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 nebula, 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 toward the central point; others offering "the singularly beautiful and striking phenomenon, of a sharp and brilliant star, surrounded by a perfectly circular disk or atmosphere;" others, again, of more rare occurrence, are annular, exhibiting, in the central opening, a faint hazy light; and, last of all, come nebula, which have "exactly the appearance of planets, -round, or slightly oval disks, 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 consists 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 atmosphere, around particular stars ;-what, we naturally ask, is the nature and destination of this nebulous matter? Is it

absorbed by the stars, in whose neighborhood 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 sagely 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, have furnished one of the most profound mathematicians of his 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 a part of a universally diffused phosphorescent vapor, 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 this highly satisfactory reasoning, I cannot enter, but must refer the reader to the work itself; and I am quite sure, that no candid mind can resist the conclusion to which he comes, that, whatever may be the + Laplace.

* Herschel's Astronomy.

scientific merits of this hypothesis, they cannot, in sound reason, affect at all the view of the universe as the work of a wise and great Creator. "Let it be supposed," observes he in conclusion, "that the point to which this hypothesis leads us, is the ultimate point of physical science; that the furthest glimpse we can obtain of the material universe by our natural faculties, shows it to be occupied by a boundless abyss of luminous matter; still, we ask, how space came to be thus occupied,-how matter came to be thus luminous ? If we establish, by physical proofs, that the first fact which can be traced in the history of the world is, that 'there was light,' we shall still be led, even by our natural reason, to suppose that, before this could occur, 'God said, Let there be light.""

Dr. Nichol, who adopts the hypothesis of Laplace, as to the gradual conversion of nebulæ into stellar and planetary systems, and illustrates it in a very striking manner, deduces from it the following pleasing and sublime views :

"The ideas I have presented to you-august and strange though they are should not appear in contradistinction to what every moment is passing around us. Supposing these phenomena did unfold the long growth of worlds, where is the intrinsic difference between that growth and the progress of the humblest leaf, from its seed, to its intricate and most beautiful organization? The thought that one grand and single law of attraction, operating upon diffused matter, may have produced all those stars which gild the heavens, and, in fact, that the spangling material universe is, as we see it, nothing other than one phase of a mighty progress, is indeed truly surprising; but I appeal to you again, in what essential it were different from the growth of the evanescent plant? There, too, rude matter puts on new forms, in outward shape most beauteous, and in mechanism most admirable : and there cannot be a more astonishing process, or a mightier power, even in the growth of a world! The thing which bewilders us, is not any intrinsic difficulty or disparity, but a consideration springing from our own fleeting condition. We are not rendered incredulous

by the nature, but overwhelmed by the magnitude, of the works; our minds will not stretch out to embrace the periods of this stupendous change. But time, as we conceive it, has nothing to do with the question; we are speaking of the operations, and tracing the footsteps, of One who is above all time; we are speaking of the energies of that Almighty Mind, with regard to whose infinite capacity, a day is as a thousand years, and the lifetime of the entire human race but as the moment which dies with the tick of the clock which marks it-which is heard and passes."

FIFTH WEEK-SATURDAY.

XII. THE STARRY HEAVENS.-BINARY STARS.

THERE is yet another singular phenomenon in the starry heavens, which shall form the subject of this day's paper, I allude to the curious fact of the existence of binary revolving stars. These are very numerous. Sir William Herschel has enumerated upwards of 500, and Professor Strave, of Dorpat, has recently added to this number between 2000 and 3000. When these combinations were first observed, it was thought probable, that their extreme apparent proximity would enable astronomers to ascertain their distance from the earth, by the discovery of an annual parallax ; for supposing, as might naturally be expected, that one of the combined stars should be nearer the earth than the other, and that both should prove to be stationary in relation to each other, the motion of the earth in her orbit would cause these stars to alter their apparent position; and, if that should be the case, even in the slightest appreciable degree, this circumstance would furnish data, on which calculations

* Architecture of the Heavens, pp. 143, 144.

of the greatest importance might be founded.* This consideration induced Sir William Herschel to turn his attention to the double stars, and to subject them to careful and minute measurements; but he had scarcely begun his task, when he was arrested by phenomena of a very unexpected character. Instead of the effect which might be produced by the earth's annual motion, he observed, in many instances, a regular progressive change, "in some cases bearing chiefly on their distance; in others, on their position, and advancing steadily in one direction, so as clearly to indicate either a real motion of the stars themselves, or a general rectilinear motion of the sun and the whole solar system, producing a parallax of a higher order than would result from the earth's orbitual motion, and which might be called systematic parallax.'

* We may perhaps despair of fixing the distance of any but the very nearest of the fixed stars, by means of noting their parallax, i. e. the variation which takes place in their relative position in different parts of the earth's orbit; but there is another and highly ingenious method of determining the distances of the binary stars, which has been pointed out by M. Arago. This method depends on the progressive motion of light. If the orbit of a revolving star presents nearly its edge to the observer's eye, it is evident that during one half of its revolution it is constantly receding from the observer, and, during the other half, constantly approaching him. Supposing the light of that star to take thirty days in travelling to the earth from the nearest point of its orbit, it will require more than thirty days to reach the earth from the farthest point. Hence it will appear to spend more time in one part of its orbit than in the other; and the difference between the calculated and the apparent time of its transit through the nearest and farthest halves of its orbit, though it should be but a few seconds, will supply the astronomer with the data he requires. The two observed semi-revolutions differ from each other by the double of the time which the light takes to pass across the star's orbit. Hence half the difference of time expressed in seconds, and multiplied by 200,000, the number of miles which light traverses in a second, will give the diameter of the orbit. This element known, the distance from the earth is easily found. What a new accession to our knowledge will be acquired, when, by a long and careful observance of these double stars, this discovery is made! The day in which the distance of a double star is determined," says M. Arago, "will be the day in which it may be weighed, in which we shall know how many millions of times it contains more matter than our globe. We shall thus penetrate into its internal constitution, though it may be removed from us more than 120,000,000,000,000 of leagues."

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