Sunspot

“ Now when you tell me that the sun’s path waxes faster here in the north than yonder in the south, I cannot see the reason why; for there the sun’s heat is as great in winter as it is with us in summer; and it is so much greater in summer that all vegetation on the earth is scorched by it. Therefore it seems to me more likely that the sun’s path waxes most rapidly where the heat is most intense. ”

“ And neither in England nor on the Continent do we get the great distances of desert sunsets. And great distances increase immeasurably that feeling of infinity which is the chief glory in a sunset.
The clearness of the atmosphere is important in this respect also, that it produces the effect upon the colours of the sunset that they seem more like the colours we see in precious stones than the colours a painter throws on a canvas. There is no milkiness or murkiness in them. The sky is so clear that we see a colour as we see the red in a ruby. We see deep into the colour. ”

“ It is owing to an atmosphere which surrounds the sun, as the air does the earth. When we look horizontally through our own air, as at sunrise and sunset, we gaze through greater thicknesses of it than when we turn our eyes to the zenith. So when we look at the edge of the sun, the line of sight passes through greater depths of this solar atmosphere, and it dims the light shining behind it more than at the centre, where it is thin. ”

“ The sun both at sunrise and at sunset glows with a light which is much more ruddy than the beams it dispenses at noonday. But at sunset or at sunrise the rays which reach our eyes have much more of our atmosphere to penetrate than they have at noon, and accordingly the atmosphere imparts to them that ruddy colour so characteristic and often so lovely. ”

“ B. Not so either: the inhabitants of the torrid zone have much more heat than we have, as the sun's rays fall perpendicularly twice in the course of a year, on every place within the tropics, while they shine more or less obliquely on the rest of the world, and almost horizontally at the poles; for during their long day of six months, the sun moves round their horizon without either rising or setting; the only observable difference, is that it is more elevated by a few degrees at mid-day, than at midnight. ”

“ The colour of the atmosphere—the usual blue tint of the sky—arises from the blue rays of the spectrum being reflected more than the rest by the aerial particles, and the less vapour the bluer the sky, because the vapour gives it a whitish or misty tint. At sunset and sunrise the sky is red or yellow, like gold, or of crimson hue. This is because the sun’s rays have so much farther to come to us at sunrise or sunset, as you will readily perceive if you draw a line from the sun to the sides and then to the top of the arc of the heavens. ”

“ The solar clouds are not little beads of water; they are little beads of white-hot material so dazzlingly bright as to radiate forth the characteristic brilliance and splendour of the sun. The solar clouds drift to and fro; they are occasionally the sport of terrific hurricanes; they are sometimes driven away from limited areas, and in their absence we see merely the black interior of the solar globe, which we call a sun-spot. Now comes the important question as to the material present in these clouds which confers on the sun its ability to radiate forth such abundant light and heat. ”

“ Now a highly colored sunset is not, in itself, a remarkable phenomenon, and it may occur at any time of the year, and owe its origin to any one of several causes, very simple in themselves, as refraction by the atmosphere of the sun’s rays, which are thrown upon the sky after the orb itself has passed from sight, or a peculiarly humid condition of the upper air, or a remarkable electric condition, such as sometimes precedes a thunder storm. But the late brilliant sunsets do not belong to the category of ordinary phenomena. ”

“ The sun has thrown its shadow upon the pewter dial two hours beyond the meridian line. Great cream colored heads of thunder-clouds are lifting above the sharp, clear line of the western horizon; the light breeze dies away, and the air becomes stifling, even under the shadow of my withered boughs in the chamber-window. The white-capped clouds roll up nearer and nearer to the sun, and the creamy masses below grow dark in their seams. ”

“ Influence of the sun-spot period.—Sun spots are certainly less hot than the surrounding parts of the sun's surface, and, in view of the intimate dependence of the earth upon the solar radiation, it would be in no way surprising if their presence or absence from the sun's face should make itself felt in some degree upon the earth, raising and lowering its temperature and quite possibly affecting it in other ways. Ingenious men have suggested many such kinds of influence, which, according to their investigations, appear to run in cycles of eleven years. ”

“ Rising out of the horizon at six o’clock, the sun passed exactly through the zenith, and went down perpendicularly in the west into the boundless ocean. Who can wonder that this daily disappearance of the sun has had so large a share in the poetry and the religion of our race? In every land, under every climate, it is the one spectacle which is ever new and ever fascinating. ”

“ It can readily be understood that a place recognized to be within the tropics, may, by reason of its proximity to the sea, its altitude, relation to mountain chains, and other natural surroundings, have a climate so modified that the actual sunlight may have less influence than in localities which may be situated upon the borders or even within the temperate zones. Another factor influencing local conditions may be the color of the soil and the resulting modification of the intensity of the heat rays coming from it, because the radiation from the soil is of importance. ”

“ But let us see what the cycle association between solar spots and terrestrial weather actually is, or rather of what nature it promises to be, for as yet the true nature of the association has not been made out.
It has been found that in a period of about eleven years the sun’s surface is affected by what may be described as a wave of sun-spots. There is a short time—a year or so—during which scarce any spots are seen; they become more and more numerous during the next four or five years, until they attain a maximum of frequency and size ”

“ Rays from the sun, passing on all sides of the Earth, are refracted through the atmosphere and bent inward. You must have steered over into some of these rays just now, and then turned back from them. Somewhat farther on all these refracted rays will meet at a common centre, which they will illuminate, and we shall have an oasis of rainbow-tinged sunlight in this great desert of shadow. The sun will then appear to us to be an enormous circle of dull light entirely surrounding the Earth. ”

