At the outset there arises the doubt whether our Sidereal System is anaggregate at all, in such sense as is implied by conformity to the law ofEvolution and Dissolution -- whether it does not transcend those limits impliedby conformity to the law. When, reducing its stars and their distances todimensions that may be imagined, we think of them as comparable to peas onehundred miles apart, the conception of them as forming a whole held togetheronly by mutual gravitation seems somewhat strained. The assumed unity seemsmore questionable on observing the marks of independence in the dispersedparts. Besides multitudinous cases of the kind above described in which star-clustersapparently carry on their transformations irrespective of the Sidereal Systemas a whole, there are some far larger local transformations that appear tobe of kindred nature. I refer to those going on in the Magellanic cloudsor nubeculae, major and minor -- two closely-packed agglomerations, not,indeed, of single stars only, but of single stars, of clusters regular andirregular, of nebula, and of diffused nebulosity. That these have been formedby mutual gravitation of parts once widely scattered, there is evidence inthe 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 consistwith any process of evolution, we must infer that they are passing throughthe counter-process of dissolution: the resulting nebulous matter havingalready enveloped large portions of their miscellaneous components; a conclusionreceiving support from the fact that while the one lies in a space devoidof 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 considerabledifficulties in the way of regarding our Sidereal System as a whole, subjectto the processes of evolution and dissolution.
Nevertheless sundry traits seem to imply that throughout a past so immensethat the time occupied in the evolution of a solar or stellar system becomesby comparison utterly insignificant, there has been a gathering togetherof the matter of our Universe from a more dispersed state; and its disc-likeform, or else annular form, indicated by the encircling appearance of theMilky Way, rises the thought that it has a combined motion within which allminor 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 nebulaare chiefly congregated, yields further evidence that our Sidereal Systemhas some kind of unity, and that during an immeasurable past it has undergonetransformations due to general forces. If, then, we must contemplate thevisible Universe as an aggregate, subject to processes of evolution and dissolutionof the same essential nature as those traceable in minor aggregates, we cannotavoid asking what is likely to be its future.
