have been distant from the Earth, less than 19 billions of miles.

In order, therefore, tnat astronomers may know this star when spoken of, it is called y Draconis, that is, the star in the constellation of the Dragon, which is marked by the Greek letter y. Some of the stars which are distinguished for their superior brilliancy, have particular names attached to them ;-such as Sirius, in the right shoulder of the constellation Orion; Rigel, in his left foot; Arcturus, &c.

The principal fixed stars, which lie within a convenient distance of the moon's path, are used for taking Lunar distances, in order to enable mariners to deduce their longitude. The distances of particular stars from the moon, at certain regularly recurring times, when the moon is visible, are calculated at Greenwich, and set down for some years in advance according to Greenwich time. As the motion of the moon is quicker than that of any other heavenly body as seen from the earth, these lunar distances soon change. If then a person on the ocean wishes to know his longitude, and he finds, for instance, that on such a day and hour, according to the Nautical Almanack such a particular star is so many degrees distant from the moon, but that this lunar distance occurs as seen from the ship, an hour sooner than the Greenwich time :-in this case, his longitude is 15° W. If the recorded distance had occured an hour later, his longitude would have been 15° E.

The stars beyond the 7th magnitude are called telescopic stars. Those, which are visible to the naked eye at any one time, are supposed not to exceed 2,000, notwithstanding the countless assemblage which appears to be present. This results from a sort of optical delusion, whereby the eye is disconcerted by the apparent want of order: but, with the telescope, Sir. W. Herschel computed that a small portion of the heavens, not exceeding 15° in length, by 2° in breadth, exhibited not less than 50,000 stars, from which it has been calculated that the same instrument would make visible in the whole starry sphere, not less than 75 millions of stars! The mind shrinks within itself at the contemplation of such a vast array,—and still more, when it is considered that this number is limited by the imperfection of human contrivances; for there can be no doubt, that, if our telescopes were more powerful, the number of visible stars would be greatly increased. This observation may refer to that thin gauzy band of light, which seems to surround the dome of the heavens on a clear evening, when the moon is absent. It has the name of the Galaxy, or Milky-way. By the power of modern instruments this has been shown to be a vast congregation of stars so small, or so far off, that to an observer on our Earth they present only, by their association, a dim zone of light. The elder Herschel observed about 600 stars in his telescope at the same time, and they continued as numerous for a quarter of an hour. He reckoned up in one portion of the Milky-way, about 250,000

stars.

The stars are always spoken of as being fixed; and if we regulate our expresions by the analogy of general_movements, they are certainly fixed; but astronomers have of late years seen reason to believe that a very minute motion may be detected in some stars; that is, that a certain group of stars does not present the same relative distances between the stars of which it is formed at one time, as at another. These quantities of motion, or of difference, are, however, so inconceivably small, that they belong to the refinements of astronomy, and need not be discussed here.

But we have now to notice a very remarkable circumstance, which seems to afford evidence that the stars are luminaries like our Sun, and have planets revolving round them; that each one

Informs a system in the boundless space, And fills with glory its appointed place:, When the stars are observed with close attention by means of a good telescope, many of them are found to be double; that is, to consist of two smaller stars, the dark division between them being too faint to be distinguished in an ordinary observation. In some instances, this may occur from one star being almost directly behind another; and though at an immense distance off from the first, yet seeming to our vision to lie in the same line: but, in other instances, it is found that one star revolves round the other, or the two revolve round some point situated between them. Very little was known on this subject until of late years, when Sir W. Herschel, and afterwards Sir J. South and Sir J. Herschel, distinctly showed that such a revolving motion was perceptible; at one time the satellite,

or smaller of the two stars, would disappear, as if it had passed round behind the other in the course of its motion, just as Jupiter or Venus is sometimes invisible to us, on account of being on the opposite side of the Sun; or the satellites of Jupiter, by passing round the body of that planet. There is a double star (see fig. 47,) in the constellation called the Great Bear, in which the two component stars revolve round each other in about 60 years; nearly a whole circuit has been performed since its discovery in 1781. About 3000 of these double stars have been observed, and formed into a catalogue, in which their positions, with respect to latitude and longitude, and the relative positions of the two component stars of each, are entered with great exactness, in order that future observers may have the means of comparing the different appearances of these stars at different times.

