August 1, 1888.] 



♦ KNOWLEDGE 



231 



suns naturally became more certain and more general. As 

 they studied the members of the solar system with the 

 telescope, they began to recognise features of resemblance 

 between other planets and the earth, which confirmed them 

 in the opinion that all the planets are worlds. With grow- 

 ing knowledge the doctrine of life in other worlds grew in 

 iavour and in interest. Christian Iluyghens spoke earnestly 

 in its favour. Fontenelle was enthusiastic in urging it ; 

 writers like Drs. Dick and Clhalmers gave to it an almost re- 

 ligious colouring ; and at last when Dr. \Vhewell, after advo- 

 cating the doctrine of other worlds in his contribution to the 

 " Bridgewater Treatises," called it seriously in question in 

 his " Plurality of Worlds," the venerable Brewster (Sir 

 David of that ilk) was moved in bis wrath to denounce the 

 Master of Trinity as one who strove to shake men's faith in 

 a doctrine which he described as " the hope of the philo- 

 sopher and the faith of the Christian." 



The subject had reached this position when I was led to 

 take it up, not — let me admit now — for its own sake, but as 

 a convenient subject with which to associate the results of 

 scientific researches which I could in no other way bring 

 before the notice of the general reading public. That the 

 subject, though not scientific, and though for my own part 

 I had been rather wearied by the over-warm discussions of 

 Whewell and Brewster, has an attraction of its own, is well 

 shown by the circumstance that though I had a strictly 

 scientific purpose in writing my " Other Woi-lds Than 

 Ours," I became quickly interested in the philosophic pro- 

 blem with which 1 had ostensibly undertaken to deal. 



I think I was the first to recognise the change which the 

 researches of the last half century or so should introduce 

 into our ideas I'especting other worlds. So long as men 

 recognised the past of the earth and of the solar system as 

 measurable by a few thousand of years, it was natural that 

 they should regard the planets as simply a family of worlds, 

 all in the same stage of world life. Their view of the solar 

 system may be compared to the view we should take of a 

 plant;ition known to be but a few years old, in which we 

 should exiiect to find no marked varieties uf age or con- 

 dition among the trees — supposed all to be of one kind. 

 But precisely as one who appro.ached a portion of " the 

 forest primeval " would expect to find, even among trees 

 of the same order, all varieties of age, the seedling, the 

 sapling, the tree growing old and decayed, and the dead and 

 withered stump, so, recognising, as science now does, that 

 the age of the solar system must be measured by tens if not 

 by hundreds of millions of years, we must admit the 

 probability, one may faii-ly say the certainty, that we shall 

 find in that system every stage of orb life — from those orbs 

 which being very large and massive have passed through 

 but a small proportion of their exceedingly long lives, to 

 those which being much smaller have passed to their mid 

 career or onward even through the whole of their lives to the 

 condition of planetary death. 



I did not myself perceive this truth as distinctly as I 

 have just presented it. A long time passed before I saw 

 that the larger orbs must be the younger and the smaller 

 the older, unless (as in some few cases may have happened) 

 some great diflference in the time of beginning orb life may 

 have caused a smaller but later-starting orb to be at this 

 present time younger than a somewhat larger planet. 

 (Saturn, for example, appears to be younger than Jupiter, 

 though being smaller he might be expected to be somewhat 

 more advanced in planetary life ; but in the fulness of time, 

 I know not how many millions of years, Saturn will advance 

 beyond Jupiter in development, even as our earth has long 

 since passed both, and as the moon has long since passed the 

 earth.) When first the thought presented itself to me that 

 in the solar system there must co-exist many ditlerent -stages 



of orb life, I saw it simply in that general way, and had no 

 idea of the harmonious series into which I should later be 

 able to arrange the various oibs attending on the sun. 



So .soon, however, as the connection between size and 

 relative age is perceived, we see at once that the vaiious 

 orders of bodic.? within the .solar system can be clas.sificd 

 according to the several stages of orb life which they may 

 be expected to illustrate, and that as a matter of fact they 

 seveially present the characteristics which we are thus led 

 to expect. The largest orb of all — the sun— represents the 

 first or glowing vaporous stage, the babyhood of orb life; 

 the giant planets, Jupiter and Saturn, present all the 

 characteristics of the second or fiery stage; the earth cer-- 

 tainly, and Venus probably, present the characteristics of 

 mid life ; old age is recognised in Mars and Mercury ; and, 

 finally, the death stage is presented in the arid and desolate 

 surface of our companion planet, the moon. 



For a long time I was content with the advance (for such 

 it seems to me) beyond the old-fashioned view. So soon as 

 we recognise that the life-bearing .stage is but a part, and it 

 may be but a small part of an orb's careei-, we find a new 

 meaning given to the universe of suns and solar systems. 

 An extension of our ideas in regard to time, in some degree 

 akin to the extension which they had already received in 

 regard to space, is thus obtained. Doulitless it was a grand 

 and impressive thought in old times to recognise each orb in 

 the solar system as in the fulness of its life-bearing career, 

 and to extend the same idea to the star-depths in such sort 

 that each sun might be regarded as the centre of a solar 

 system, each member of which, save the central orb, is now 

 an abode of life. Yet is there in this view, which presents 

 the whole universe as the scene of omnipresent life, a certain 

 element of bitterness. Sunjit amari illiquid. Before those 

 midtitudinous orbs became the abode of life there would 

 have bten universal lifelessness ; and after they cease to be 

 inhabited or fit for habitation (and no created thing can 

 endure for ever) there will be universal death. But accord- 

 ing to the view which I have suggested (the view, be it 

 remembered, to which all the evidence points), though the 

 number of habitable orbs be greatly diminished, it yet 

 remains to all intents and purposes infinite, while, instead of 

 regarding the duration of life in the univers'e as finite, we 

 can perceive that it is eternal in time, even as it is infinite 

 in spatial extension. For if, when we look at any star we 

 infer, from what we know about our own star — the sun — 

 and his family of attendant orbs, that at least one member 

 of that star's family is the abode of life like our earth, 

 at least one has been the abode of life in the past, though 

 now dead like the moon, while at least one, like the giant 

 Jupiter or his brother Saturn, though not yet the abode of 

 life will become so hereafter, then repeating that lesson for 

 all the stars visible to the naked eye, telescopic, or (far past 

 telescopic range) visible in the mind's eye, we may say : 

 There in those depths are millions, ten hundred thousands 

 of millions of orbs the abode of life now, as many that were 

 the abode of life millions of years ago, as many that will be 

 the abode of life hereafter. 



But while thLs extension of the old-fashioned views is 

 impressive in it.self and amply justified by the evidence 

 from analogy, sufficient account is not taken of all the 

 features of variety and of actual diflferenco which dis- 

 tinguish planet from planet (even within our solar system) 

 and sun from sun within the sidereal system. It is as 

 though an insect after studying from within its own free 

 home the various trees thence discernible in the forest, 

 should have come first to the conclusion that other trees 

 besides its own are the abode of life, and next, that .some 

 trees are much younger than its own tree home, and may 

 therefore be quite unfit as yet to be inhabited by insect 



