University of Virginia Library

Chapter 23
Dissolution

§177. When, in Chapter 22, we glanced at the cycle of changes through which every existence passes, in a short time or in a time almost infinitely long — when the opposite re-distributions of matter and motion implied were severally distinguished as Evolution and Dissolution. the natures of the two, and the conditions under which they respectively occur, were specified in general terms. Since then, we have contemplated the phenomena of Evolution in detail, and have followed them out to those states of equilibrium in which they all end. To complete the argument we must now contemplate, somewhat more in detail than before, the complementary phenomena of Dissolution. Not, indeed, that we need dwell long on Dissolution, which has none of those various and interesting aspects which Evolution presents; but something more must be said than has yet been said.

It was shown that neither of these two antagonist processes goes on unqualified by the other, and that a movement towards either is a differential result of the conflict between them. An evolving aggregate, while on the average losing motion and integrating, is always, in one way or other, receiving some motion and to that extent disintegrating; and after the integrative changes have ceased to predominate, the reception of motion, though perpetually checked by its dissipation, constantly tends to produce a reverse transformation, and eventually does produce it. When Evolution has run its course — when an aggregate has reached that equilibrium in which its changes end, it thereafter remains subject to all actions in its environment which may increase the quantity of motion it contains, and which in course of time are sure, either slowly or suddenly, to give its parts such excess of motion as will cause disintegration. According as its size, its nature, and its conditions determine, its dissolution may come quickly or may be indefinitely delayed — may occur in a few days or may be postponed for billions of years. But exposed as it is to the contingencies not simply of its immediate neighbourhood but of a Universe everywhere in motion, the time must at last come when, either alone or in company with surrounding aggregates, it has its parts dispersed.

The process of dissolution so caused we have here to look at as it takes place in aggregates of different orders. The course of change being the reverse of that hitherto traced, we may properly take the illustrations of it in the reverse order — beginning with the most complex and ending with the most simple.

§178. Regarding the evolution of a society as at once an increase in the number of individuals integrated into a corporate body, an increase in the masses and varieties of the parts into which this corporate body divides, as well as of the actions called their functions, and an increase in the degree of combination among these masses and their functions; we shall see that social dissolution conforms to the general law in being, materially considered, a disintegration, and, dynamically considered, a decrease in the movements of wholes and an increase the movements of parts; while it further conforms to the general law in being, caused by an excess of motion in some way or other received from without.

It is obvious that the social dissolution which follows the aggression of mother nation, and which, as history shows us, is apt to occur when social evolution has ended and decay has begun, is, under its broadest, aspect, the reception of a new external motion; and when, as sometimes happens, the conquered society is dispersed, or when its component divisions fall apart, its dissolution is literally a cessation of those corporate movements which the society, both in its army and in its industrial bodies, presented, and a lapse into individual or uncombined movements.

Again, social disorder, however caused, entails a decrease of integrated movements and an increase of disintegrated movements. As the disorder progresses the political actions previously combined become uncombined: there arise the antagonistic actions of riot or revolt. Simultaneously, the industrial and commercial processes that were co-ordinated throughout the body politic, are broken up; and only the local, or small, trading transactions continue. And each further disorganizing change diminishes the joint operations by which men satisfy their wants, and leaves them to satisfy their wants, as best they can, by separate operations. Of the way in which such distintegrations are set up in a society that has evolved to the limit of its type, and reached a state of moving equilibrium, a good illustration is furnished by Japan. The finished fabric into which its people have organized themselves, maintained an almost constant state so long as it was preserved from fresh external forces. But as soon as it received an impact from European civilization, partly by armed aggression, partly by commercial impulse, partly by the influence of ideas, this fabric began to fall to pieces. There is now in progress a political dissolution. Probably a political reorganization will follow; but, be this as it may, the change thus far produced by an outer action is a change towards dissolution — a change from integrated motions to disintegrated motions.

