574 



NATURE 



[February 14, 1895 



w 



THE SUN'S PLACE IN NATURE.' 



THEN', in |SS6, it became my duty to give a course of 

 lectures here, 1 thuujhl it advisable to deal with the sun 

 and stars, not w.th lefercnce specially to solar ph)sics, but in 

 order to give a geneial idea of two impjrtant lines of work 

 which were running! hen nearly piiallel to each other, and pro- 

 mUed soon to meet, w.ih ihe tjieaiest benefit to science. Only 

 a very little was said in those lectures touching the relation of 

 stars to nebuli, and the variou- views which have been held 

 time out of mind with regard to the special nature of both these 

 classes of celestial bodies. Sach questions, however, have 

 always had the greatest interest lor mankind, for th >se at all 

 events among us who Iikc'o know someihini;atiout the universe 

 in which our lot is cast. No .livi.lends, unfortunately or fortun- 

 ately, depend upon the discussion or even the application of 

 any branches ol Inquiry which are necessary in order to make 

 progress along the lines of thought thus opened up; scant 

 attention is paid to them by educational bodies, for they lead 

 to no profession ; hut in siiiie of that, some of the noblest 

 triumphs of the human m.nd have been made in that legion 

 where man finds him.elf face to face with the mysteries of the 

 distant heavens. . . ■ . ■ 



To consider completely the Sun s Place in Nature, which is 

 the subject I have chostn for this present course of lec- 

 tures, the relation of these two apparently different classes of 

 celestial bodies to whi^h I have referred, must be gone into. 

 Thanks to the advance of modern science, I shall be able by- 

 and-by to throw upon the screen pictures of clusters of stars, 

 and of nebulae, in which you will see those bodies very much 

 better than you could do if to-night you were in one of 

 the best equipped observatories in the world, for it so happens 

 that the enormous progress which has recently been made in 

 the application of photography to astronomical work enables us 

 to get permanent records of parts of them which are so dim that 

 they never have been and never will be direcily revealed to the 

 eye of mortals. ■ , . j- 



When we compare these two great groups of celestial bodies 

 we find that, at all events in appearance, there is an enormous 

 difference between them ; that a nebula is certainly unlike a 

 star, or even an ordinary star cluster. This is so obvious that 

 even those who first observed those very few nei)ula; which are | 

 visible to the naked eye (such a one, for instance, as that which 

 is now beautifully visible to us in the early night in the nebula 

 of Orion, or the other in Andromeda, which we can see almost 

 throughout the year), the greatest wonderment was caused by 

 their strange appearance. 



Let us go back 150 years. I have here a book ("Les 

 Hypotheses Cosmogoniques"), recently written by a distin- 

 guished French astronomer, M. Wolf, which contains a 

 reference to what the French philosopher .Maupertuis said 

 about them in the year 1 745. ' ' The first phenomenon is that of 

 those brilliant patches in the sky which are named nebul.ne, and 

 have been considered as masses or groups of small stars ; but 

 our a-tionomers, with the aid of better telescopes, have only seen 

 them a« great oval areas, luminous and with a light brighter 

 than the rest of the heavens. Huygens first discovered one in 

 the constellation of Orion ; llallcy, in the Philosophical Irain- 

 adioiis, pointed out six, the first in the Sword of Or^on, the 

 second in the con-.tellation of Sagittarius, thethird in the Centaur, 

 the fourth before the right foot of .\ntinous, the fifth in lUrcuIci, 

 and the sixth in An Iromeda. Five of these spots having been 

 obs'ived with a reflector of 8 ft., only one of them, the fourth, 

 could le taken for a group of stars ; the others seem to be great 

 shilling areas, and do not differ among themselves, except that 

 tome are more round and others more oval in shape. It seems 

 aUo that in the first the little stars which one discovers with the 

 telescope are not capable of causing this brightness, llallcy was 

 much struck with these phenomena, which he believes capable 

 of explaining a thing which seemed difficult to understand in 

 the H)ok of (ienesis, viz. that light was created before the sun. 

 Durham regards them as holes through which one discovers an 

 immense region o( light, and finally the empyrean heaven itself. 

 He professes to have been able to distinguish that the stars 

 which are seen in tome of them arc very much less distant fiom 

 ui than the tpoti of light themielvej."'' 



' R!»i»ed from »Horthinil n««« of a courie of leciures lo working mm 

 al llii MuKUin of IVaclical Gto'ogir daring NovcmUcr and Dectmttr, 



' '■ O.icoi" •iir le« diff''renKi fuurtt de« A«lr««," chap. vi. pp. 104-14. 



