May 26, 1882] 



• knovv^ledg:e • 



623 



attributed to Aristotle, the Hypothesis that animals are 

 automata (a most interesting essay), Sensation, Evolu- 

 tion in Biology, " The Origin of Species " (an essay of 

 somewhat melancholy interest just now), and the connection 

 of the biological sciences with medicine. lu all these 

 essays Professor Huxley shows the love of truth, the 

 plainness of speech, the strong common sense, which 

 characterise all his writings, while his profound knowledge 

 of those matters whereon he speaks as one having authority, 

 and not as a (mere) scriV)e, gives to these writings a scientific 

 value altogether apart from their personal and literary 

 qualities. Every one who wishes to be on a level with the 

 seientilic thought of the day must read this work. 



SOLAR ENERGY. 

 Bv Db. Siemens. 



WIIEX communicating to the Royal Society, on JIarcli 2, my 

 speculation on tho conservation of solar eueigy, I was 

 aware that I might, perhaps, give displeasure to those who strongly 

 adhere to what may be called text-book iaformatiou on tho subject ; 

 I cannot, therefore, feel surprised that llr. Proctor refuses to 

 accept either my explanation or the mathematical proof by which 

 I endeavoured to establish the fundamental condition of Riy theory 

 that of solar fan-like action in a space tilled indefinitely with at- 

 tenuated matter. I am bound to admit that in replying (neces- 

 sarily somewhat hurriedly) to Mr. Archibald's letter in Nature, I 

 ased the word "moment" where "force" might havo been more 

 correctly employed, but with this exception I fully maintain my 

 mathematical statement of the problem. 



It is by no means necessary, as maintained by Mr. Proctor in the 

 Cornhill Magazine article, that centrifugal force, acting upon tho 

 circulating matter, should balance the force of solar gravitation 

 Dpon the same ; it is in effect less tlian the thousandth part ; and yet 

 continuous equatorial outflow must take place. Astronomers havo 

 hitherto regarded the atmosphere suiTounding a heavenly body as 

 taking part wholly in its rotatory motion, in which caso the only 

 effect produced by rotation will be ellipticity, or a permanent rise of 

 the atmospheric column in the equatorial regions unaccompanied 

 by continuous motion. The fundamental difference in my assump- 

 tion is the surrounding matter indefinitely extended into space, 

 which cannot be supposed to take part in the rotatory movement of 

 the gaseous matter in immediate contact with the rotating ellipsoid. 

 In this case there is no elliptic atmosphere to be maintained in 

 balance by its greater depth in the equatorial i-egions, and the 

 tendency to rise to a greater height in that direction in order to 

 attain a statical balance, can only result in equatorial motion, or in 

 tho circulating current, which I make the basis of my hypothesis. 



It would bo idle to attempt further argument on this subject ; but 

 aolar eclips; observations mast bsfore long decide tho question 

 either in favour of Mr. Proctor or myself. C. W. Siemens. 



[It is singular to find a man of Dr. Siemens' calibre, when 

 possessed by a paradox (which has happened to Galileo and Kepler 

 and Newton) adopting tho tone of our Hampdens, Croslands, and 

 their like, who have always " been told that tbere would bo strong 

 opposition to their views." I must confess, too, I am rather amused 

 to find that I, of all men, should be regarded as " strongly adhering 

 to text book science," who have been held utterly wanting in 

 respect for mere authority. On this very subject about which Dr. 

 Siemens h.as advanced the.se new views, I have done at least as much 

 as any living writer to dispossess long established ideas, — only, 

 having based ray views (1) on sound and sufficient knowledge of 

 what had been already done, and (2) on mathematical reasoning, 

 I have seen them, after rather obstinate contest, take their 

 place among accepted truths. Dr. Siemens will find that I was 

 the first to assert, as demonstrably established, the configuration 

 of the solar corona which his theory requires, and which actually 

 exists (though it does not prove hi.s theorj-),'at a time when such 

 men as Sir John Herschel (grand old man) and Sir George Airy 

 held the terrestrial theory of the corona to be admissible.* Apart 



• Singularly enough, I had barely laid down my pen after writing 

 my reply to Dr. Siemens, when I read in Nature a passage forming 

 a strange commentary on the above remarks. When in 1869 1 

 showed, by mathematical reasoning (which Sir John Hershel and 

 Sir G. Airy both, iu letters to me, admitted to bo sound and suffi- 

 cient — as they were, 'of course, to any mathematician), Mr. Loekyer, 

 of whom it was jestingly said a few months later, that "he called 



from what I havo endeavoured to establish, myself, with moro or less 

 success, outside of text-book astronomy, 1 havealways shown readiness 

 to accept tho extra-teit-book science of others — whore it really is 

 science. If, then, I do not accept Dr. Siemens' explanation, it is 

 because I hold it to be entirely unscientific — though Dr. Siemens is 

 a man of science, and one of woll-descrvod reputation in his own 

 departments. If I reject what Dr. Siemens calls tho mathematical 

 proof of tho fundamental conditions of his theory, it is bccanso 

 there is nothing mathematical about it. Apart from tho mistake 

 (in one sense quite insignificant, in tho other exceedingly signifi- 

 cant) in the use of a familiar expression, tho so-callod proof proves 

 nothing; it is the mere hcginning of a statement of certain im- 

 P't.^sihle cotiditions. 