Even where a society that has developed into the highest form permitted by the characters of its units, begins to dwindle and decay, the progressive dissolution is still essentially of the same nature. Decline of numbers is, in such case, brought about partly by emigration; for a society having the fixed structure in which evolution ends, is one that will not yield and modify under pressure of population: so long as its structure is plastic it is still evolving. Hence the surplus population is continually dispersed: the influences brought to bear on the citizens by other societies cause their detachment, and there is an increase of the uncombined motions of units instead of an increase of combined motions. Gradually as the society becomes still less capable of changing into the form required for successful competition with more plastic societies, the number of citizens who can live within its unyielding framework becomes positively smaller. Hence it dwindles both through continued emigration and through the diminished multiplication that follows innutrition. And this further dwindling is similarly a decrease in the total quantity of combined motion and an increase in the quantity of uncombined motion — as we shall presently see when we come to deal with individual dissolution.

Considering, then, that social aggregates differ so much from aggregates of other kinds, formed, as they are, of units held together loosely and indirectly, in such variable ways by such complex forces, the processes of dissolution among them conforms to the general law quite as clearly as could be expected.

§179. When from these super-organic aggregates we descend to organic aggregates, the truth that Dissolution is a disintegration of matter caused by the reception of additional motion from without, becomes easily demonstrable. We will look first at the transformation and afterwards at its cause.

Death, or that final equilibration which precedes dissolution, is the bringing to a close all those many conspicuous integrated motions that arose during evolution. The impulsions of the body from place to place first cease; presently the limbs cannot be stirred; later still the respiratory actions stop; finally the heart becomes stationary and, with it, the circulating fluids. That is, the transformation of molecular motion into the motion of masses, comes to an end. The process of decay involves an increase of insensible movements; since these are far greater in the gases generated than they are in the fluid-solid matters out of which the gases arise. Each of the complex chemical units composing an organic body, possesses a rhythmic motion in which its many component units jointly partake. When decomposition breaks up these complex molecules, and their constituents assume gaseous forms, there is, besides that increase of motion implied by diffusion, a resolution of such motions as the complex molecules possessed, into motions of their constituent molecules. So that in organic dissolution we have, first, an end put to that transformation of the motions of units into the motions of aggregates, which constitutes evolution, dynamically considered; and we have afterwards, though in a subtler sense, a transformation of the motions of aggregates into the motions of units. Still it is not thus shown that organic dissolution answers to the general definition of dissolution — the absorption of motion and concomitant disintegration of matter. The disintegration of matter is, indeed, conspicuous enough; but the absorption of motion is not conspicuous. True, the fact that motion has been absorbed may be inferred from the fact that particles previously integrated into a solid mass, occupying a small space, have most of them moved away from one another and now occupy a great space; for the motion implied by this expansion must have been obtained from somewhere. But its source is not obvious. A little search, however, will bring us to its derivation.

At a temperature below the freezing point of water, decomposition of organic matter does not take place. Dead bodies kept at this temperature are prevented from decomposing for an indefinitely long period: witness the frozen carcases of mammoths (elephants of a species long ago extinct) that are found imbedded in the ice at the mouths of Siberian rivers; and which, though they have been there for many thousands of years, have flesh so fresh that when at length exposed it is devoured by wolves. What, now, is the meaning of such exceptional preservations? A body kept below freezing point, is a body which receives very little heat by radiation or conduction; and the reception of but little heat is the reception of but little molecular motion. That is to say,in an environment which does not furnish it with molecular motion passing a certain amount, an organic body does not undergo dissolution. Confirmatory evidence is yielded by the variations in rate of dissolution which accompany variations of temperature. All know that in cool weather the organic substances used in our households keep longer, as we say, than in hot weather. Equally certain, if less familiar, is the fact that in tropical climates decay proceeds much more rapidly than in temperate climates. Thus, dispersion of the dead body into gases is rapid in proportion as the molecular motion received from without is great. The still-quicker decompositions produced by exposure to artificially-raised temperatures, afford further proofs: instance those which occur in cooking. The charred surfaces of parts much heated, show us that the molecular motion absorbed has served to dissipate in gaseous forms all the elements but the carbon.

