lOO 



NATURE 



{Dec. 2, 1880 



Aurora observed at Ovoca, Co. Wicklow, November 3.— 

 Observations from 5.30 p.m. to Midnight 

 At 5.30 p.m. 5-ellow lights tinged with red were coming up all 

 round the horizon ; these at intervals formed indistinct columns 

 to the south-west and north-west. At 6.30 there were faint 

 reddish lights forming fans at different points ; these were 

 succeeded by red and orange lights that rose forming glows, 

 columns, and pencils; while at 7.30 a bright silver-white arch 

 appeared to the north — the horns from this arch were pencils of 

 white, which seemed to cross the arch ; they were very numerous, 

 appearing and disappearing nearly instantaneously ; from about 

 four to seven appeared at one time. Some of them were very 

 long, shooting up to the zenith. After the arch had dissolved 

 a-.vay, brilliant narrow, well-defined, thin columns of silver light 

 shot up, the most marked coming up to the north-west at 7.40 ; 

 this darted up suddenly, and moved gradually southward, and 

 when about due west, close to the church tower, it disappeared 

 at 7.45. 



These silver lights solely occurred between the west and north- 

 ea t, while all round the horizon red and orange lights were 

 rising; these sometimes congregated at the zenith in a mass. 

 At Ttso t«o brilliant silver pencils rose to the north-north-east, 

 but disappeared nearly instantaneously. 



From S p m. to 8.50 there were orange and red glows of 

 light sometimes in indistinct columns ; but at the latter hour there 

 appeared to the north-west a vivid display of silver light that 

 lasted about five minutes ; this was succeeded by a deep orange 

 cloud that travelled up to the zenith. From 9 to 10.30 there 

 was an orange to red glow round the horizon, while at intervals 

 from the north-\^•est rose pencils of silver light, five very bril- 

 liant ones rising at 10.30. They were succeeded by a bright 

 silver glow over the whole of the western heaven, across which 

 at intervals passed glows of red and orange light ; columns also 

 rose, while at times horizontal streaks of brilliant silver lights 

 appeared and disappeared in a flash. At II tlrere was an 

 orange glow round the horizon ; this, with spurts of light coming 

 up between the south-west and north-east, were all that was 

 observed up to midnight. G. H. Kinah.\n 



MR. SPENCER AND PROF. TAIT 



WHEN, in Nature for July 17th, 1879, while reviewing 

 Sir Edmund Beckett's book, Prof. Tait lugged 

 in Mr. Kirkman's travesty of the definition of Evolution, 

 most readers probably failed to see why he made this not 

 very relevant quotation. But those who remembered a 

 controversy which occurred some years previously, pos- 

 sibly divined the feeling which prompted him thus to go 

 out of his way. 



At the time I said nothing ; but having recently had to 

 prepare a new edition of " First Principles," and thinking it 

 ■well to take some notice of books, and parts of book;, 

 that have been written in refutation of that work, I 

 decided to deal also with Mr. Kirkman's implied criticisin, 

 in which Prof. Tait so heartily concurred ; and by way of 

 gauging Prof. Tait's judgment on this matter, 1 thought 

 it not amiss to give some sainples of his judgment on 

 jTiattcrs falling within his own department. To make it 

 accessible to those possessing previous editions of " First 

 Principles,' ' the Appendix containing these replies to critics 

 was published as a pamphlet. 



In the inaugural lecture of this session, recently given 

 to his students, part of which is published in the last 

 number of N.\TURE, Prof. Tait first of all recalls a pas- 

 sage from the preceding controversy. From this he 

 quotes, or rather describes, a clause wdiich, standing by 

 itself, appears sufficiently absurd ; and he marks the 

 absurdity by a dou'ole note of admiration. Whether 

 when taken with its context it is absurd, the reader will 

 be able to judge on reading the passage to which it 

 belongs. 



