certain that the nearest of them does not approach our sun so near as nineteen billions of miles! The calculation by which this inconceivable distance is established, is entirely satisfactory, and may readily be understood. I shall state it in as popular a manner as I can. As the earth moves round the sun at the average distance of about 95,000,000 of miles, it follows that she must be nearer those fixed stars that lie in the plane of her orbit, at one period of the year than at another, by double that distance, or 190,000,000 of miles; but it has been found that an approach of this immense amount makes not the very slightest perceptible alteration in the apparent size of these bodies; and hence we justly conclude, that 190,000,000 of miles is but as a point in comparison of the space which still intervenes between us and them. On this fact, we may form a loose estimate of a distance within which the stars, situated as I have mentioned, cannot be stationed. But we must take another and somewhat more scientific method of judging with regard to the distance of those stars which are otherwise situated. It might be expected, that the vast diameter of the earth's orbit would produce some perceptible amount of annual parallax in the stars; that is to say, that in moving over this immense space, some change would be effected in their relative position, just as a lateral movement of a few miles along a road produces a change in the outline even of the most distant hills. Were this the case, the distance of the stars might be ascertained with some degree of accuracy. But it is not so: "After exhausting every refinement," says Sir John Herschel," astronomers have been unable to come to any positive or coincident conclusion upon this head; and it seems, therefore, demonstrated, that the amount of such parallax, even for the nearest fixed star which has hitherto been examined with the requisite attention, remains still mixed up with, and concealed among, the errors incidental to all astronomical demonstrations. Now, such is the nicety to which these have been carried, that, did the quantity in question amount to a single second, (that is, did the radius of the earth's orbit subtend, at the nearest fixed star, that

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minute angle,) it could not possibly have escaped detection and universal recognition." Hence, by a simple mathematical process, he is led to the conclusion that the distance of the stars cannot be so small as 4,800,000,000 radii of the earth, or 19,200,000,000,000 miles! But, for any thing we can tell, the very nearest of them may be much farther removed from us than even this inconceivable distance.

Now, with regard to the size of these bodies, remote as they are, science has invented a way of forming some comparative estimate. Dr. Wollaston, by experiments on the light of Sirius, the brightest of the fixed stars, has ascertained that his splendor, when it reaches our earth, is twenty billions of times inferior in intensity to that of the sun. That the sun, therefore, might be made to appear no brighter than Sirius, he would require to be removed from us 141,400 times his actual distance; but this is scarcely two thirds of the distance beyond which we know the nearest fixed star to be actually placed. It follows, therefore, that the light of Sirius, and probably also his bulk, is much greater than that of our sun. Dr. Wollaston, on data that cannot easily be disputed, has assumed the distance of Sirius to be so great, that his intrinsic light must be nearly equal to fourteen suns. Sir John Herschel, taking a more modest and cautious, but perhaps not truer, estimate of his distance, concludes that, "upon the lowest possible computation, the light really thrown out by Sirius, cannot be so little as double that emitted by the sun; or that Sirius must, in point of intrinsic splendor, be at least equal to two suns, and is, in all probability, vastly greater."

I cannot better conclude this paper, than by the judicious remarks with which the eminent philosopher, above quoted, follows up his statements on the size and distances of the fixed stars. "For what purpose," says he," are we to suppose such magnificent bodies scattered over the abyss of space? Surely not to illuminate our nights, which an additional moon, of the thousandth part of the size of our own, would do much better; nor to

sparkle as a pageant, void of meaning and reality, and bewilder us among vain conjectures. Useful, it is true, they are to man, as points of exact and permanent reference; but he must have studied astronomy to little purpose, who can suppose man to be the only object of his Creator's care, or who does not see, in the vast and wonderful apparatus around us, provision for other races of animated beings. The planets, as we have seen, derive their light from the sun; but that cannot be the case with the stars. These, doubtless, then, are themselves suns, and may, perhaps, each in its sphere, be the presiding centre, round which other planets, or bodies of which we can form no conception, from any analogy offered by our own system, may be circulating."*

FIFTH WEEK-THURSDAY.

X. THE STARRY HEAVENS.-IMMENSITY OF THE UNIVERSE.

ON casting the eye across the heavens, it is arrested by a streak of faint light, which passes athwart the whole sky, in the direction, speaking loosely, of east and west. This streak is called the milky way, in allusion to a wellknown childish fancy of heathen mythology. When we regard the stars, with reference to this permanent band, we find that, in proportion as they recede from it on either side, they gradually become less and less numerous, till, towards the extreme north and south, there is an obvious deficiency in the comparative richness of the garniture with which the mighty dome is adorned. On applying the telescope to the diffused light of this remarkable part of the heavens, the astronomer is lost in admiration, to find, that this appearance is occasioned by an amazing multitude of stars, too minute to be detected by the naked eye, and too numerous to be accurately calcu*Herschel's Astronomy, p. 380.

lated, "scattered by millions, like glittering dust, on the black ground of the general heavens." Sir William Herschel informs us, that, on calculating a portion of the milky way, about ten degrees long, and two and a half broad, he found it to contain 258,000 stars,-a quantity so great, in so small a space, that the moon would eclipse 2000 of them at once! Now, all these are suns, probably at as great a distance from each other, as our sun is from Sirius, a distance so incomprehensible, when stated in miles, that the best way of forming some clear idea of it, is, to compare it with the velocity of some moving body with which we are acquainted. We know of nothing so swift as light, which moves at the rate of 12,000,000 miles in a minute; and yet, light would be at least three years in passing between the sun and Sirius. Let any one, then, comprehend, if he is able, the distances implied in the conception, that the minute and thickly studded sparks of the milky way, are suns, each so far separated from each other, that it would require three years for the light of the one to reach the other! And yet this astonishing view is not a mere gratuitous imagination, but a calm philosophical deduction from observed facts and obvious analogies.

But this stretch of the mental powers is little, compared with what is required for comprehending the conclusions we are led to form, from other celestial phenomena. In various parts of the heavens, and in all quarters, there are discovered either small groups of stars, or certain dusky spots, called nebula, which the power of the telescope has multiplied to thousands of greater or less distinctness and magnitude.* Now, these nebulæ, when subjected to a very strong magnifying power, generally resolve themselves into vast assemblages of minute stars, "crowded together," as Sir John Herschel expresses it, "so as to occupy almost a definite outline,

*In the northern hemisphere, after making all allowances, those whose places are fixed, cannot be fewer than between one and two thousand; and you will have a good idea how plentifully they are distributed, by remarking, that this is at least equal to the whole number of stars which the naked eye perceives on any ordinary night.”—Nichol's Architecture of the Heavens, p. 47.

and to run up to a blaze of light in the centre, where their condensation is usually the greatest." "Many of 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? 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 nebula 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 posi