In about fifty instances the stars have been found to be triple, or three stars revolving about a common centre. In some few cases four, and even five stars have been detected revolving in this way; thus furnishing a further analogy to the composition and relative action of the different bodies which form our own system.

Another peculiar appearance which presents itself in the heavens are nebula, which are dim, whitish, cloudy patches, observable at some parts of the firmament. When examined with a powerful telescope, many of them are found to consist of clusters of very minute stars, so thickly studded together, that the light of all is combined into one faint sheet, as it were, of light, and thus presents the thinly-luminous appearance by which the nebulæ are distinguished. In other instances, however, the most powerful telescopes have been unable to separate the nebulæ into stars, or clusters of stars; but the whole maintains the same thin and milky appearance, whether seen with or without the aid of the telescope. In this latter case, it is supposed that the nebulæ are formed of clusters of stars as in the former case; but that they are so extremely distant, that the light they shed is unable to reach the eye, except in a combined form from the whole of the nebulæ taken together. Some of these nebula appear like a faint luminous atmosphere surrounding a star of some brilliancy. Sir W. Herschel has left descriptions of about 2000 nebulæ, which he observed at different parts of the heavens.

It is considered to be probable, that the fixed stars are SUNS, having planets revolving round them in the immensity of space; and it has been observed, that there are stars of all the colours of the spectrum. The stars are usually discovered by the eye from planets by their twinkling, which arises, probably, from some unequal refraction of light, in consequence of the distance of its path. There are stars seen now in the heavens which did not appear formerly, and many have disappeared, which are recorded as shining with brilliancy in former ages. Some stars appear and disappear alternately; of others the magnitude and brilliancy are variable.

When we come, therefore, to consider the vast distance of the fixed stars with the progressive, though rapid, motion of light, it is quite clear that many stars which now appear shining, may have been annihilated long ago, and that the last beams which they shed may take years in reaching this earth. If our Sun were suddenly extinguished, we should not know it until eight minutes after the extinction; and if it were suddenly rekindled, its rays would take eight minutes in order to reach us.

How distant some of the nocturnal suns!
So distant, says the sage, 'twere not absurd
To doubt, if beams, set out at Nature's birth,
Are yet arrived at this our foreign world;

Yet nothing half so rapid as their flight.-YOUNG. In order to acquire a knowledge of the aspect of the heavens, it is necessary for those who live in the northern hemisphere to direct their attention to the polar star. This is one of the chief stars of the constellation termed the Little Bear, (see fig. 47,) and is of the second magnitude. It is about 14° from the pole; and, saving the small circle which it thus describes, it is always in the same position at every hour of the day and night, and at every season of the year. To the point, from which this star is about 14° distant, there is, southward, a corresponding point, round which two points the concave sphere of the heavens, studded with stars, seems to turn; this being, in reality, due to the diurnal motion of the earth on its axis. The stars round about these two points are called circumpolar stars, as revolving constantly about the poles; and those which, in consequence, never set to our and more northern latitudes, are

termed stars of perpetual apparition, because they are constantly above the horizon. The stars a and B, in the Great Bear are called the Pointers, because, if we follow them, they lead almost in a right line to the Pole-Star :-they serve, therefore, to point out this star. After the Great and Little Bears, which are very conspicuous, and easy to remember, the other principal constellations may be readily recognised. Nearly surrounding the Little Bear is the constellation Draco. In the upper corner of the right hand, appear parts of the constellations Lynx and Camelopardalus; and at the lower corner of the left hand, part of the constellation Boötes.

The constellation Orion, the Pleiades, and the star Arcturus, of the first magnitude, are known in Scripture. The term Mazzaroth, used in the book of Job, xxxviii. 32, is supposed to imply the constellations of the Zodiac, which are thought to be meant by Joseph, when he spoke of the sun, moon, and eleven stars, bowing down to pay him homage, himself being the twelfth.-Gen. xxxvii. 9. But the science of astronomy was not much encouraged at any time among the Jewish people, lest they might the more easily be allured to join in the idolatries of the neighbouring nations, all of whom eagerly gave themselves up to the worship of the "heavenly host."

