from this glimpse; but it is something to set eyes upon the very core of the solar system.
The black spot is generally surrounded by a fringe brighter than the nucleus, though dull compared with the adjoining surface. This fringe (or penumbra) is also something seen through an opening in the sun’s outer luminous covering. It is part of a dense, cloudy atmosphere, situated at a vast depth below the surface of the photosphere: a great cavity, in fact, with a floor of cloud.
But there is still another, a third covering of the sun’s; the existence of which is revealed during a total eclipse of the sun. A circlet of pale light is then seen surrounding the two orbs, and in the midst of this sometimes rosy peaks of enormous height,—more than 40,000 miles high. This circlet, or corona, must be something aërial, belonging either to the sun or the moon. But the moon has no appreciable atmosphere. It is then the sun’s outermost covering,—a transparent atmosphere with no light of its own, but freely transmitting that of the photosphere: and the crimson mountains are clouds in it. This summer there has been an opportunity of observing these and other interesting phenomena in the eclipse that took place on the 18th of July.
Dependent as our world is upon the sun, it is not unreasonable to suppose we might feel some effect from those solar disturbances of which the spots are an evidence. Are our summers hotter, or our winters colder, crops more abundant, or falls of rain heavier, when spots prevail? These are points busily investigated, not yet cleared up. But that there is a connection between the spots and the magnetic state of the earth, General Sabine, the able and energetic leader in this field of inquiry (Terrestrial Magnetism), has established beyond doubt. Last September, a very remarkable fact was observed by Mr. Carrington, of Reigate. He saw a spot of intense brightness on the sun, which endured ten minutes; and, a week later, going to the Kew Observatory, found that during those same ten minutes the magnets had experienced most extraordinary deviations.
But not only does the sun, like his dependent worlds, revolve upon an axis. Like them, too, he moves obedient to a mighty influence from without, which draws him along at the rate, it is believed, of about 400,000 miles a day,—little more than a quarter of the speed with which the earth travels round him. Is he travelling in company with other suns round some great central sun? M. Maedler, the Prussian astronomer, has devoted many years of his life to this abstruse inquiry. He holds that the sun, with its attendant planets, is advancing towards a point in the constellation Hercules. The solar system, then, is not flung aside into some corner of the universe, “a law unto itself.” It is bound up with other systems, obeys the influence of other vaster centres of force, and—how can we believe otherwise?—of life; and is to visit inconceivably remote regions of space.
“If you ask me whether the sun is inhabited,” said Arago, “I am bound to reply, I know nothing about the matter. But if you say, can the sun be inhabited? Yes, certainly: and that too by beings of an organisation not wholly unlike our own, is my answer.” That dense and cloudy inner atmosphere we have spoken of may effectually protect it from the dazzling light of the photosphere, and conduct but little of its heat. Besides, though we have called it an ocean of flame, it is possible that the intensity of the light and heat given out may be due to the enormous depth of luminous matter; so that the vividness of any one particular film might not surpass that of an Aurora Borealis. So said Sir William Herschel.
Such, then, is the parentage of the sunbeam. But what are the sunbeams? What do they bring us on their radiant wings? Not light alone. Heat, chemical force (actinism), perhaps electric force, are in them, linked together in close, but not indissoluble union. And when they reach man’s domain, he has to some extent power over them. By cunningly-devised experiments, he dissolves the union, that he may search more thoroughly into the nature of each, and through this better knowledge find out perhaps something more about their birthplace. Thus even light, besides what we may call its direct revelations, has yielded to subtle modes of questioning a fragment of knowledge as to the nature of the photosphere.
Light, we may remind the reader, is of two kinds—natural and polarised. Polarisation is a hard word. It means the modification a ray of light undergoes in certain circumstances, through which it acquires different properties on one side to what it has on the other. And as it is ascertained under what circumstances light becomes polarised; so, vice versâ, if light be polarised, the circumstances under which it became so, the nature of its source, may be arrived at with tolerable certainty. There is a wonderful little instrument,—a blackened tube, with a plate of rock-crystal at one end, and of Iceland spar at the other,—called a Polariscope, which tests the two kinds of light. Look at something through this, and you will see two images of it in part overlapping one another. If the light reflected by this something be polarised, the two images will be of different colours,—complementary colours, one red, the other green, and so on. If it be natural light, both images will be white. Light that is emitted at a very small angle from a burning solid or liquid body is polarised. But from a burning gaseous substance, however small the angle at which it issues, it is natural light. Examined by this test, the sun’s luminous covering is concluded to be gaseous, (and flame is neither more nor less than burning air or gas): for it forms only white images in the Polariscope, though of course the rays from the edges do come at a very small angle. In what manner made luminous is unknown, though there are weighty reasons for suspecting electricity to be the agent.
Merely to sketch in outline what is already known of the work accomplished by the sun’s rays, would lead us within the precincts of almost every science. Herschel has told us that they are the primary source of all motion on the earth. Like the Prince whose kiss awoke the Sleeping