500 EQUILIBRATION. 



Fully to comprehend the process of equilibration, is not 

 easy; since we have simultaneously to contemplate various 

 phases of it. The best course will be to glance separately at 

 what we may conveniently regard as its four different 

 orders. The first order includes the comparatively 



simple motions, as those of projectiles, which are not pro- 

 longed enough to exhibit their rhythmical character; but 

 which, being quickly divided and subdivided into motions 

 communicated to other portions of matter, are presently dis- 

 sipated in the rhythm of ethereal undulations. In 

 the second order, comprehending the various kinds of vi- 

 bration or oscillation as usually witnessed, the motion is used 

 up in generating a tension which, having become equal to it 

 or momentarily equilibrated with it, thereupon produces a 

 motion in the opposite direction, that is subsequently equili- 

 brated in like manner: thus causing a visible rhythm, that 

 is, however, soon lost in invisible rhythms. The third 

 order of equilibration, not hitherto noticed, obtains in those 

 aggregates which continually receive as much motion as 

 they expend. The steam engine (and especially that kind 

 which feeds its own furnace and boiler) supplies an example. 

 Here the force from moment to moment dissipated in over- 

 coming the resistance of the machinery driven, is from mo- 

 ment to moment re-placed from the fuel ; and the balance of 

 the two is maintained by a raising or lowering of the ex- 

 penditure according to the variation of the supply : each in- 

 crease or decrease in the quantity of steam, resulting in a rise 

 or fall of the engine's movement, such as brings it to a bal- 

 ance wdth the increased or decreased resistance. This, which 

 we may fitly call the dependent moving equilibrium, should 

 be specially noted; since it is one that we shall commonly 

 meet with throughout various phases of Evolution. The 

 equilibration to be distinguished as of the fourth order, is the 

 independent or perfect moving equilibrium. This we see 

 illustrated in the rhythmical motions of the Solar System; 

 which, being resisted only by a medium of inappreciable 