“ In certain regions of the photosphere several dark patches are usually visible, which are called ‘sun-spots.’ At occasional times they are almost entirely absent from the solar disc. It has been observed that they occupy a zone extending from 10° to 35° north and south of the solar equator, but are not found in the equatorial and polar regions of the Sun. A sun-spot is usually described as consisting of an irregular dark central portion, called the umbra; surrounding it is an edging or fringe less dark, consisting of filaments radiating inwards called the penumbra. ”

“ It was the summer of the southern ocean—pure, pleasant breezes with the sun, and clear, calm, sparkling nights by moon or stars. Little or no rain falls, except in the winter months, and as a consequence where the soil is fine and dry, dust covers everything in impalpable clouds, at the same time affording a desirable atmosphere for that lively individual, the flea! ”

“ The sun is daily seen to rise in the eastern part of the sky, to travel across the sky, to reach its highest position in the south in the middle of the day, then to sink, and finally to set in the western part of the sky. But its daily path across the sky is not always the same: the points of the horizon at which it rises and sets, its height in the sky at midday, and the time from sunrise to sunset, all go through a series of changes, which are accompanied by changes in the weather, in vegetation, etc. ”

“ The sun spots are the most extensively studied and the least understood of all solar phenomena. That they are large-scale interruptions in the photosphere, and at the same time the most striking evidence of atmospheric circulation, there can be no doubt. Observations made near the sun's limb, to determine whether the spots are elevations or depressions with reference to the photosphere, seem not to be reliable, perhaps because of abnormal refractions in the strata overlying and surrounding the spots. ”

“ About the time of the sun's reappearance, and for a week or two after it, these clouds were not more a subject of admiration to us on account of their novelty, than from the glowing richness of the tints with which they were adorned. It is, indeed, scarcely possible for nature, in any climate, to produce a sky exhibiting greater splendour and richness of colouring than we at times experienced in the course of this spring. ”

“ Again, if we look at the principal group of springs from the high mound above the middle terrace, we can see the same variety of brilliant coloring. The wonderful transparency of the water surpasses anything of the kind I have ever seen in any other portion of the world. The sky, with the smallest cloud that flits across it, is reflected in its clear depths, and the ultramarine colors, more vivid than the sea, are greatly heightened by the constant gentle vibrations. ”

“ These suns, as they rose slowly and steadily, amidst clouds and storms, in their ascendant, so they have not rushed from their meridian to sink suddenly in the west. Like the mildness, the serenity, the continuing benignity of a summer’s day, they have gone down with slow-descending, grateful, long-lingering light ”

“ The chief of these is the amount of sunshine which he enjoys for weeks and even months together, when the sun 110 often rises in a cloudless sky, shines for several hours with a brightness and warmth surpassing that of the British summer, and then sinks without a cloud behind the secondary ranges of the Maritime Alps, displaying in his setting the beautiful and varied succession of tints which characterise that glorious phenomenon of the refraction of light, a southern sunset ”

“ Those opaque azure clouds, to which you saw a few minutes ago one of those beings directing his course, are works of art and places in which they move through different regions of their atmosphere and command the temperature and the quantity of light most fitted for their philosophical researches, or most convenient for the purposes of life. On the verge of the visible horizon which we perceive around us, you may see in the east a very dark spot or shadow, in which the light of the sun seems entirely absorbed ”

“ The sunset was the same miracle of beauty that it usually is near the Equator, but below and beyond them there hovered a gray-green void that slowly spread like some disfiguring disease over the fair face of the sky. ”

“ Each of these conditions varies from day to day for every locality throughout the continent. The sun is highest in the heavens in the torrid zone, being twice vertically overhead each year at every locality, and the hours of light and darkness each day are approximately equal throughout the year. North of the torrid zone, however, the rays of the sun become more and more oblique to the earth's surface, and hence insolation becomes weaker and weaker for a given period of sunshine as one travels from south to north. ”

“ The nights are especially beautiful in this region. We were interested in observing the remarkable brilliancy of the sky; the stars do not seem to sparkle, as with us at the north, but shed a soft, steady light, making all things luminous. This is the natural result of the clearness of the atmosphere. One is surprised at first to find the moon apparently so much increased in size and effulgency. ”

“ Never, however, have I observed the sky of a deeper, darker, and purer blue. It was to examine this colour that I ascended the Aletschhorn, and I wished to observe it where the hue was deepest and the polarisation most complete. You can look through very different atmospheric thicknesses at right angles to the solar beams. When, for example, the sun is in the eastern or western horizon, you can look across the sun’s rays towards the northern or southern horizon, or you can look across them to the zenith. ”

“ It is in the brilliant photosphere that the dark areas known as sun-spots appear. Some of these dark spots—they are dark only by contrast with the photosphere surrounding them—are of enormous size, covering many thousands of square miles of surface. What they are we cannot positively say. They look like great cavities in the sun's surface. Some think they are giant whirlpools. Certainly they seem to be great whirling streams of glowing gases with vapours above them and immense upward and downward currents within them. Round the edges of the sun-spots rise great tongues of flame. ”

“ The solar heat, which reaches each point of the globe, varies at different hours of the day; it is null when the sun is beneath the horizon; during the year it varies also with its declination; and the expression changes its form as the latitude of the point under consideration is greater or less than the complement of the obliquity of the ecliptic. ”

“ Always, whether the sun is very much spotted or quite free from spots, something unusual in the way of weather must be going on somewhere, demonstrating in the most significant way the influence of sun-spots or the want of sun-spots on the weather. ”

“ Even from where we are we can observe its continents, its polar snows which melt in the spring, its canals which also change with the seasons, its humid plains periodically varied by vegetation, its clouds, generally very light, but dense enough towards the polar regions, its mists in the mornings and especially in the evening, above all, the perpetual changes, incomparably more intense than those of the Earths surface—in a word, all those manifestations of an activity greater than that of our own home of the present day. ”