We ought not to omit to mention, that in the Southern Hemisphere is the constellation called the CROSS, which, from the disposition of the principal stars, is a type of that sacred emblem; it is almost entirely enveloped by the southern part of the milky way, as shown in the figure. This is, perhaps, one of the justest configurations that astronomers have ever made, and is thus alluded to by the poet Rogers, who also speaks of the superior radiance of the stars in the heavens below the line:

...

........ And now in opener skies

Stars yet unnamed of purer radiance rise!
Stars, milder suns, that love a shade to cast,
And on the bright wave fling the trembling mast!
Another firmament! the orbs that roll,

Singly or clustering, round the southern pole!

Nor yet the four that glorify the night

Ah, how forget, when to my ravished sight
The CROSS shone forth in everlasting light!

The mariners in the Lusiad also thus apostrophize this constellation:

While nightly thus the lonely seas we brave,
Another Pole-star rises o'er the wave;
Full to the south a shining CROSS appears;
Our heaving breasts the blissful omen cheers.
Seven radiant stars compose the hallowed sign,
That rose still higher o'er the wavy brine.

B

its circular course through the ecliptic. The Earth completes one revolution on its axis in twenty-three hours and fifty-six minutes, which is termed a sidereal day, being the time which elapses from any star coming upon the meridian till its arriving there again; this would, therefore, be the length of the day, were the Earth stationary ; but, as we said before in other words, the Earth advances nearly one degree in its orbit in one day, or the Sun seems to move this space in the ecliptic.

When the Moon, in her passage round the Earth, passes over any of the fixed stars or planets, she is said to occult, or hide them; and such a phenomenon is termed an occultation, an observation of which is useful in determining longitude.

One of the latest opinions respecting the cause of shooting stars is, that they are fragments of planets, which, in the course of their revolutions, come, at certain times, within visible range of the earth.

Having had occasion, more than once, to refer to the discoveries made by Sir William Herschel, in the celestial regions, we cannot altogether dismiss the subject, without describing the stupendous and wonderful instrument, which he himself constructed, and with which he enriched the modern state of astronomical knowledge. The magnifying powers of this instrument exceeded all that had ever been known, previously or since.

We will suppose the reader to be at least moderately acquainted with the principles and use of the common refracting telescope: he will therefore observe that the subjoined figure affords a representation of Herschel's REFLECTING Telescope:

Fig. 47.

Let us suppose A B to be a concave reflector, and ra, rB to be rays proceeding from a distant object, such as a star. The reflector A B is not placed symmetrically across the tube, but has such a degree of inclination given to it, as will bring the rays to a focus at F, near the margin of the mouth of the tube. The eye of the observer being now placed at that point, he will see the image formed by the focalization of the rays. The object to be obtained in thus bringing the rays to a focus at the margin of the tube, instead of at the centre of its diameter, is, that the body and head of the observer may intercept as few rays as possible; for it will be seen that it is quite impossible for him to look into the tube, without obstructing the passage of some of the light proceeding from the object. But this obstruction is thus limited as much as possible.

This telescope was begun by Sir William in the year 1785, by the pecuniary aid afforded to him by King George the Third, who was his patron. Herschel superintended the whole of the construction of it himself; and he had as many as forty workmen employed upon it at once. In February, 1787, he had the first view through this telescope, although it was not completely finished till August, 1789.

The great reflector A B was forty-eight inches in diameter of polished surface. A speaking trumpet was fitted to the side of the telescope, for the observer to communicate the result of his observations to an assistant below, who was stationed in a small house, and provided with various instruments for measuring time, the positions of the stars, &c. This vast tube was moved about in any direction, by means of a large and complicated apparatus. The eye-pieces, through which the observer viewed the reflected image of an object, were held at the mouth of the tube by a sliding apparatus, by which the attention could be directed to any particular part of the speculum A B.

The frame-work of this instrument having been found to be greatly decayed, after it had remained thirty years in its place, the whole was taken down and replaced by a smaller one on the like construction by Herschel's son, one of the most distinguished astronomers of modern days.