The nature and causes of Dissolution are thus clearly displayed by the aggregates which so clearly display the nature and causes of Evolution. One of these aggregates being made of that peculiar matter to which a large quantity of constitutional motion gives great plasticity, and the ability to evolve into a highly complex form, (§103); it results that after evolution has ceased, a small amount of molecular motion added to that already contained in its peculiar matter, suffices to cause dissolution. Though at death there is reached an equilibrium among the sensible masses, or organs, which make up the body; yet, as the insensible units or molecules of which these organs consist are chemically unstable, small incident forces suffice to overthrow them, and hence disintegration proceeds rapidly.

§180. Most inorganic aggregates, having arrived at dense forms in which comparatively little motion is retained, remain long without marked changes. Each has lost so much motion in passing from the unintegrated to the integrated state, that much motion must be given to it to cause resumption of the unintegrated state; and an immense time may elapse before there occur in the environment, changes great enough to communicate to it the requisite quantity of motion. We will look first at those few inorganic aggregates which retain much motion, and therefore readily undergo dissolution.

Among these are the liquids and volatile solids which dissipate under ordinary conditions — water that evaporates, camphor that wastes away by the dispersion of its molecules. In all such cases motion is absorbed; and always the dissolution is rapid in proportion as the quantity of heat or motion which the mass receives from its environment is great. Next come the cases in which the molecules of a highly integrated or solid aggregate, are dispersed among the molecules of a less integrated or liquid aggregate; as in aqueous solutions. One evidence that this disintegration of matter has for its concomitant the absorption of motion, is that soluble substances dissolve the more quickly the hotter the water: supposing always that no elective affinity comes into play. Another and still more conclusive evidence is, that when crystals of a given temperature are placed in water of the same temperature, the process of solution is accompanied by a fall of temperature — often a very great one. Omitting instances in which some chemical action takes place between the salt and the water, it is a uniform law that the motion which disperses the molecules of the salt through the water, is at the expense of the molecular motion possessed by the water. An allied and still better example is furnished by cases in which the dissolution of two solids results from mixing them, as happens with snow and salt. Here dissolution necessitates so great an absorption of molecular motion as greatly to lower the temperature of the liquid produced.

Masses of sediment accumulated into strata, afterwards compressed by many thousands of feet of superincumbent strata, and reduced in course of time to a solid state, may remain for untold millions of years unchanged; but in subsequent millions of years they are inevitably exposed to disintegrating actions. Raised along with other such masses into a continent, denuded and exposed to rain, frost, and the grinding actions of glaciers, they have their particles gradually separated, carried away, and widely dispersed. Or when, as otherwise happens, the encroaching sea arrives, the undermined cliffs formed of them fall from time to time; the waves, rolling about the small pieces, and in storms knocking together the larger blocks, reduce them to boulders and pebbles, and at last to sand and mud. Even if portions of the disintegrated strata accumulate into shingle banks which afterwards become solidified, the process of dissolution, arrested though it may be for some enormous geologic period, is finally resumed. As many a shore shows us, the conglomerate itself is sooner or later subject to the like processes; and its cemented masses of heterogeneous components are broken up and worn away by impact and attrition — that is, by communicated mechanical motion.

When not thus effected, the disintegration is effected by communicated molecular motion. A consolidated stratum in some area of subsidence, brought down nearer and nearer to the regions occupied by molten matter, comes eventually to have its particles brought to a plastic state by heat, or finally melted down into liquid. Whatever may be its subsequent transformations, the transformation then exhibited by it is an absorption of motion and disintegration of matter.

Thus be it simple or compound, small or large, a crystal or a mountain-chat, every inorganic aggregate on the Earth undergoes, at some time or other, a reversal of those changes undergone during its evolution. Not that it usually passes back from the perceptible into the imperceptible, during any period in which it is or can be exposed to human observation. It does not become aeriform and invisible, as organic aggregates do in great part, though not wholly. But still its disintegration and dispersion carry it some distance on the way towards the imperceptible; and there are reasons for thinking that its arrival there is but delayed. At a period immeasurably remote, every such inorganic aggregate, along with all undissipated remnants of organic aggregates, must be reduced to a state of gaseous diffusion, and so complete the cycle of its changes.

