off, we may shift our own place considerably without its apparent position being altered. This simple fact lies at the root of all the knowledge attained respecting the distance, size, and motion of the heavenly bodies; and goes scientifically by the name of parallax. By means of it the sun’s distance has been ascertained with as much certainty as if a rule could be laid along to measure it. To arrive, indeed, at perfect accuracy, more recondite means have been and still are adopted. Witness the recent astronomical expedition to Chili, sent by the Americans to verify and rectify the calculation by a series of observations of Venus. But these are niceties important only to astronomers. It has been said that the Condor eagle could fly round the earth in a week if helped by favouring winds. That kingly bird would have to spread his wings for nearly seventy-three years to reach the sun, for the journey is ninety-five millions of miles long. A sunbeam does it in about eight minutes.
The distance known, we can understand that it was a comparatively easy task to find out the actual size of the great parent who sends his bright offspring to vivify we know not yet how many worlds. It is as large as fourteen hundred thousand globes like ours rolled into one. This includes the atmospheres which surround the sun; and it is not at present known whether these form so fractional a part of the entire bulk as does the atmosphere of the earth. The size of the solid globe within that wonderful light or photosphere, which latter alone is what our eyes behold, we do not know. There is one fact which may perhaps indicate that the sun’s atmospheres do occupy a vast depth; namely, that in proportion to its bulk the sun is four times lighter than the earth.
Each science has its own special class of difficulties to contend with: formidable dragons guarding the magician’s castle. The chemist, the meteorologist, still more the physiologist, are baffled by the silence and secresy with which nature prepares her effects, and by the multitude of causes conspiring to or modifying one result. The astronomer has, above all other students of nature, to contend with the confused evidence the senses give in regard to motion and position, furnishing us not with facts at all, but only with the materials out of which facts have slowly to be elaborated. It took five or six thousand years to ascertain whether our earth move or the sun move; astronomy being throughout the whole period more or less cultivated by one nation or another.
We have not now to account for the sun’s varying apparent position. The great circle he with irregular speed seems to describe, is the result of the earth’s shiftings, and belongs therefore to a study of the earth as a planet. But has he any movements of his own? A Dutchman, Fabricius, was the first to find the answer; by help of those remarkable appearances, the spots on the sun, the discovery of which may be reckoned one of the first fruits of the telescope. For though they had occasionally been seen by persons gifted with rare powers of sight as early as the time of Charlemagne, and before that by the Chinese, and perhaps the Peruvians, no suspicion of their real nature had been aroused; nor could they be observed long enough to deduce any kind of conclusion from them.
Armed with their new invention, the telescope, Fabricius, Galileo, and others, saw some of the spots appear on the eastern limb of the sun, reach the centre in six or seven days, disappear at the western edge in seven more, and, after an interval of nearly fourteen lays, reappear at the east, to repeat their course. Now these appearances could be accounted for in two ways: either that the spots are a part of the sun, and revolve with him on his axis, or that they are dark bodies at a very short distance from the surface, travelling round a motionless sun. Happily, besides these dark spots, there are spots of light, of especial brightness. These, if they were independent bodies revolving round the sun, would not disappear immediately after passing the edge, lost in the light of the photosphere, as the dark spots would: they would be seen a little longer. And that this does not happen, is conclusive that they are something belonging to the sun. Whilst the earth takes only twenty-four hours, the sun takes twenty-five days to revolve upon his axis, or thereabouts,—for, owing to changes which take place in the actual size and movements of the spots themselves, the learned are not quite agreed as to the exact period of rotation.
What are the spots? Astronomers have watched them as anxiously as a mother watches her child’s face, in the hope they would reveal something of what goes on beneath that mantle of flame which envelopes the dark and solid globe. Every spot is carefully mapped down, its course followed, its minutest change noted. They do not appear on all parts of the disc, but in two parallel zones on both sides of the sun’s equator, in a position, in fact, which nearly corresponds with those regions of the earth in which the trade-winds prevail. In duration they vary greatly. Some disappear in the course of a single revolution. Others—but this is rare—have been known to last six or seven months. Some years, the sun is scarcely a single day free from them: in others, there will be none on perhaps a hundred out of the three hundred and sixty-five. These variations are periodical. For five or six years the spots progressively increase in number and size, and then for five or six more diminish; after which they again begin increasing. They have been on the increase for the last five years, and will reach the maximum this year. Not the least remarkable feature is their enormous size. The earth might be flung through some of them without touching. Nay, last summer, there were spots sixty thousand miles across. Yet they disappear with rapidity, closing up at the rate of a thousand miles a day.
“Closing up:” the expression implies that they are an opening in something. That curtain of flame, the photosphere, which surrounds the sun as flame does the wick of a candle, is, by an unknown cause, powerful currents or atmospheric disturbances of some kind, reft asunder; and it is the body of the sun we have a glimpse of in that dark spot. There it is, dark and mysterious, yet solid, actual. Little enough can be made out