, they 

 too, in a like manner, will develop nebulous secondaries after their own 

 likeness, both in form and motion. 



It is the satellites so formed of the out-left rings of the condensing 

 nebulous planets in our system that have been under discussion in this 

 paper. 



That the nebulous planet thus formed will be given a motion of ro- 

 tation in the same direction as that of its primary is due to the fact 

 that the exterior planetoids have a greater virtual velocity than the 

 interior ones have. This will become evident from the following con- 

 siderations : 



Let us consider, first, the effect produced on its rotation by one of 

 the outer planetoids as it coalesces with this preponderating mass. As 

 the two bodies approach conjunction, the small one will be drawn 

 inward to meet the larger one, and this contraction of its orbit so in- 

 creases its orbital velocity that, at the time of meeting, this velocity is 

 greater than that of the controlling mass, and on striking it will give 

 the latter an impulse to rotate in the direction of its orbital motion ; 

 while, on the other hand, one of the interior planetoids, by being drawn 

 outward, will have its motion diminished to such a degree that, on meet- 

 ing, it will give the larger one an impulse to rotate in the same direc- 

 tion as that which the outer one gave to it. 



Now, if this nebulous globe be not disturbed by some external force, 

 it will form the outer planet of the then future solar system. 