§181. For the Earth as a whole, when it has gone through the entire series of its ascending transformations, must remain exposed to the contingencies of its environment; and in the course of those ceaseless changes going on throughout a Universe of which all parts are in motion, must, at some period beyond the utmost stretch of imagination, be subject to energies sufficient to cause its complete disintegration. Let us glance at the energies competent to disintegrate it.

In his essay on "The Inter-action of Natural Forces," Prof. Helmholtz states the thermal equivalent of the Earth's movement through space, as calculated on the now received datum of Mr. Joule. "If our Earth," he says, "were by a sudden shock brought to rest in her orbit — which is not to be feared in the existing arrangement of our system — by such a shock a quantity of heat would be generated equal to that produced by the combustion of fourteen such Earths of solid coal. Making the most unfavourable assumption as to its capacity for heat, that is, placing it equal to that of water, the mass of the Earth would thereby be heated 11,200 degrees; it would therefore be quite fused, and for the most part reduced to vapour. If then the Earth, after having been thus brought to rest, should fall into the Sun, which of course would be the case, the quantity of heat developed by the shock would be 400 times greater." Now though this calculation seems to be nothing to the purpose, since the Earth is not likely to be suddenly arrested in its orbit and not likely therefore suddenly to fall into the Sun; yet, as before pointed out (§171), there is a force at work which it is held must at last bring the Earth into the Sun. This force is the resistance of the ethereal medium. From ethereal resistance is inferred a retardation of all moving bodies in the Solar System — a retardation which some astronomers contend even now shows its effects in the relative nearness to one another of the orbits of the older planets. If, then, retardation is going on, there must come a time, no matter how remote, when the slowly diminishing orbit of the Earth will end in the Sun; and though the quantity of molar motion to be then transformed into molecular motion, will not be so great as that which the calculation of Helmholtz supposes, it will be great enough to reduce the substance of the Earth to a gaseous state.

This dissolution of the Earth and, at intervals, of every other planet, is not, however, a dissolution of the Solar System. All the changes exhibited throughout the Solar System, are incidents accompanying the integration of the entire matter composing it: the local integration of which each planet is the scene, completing itself long before the general integration is complete. But each secondary mass leaving gone through its evolution and reached a state of equilibrium among its parts (supposing that the available time suffices, which in the cases of Jupiter and Saturn it may not), thereafter continues in its extinct state, until, by the still-progressing general integration, it is brought into the central mass. And though each such union of a secondary mass with the central mass, implying transformation of molar motion into molecular motion, causes partial diffusion of the total mass formed, and adds to the quantity of motion that has to be dispersed in the shape of light and heat; yet it does but postpone the period at which the total mass must become completely integrated, and its excess of contained motion radiated into space.

§182. Here we come to the question raised at the close of the last chapter — Does Evolution as a whole, like Evolution in detail, advance towards complete quiescience? Is that motionless state called death, which ends Evolution in organic bodies, typical of the universal death in which Evolution at large must end? And have we thus to contemplate as the outcome of things, a boundless space holding here and there extinct Suns, fated to remain for ever without further change?

To so speculative an inquiry, none but a speculative answer is to be expected. Such answer as may be ventured, must be taken less as a positive answer than as a demurrer to the conclusion that the proximate result must be the ultimate result. If, pushing to its extreme the argument that Evolution must come to a close in complete equilibrium or rest, the reader suggests that for aught which appears to the contrary there must result a Universal Death which will continue indefinitely, two replies may be made. The first is that the evidence presented in the heavens at large implies that while of the multitudinous aggregates of matter it presents, most are passing through those stages — which must end in local rest, there are others which, having barely commenced the series of changes constituting Evolution, are on the way to become theatres of life. The second reply is that when we contemplate our Sidereal System as a whole, certain of the great facts which science has established imply potential renewals of life, now in one region now in another, followed, possibly, at a period unimaginably remote by a more general renewal. This conclusion is suggested when we take into account a factor not yet mentioned.

