beautiful seems almost dormant. Philosophy, after having been awhile predominant, lapses for a long season into neglect ; and then again slowly revives. Each science has its eras of deductive reasoning, and its eras when attention is chiefly directed to collecting and colligating facts. And how in such minor but more obtrusive phenomena as those of fashion, there are ever going on oscillations from one extreme to the other, is a trite observation.

As may be foreseen, social rhythms well illustrate the irregularity that results from combination of many causes. Where the variations are those of one simple element in national life, as the supply of a particular commodity, we do indeed witness a return, after many involved movements, to a previous condition-the price may become what it was before: implying a like relative abundance. But where the action is one into which many factors enter, there is never a recurrence of exactly the same state. A political reaction never brings round just the old form of things. The rationalism of the present day differs widely from the rationalism of the last century. And though fashion from time to time revives extinct types of dress, these always re-appear with decided modifications.

§ 88. The universality of this principle suggests a question like that raised in foregoing cases. Rhythm being manifested in all forms of movement, we have reason to suspect that it is determined by some primordial condition to action in general. The tacit implication is that it is deducible from the persistence of force. This we shall find to be the fact.

When the prong of a tuning-fork is pulled on one side by the finger, a certain extra tension is produced among its cohering particles; which resist any force that draws them out of their state of equilibrium. As much force as the finger exerts in pulling the prong aside, so much opposing force is brought into play among the cohering particles. Hence, when the prong is liberated, it is urged back by a force equal

to that used in deflecting it. When, therefore, the prong reaches its original position, the force impressed on it during its recoil, has generated in it a corresponding amount of momentum-an amount of momentum nearly equivalent, that is, to the force originally impressed (nearly, we must say, because a certain portion has gone in communicating motion to the air, and a certain other portion has been transformed into heat). This momentum carries the prong beyond the position of rest, nearly as far as it was originally drawn in the reverse direction; until at length, being gradually used up in producing an opposing tension among the particles, it is all lost. The opposing tension into which the expended momentum has been transformed, then generates a second recoil; and so on continually-the vibration eventually ceasing only because at each movement a certain amount of force goes in creating atmospheric and etherial undulations. Now it needs but to contemplate this repeated action and reaction, to see that it is, like every action and reaction, a consequence of the persistence of force. The force exerted by the finger in bending the prong cannot disappear. Under what form then does it exist? It exists under the form of that cohesive tension which it has generated among the particles. This cohesive tension cannot cease without an equivalent result. What is its equivalent result? The momentum generated in the prong while being carried back to its position of rest. This momentum too-what becomes of it? It must either continue as momentum, or produce some correlative force of equal amount. It cannot continue as momentum, since change of place is resisted by the cohesion of the parts; and thus it gradually disappears by being transformed into tension among these parts. This is retransformed into the equivalent momentum; and so on continuously. If instead of motion that is directly antagonized by the cohesion of matter, we consider motion through space, the same truth presents itself under another form. Though here no opposing force seems at work, and therefore

no cause of rhythm is apparent, yet its own accumulated momentum must eventually carry the moving body beyond the body attracting it; and so must become a force at variance with that which generated it. From this conflict, rhythm necessarily results as in the foregoing case. The force embodied as momentum in a given direction, cannot be destroyed; and if it eventually disappears, it re-appears in the reaction on the retarding body; which begins afresh to draw the now arrested mass back from its aphelion. The only conditions under which there could be absence of rhythm -the only conditions, that is, under which there could be a continuous motion through space in the same straight line. for ever, would be the existence of an infinity void of everything but the moving body. And neither of these conditions can be représented in thought. Infinity is inconceivable ; and so also is a motion which never had a commencement in some pre-existing source of power.

Thus, then, rhythm is a necessary characteristic of all motion. Given the co-existence everywhere of antagonist forces-a postulate which, as we have seen, is necessitated by the form of our experience—and rhythm is an inevitable corollary from the persistence of force.

CHAPTER XI.

RECAPITULATION, CRITICISM, AND RECOMMENCEMENT.

§ 89. Let us pause awhile to consider how far the contents of the foregoing chapters go towards forming a body of knowledge such as was defined at the outset as constituting Philosophy.

In respect of its generality, the proposition enunciated and exemplified in each chapter, is of the required kind—is a proposition transcending those class-limits which Science, as currently understood, recognizes. "The Indestructibility of Matter" is a truth not belonging to mechanics more than to chemistry, a truth assumed alike by molecular physics and the physics that deals with sensible masses, a truth which the astronomer and the biologist equally take for granted. Not merely do those divisions of Science which deal with the movements of celestial and terrestrial bodies postulato "The Continuity of Motion," but it is no less postulated in the physicist's investigations into the phenomena of light and heat, and is tacitly, if not avowedly, implied in the generalizations of the higher sciences. So, too, "The Persistence of Force," involved in each of the preceding propositions, is co-extensive with them, as is also its corollary, "The Persistence of Relations among Forces." These are not truths of a high generality, but they are universal truths. Passing to the deductions drawn from them, we see the same thing. That force is transformable.

and that between its correlates there exist quantitative equivalences, are ultimate facts not to be classed with those of mechanics, or thermology, or electricity, or magnetism; but they are illustrated throughout phenomena of every order, up to those of mind and society. Similarly, the law that motion fol. lows the line of least resistance or the line of greatest traction or the resultant of the two, we found to be an all-pervading law; conformed to alike by each planet in its orbit, and by the moving matters, aërial, liquid, and solid, on its surface -conformed to no less by every organic movement and process than by every inorganic movement and process. And so likewise, in the chapter just closed, it has been shown that rhythm is exhibited universally, from the slow gyrations of double stars down to the inconceivably rapid oscillations of molecules-from such terrestrial changes as those of recurrent glacial epochs and gradually alternating elevations and subsidences, down to those of the winds and tides and waves; and is no less conspicuous in the functions of living organisms, from the pulsations of the heart up to the paroxysms of the emotions.

Thus these truths have the character which constitutes them parts of Philosophy, properly so called. They are truths which unify concrete phenomena belonging to all divisions of Nature; and so must be components of that complete, coherent conception of things which Philosophy seeks.

§ 90. But now what parts do these truths play in forming such a conception? Does any one of them singly convey an idea of the Cosmos: meaning by this word the totality of the manifestations of the Unknowable? Do all of them taken together yield us an adequate idea of this kind? Do they even when thought of in combination compose anything like such an idea? To each of these questions the answer must be-No.

Neither these truths nor any other such truths, separately