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Show (, 204 EXPLANATIONS. :natter, and the steps of the process by which it acqutrecJ its present forms. · It would nevertheless strengthen the presumption, and, indeed, place it near to ascertained tr~ths, if we were to obtain strong evidence for \!\-·hat ~as h1thert<;> ~een called the nebular hypothesis .. 'l:~he ev.tdence for tt ts sketched in the Vestiges: it is exhtbtted w1th greater clearne~s, and in elegant and impressive language, tn Professor Ntc~?l's 1\ Views of th.e Architecture of the J!eavens_. The pos1tlon held by this hypothesis in the phtl?sophtcal worl~ '!hen my book was written, is shown wtth tolerable. ~Isbnctnoss in the Edinburuh Review for 1838, where tt IS spoken of in the following general terms: "These views of the origin and destiny of the various systen1 of wor.lds ·which fill the immensity of space, break upon the mtnd with all the interest of novelty, and all the brightness of truth. Appealing to our imagination by their grandeur, and to our reason by the severep~inciples on which they res~, the mind feels as if a revelation had been vouchsafed to It of the past and future history of the universe." It may .also be remarked, that this writer considered the hypothesis as " confirming rather than opposing the Mosaic cosmogony, whether ~Uegorically or lite_rally interl?r.eted." 'Vith this testimony to the mathematical expositions of MM. La Place and Comte, I rest content, as the expositions themselves would be unsuitable in a popular treatise. But the. hypothesis has been favorably entertained in many authoritative quarters during the last few years, and probably would have continued to be so, if no attempt had been made to enforce by it a system of nature on the principle of universal order. . The chief objection taken to the theory IS, that the ex· istence of nebulous matter in the heavens is disproved by the disco\·eries made by the Earl of Rosse's telescope. By this wond::ous tube, .we are told, it is s~own to be" an unwarrantable assumption that there at·e In the heave~ly spaces any masses of matter different from s0li_d bodtes composing planetary systems."* The nebulre, tn sho_rt, are said to be now shown as clusters of stars, rende~ed apparently nebulous only by the vast distance at whtch they are placed. There is often seen a greater vehemence and rashness in objecting to than in presenting hypothettes, and we appear to have here an instance of such basry 1\ ,. North British Revie.w, iii., 477. N .EBULAR llYPOTHESJI!). 20:> counter-generalization. The fact is, that the nebulre were always unde~~tood to be of two kinds: 1, nebulre which were only dtstant clusters, and which yielded one after another, to th~ resolving powers of telescope;, as these p~n,yers we~·e Increased; 2, nebulre comparatively near, whtch no tnca·ease of telescopic power affected. Two classes of objects wh_olly different were, from their partial res~mblan_ce, recog·~,tsed by one name, and hence the confu. 3wn whteh has ansen upon the subject. The resolution of a great quantity of the first kind of nebulre by Lord Rosse's telescope was of course expected and it is a fact though in itse~f interes~ing, of no conseq~ence to the neb' ular hypoth~sts. It will be only in the event of the second class b_etng also resolved, and its being thus shown th.at there IS only one class of nebulre, that the hypothesis WI1l suffer. Such, at least, I conclude to be the sense of a passage which I take leave to transfer, in an abridged form, from a recent edition of Professor Nichol's work u I. By fa~ the gr~ater number of the milky streaks, or spots, whose places have hatherto been recorded, lie at the outermost, or nearly at the outermost bo:mda.ry of the sph.ere previously reached by our telescopes ; anc~ m th1s case there 1s no certain principle on the ground upon whiCh a fure nebula can be distinguished fro~ a clm:ter so .remote that on y the general or fused light of its myr1ad~ o~ constituent orbs can be seen. Sometimes--resting on a pecuhar1ty of form or other ch~ract.eristic-the astronomer may yenture a guess that such an obJt~ct IS probably a firmament · as lll~eed, I was bold enough to do in former editions of this ~ork \nth r~gard to several. which have since been r~solved ; but in th·e· mam he can tell. httl~ ~oncerning them, ~r have any other behef than that, as w1th simJlar masses near him, a great, probably th~ great.er number, are true clusters, grand arrangements of stars, mcredibly remote, but resembling in all things our own home galaxy. Now the application to such objects of a new and enlar~ed power of vision could be attended only by one resultmagm~ cent, but far from unexpected: and it is here that the six feet mu-ror has achieved its earliest triumphs. Under its piercing glance, great numbers of the milky specks have unfolded their starry constituents ; some of these, which previously were almost unresolved, shining with a lustre equivalent to that. of our bnghtest orbs to the naked eye. How far it will go with its resolving powP.r has not yet been ascertained; but I perceive that Sir James South has given his authority that some spots examined by it continue intractable. 11 II. The influence of the new discoveries either to impair or strengthen the foundatio.ns of the nebular hypothesis, must clearly be .looked for among their bearings on less remote and ambiguous obJects. Now the new asrects of these may lead us to question our .former opinions a!1 to the existence of the supposed filmy self. lummous masses; or they max throw doubt on the reality fif thoae |