milky-way, formed in old times, and even still forms, a familiar example of a nebulous, or semi-nebulous cluster. And the fact of its being a mark for navigation, (whence the word Pleiades, from Tλεî, to navigate,) rendered it more familiar. To short-sighted persons, these stars present the aspect of a confused mass of light; but to those of longer sight, or such as are aided by telescopes, the principal stars of the group become detached, and are seen separately; though from the earliest ages their number has been disputed, some seeing more than others. Here, however, was an example, on a smaller scale, of what was constantly observed in the milky way. Besides the light of the apparently component stars, there was also a confused radiance, a nebulous haze, which proceeded either from the commingling of the rays of these luminaries, or from something not clearly discerned, the images of other stars "not individually perceptible." The progress of discovery has shown clearly the cause of this nebulosity. Instead of six, seven, or eight stars, sixty-four were, nearly a century ago, discerned in this interesting group.

The earliest of what were called nebulæ, really outside of the milky-way, of which any recorded discovery was made, was the patch of light in the girdle of Andromeda. This appears to have been first noticed by Simon Marius in 1612. That astronomer very aptly compared its feeble light to that of a candle seen through a piece of horn. Beautiful and symmetrical in shape, it resembles, under telescopes of higher power than could then be brought to bear upon it, a foreshortened view of several rings or girdles of light, encircling each other.

Within six years after, and perhaps even as early, for a published allusion to it was issued in 1618,-Cysatus, a Swiss astronomer, first discovered the great nebula in the sword-belt of Orion. It was afterwards again discovered (for it was evidently an independent observation,) by Huyghens in 1656. He, in his Systema Saturnium, published in 1659, thus speaks of its strange appearance :

"Astronomers have counted in the sword of Orion three stars very near to each other. Happening in 1656 to observe the star which occupies the centre of the group, instead of one I perceived twelve stars; a result which, by the way, is not rarely obtained with telescopes. Of these stars there are three which, like the first, almost touched each other; while there were four others which seemed to shine through a cloud, insomuch that the space surrounding them appeared to be much more luminous than the rest of the sky, which was quite black. One would have thought that it was an opening in the heavens through which a brighter region beyond was visible.'

This nebula has been at least one of the most noted in the heavens; and, even more than the milky-way, tended to confirm the suspicion entertained by many astronomers, that its "spectral light" could not proceed from the mingling of the rays of the

observed stars in the region, as their number was wholly insufficient to cause, by such means, the strange luminous appearance. The third nebula to which the attention of astronomers was distinctly called, was that situated between the head and bow of Sagittarius. It was noticed by Hevelius soon after the year 1660, and afterwards observed and remarked upon by Abraham Thle.

The nebula near Centauri was discovered by Halley in 1677, whilst he was engaged in constructing his southern catalogue of stars. It was then remarked as beautifully round in form; and when lately observed by Sir John Herschel at the Cape, was pronounced by him as beyond all comparison the richest and largest object of the kind in the heavens, having a diameter equal to two-thirds that of the moon.

In 1681 Kirch discovered a nebulous spot near the right, or northern, foot of Antinous; and in 1714 Halley discovered the brilliant and remarkable nebula, then supposed to be nearly round in form, but fringed on the borders, between the stars and n in the constellation Hercules.

In 1716, when Halley undertook an enumeration of all the known nebulæ, these six were all that had been discovered. But Lacaille, some thirty years after, during his residence at the Cape of Good Hope, determined the position of twenty-eight others, in fourteen of which his best telescopes showed nothing definite, while the other fourteen were, by the same telescopes, resolved into stars. Year after year the number of these objects increased, in consequence of a more diligent searching of the heavens; and at length, in 1771, Messier communicated to the Academy of Sciences a catalogue containing sixty-eight new ones, making in all one hundred and three, of which he gave drawings, in order that astronomers, when searching for comets, might not be misled into the supposition that they had found them when these vague spots of light came first under their notice.

The nebulæ now began to assume the position which they afterwards occupied that of the great enigma of the universe. As the power of the telescope was increased, it became perfectly evident that the newly found radiance could not be produced by the commingling of the beams of discovered stars in the immediate regions where it appeared. It seemed, indeed, wholly independent of those beams, and really to proceed from a source of some kind beyond and behind those stars, at further distance in the undiscovered depths of infinitude.

Meantime, excited curiosity sought for new and more perfect discoveries in the increase of magnifying powers, in which researches Sir William Herschel took the lead. Attention was again and again directed to the milky-way; and numerous stars, of lesser magnitude than those previously observed, clearly shone out amid the diffused nebulous radiance, which nevertheless

appeared more and more independent of their lustre and of the lustre of their better known and more brilliant companions,every increase of power with which it was observed only making it brighter, and throwing it, so to speak, farther back, beyond the region of the stars, which thus might be considered as occupying a position intermediate between it and us.

The question then arose, "What were these spots of light in the undiscovered depths of infinitude." Lacaille suggested that the nebulæ were of two kinds, some really, others only apparently such; those apparently such being resolvable into stars by increased magnifying powers, the real nebulæ consisting of diffuse luminous matter, distributed in different portions of the celestial vault. On his return from the Cape of Good Hope, he stated, in the memoirs of the Academy of Sciences for 1755, that—

"It is not certain that the whiteness of these parts (the magellanic clouds and the white spaces of the milky-way) is caused, as is generally supposed, by clusters of stars, more closely packed together than in other parts of the heavens; for, however attentively I examine the best defined borders of the milky-way, or the clouds of Magellan, I perceived with the fourteen-feet telescope only a whiteness in the ground of the heavens, without seeing more stars than in other parts where the ground was dark."