For hitherto we have considered only that equilibration which is taking place within our Solar System and within similar systems; taking no note of that immeasurably greater equilibration which remains to take place: ending those motions through space which such systems possess. That the stars, in old times called fixed, are all in motion, has now become a familiar truth, and that they are moving with velocities ranging from say 10 miles per second up to some 70 miles per second (which last is the velocity of a "runaway star" supposed to be passing through our Sidereal System) is a truth deduced from observations by modern astronomers. To be joined with this is the fact that there are dying stars and probably dead stars. Beyond the evidence furnished by the various kinds of light they emit, of which the red indicates relatively advanced age, there is the evidence that in some cases bright stars have attendants which are dark or almost dark: the most conspicuous case being that of Sirius, round which revolves a body of about one-third its size but yielding only 1/30000th part of its light — a star approaching to our Sun in size, which has gone out. The implication appears to be that beyond the luminous masses constituting the visible Sidereal System, there are non-luminous masses, perhaps fewer in number perhaps more numerous, which in common with the luminous ones are impelled by mutual gravitation. How then are to be equilibrated the motions of these vast masses, luminous and nonluminous, having high velocities?

This question may be divided into two, a major and a minor, of which the minor admits of something like an answer, while the major seems unanswerable.

§182a. Scattered through immensurable space, but more especially in and about the region of the Milky Way, are numerous star-clusters, varying in their characters from those which are hardly distinguishable from unusually rich portions of the heavens, to those which constitute condensed swarms of stars; kinds of which may be named, as at the one extreme, 24 Persei, 103 Cassiopeia and 32 Cygni, and at the other extreme, 13 Herculis and 2 Aquarei. The varieties between these extremes were regarded by Sir William Herschel as implying progressive concentration; and in his opinion Sir John Herschel apparently agreed. Pursuing the argument the latter wrote: —

"Among a crowd of solid bodies of whatever size, animated by independent and partially opposing impulses, motions opposite to each other must produce collision, destruction of velocity, and subsidence or near approach towards the centre of preponderant attraction; while those which conspire, or which remain outstanding after such conflicts, must ultimately give rise to circulation of a permanent character." (Outlines of Astronomy, 9th ed., p. 641.) The problem, however, is here dealt with purely as a mechanical one: the assumption being that the mutually arrested masses will continue as masses. Writing in 1849 Sir John Herschel did not take account of the results reached and verified during the few preceding years by Mayer and Joule, respecting the quantitative equivalence between motion and heat. But accepting, as we must now do, the conclusion drawn by Helmho1tz (§171) congruous with one previously drawn by Mayer, we are obliged to infer that stars moving at the high velocities acquired during concentration, will, by mutual arrest, be dissipated into gases of extreme tenuity constituting what we conceive as nebulous matter. When we infer this the problem becomes different; and a different conclusion seems unavoidable. For the diffused matter produced by such conflicts must form a resisting medium, occupying that central region of the cluster through which its members from, time to time pass in describing their orbits — a resisting medium which they cannot move through without having their velocities diminished. Every additional collision, by augmenting this resisting medium, and making the losses of velocity greater must aid in preventing the establishment of that equilibrium which would else arise; and so must conspire to produce more frequent collisions. And the nebulous matter thus formed, presently enveloping the whole cluster, must, by continuing to shorten the gyrations of the moving masses, entail an increasingly active integration and reactive disintegration of them, until they are all dissipated.

Products of the kind implied are presented in the large diffused, and irregular nebulae, such as the one in Orion Sir John Herschel describes them (p. 650) as "very great in extent," "irregular and capricious in their shapes," "no less so in the distribution of their light," and not having "any similarity of figure or aspect." And then he remarks that "they have one important character in common" — "they are all situated in or near the borders of the Milky Way." That is to say, they are found in that region of the heavens in which star-clusters also are most abundant. Thus in their distribution and in their characters these nebulae are congruous with the supposition that they have resulted from dissipation of clusters arising in the way described.