Tho question whether or not the atmosphere of a heavenly body 

 extends indefinitely into space, its outer parts not sharing tho ro- 

 tation of tho planet, has no real bearing on Dr. Siemens' views. 

 So far from hitherto regarding tho atniosphoro as wholly sharing 

 in the rotatory motion, I consider it far more likely that the rotating 

 atmosphere merges into tho general atmosphere of space. But tho 

 laws of motion remain. A gaseous mass, wherever it may be, is 

 urged sunwards by tho sun, and can only fail to tend sunwards 

 when his attraction is counterbalanced by tho attraction of some 

 other heavenly body. The tendency, when not thus counterbalanced, 

 may not load to motion sunwai'ds, because it may bo balanced by 

 centrifugal tendency or by elastic forces ; but these elastic forces are 

 generated by the solar attraction, and cannot jiossibly generate con- 

 stant efflux from him. There is no difference between a cubic foot 

 of gaseous matter opposite tho sun's equator but outside his ro- 

 tating atmosphere, and an equatorial cubic foot of such matter 

 within his atmosphere, so far as the nature of the forces at work 

 is concerned, e:tc(?p( that the former, having less rotational motion, 

 has relatively less centrifugal tendency. The best Dr. SicJnens 

 could do for his theory would be to have all tho rotational move- 

 ment of the sun at work to produce recession- — and that would not 

 suffice; yet ho makes it a strong jjoint of his reasoning that the 

 gaseous matter which he waiats to be continually receding, cannot 

 be supposed to take part in tho rotatory motion of the gaseous matter 

 in immediate contact with the rotating elHpsoid. 



It would indeed be " idle to attempt further argument on 

 this subject," if the first principles of hydrodynamics are set on 

 one side in the attempt to establish Dr. Siemens' paradox — for 

 paradox it unqnestionably is. But eclipse observations will not 

 help to make the matter clearer. The appeai-ance presented by the 

 corona would be practically the same, whether the movements 

 imngined by Dr. Siemens took place, or those movements of cos- 

 mical dust, under the action of gravity, which astronomers 

 recognise. 



I note that Dr. Siemens does not c insider at all tho equally 

 decisive diMpronf of his theory (as a sufficient explanation of solar 

 and stellar work) afforded by the shining of tho fixed stars. \\c know 

 that if there is no utilisation of star rays in space, Arcturus and 

 Aldebaran are suns pouring out second by second much more light 

 and presumably much more heat than our sun ; Sirius pours out 

 at least 200 times as much ; and on the average, every star wo see, 

 and every star brought into view by the most powerfnl telescope, is 

 a rival of ours. If their rays are utilised, those stars aro, on the 

 average, very much larger than our sun, and only so mnch is 

 wasted as we can measure — that is, still, many millions of miilions 



himself owner of half the corona," remarked in Nature that it was 

 absurd of mo to express an opinion where " even the workers " 

 (meaning himself, I think), could not decide. Though ho did 

 decide ; for having started a theory of the sun with which 

 the great extension of the corona was inconsistoKt, bo insisted 

 very positively that tho corona is, in tho main, a terrestrial 

 phenomenon. I was content to wait ; but pointed out observa- 

 tions by which the real nature of the corona might be shown (to 

 those who could not follow the mathematical proof), and others by 

 which Mr. Lockyer's more general theory of the solar atmosphere 

 could bo disproved. 'J'hese observations, as it chanced, were made 

 during the next eclipse (the latter by Professor Young). Little by 

 little " tho workers," meaning Mr. Loekyer, had to yield more and 

 more of the corona to the sun, until now we find in Nature, Professor 

 Newcomb's picture of a corona extending many million miles from 

 the sun, described by Mr. Loekyer as certainly representing a solar 

 appendage. But the amusing thing is, that though Mr. Lockyer's 

 theories aro dead, " still in their ashes burn their wonted fires." 

 Ho thus describes in the Daily Neirs the state of scientific opinion 

 which differs so diametrically from what was once his own : — 

 "Certain and sure evidence was obtained that the outer atmosphere 

 extends much further from the sun than had been previously sup- 

 posed by thniie mast competent to form a just opinion." I would 

 submit that to have formed and maintained for years a >vrong 

 opinion is not proof positive of superior ability to form a right one 



