In the year 1826, Heinrich Schwabe of Dessau, elated with the hope of speedily delivering himself from his hereditary incubus of an apothecary's shop, obtained from Munich a small telescope and began to observe the sun. His choice of an object for his researches was instigated by his friend Harding of Göttingen. It was a peculiarly happy one. The changes visible in the solar surface were then generally regarded as no less capricious than the changes in the skies of our temperate regions. Consequently, the reckoning and registering of sun-spots was a task hardly more inviting to an astronomer than the reckoning and registering of summer clouds. Cassini, Keill, Lemonnier, Lalande, were unanimous in declaring that no trace of regularity could be detected in their appearances or effacements. Delambre pronounced them “more curious than really useful.” Even Herschel, profoundly as he studied them, and intimately as he was convinced of their importance as symptoms of solar activity, saw no reason to suspect that their abundance and scarcity were subject to orderly alternation. One man alone in the eighteenth century, Christian Horrebow of Copenhagen, divined their periodical character, and foresaw the time when the effects of the sun's vicissitudes upon the globes revolving round him might be investigated with success; but this prophetic utterance was of the nature of a soliloquy rather than of a communication, and remained hidden away in an unpublished journal until 1859, when it was brought to light in a general ransacking of archives.

On the 2d of June 1858, Giambattista Donati discovered at Florence a feeble round nebulosity in the constellation Leo, about one-tenth the diameter of the full moon. It proved to be a comet approaching the sun. But it changed little in apparent place or brightness for some weeks. The gradual development of a central condensation of light was the first symptom of coming splendour. At Harvard, in the middle of July, a strong stellar nucleus was seen; on August 14 a tail began to be thrown out. As the comet wanted still over six weeks of the time of its perihelion-passage, it was obvious that great things might be expected of it. They did not fail of realisation.

Not before the early days of September was it generally recognised with the naked eye, though it had been detected without a glass at Pulkowa, August 19. But its growth was thenceforward a surprisingly rapid one, as it swept with accelerated motion under the hindmost foot of the Great Bear, and past the starry locks of Berenice. A sudden leap upward in lustre was noticed on September 12, when the nucleus shone with about the brightness of the pole-star, and the tail, notwithstanding large fore-shortening, could be traced with the lowest telescopic power over six degrees of the sphere. The appendage, however, attained its full development only after perihelion, September 30, by which time, too, it lay nearly square to the line of sight from the earth.

By observations made during a series of five remarkable eclipses, comprised within a period of eleven years, knowledge of the solar surroundings was advanced nearly to its present stage. Each of these events brought with it a fresh disclosure of a definite and unmistakable character. We will now briefly review this orderly sequence of discovery.

Photography was first systematically applied to solve the problems presented by the eclipsed sun, July 18, 1860. It is true that a very creditable daguerreotype, taken by Busch at Königsberg during the eclipse of 1851, is still valuable as a record of the corona of that year; and some subsequent attempts were made to register partial phases of solar occultation; but the ground remained practically unbroken until 1860.

In that year the track of totality crossed Spain, and thither, accordingly, Mr. Warren De la Rue transported his photo-heliograph, and Father Secchi his six-inch Cauchoix refractor. The question then primarily at issue was that relating to the nature of the red protuberances. Although, as already stated, the evidence collected in 1851 gave a reasonable certainty of their connection with the sun, objectors were not silenced; and when the side of incredulity was supported by so considerable an authority as M. Faye, it was impossible to treat it with contempt. Two crucial tests were available.

Until nearly a hundred years ago the stars were regarded by practical astronomers mainly as a number of convenient fixed points by which the motions of the various members of the solar system could be determined and compared. Their recognised function, in fact, was that of milestones on the great celestial highway traversed by the planets, as well as on the byeways of space occasionally pursued by comets. Not that curiosity as to their nature, and even conjecture as to their origin, were at any period absent. Both were from time to time powerfully stimulated by the appearance of startling novelties in a region described by philosophers as “incorruptible,” or exempt from change. The catalogue of Hipparchus probably, and certainly that of Tycho Brahe, some seventeen centuries later, owed each its origin to the temporary blaze of a new star. The general aspect of the skies was thus (however imperfectly) recorded from age to age, and with improved appliances the enumeration was rendered more and more accurate and complete; but the secrets of the stellar sphere remained inviolate.

In a qualified, though very real sense, Sir William Herschel may be called the Founder of Sidereal Astronomy. Before his time some curious facts had been noted, and some ingenious speculations hazarded, regarding the condition of the stars, but not even the rudiments of systematic knowledge had been acquired. The facts ascertained can be summed up in a very few sentences.