What may we say concerning the future of one of these vast irregular nebulae? The first remark is that as, in conformity with the foregoing speculation, it contains the matter not of one star but of many stars, so in conformity with its aspect it is not a nebulous mass of the kind out of which a single star or sun originates: being so large that it covers numerous interstellar spaces. The second remark is that when its widest diffusion has been reached concentration will commence, and the implication is that after an immense period a rotating nebula of one or other of the kinds so abundantly exemplified will result. That a spiral nebula is produced by concentration of one of these vast diffused masses, containing the matter of many stars, is an inference supported by the fact that in some spiral nebulae many stars and nebulous stars embedded within the spiral structure have manifestly been formed or are forming while the general concentration is going on — instance 74 Piscium, 100 Comae, and M. 51 Canum Venaticorum — and suggesting that a new concentrating cluster will eventually arise. If so, the implication appears to be that there will eventually again arise a process like that just suggested — collisions of concentrating masses and progressing diffusion until the nebulous form is again produced.

If in pursuance of this view we regard (1) the star-clusters variously condensed, (2) the diffused and irregular nebulae, (3) the spiral and other nebulae that are concentrating into star-systems, as exhibiting different stages of the same process, then the implication is that in many thousands of places throughout our Sidereal System there are going on alterations of Evolution and Dissolution. And this conception may be taken as a sufficient answer to the inference above drawn that equilibration must end in universal death — a speculative demurrer to a speculative conclusion.

§182b. There still presents itself the question which, unanswerable though it may be, we cannot ignore — What are we to think concerning the future of the visible Universe? To the conception of alternating evolutions and dissolutions taking place in multitudinous different parts of it, there must be joined the conception of it as either remaining in its present state or as changing; and that rises the question — Changing towards what other state? That its state must change is clear: the irregular distribution of it being such as to render even a temporary moving equilibrium impossible.

At the outset there arises the doubt whether our Sidereal System is an aggregate at all, in such sense as is implied by conformity to the law of Evolution and Dissolution — whether it does not transcend those limits implied by conformity to the law. When, reducing its stars and their distances to dimensions that may be imagined, we think of them as comparable to peas one hundred miles apart, the conception of them as forming a whole held together only by mutual gravitation seems somewhat strained. The assumed unity seems more questionable on observing the marks of independence in the dispersed parts. Besides multitudinous cases of the kind above described in which star-clusters apparently carry on their transformations irrespective of the Sidereal System as a whole, there are some far larger local transformations that appear to be of kindred nature. I refer to those going on in the Magellanic clouds or nubeculae, major and minor — two closely-packed agglomerations, not, indeed, of single stars only, but of single stars, of clusters regular and irregular, of nebula, and of diffused nebulosity. That these have been formed by mutual gravitation of parts once widely scattered, there is evidence in the barrenness of the surrounding celestial spaces: the nubecula minor especially, being seated, as Humboldt says, in "a kind of starless desert." And since the traits of these chaotic aggregates are such as do not consist with any process of evolution, we must infer that they are passing through the counter-process of dissolution: the resulting nebulous matter having already enveloped large portions of their miscellaneous components; a conclusion receiving support from the fact that while the one lies in a space devoid of stars the other has around it numerous outlying nebula and star-clusters, which must in course of time be drawn into it. Thus there are considerable difficulties in the way of regarding our Sidereal System as a whole, subject to the processes of evolution and dissolution.

Nevertheless sundry traits seem to imply that throughout a past so immense that the time occupied in the evolution of a solar or stellar system becomes by comparison utterly insignificant, there has been a gathering together of the matter of our Universe from a more dispersed state; and its disc-like form, or else annular form, indicated by the encircling appearance of the Milky Way, rises the thought that it has a combined motion within which all minor motions are included. Moreover the contrast between the galactic circle, with its closely packed millions of stars dotted with numerous star-clusters, and the regions about the galactic poles, in which the more regular nebula are chiefly congregated, yields further evidence that our Sidereal System has some kind of unity, and that during an immeasurable past it has undergone transformations due to general forces. If, then, we must contemplate the visible Universe as an aggregate, subject to processes of evolution and dissolution of the same essential nature as those traceable in minor aggregates, we cannot avoid asking what is likely to be its future.

