Imagens das páginas
PDF
ePub

more, therefore, might we expect that the solar equilibrium would be disturbed by planetary action, when all that has been revealed respecting him tends to show that the mightiest conceivable forces are always contending beneath his photosphere, one or other needing only (it may well be) the minutest assistance from without to gain a temporary mastery over its rivals! And if, as recent observations tend to show, the mightiest of the planets sympathises with solar action—if, when the sun is most disturbed, the belts of Jupiter are also subject (as of late and in 1860) to strange phenomena of change, how readily do we find an explanation of what otherwise would seem so mysterious, when we remember that as Jupiter disturbs the mighty mass of the sun, so the sun would reciprocally disturb the mass of the largest of his attendant orbs.

In conclusion let me remark that I by no means urge the somewhat startling theory here put forward as definitely to be adopted. It does seem, however, to afford an explanation, or at least some account, of many striking facts which at first sight seem in no way associated; and therefore it is not to be safely dismissed without further and very careful examination. I have made no reference hitherto to the circumstance which first directed my attention in a special manner to this particular theory; the fact, namely, that with the photographs of the late eclipse before me, the conception of eruptive action seemed forced upon me as the true explanation of the corona's peculiarities. But the direct evidence thus afforded by the aspect of the Corona is not to be neglected, simple though it is in character. It is in this respect that the photographs of the late eclipse are, as I think, calculated to be most useful. We can study at our leisure appearances which during an eclipse must be hastily examined, under circumstances not favourable to the calm exercise of the reasoning faculties. As time progresses, and other photographic records of the corona are placed at our disposal, I believe the definite solution of the problems it presents may be confidently anticipated.

Fraser's Magazine for April, 1871.

299

THE CORONA AS A PHENOMENON OF

ERUPTION.

BEFORE adducing fresh evidence in favour of the eruption theory, I think it desirable to make a few preliminary remarks on the subject of the accumulation of evidence in favour of theoretical views. It has been urged once or twice, and that by persons to whose opinion I feel bound to pay respectful attention, that in advocating a theory I have shown myself somewhat too apt to adopt a tone resembling special pleadingthat I have endeavoured to show not merely that certain arguments favour the theory, but that all the known circumstances of the case point in the same direction. This has been said, in particular, of those reasonings by which I endeavoured to convince others as I was convinced myself, two years since, that the corona is a solar appendage, and not, as had been urged, a mere phenomenon of our atmosphere or due to the illumination of matter lying between the earth and the moon. I dwelt very earnestly on my views about the corona, because I felt that when the evidence was duly weighed, the atmospheric theory could not but be regarded as disposed of, and that the labours of eclipse observers should be directed to determine the nature of the solar surroundings, and not to the inquiry whether

in the corona solar surroundings were in question at all. It was urged (and not untruly) that a variety of circumstances seemed to favour the atmospheric theory, and that the consideration of these circumstances had led others to entertain an opinion different from that which I was advocating. .

The circumstance that the observations made during the late eclipse have at length definitely convinced even those who had been most doubtful, that the corona is a solar appendage, and that the able observer, Janssen, has, in the most uncompromising terms, enunciated the opinion which I advocated so earnestly two years ago,' places me in a position to defend with some confidence that method of advocacy which has been deprecated.

It seems to me, then, that those who oppose the accumulation of evidence in favour of a theory—that is, the attempt to show that all the known circumstances favour the theory—have not sufficiently kept the fact in mind that the only circumstance which can justify the advocacy of a theory at all, is the conviction

? He writes, “Le résultat de mes observations à Sholoor indique, sans aucun doute, l'origine solaire de la couronne et l'existence de matières au-delà de la chromosphère;' and again, ‘Rien de plus beau, de plus lumineux, avec des formes spéciales qui excluent toute possibilité d'une origine atmosphérique terrestre. ... Je crois tranchée la question de savoir si la couronne est due à l'atmosphère terrestre, et nous avons devant nous la perspective de l'étude des régions extra-solaires, qui sera bien intéressante et féconde.' The expressions here used are singularly emphatic, and they are the more effective that Janssen himself had adopted no definite theory of the corona, while M. Faye, to whom they were addressed, had once been the chief advocate of a non-solar interpretation-though (as appears from some expressions in Janssen's letter) M. Faye had of late adopted the theory now shown to be the just one.

on the part of the theorist that the theory is the true one. If he merely conceives that the theory is more probable than some other theory or theories which have been discussed, he should only present those facts which appear to favour the theory, making careful mention of the circumstance that other facts seem less favourable or even contradictory to the theory. Until he can show that not one known fact opposes the theory, or seems difficult of explanation in connection with it, he has no right to advocate the theory at all (in the proper sense of these words). But the case is altogether different when he is convinced that a theory is the correct one. For this conviction can only arise from the fact that every known fact has been carefully compared with the requirements of the theory, and found to be altogether in accordance with it. It is only to false but plausible theories that Voltaire's description applies : 'A theory is like a mouse which passes through nineteen holes, and is stopped at the twentieth. The very first duty of a theorist who conceives that he has lighted upon the true explanation of any physical phenomenon, is to test his theory by bringing it into the presence of every single known fact respecting that phenomenon, and to forsake it at once if a single fact is opposed to it. Supposing it stands such a test, how can the theorist otherwise present it to the world than as in accordance with all known facts, showing carefully that this is so in the case of each particular fact? His doing this may have an air of special pleading to those who conceive that

« AnteriorContinuar »