THE LAW OF EQUILIBRIUM 141 



command of the Prime Resultant, and that instead of 

 falling down in straight lines, as they would do were their 

 mutual attractions dissolved, they fall with a spiral twist 

 that carries them perpetually round and round their com- 

 mon center of gravity. In short, the solar system, I hold, 

 is an immense clock driven by its own descending weight. 



This mechanical principle is capable of unlimited ex- 

 tension, upward and downward. It applies as well to 

 molecules as to stars, to cohering particles as well as to 

 cosmic orbs separated by the full span of the universe. 

 The sun's next door neighbor is Alpha Centauri, ten 

 thousand times farther from him than Neptune, his outer- 

 most planet. Think of this, or any, pair of stars, or of any 

 combination of pairs or clusters of stars, in their relation 

 to the sum of the universe, and there will be borne in upon 

 you the realization that the whole body of the macrocosm 

 is perpetually writhing within itself in the throes of 

 equilibristic evolution. The physical universe is built on 

 the principle of action, not stagnation ; on that of autom- 

 atism, not blind chance ; on perpetuity, not finiteness. 



Concentrating our attention on the solar system, we 

 note that the planets revolve around the sun in (seeming) 

 ellipses, that their radii vectores sweep over equal areas 

 in equal times, and that the cubes of their distances are 

 proportional to the squares of their periodic times. The 

 problem before us is to prove that these phenomena are 

 incidental to the normal operation of the principle of the 

 lever but, mark you, not of a stationary lever, but of one 

 whose pendent weights are in the act of falling. 



To begin with, what is the principle of the simple 

 lever or balance arm! It is this: Suppose a bar to be 

 supported on a pivot so as to rotate in a horizontal plane, 

 then, in order that its arms, if unequal in length, shall 

 balance, the weights at the ends must ~be inversely pro- 

 portional to those lengths. That is to say, if one of the 

 arms be half the length of the other, the weight on the 

 shorter end must be doubled, if one-third the length, 

 trebled, and so on. 



