264 THE RHYTHM OF MOTION. 



one force over the other — must prevent uniformity of move- 

 ment. And if the movement cannot be uniform, then, in 

 the absence of acceleration or retardation continued through 

 infinite time and space, (results which cannot be conceived) 

 the only alternative is rhythm. 



A secondary conclusion must not be omitted. In the last 

 chapter we saw that motion is never absolutely rectilinear; 

 and here it remains to be added that, as a consequence, 

 rhythm is necessarily incomplete. A truly rectilinear 

 rhythm can arise only when the opposing forces are in ex- 

 actly the same line ; and the probabilities against this are in- 

 finitely great. To generate a perfectly circular rhythm, the 

 two forces concerned must be exactly at right angles to each 

 other, and must have exactly a certain ratio; and against 

 this the probabilities are likewise infinitely great. All other 

 proportions and directions of the two forces will produce an 

 ellipse of greater or less eccentricity. And when, as indeed 

 always happens, above two forces are engaged, the curve de- 

 scribed must be more complex; and cannot exactly repeat 

 itself. So that in fact throughout nature, this action and re- 

 action of forces never brings about a complete return to a 

 previous state. Where the movement is much involved, 

 and especially where it is that of some aggregate whose units 

 are partially independent, anything like a regular curve is 

 no longer traceable ; we see nothing more than a general os- 

 cillation. And on the completion of any periodic move- 

 ment, the degree in which the state arrived at differs from 

 the state departed from, is usually marked in proportion as 

 the influences at work are numerous. 



§ 83. That spiral arrangement so general among the 

 more diffused nebulae — an arrangement which must be as- 

 sumed by matter moving towards a centre of gravity 

 through a resisting medium — shows us the progressive estab- 

 lishment of revolution, and therefore of rhythm, in those 

 remote spaces which the nebulas occupy. Double stars, 



