extended shape, at a distance from the border of the great one, to which it runs in a parallel direction, resembling the shoals that are seen near the coasts of some islands.

. Dr. Herschel concludes his account of the Construction of the Heavens with some observations on a few heavenly bodies, which, from their singular appearance, left him in doubt where to class them; of these he notices six. The first precedes v Aquarii 5'.4 in time, and is l' more north. By means of his twenty feet reflector it was well defined, and had much of a planetary appearance, being all over of an uniform brightness, in which it differs from nebulæ : its light seems, however, to be of a starry nature, which suffers not nearly so much as the planetary disks are known to do when much magnified. The second of these bodies precedes, the 13th of Flamstead's Andromeda, about 1'.6, and is 22′ more south. It has a round, bright, pretty well-defined' planetary disk of about 12" diameter, and is a little elliptical. The third follows ẞ Ophiuchi 4'.1 in time, and is 23′ more north. It is round, tolerably well defined, and pretty bright; its diameter is about 30". The fourth follows Sagitta 17'.1 in time, and is 2' more north. It is perfectly round, pretty bright, and well defined, and is about 45" in dia meter. The fifth follows the 21st Vulpeculæ 2'.1 in time, and is about 1° 46′ more north. This is exactly round, of an equal faint light throughout, and about ' in diameter. The sixth precedes h Cygni 8,1 in time, and 1° 26' more south. It is perfectly round, and of an equal faint light; its diameter is 1', and the edges are well defined. The planetary appearance of the first two is so remarkable, that they can scarcely be considered as nebulæ; their light is so uniform, as well as vivid; the diameters are so small and well defined, as to make it almost impossible that they should belong to that species of bodies. On the other hand, the effect of different powers

seems to be much against their light being of a pla¬ netary nature, since it preserves its brightness nearly in the same manner as the stars do in similar trials. If we could suppose them to be single stars with large diameters, we shall find it difficult to account for their not being brighter, unless we should admit that the intrinsic light of some stars may be much inferior to that of the generality, which, however, can hardly be imagined to extend to such a degree. We might suspect them to be comets about their aphelion, if the brightness as well as the magnitude of the diameters did not oppose the idea; so that, after all, we can hardly find any hypothesis so probable as that of their being nebula; but then they must consist of stars that are compressed and accumulated in the highest degree. If it were not,' says the Doctor, perhaps too hazardous to pursue a former surmise of a renewal in what I figuratively called the laboratories of the universe, the stars forming these extraordinary nebulæ, by some decay or waste of nature, being no longer fit for their former purposes, and having their projectile forces, if any such they had, retarded in each other's atmosphere, may rush at last together, and, either in succession, or in one general tremendous shock, unite into a new body. Perhaps the extraordinary and sudden blaze of a new star in Cassiopeia's chair, in the year 1572, might probably be of such a nature.'

As a summary of what has been said, we may observe, that, in looking beyond the solar system, we have contemplated innumerable suns, which may be, which probably are, the foci of as many planetary systems, and which are spread out in the immensity of space, and at such a distance from the Earth, that not only the diameter of that body, but the diameter of its orbits, would be totally invisible. Many stars we have seen experience very remarkable periodical variations in their splendor and colour: there are some which have appeared all at once, and disap

peared after having, for some time, spread a brilliant light. What prodigious changes must have operated on the surfaces of these great bodies, to be thus sensible at the distance which separates them from us! and how much they must exceed those which we observe on the surface of the Sun! All those bodies which are become invisible remain in the same place in which they were observed, and hence, La Place thinks, there may exist in space obscure bodies as considerable, and, perhaps, as numerous, as the stars. A luminous star, of the same density as the Earth, our author says, and whose diameter should be 250 times larger than that of the Sun, would not, in consequence of its attraction, allow any of its rays to arrive at us; it is, therefore, possible that the largest luminous bodies in the universe may, through this cause, be invisible. A star, which, without being of this magnitude, should yet considerably surpass the Sun, would perceptibly weaken the velocity of its light, and thus augment the extent of its aberration. This difference in the aberration of stars and their situation, observed at the moment of their transient splendor; the determination of all the changeable stars, and the periodical variations of their light; in a word, the motions peculiar to all those great bodies which influenced by their mutual attraction, and by their primitive impulses, describe immense orbits, should, relatively to the stars, according to La Place, be the principal objects of future astronomy.

We have seen that these stars, far from being disseminated at distances equal in space, are united in various groups, each consisting, perhaps, of many millions of stars. Our Sun, and the most brilliant stars, probably make part of one of these groups, which, seen from the spot in which we are situated, seems to encircle the heavens, and form the milky way. The great number of stars, which are seen at once in the field of a large telescope, directed towards

this way, proves its immense depth, which surpasses a thousand times the distance of Sirius from the Earth; as it recedes, it terminates, by presenting the appearance of a white and continued light, of small diameter; for then the irradiation which exists, even in the most powerful telescopes, covers and obscures the intervals between the stars. It is then probable that those nebulæ, without distinct stars, are groups of stars seen from a distance, and which, if approached, would present appearances similar to the milky way.

'The relative distances of the stars which form each group are, at least, a hundred thousand times greater than the distance of the Sun from the Earth. Thus we may judge of the prodigious extent of these groups by the number of stars which are perceived in the milky way, if we afterwards reflect on the small extent and infinite number of nebula which are separated from one another by an interval incomparably greater than the relative distance of the stars of which they are formed; the imagination, lost in the immensity of the universe, will have difficulty to conceive its bounds.'-[Pond's Translation of La Place's Astronomy.]

Astronomical Occurrences.

THE Sun enters the sign Capricorn on the 22d of December, at 27 m. past 2 in the morning. On the 7th, at 45 m. past 10 in the evening, the planets Mars and Jupiter will be in conjunction; the former will be 43′ south: and, on the 9th, there will be a conjunction of the planets Mercury and Herschel, the former being 25' south. Mercury will be in his superior conjunction at past 1 at noon on the 21st; and the Herschel will be in conjunction at past 7 in the evening of the 3d,

TABLE

Of the Sun's Rising and Setting every fifth Day of

the Month.

Sunday, December 1, Sun rises 56 m. past 7

Wednesday,

Friday,

Monday,

Saturday,

Thursday, .
Tuesday,

31,

sets 4 m. past 4

59

8

Equation of Time. [See Occurrences for January.]

m. sec.

Dec. 1, from the time on the dial subtract 10 38

3

21,

26, to the time on the dial add 1

31,

3 28

The Moon is at full on the 4th of December, at 51 m. past 8 in the evening: she enters her last quarter at 52 m. past 3 in the morning on the 12th. The Moon is at change, or new Moon, on the 18th, at 37 m. past 10 at night; and she enters her first quarter on the 26th, at 52 m. past 1 in the afternoon.

The Moon will be eclipsed, visible in these parts, on the 4th of December, the description of which is as follows:

Digits eclipsed 8° on the Moon's south limb.

17880

None of the eclipses of Jupiter's first satellite will be visible in the neighbourhood of London during the month of December; but, on the 24th day, at 4 m. past 7 in the morning, an immersion of the second satellite may be seen with a good glass.