In his Outlines of Astronomy (pp. 630-1), Sir John Herschel refers to speculations respecting the rotation of our Sidereal System in the plane of the galactic circle. Dismissing the hypothesis of Mädler that the centre of rotation is in the Pleiades, he thinks that no opinion can reasonably be formed whether rotation exists or not, until after some thirty or forty years of observations of a special class. In any case, however, the irregularities of the Milky Way necessitate the conclusion that there is going on, and must continue to go on, a general change of structure. The greater massiveness of it in the northern than in the southern hemisphere, the cleft form, the breach of continuity, the branchings, the narrow connecting necks, and the parts that are almost or quite islanded, exclude the idea of equilibrium, whether the system as a whole be stationary or whether it be rotating. In §150, when referring to the fate of nebulous rings, I cited the option of Sir John Herschel to the effect that a nebulous ring would not break at one place and collapse, but would break at many places and form separate masses. I joined with it the opinion of Sir G. B. Airy, to whom I put the question whether these would remain separate, and who agreed that the masses thus formed, parting more widely at some one place, would eventually collapse into a single mass. Parallel conclusions respecting changes in the Milky Way seem legitimate, or rather, indeed, seem necessitated. Separation of it into parts — minor Sidereal Systems — is a result to which its present aspect points. That such minor sidereal systems could remain permanently independent is not to be supposed. Mutual attraction would cause in some cases the formation of binary sidereal systems, and in other cases coalescence, according to the directions and amounts of their respective proper motions. The implication is that there may be repeated, on vaster scales, changes like those described as occurring in star-clusters: local concentrations taking place within these minor sidereal systems, with resulting evolutions and dissolutions, at the same time that the minor sidereal systems themselves, progressively uniting, become more condensed, and consequently the scenes of more active changes of like kinds. If, giving imagination the rein, we suppose this process carried to its limit, and ultimately to present on an immensely larger scale the kind of change which the nubeculae exhibit, there arises the thought of a progressing destruction of the molar motions possessed by the concentrating stars, and a simultaneous diffusion of their substances, which, as the process comes to a close, spreads the matter of the Sidereal System in its nebulous form throughout the whole of that space which it originally filled — a diffusion reversing the preceding concentration — a dissolution that prepares the way for a new evolution. Reduced to its abstract form, the argument is that the quantity of motion implied by dispersion must be as great as the quantity of motion implied by aggregation, or rather must be the same motion, taking now the molar form and now the molecular form; and if we allow ourselves to conceive this as an ultimate result there arises the conception not only of local evolutions and dissolutions throughout our Sidereal System but of general evolutions and dissolutions alternating indefinitely.

But we cannot draw such a conclusion without tacitly assuming something beyond the limits of possible knowledge, namely, that the energy contained in our Sidereal System remains undiminished. Continuance of such alterations without end presupposes that the quantity of molecular motion radiated by each star in the course of its formation from diffused matter, shall either not escape from our Sidereal System or shall be compensated by an equal quantity of molecular motion radiated into it from other parts of space. If the ether which fills the interspaces of our Sidereal System has a boundary somewhere beyond the outermost stars, it is inferable that motion is not lost by radiation beyond that boundary; and if so the original degree of diffusion may be resumed. Or if, supposing that the ether is unbounded, the temperature of space is the same within and without our Sidereal System, then it is inferable that the quantity of motion contained within our Sidereal System remaining undiminished, its alternate concentrations and diffusions may continue undiminished. But we shall never be able to say whether either condition is fulfilled.

We may indeed dismiss such questions as passing the bounds of rational speculation. They have here been touched upon for the purpose of showing that it is not inferable from the general progress towards equilibrium that a state of universal quiescence or death will be reached; but that if a process of reasoning ends in that conclusion, a further process of reasoning points to renewals of activity and life.

Here, however, it is needless for the adequate presentation of the general doctrine, that Evolution and Dissolution should be traced in either direction to their ends. In §93 it was said that no actual philosophy can fill out the scheme of an ideal philosophy — cannot even of a small aggregate trace the entire history from its appearance to its disappearance, and must be immeasurably far from doing this with the all-comprehensive aggregate.

But unable though we must ever remain to give a complete account of the transformation of things, even in any of its minor parts, and still more in its totality we are able to recognize throughout it the same general law; and may reasonably infer that it holds in those parts of the transformation which are beyond the reach of our intelligence as it does in those parts which are within its reach.

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