Herschel, however, advanced, and maintained for years, a different opinion. So many of the nebulæ seen by ordinary instruments had, by his larger telescopes, been resolved into clusters of stars, that he asserted his belief that all nebula consist of such clusters; and that there exists no essential difference between those of the most dissimilar appearance, besides that of greater or less distance, or greater or less condensation of the component stars. And though, when the power of his mightiest telescope failed to effect any resolvability in some of the patches of hazy light, he was afterwards induced to modify his opinion, yet is there now every reason to believe that his first grand conception was a right one, since the very objects which caused him thus to modify his opinion have since given signs of resolvability.

The contributions of Sir William Herschel to this portion of astronomical science may truly be described as enormous." In 1786 he published a catalogue of 1000 nebulæ, or clusters of stars. Three years afterwards a catalogue quite as extensive, succeeded this; and to these, in 1802, was added a third catalogue of 500, making altogether 2500.

Under the powerful instruments of this wonderful man the nebulæ assumed so many shapes as to baffle the imagination. The white radiance of the milky-way was much of it gradually resolved into discrete stars and star-dust, with which the deep back-ground of heaven appeared to be powdered. But the same power brought into view other nebulous spots, in positions where their existence had not been at all suspected; and these, apparently, in every

various state of condensation, from a thin pale cloud to brilliant but unresolvable light.

Such wonderful bodies, presenting such varieties of appearance, and coming into view, one after another, in nearly every region of the heavens, suggested at length to that eminent astronomer the idea that throughout the regions of space there might be dispersed a sort of gaseous or elementary sidereal matter, which gradually subsided or gathered into denser bodies. And, assuming that in the progress of this subsidence there would be local centres of condensation subordinate to the gradual tendency, he conceived that in this manner solid nuclei might probably be formed which would necessarily exert a more attractive force on the diffused matter around. By the local gravitation of these nuclei the progress of condensation would naturally be accelerated; and each, thus condensing, and so absorbing, the nebulous matter in its own immediate neighbourhood, might ultimately become a star, and the whole nebula finally assume the condition of a starry cluster.

Nor were there wanting apparent indications of every stage of this progress in the various and uncertain "lumps" or "patches" of light which Sir William's great telescope had revealed as existing in nearly every quarter of the wide regions of immensity to which he directed it. So close was the resemblance presented to the eye of the observer by difference in distance, to that which would naturally be presented by different stages of progress, that, when they began to be resolved into imaginary classes, there appeared in the different classes to be indications of something like the regular stages of progress from the first gradual condensation of sidereal nebulous matter to the formation of solid nuclei and starry clusters; and that, too, in every modification of form to which the general principle might be considered to apply. The more or less advanced state of a nebula towards its aggregation into distinct stars, and these stars themselves towards a denser nucleus, were thus considered as indicative of the periods of time, the vast sidereal eras, through which they had respectively passed.

Can we marvel that the human mind became intoxicated by this grand though illegitimate conception? That the creative genius of La Place should see therein the mode of the formation of a universe-yea, of our own universe? That the christian student of science should for a season feel perplexed, and the infidel raise a shout of rejoicing? For the first time did atheism, and those semi-atheistic systems, Pantheism and Boodhism, find a shew of evidence in their favour. For the first time did it appear how a universe could be formed without a God. The sceptic laughed; the pseudo-philosopher transferred us from the rule of a living, operating, and intelligent Deity, to that of mere principles and laws. And even some observant Christians began to think it

possible that our ideas of creation would have to be modified. The enigma of many centuries at least appeared to be resolved; and in its resolution to bring out facts or axioms which naturally had a renewing influence on all philosophical theories, moulding the opinions of the studious portion of mankind into new shapes, and giving birth to speculations and systems soon to be dissipated. The nebular theory prevailed.

In the progress of discovery, the southern hemisphere was next subjected to the searching ken of Sir John Herschel's mighty telescope, and revealed still more gorgeous wonders. In the northern one, few of the nebulæ exceeded in size a twentieth portion of the moon's disc. In the southern hemisphere vast numbers exceeded the size of the full noon, some of them to an extent surpassing all conception. In the northern hemisphere there were eight portions of the heavens around which the nebulæ most generally prevailed. In the southern one they were distributed throughout its entire extent; while the stupendous size of some of them threw entirely into the shade those luminous clouds in the sword-belt of Orion, and near to a Centauri, which had for several centuries been such objects of wonder. In the constellation Argo, for example, diffused around the star 7, is a nebula which consists of diffused, irregular nebulous patches, extending over a space on the heavens about five times greater than the whole disc of the moon. It lies, apparently, far behind and beyond that part of the milky-way which traverses the southern firmament, twelve hundred of whose stars may be seen projected upon a small part of its extent; and such is its apparent distance, that no portion of it has shown the least tendency to be resolved into distinct and separate stars.

Nor was this the greatest marvel that the "Cape Observations" were destined to reveal. Not more did the nebula in Argo surpass the faint patches of light with which the northern hemisphere was in various localities jotted over, than it was itself surpassed by the magellanic clouds already observed by Lacaille, but whose feeble instruments disclosed, comparatively, nothing of their greatness. These immense districts of strangely varying light were named the Nebecula major and the Nebecula minor, the first occupying a superficial area of forty-two square degrees, the other a space of about ten square degrees. And, instead of each being a single nebula, they seemed to be masses of nebula crowded together, as though Sir William Herschel's surmised grand centre of the universe-"THE THRONE OF GOD"-were there in its great and awful reality; or that, according to his other dream, the nebulous sidereal matter had in that district found its great centre of attraction; and a galaxy, or series of galaxies, were here in process of formation, of which our "milky-way" was as a mere outlier, and which would eventually surpass, in its grand and gorgeous dimensions, all the universe besides.