Now the corona of the sun may be compared to some rare animal which we only see by paying a visit to some distant land, and may consider ourselves even then fortunate to get a glimpse of; and it might be thought that the habits of such an animal are not likely to be of any great importance in our everyday life. But so far from this being the case in regard to the corona, it is more than possible that the knowledge of its changes may be of vital interest to us. I have already said that, as yet, we have no satisfactory account of the reason why changes in sun-spots seem to influence changes in our magnets on the earth; but one of the theories put forward in explanation, and one by no means the least plausible, is that this influence may come, not from the sun-spots themselves, but from some other solar phenomenon which varies in sympathy with them; and in particular that it may come from the corona.Corona may influence magnets. These wings which reach out at sun-spot minimum can be seen to extend a considerable distance, and there is no reason to suppose that they actually cease at the point where they become too faint for us to detect them further; they may extend quite as far as the earth itself and even beyond; and they may be of such a nature as to influence our magnets. As the earth revolves round the sun it may sometime plunge into them, to emerge later and pass above or below them; as again the wings spread themselves at sun-spot minimum and seem to shrink at maximum, so our magnets may respond by sympathetic though very small vibrations. Hence it is quite possible that the corona is directly influencing the magnetic changes on the earth.
Possible importance of corona.
But it may be urged that these changes are so slight as to be merely of scientific interest. That may be true to-day, but who will be bold enough to say that it will be true to-morrow? If we are thinking of practical utility alone, we may remember that two great forces of Nature which we have chained into the service of man, steam and electricity, put forth originally the most feeble manifestations, which might readily have been despised as valueless; but by careful attention to proper conditions results of overwhelming practical importance have been obtained from these forces, which might have been, and for many centuries were, neglected as too trivial to be worth attention. Recently the world has been startled by the discovery of new elements, such as radium, whose very existence was only detected by a triumph of scientific acuteness in investigation, and yet which promise to yield influences on our lives which may overwhelm in importance all that has gone before. And similarly it may be that these magnetic changes, when properly interpreted or developed, may become of an importance in the future out of all proportion to the attention which they have hitherto attracted. Hence, although perhaps sufficient has already been established to show the immense consequences which flow from Schwabe’s remarkable discovery of the periodicity in solar spots, we may be as yet only on the threshold of its real value.
From what little causes great events spring! How little can Schwabe have realised, when he began to point his modest little telescope at the sun, and to count the number of spots—the despised spots which he had been assured were of no interest and exhibited no laws, and were generally unprofitable—that he was taking the first step in the invention of the great science of Solar Physics!—a science which is, I am glad to say, occupying at the present moment so much of the attention, not only of the great Yerkes Observatory, but of many other observatories scattered over the globe.
CHAPTER VI
THE VARIATION OF LATITUDE
If we should desire to classify discoveries in order of merit, we must undoubtedly give a high place to those which are made under direct discouragements. In the last chapter we saw that Schwabe entered upon his work under conditions of this kind, it being the opinion of experienced astronomers who had looked at the facts that there was nothing of interest to be got by watching sun-spots. In the present chapter I propose to deal with a discovery made in the very teeth of the unanimous opinion of the astronomical world by an American amateur, Mr. S. C. Chandler of Cambridge (Massachusetts). It is my purpose to allow him to himself explain the steps of this discovery by giving extracts from the magnificent series of papers which he contributed to the Astronomical Journal on the subject in the years 1891-94, but it may help in the understanding of these extracts if I give a brief summary of the facts. And I will first explain what is meant by the “Variation of Latitude.”
Latitude.