12 



KNOWLEDGE 



[Jantabt 1, 1898. 



RICHARD PROCTOR'S THEORY OF THE 

 UNIVERSE. 



By C. Easton. 



RICHARD PKOCTOR, the founder of this magazine, 

 amongst the other services that he has rendered 

 to science, deserves the credit of being the first 

 to offer a sohition of the problem of the structure 

 of the heavens by studying it from a general 

 point of view, whilst at the same time basing his theory 

 on direct observation. Huyghens, Thomas Wright, Kant, 

 Lambert, and others, had already touched on this great 

 problem, but they had to content themselves with 

 reasonings; they misused the arguments per annlofiiuin, 

 having very few facts to go upon. The two Herschels 

 collected an enormous quantity of facts and precise data 

 relating to the problem, but they were reluctant to 

 draw from them any definite conclusions. Sir William 

 Herschel himself abandoned a considerable number of his 

 early ideas pn the structure of the heavens, although he 

 did not declare in a definite manner what changes must 

 be made in it. As for his son, he demonstrated the 

 untenability of the cloven iliac theoni, and of the funda- 

 mental suppositions made by his illustrious father, 

 especially in the face of the evidence drawn by Sir John 

 himself from his telescopic observations of the Milky Way. 

 Contrary to what has been often said. Sir John Herschel 

 has stated expressly and exclusively — at least in his books 

 — the theory generally attributed to him of the galactic 

 ring, although he seems to have found in this theory the 

 fewest obstacles to the explanation of the phenomenon. 



From the beginning. Proctor insisted, when discussing 

 the conceptions of Sir John Herschel, that neither the 

 cloven disc theory nor the theory of a galactic ring could 

 adequately explain the observed facts. In the case of the 

 second theory, Proctor only indicates its insufiiciency in a 

 general manner. Even the principal features of the Galaxy, 

 he says, offer too great difficulties for the annular theory, 

 and he boldly sketches a more complicated figure, which, he 

 says, replaces with advantage Sir John Herschels theory 

 explaining the principal details of the ililky Way. 



Whilst recognizing that the extreme complexity of the 

 details in the Milky Way may never perhaps allow of a 

 complete solution, Proctor was convinced that " the bolder 

 and more striking features of that circle may be studied 

 with a better hope of their being successfully interpreted." 

 He has been reproached with too much audacity, and, 

 indeed, one hesitates to subscribe with Proctor to " the 

 spiral curve, which [as] depicted seems so satisfactorily 

 to account for several of the more strikmg features of the 

 Milky Way as to suggest the idea that it corresponds some- 

 what closely to the real figure of that star-stream." But it 

 seems to me that the advantages of his researches are 

 much superior to the disadvantages. Those who approach 

 with hesitation and prudence by far other ways will not be 



the Galaxy, which .... would come to be 



regarded as a Bat ring, or aome other re-entering form of immense 

 and irregular bi eadth and thickness . . . ." (Sir John Herschel, 

 " Outlines," § 788.) He prefers to represent the Milky Way as of an 

 annular form, but he takes care not to pronounce definitely on this. 

 " • • ■ an impression amounting almost to convietion tliat the 

 Milty Way is not a mere stratum, but annular ; or at least that our 

 system is placed within one of tlie poorer or almost vacant parts of 

 its general mass ..." (Mary Somerville, " The Connexion of the 

 Physical Sciences," 1846, p. 419.) 



In speaking of the lateral offsets which quit the main stream of 

 tlie Milky Way, and which he regards as the " couTexities of curved 

 surfaces Tiewod tangcntially, or planes seen edgeways " (" Outlines," 

 § 792), he eridcntly docs not trouble to bring them 'into accord with 

 the theory of a galactic ring. 



led astray by the errors of Proctor's method ; and, on the 

 other hand, pioneers of science such as he exercise a great 

 moral influence — their digressions, though sometimes over- 

 bold, refresh and stimulate the zeal of others. 



This gigantic arch of the Milky Way, spreading out before 

 all eyes the sublime enigma of its starry ramifications, seems 

 to defy the indefatigable seekers bending over their calcu- 

 lations. Let others strive to draw some evidence of the 

 aspect of the Milky Way from its chief outlines. 



However, Proctor would doubtless himself recognize 

 to-day that his theory does not now correspond with the 

 actual state of science ; and it is strange that in treatises 

 of astronomy his well-known drawing is reproduced as if 

 the theory could still be accepted, although more than one 

 judicious remark of Proctor's preserves his reputation. At 

 the period when he formulated his theory, Proctor had not 

 at his disposal, in short, any but the results obtained by 

 the two Herschels and by F. G. W. Struve : and, besides, 

 the work of the latter was soon reduced by Encke to its 

 .just proportions — that is to say, to a negative result, or one 

 nearly so. Almost all the modern work in this branch of 

 astronomy has been done since Proctor's time — that of 

 Heis,Houzeau, Gould, Celoria, Kapteyn, Ristenpart, Plass- 

 mann, etc. ; and in particular, though basing his researches 

 on the constitution of the Milky Way, he could not con- 

 sult either the admirable photographs of Barnard, Wolf, 

 Roberts, Russell, nor the modern drawings of it — that is 

 to say, that he possessed scarcely any facts about the whole 

 northern half of the zone. 



Also, the explanation furnished for the figure imagined 

 by Proctor could not be considered as satisfactory to-day, 



(^ oc 4 -i * op. 



t^^ 



4--:^^..^ 



■•fc s 



% "^'Sht^rtoa*' 





^- --^^ _,-' <y 



d'tw.x 

 The Milky Way according to Proctor. 



even for the main lines of the Galaxy. Many of his obser- 

 vations, however, are still valuable. When he says that 

 where the line of sight is directed tangentially to either 

 loop, the Milky Way may be expected to have greater 

 width than elsewhere, he furnishes the best explanation 

 of the curious fan-shaped expansions of the Milky Way on 

 each side of the no less remarkable gap in Argo. His 

 explanation of the Coal Sack in Crux — "the apparent inter- 



* Sir John Herschel, although he described with iuuch particularitv 

 the southern half of the Milky Way, treated rather lightly the 

 northern parts. Thus he says in his "Cape Observations," p. 386, 

 speaking of the region in the Eagle, which is nevertheless curious : 

 " After which |^A Aquilae] this main stream runs northward through 

 Aquila without any fui-ther distinguishing feature. . . ." 