NC. 1320, VOL. 51] 



I need no: follow the quotation any further, but you see 

 that 150 years ago some of our keenest intellects we-e struj 

 gliDg with the questions involved in mystery which had been 

 started by the discovery of these nebulous bodies in space. That 

 was in the year 1745. Soon after this, in the year 1755, Kant, 

 who was a German, though he was by direct descent a 

 Scotchman, brought out an hypotlie-,is in which he attempted 

 to show thit there was the closest possible connection between 

 stars and the clusters and nebula; of which Maupertuis spoke, 

 lie held distinctly that the stars were produced by some action 

 brought about in nebulae ; in other words, that the nebula: 

 represented a first stage out of which stars, representing a later 

 stage, were produced by certain proce^ses of evolution. 



From 1755 we pass to 1796, at which date we find a great 

 Frenchman (Laplace) pr.actically lediscovering and reasserting 

 the same thing. It is believed that he knew nothing of Kant's 

 prior work, and therefore we have the advantage of dealing 

 wi h the results of the thoughts of two great minds. Laplace 

 came to the same conclusion as Kant, so far as it »ent, but he 

 went further than Kant did, beciuse he held that the nebul* 

 really represent enormous masses of clastic gas at high tem- 

 perature, and that therefore the stars, which he conceived, as 

 Kant had conceived, to be produced l>y evolutionary processes 

 from these nebulae, were really produced from incandescent 

 masses of gas. 



Now, seeing that our sun ii a star, it is perfectly clear from 

 this that both Kant and Laplace agreed that the sun, represent- 

 ing a star, had originally been produced from a nebula. Thai 

 is my first point. 



About the time of Laplace, i.e. about 1796, Sir William 

 Herschel was making England famous by the discoveries 

 rendered possible by that w.ndeiful telescope which he had 

 erected at Slough. There, for the first time, the possible sim- 

 ilarities and the possible differences of these two great groups 

 of celestial bodies were subjected to the most minute and lab- 

 orious scrutiny. Well, he came a'.solutely to ihe sa'iic conclu- 

 sion as his predecessors had done, and (or Sir William Herschel 

 there was no doubt whatever that from the most irregular 

 nebula ti the densest star theie was a gradual process of 

 change ; that there was no radical difference, but that the star 

 represented simply the result of certain evolutionary changes. 

 This view thus strengthened held the field for some years ; then 

 a larger telescope was made by Lord Rosse, a 6fool mirror was 

 now available instead of the 4foot one which had been erected 

 by Herschel at Slough. Lord Rosse— you will fiml the 

 whole story admirably told in Prpl. Nichols book, " Ihe 

 Architecture of the Heavens "—came to the conclusion that 

 when he observed a so called nebula on the finest possible 

 nights, when the air was stillest, and the magnifying power which 

 he could use was greater than usual, he could see what he called 

 the possibility of a resolvabiliiy in it. That is to say, nebulx 

 might after all really be star clusters, only immensely 

 rem.te, so that Ihe light of all the stars was, as it we"- «» 

 welded together as to give that appearance of a candle 

 seen through horn, which Maupertuis and his predecessors 

 had observed. 



Next wecome to the year 1862, and we find a new instrument 

 brought to bear, which at once drove into thin air all the state- 

 ments which had been made on what had turned out to be a 

 line of inquiry which was incapable of giving a final verdict. 

 It so happened that in that year there was a very powerful 

 combination formed by a distinguished chemist and philo- 

 sopher. Dr. William Allen Miller, the Treasurer of the Royal 

 Society, who had already done most admirable spectroscopic 

 work, and a neighbour of his, Mr. Iluggins, who had 

 mounted a powerful telescope in 1856. The spectroscope, 

 which was then practically a new instrument, was applied lo 

 the telescope. , 



I need not say much about the spectroscope, as I have alnady 

 had an opportunity of describing it to some of you, but I may 

 in a few words show exactly the function of this new instru 

 ment of enormous power, which has in a very few years perfectly 

 changed the aspect of astronomic science. If we pass a ray il 

 while light through a piece of glass called a prism, we find ihit 

 alter the light has so passed through, it is chinged i.nto a beau- 

 tiful bind, showing all the colours of the rainbow. I his prism 

 then is the fundamental part of the instrument which is calleil 

 the spectroscope, and Ihe most complicated spectroscope which 

 wc cin imagine simply utilises the part which this piece ol 

 1 triangular glass plays in breaking a beam of light of any colour 



