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them," adds this astronomer, 66 are of an exactly round figure, and convey the complete idea of a globular space, filled full of stars, insulated in the heavens, and constituting, in itself, a family or society apart from the rest, and subject only to its own internal laws. It would be a vain task to count the stars in one of these globular clusters. They are not to be reckoned by hundreds; and, on a rough calculation, grounded on the apparent intervals between them at the borders (where they are seen not projected on each other), and the angular diameter of the whole group, it would appear that many clusters of this description must contain at least 10,000 or 20,000 stars, compacted and wedged together in a round space, whose angular diameter does not exceed eight or ten minutes; that is to say, in an area not more than a tenth part of that covered by the moon."

Are these numerous spangles, suns like our own, separated from each other by distances similar to those by which our solar star is separated from the other stars of the group to which he belongs? And are we, then, to believe that the system of stars to which our sun belongs, is nothing else than a nebula? And immense as are the bodies which that system embraces, and extensive, beyond all human conception, as is the space which it occupies, must we conclude, that, if viewed from the distance of the other nebule of which we have been speaking, it would appear but as a little cloud, no bigger than a man's hand? Such is, in truth, the astonishing conclusion to which the study of celestial appearances seems almost inevitably to conduct us.

Now, if we are permitted, on such a subject, to argue from analogy, we may fancy to ourselves some such idea as this, that each nebula or group of stars, bears the same reference to other groups which our planetary system does to the globes of which it is composed; and that, while they may be impressed with a rotatory motion round each other, like our satellites round their

primaries, there is some central point of unknown position, and immeasurable dimensions, round which the whole groups of the universe revolve, like our little worlds round their sun. There are not wanting reasons for such a supposition, extravagant as it may appear. The two great laws of gravitation and inertia, by which our own system is regulated and maintained, have been proved to exist with precisely the same powers, at least in some of the fixed stars. The probability, therefore, is, that these are universal qualities inherent in all material objects. This being granted, seems to imply the necessity of a balanced rotatory motion in every system of worlds, for preserving the general equilibrium of the whole; because universal attraction must prevent any body from remaining absolutely stationary. Now, the same principle appears to apply to groups of systems which applies to systems themselves. Hence, we may infer a complication of movements of the most wonderful and extensive kind, combining not merely worlds with worlds, and systems with systems, but nebula with nebulæ, embracing the whole material creation, and extending to infinity. What a magnificent view does this afford of the works of the Eternal; and what a beautiful unity does it appear to give to His operations! Could we but stretch our faculties to the conception, we might figure to ourselves the Almighty present, in some peculiar sense, in the centre of His works, and thence surveying the infinite machine which His hand had formedgroups upon groups, each containing tens of thousands of worlds, moving in constant succession before Him, without confusion and without interference,-rolling in an ethereal fluid, which bears light and heat in the waves of its never-failing tide, and which communicates life, and intelligence, and joy, to organized existences over the whole,—reflecting, wherever they move, the perfections of an Eternal Mind, and experiencing, throughout all their members, and in all their revolutions, the blessings of a Father's smile.

FOURTH WEEK—THURSDAY.

XI. THE STARRY HEAVENS.-NEBULE.

SIR WILLIAM HERSCHEL, by the use of his powerful telescopes, has made other most interesting discoveries in the starry heavens, some of which it will be the object of this paper briefly to detail, as throwing light on the condition of the universe, and demonstrating that the same mighty hand, which, “ever busy, wheels the rolling spheres" in our own system, is equally employing its amazing powers in the most distant regions, and regulating the material world every where, so far as we are able to discern, by the same laws, under some remarkable varieties of application.

We have already noticed the wonderful discovery of the apparently general arrangement, whereby the innumerable suns, of which the universe is composed, are thrown into groups, each containing vast numbers of these splendid bodies, and comprehending systems of their own. Of these nebulæ, as they are called, our own seems to be of a singular figure, forming a stratum, of which the thickness is small in comparison with its length and breadth, and which is divided into two branches, inclined at a small angle to each other, near the point in which our sun, with its planetary system, is situated. This figure seems, at least, to account for the appearances of the heavens, with their milky way, studded with innumerable stars, which branch off in one place in a remarkable manner from the main body, and which, as we have observed, decrease rapidly in numbers, in proportion to their distance from that singular belt. The other nebulæ are of various forms, and even seem to differ from each other in their nature. Sir William Herschel divides them into six classes, of which the two first appear to be distinguished merely by their relative distance

from us, but the rest to be in a state altogether different from any thing of which we have experience. These latter, he describes under the four heads of nebulæ, in which there is no appearance whatever of stars, planetary nebulæ, stellar nebulæ, and nebulous stars. Of these the variety is very great, some being formed of little flaky masses, like "wisps of cloud," adhering to small stars; others being of a round or oval form, increasing more or less in density and brightness towards the central point; others offering "the singularly beautiful and striking phenomenon, of a sharp and brilliant star, surrounded by a perfectly circular disc or atmosphere;” others, again, of more rare occurrence, are annular, exhibiting, in the central opening, a faint hazy light; and, last of all, come nebulæ, which have "exactly the appearance of planets,-round, or slightly oval discs, in some instances quite sharply terminated, in others a little hazy at the borders, and of a light exactly equable, or only a very little mottled, which, in some of them, approaches in vividness to that of actual planets." These last are bodies of enormous magnitude,—so large, indeed, that they would include the whole of our planetary system within their diameter, forming masses of solid matter, if they are solid, such as the greatest stretch of imagination cannot grasp.

"The nebulæ," says the younger Herschel, “furnish, in every point of view, an inexhaustible field of speculation and conjecture. That by far the larger share of them consist of stars, there can be little doubt; and in the interminable range of system upon system, and firmament upon firmament, which we thus catch a glimpse of, the imagination is bewildered and lost. On the other hand, if it be true, as, to say the least, seems extremely probable, that a phosphorescent, or self-luminous matter also exists, disseminated through extensive regions of space, in the manner of a cloud or fog,-now assuming capricious shapes, like actual clouds, drifted by the wind, and now concentrating itself, like a cometic at

mosphere, around particular stars ;—what, we naturally ask, is the nature and destination of this nebulous matter? Is it absorbed by the stars, in whose neighbourhood it is found, to furnish, by its condensation, their supply of light and heat? Or is it progressively concentrating itself, by the effort of its own gravity, into masses, and so laying the foundation of new sidereal systems, or of insulated stars?"*

The author naively remarks, that it is easier to propound such questions, than to offer any probable reply to them; and it would be well if other astronomers were to imitate the modesty and philosophical forbearance of this eminent man. But there are, unfortunately, philosophers, who feel pleasure in every conjecture by which an intelligent First Cause may be excluded from the universe; and the obscure and doubtful phenomena afforded by these nebulous appearances, has furnished one of the most profound mathematicians of this class with a theory, by which he attempts to show, that the whole construction of nature depends on mere unintelligent mechanical powers. He supposes, for example, that our own sun, with his planetary system, was originally nothing else than part of a universally diffused phosphorescent vapour, which, condensing into a nucleus, gave rise to a revolving sun, of excessive heat; that as the heat diminished, the solar atmosphere contracted, leaving portions of itself detached by the centrifugal motion, which became gradually condensed into solid planets and satellites; and these he, with much ingenuity, attempts to show, from mechanical considerations, would assume the form and motions which we find actually impressed on them. Mr Whewell mentions this "nebular hypothesis," as he calls it, and triumphantly shows, that even granting it could account for the phenomena, it could not be held, in the most remote degree, to prove the sufficiency of mechanical causes without intelligence and design. On his highly

* Herschel's Astronomy.

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