No sooner had the great telescope been erected by Sir W. Herschel, than he began an important series of discoveries by its means. He discovered the sixth satellite of Saturn (five only having been previously known,) on the day

apply this question to the fixed stars. Are they luminous of themselves, or do they derive their light from the sun, like the bodies of our planetary system? Think of their immense distance, and the solution of this question becomes evident. The sun, like any other body, must dwindle into a less apparent magnitude as you retire from it. At the prodigious distance even of the very nearest of the fixed stars, it must have shrunk into a small indivisible point. In short, it must have become a star itself, and could shed no more light than a single individual of those glimmering myriads, the whole assemblage of which cannot dissipate, and can scarcely alleviate, the midnight darkness of our world. These stars are visible, not because the sun shines upon them, but because they shine of themselves, because they are so many luminous bodies scattered over the tracts of immensity; in a word, because they are so many suns, each throned in centre of his own dominions, and pouring a flood of light over his own portion of these unlimitable regions. "At such an immense distance for observation, it is not to be supposed that we can collect many points of resemblance between the fixed stars and the solar star, which forms the centre of our planetary system. There is one point of resemblance, however, which has not escaped the penetration of our astronomers. We know that our sun turns round upon himself in a regular period of time. We also know that there are dark spots scattered over his surface, which, though invisible to the naked eye, are perfectly noticeable by our instruments. If these spots existed in greater quantity upon one side than upon another, it would have the general effect of making that side darker; and the revolution of the sun must, in such a case, give us a brighter and a fainter side, by regular alternations. Now, there are some of the fixed stars which present this appearance. They present us with periodical variations of light. From the splendour of a star of the first or second magnitude, they fade away into some of the inferior magnitudes; and one, by becoming invisible, might give reason to apprehend that we had lost him altogether; but we can still recognise him by the telescope, till at length he reappears in his own place, and, after a regular lapse of so many days an hours, recovers his original brightness. Now, the fair inference from this is, that the fixed stars, as they resemble our sun, in being so many luminous masses, of immense magnitude, they resemble him in this also, that each of them turns round upon his own axis; so that, if any of them should have an inequality in the brightness of their sides, this revolution is rendered evident, by the regular variations in the degree of light which it undergoes.

"Shall we say, then, of these vast luminaries, that they were created in vain? Were they called into existence for no other purpose than to throw a tide of useless splendour over the solitudes of immensity? Our sun is only one of those luminaries, and we know that he has worlds in his train. Why should we strip the rest of this princely attendance? Why may not each of them be the centre of his own system, and give light to his own worlds? It is true that we see them not; but could the eye of man take its flight into those distant regions, it would lose sight of our little world before it reached the outer limits of our system the greater planets would disappear in their turn-before it had described a small portion of that abyss which separates us from the fixed stars, the sun would decline into a little spot, and all its splendid retinue of worlds be lost in the obscurity of distance-he would at last shrink into a small indivisible atom, and all that could be seen of this magnificent system, would be reduced to the glimmering of a little star. Why resist any longer the grand and interesting conclusion? Each of these stars may be the token of a system as vast and as splendid as the one which we inhabit. Worlds roll in these distant regions; and these worlds must be the mansions of life and of intelligence. In yon gilded canopy of heaven, we see the broad aspect of the universe, where each shining point presents us with a sun, and each sun with a system of worlds-where the Divinity reigns in all the grandeur of His attributes-where He peoples immensity with His wonders; and travels in the greatness of His strength through the dominions of one vast and unlimited monarchy.

"The contemplation has no limits. If we ask the number of suns and of systems, the unassisted eye of man can take in a thousand, and the best telescope which the genius of man has constructed, can take in eighty millions. But why subject the dominions of the universe to the eye of man, or to the powers of his genius? Fancy may take its flight far beyond the ken of eye or of telescope. It may expatiate in the outer regions of all that is visible-and shall we have the boldness to say, that there is nothing there?-that the wonders of the Almighty are at an end, because we can no longer trace His footsteps ?-that His omnipotence is exhausted because human art can no longer follow him?-that the creative energy of God has sunk into repose, because the imagination is enfeebled by the magnitude of its efforts, and can keep no longer on the wing through those mighty tracts, which shoot far beyond what eye hath seen, or the heart of man hath conceived: which sweep endlessly along, and merge into an awful and mysterious infinity.

THE

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VOL. XIV.