In disproof of certain conclusions of mine, there 

 had been quoted against me the dictum ol Prof. Tait 

 concerning the laws of motion, which is that — " as 

 the properties of matter might have been such as to 

 render a totally different set of laws axiomatic, these laws 

 must be considered as resting on convictions drawn from 



observation and experiment and not on intuitive per- 

 ception." Not urging minor objections to this dictum, I 

 went on to say : — " It will suffice if I examine the nature 

 of this proposition that ' the properties of matter might 

 have been' other than they are. Does it express an ex- 

 perimentally-ascertained truth ? If so, I invite Prof. 

 Tait to describe the experiments ? Is it an intuition? If 

 so, then along with doubt of an intuitive belief concern- 

 ing things as they arc, there goes confidence in an intuitive 

 belief concerning things as they are not. Is it ari hypo- 

 thesis? If so, the implication is that a cognition of 

 which the negation is inconceivable (for an axiom is such) 

 may be discredited by inference from that which is not a 

 cognition at all, but simply a supposition. ... I shall take 

 it as unquestionable that nothing concluded can have a 

 warrant higher than that from which it is concluded, 

 though it may have a lower. Now the elements of the 

 proposition before us are these -.—As ' the properties of 

 matter might have been such as to render a totally differ- 

 ent set of laws axiomatic' [there/ore] 'these laws [now 

 in force] must be considered as resting ... not on in- 

 tuitive perception : ' that is, the intuitions in which these 

 laws are recognised, must not be held authoritative. Here 

 the cognitionposited as premiss, is that the properties of 

 matter might have been other than they are ; and the con- 

 clusion is that our intuitions relative to existing properties 

 are uncertain. Hence, if this conclusion is valid, it is 

 valid because the cognition or intuition respecting what 

 might have been, is more trustworthy than the cognition 

 or intuition respecting what is ! " ■ , r 



From which it is manifest that, when asking (of 

 course ironically) whether this alleged truth was an 

 experimentally-ascertained one, my purpose was partly to 

 ennumerate and test all imaginable suppositions respect- 

 inc- the nature of Prof. Tait's proposition, and partly to 

 show that he had affirmed something concerning the pro- 

 perties of matter which cannot be experimentally verified, 

 and therefore which, by his own showing, he has no right 

 to affirm. ' .... 



The first example which, in my recent replies to criti- 

 cisms, I have given of Prof. Tait's way of thinking, is 

 disclosed by a comparison of his views concerning our 

 knowledge of the universe as visible to us, and our kiiow- 

 ledge of an alleged invisible universe. This_comparison 

 shows that : — , 1 • 1 r 



" He thinks that while no validity can be claimed lor 

 our judgments respecting perceived forces, save as ex- 

 perimentally justified, some validity can be claimed for 

 our judgments respecting unperceived forces, where no 

 experimental justification is possible." 



Part of Prof. Tait's answer is that "the theory there 

 developed [in the " Unseen Universe "] was not put forward 

 as probable, its purpose was attained when it was shown 

 to be conceivable." To which I rejoin that whereas 

 Prof Tait said he found in this theory a support for 

 certain theological beliefs, he now confesses that he found 

 none ■ for if no probability is alleged, no support can be 

 derived. The other part of his answer concerns the 

 main issue. After pointing out that the argument of this 

 work " carried on in pursuance of physical laws established 

 by converse with the universe we know, extends them to 

 the universe we do not know," I had urged that if we 

 have '■' no warrant for asserting a physical axiom save as 

 a generalisation of results of experiments— it, conse- 

 quently, where no observation or experiment is possible, 

 reasoning after physical methods can have no place ; then 

 there can be no basis for any conclusion respecting the 

 physical relations of the seen and the unseen universes, 

 ^- since, by the definition of it, one term of the relation is 

 absent" Prof. Tait's explanation is extremely startling. 

 When following the discussion in the" Unseen Unu-erse, 

 throughout which the law of the Conservation of Energy 

 and the Principle of Continuity are extended from the 

 tangible and visible matter and motion around us to an 



