2 Ceti, on the 28th. The time of immersion will be 31 m. past 8 o'clock in the evening; that of emersion 32 m. past 9: in the former case the star will be 6', in the latter 7' south of the Moon's centre. Mercury will appear at his greatest elongation from the Sun on the 2d day; and Saturn will be in conjunction with that luminary on the 12th. The astronomical observer may be informed that eclipses of Jupiter's 1st satellite will be visible at the following times, viz. the immersions on the 2d day, at 12 min. past 6 in the morning. 3d evening. These are the principal circumstances to which the attention of the student need be called during the present month. VIEW OF THE SOLAR SYSTEM. If we were required to point to one of the grandest trophies of mental power, we should immediately select the invention of the Copernican and Newtonian hypotheses of planetary motion. Nothing can seem more disorderly than the motions of the planets; so apparently anomalous and wandering, indeed, are they, that the very name by which these bodies are now designated, was originally appropriated to them by the Greeks, from that circumstance. Viewed in the most cursory manner, the numerous brilliant spangles which deck the heavens on a clear night, must excite the liveliest admiration : shepherds and poets, who have traced them simply thus, have regarded them as chinks through which, The particular uses and application of these eclipses will be hereafter explained. the Divine glory and splendour lying beyond, are let in upon this nether world. But the energies of philosophy, directed for successive ages towards the celestial bodies, have gradually penetrated the obscurity through which they seemed to shine, and from apparent irregularity and confusion have educed order, beauty, harmony, and law. The mind of man (says the great Lord Bacon) doth wonderfully endeavour, and extremely covet this, that it may not be pensile; but that it may light upon something fixed and immoveable, on which, as on a firmament, it may support itself in its swift motions and disquisitions.' Systems indeed, and astronomical systems perhaps more than others, in many respects resemble machines. A machine is a little system created to perform, as well as to connect together in reality, those different movements and effects which the artist has occasion for. A system is an imaginary machine, invented to connect together in the fancy those different movements and effects which are already in reality performed. The machines that are first invented to perform any particular movement are always the most complex; and succeeding artists generally discover that with fewer wheels, with fewer principles of motion than had originally been employed, the same effects may be more easily produced. The first systems, in the same manner, are always the most complex, and a particular connecting chain or principle is generally thought necessary to unite every two seemingly disjointed appearances; but it may happen, and in truth has happened, that one great connecting principle is afterwards found to be sufficient to bind together all the discordant phenomena that occur in a whole species of things. Thus, instead of the cycles and epicycles, in endless and inextricable groups, to which the antient astronomers had recourse, the modern system introduces to our notice simple and independent ellipses in which the planets move, by reason of the due adjustment of the projectile and central forces. According to the modern scheme of astronomy, as now received, confirmed, and irrefragably established, each star is to be regarded as the centre and main body of a system containing planets, secondary planets, or moons, and comets; and round which those smaller bodies move, in orbits and in periods depending upon their respective central or focal luminaries. The system to which our earth belongs, being that with which we are, of necessity, connected, is to us of the greatest importance: we shall, therefore, here present a description of its principal bodies, according to the latest and most accurate discoveries. The SUN, which is placed in the centre of gravity of the whole system, and nearly in the common focus of the elliptical orbits of all the planets, is an immense spherical, or rather spheroidal body, whose mean diameter is about 110 times that of the earth, and its magnitude, therefore, about 133,000 times that of the terrestrial spheroid. It has two motions, namely, one of a revolution about the common centre of gravity of all the bodies in the system (which centre is a point usually within its own body); and the other, one of a rotation on its own axis, ascertained by tracing the appearance and disappearance of the spots on its disk, and occupying 25 of our days. To us this luminary appears to move irregularly in an elliptical orbit; but this is an illusion arising from the circumstance that the planet which we inhabit has actually a periodical revolution in such an orbit round the Sun, placed in one of its foci. Hence it happens that while the Sun appears to be passing through certain signs of the zodiac, as Aries, Taurus, Gemini, &c. our earth is really moving through the opposite signs, Libra, Scorpio, Sagittarius. The spots on the Sun are very variable, both as to magnitude and continuance. Some of them are com puted to be four or five times as large as the surface of the earth. Sometimes they diminish in magnitude; at others, they disappear all at once before they reach the edge of the disk; at others, new ones are perceived. Thus they present a perpetual irregu larity; their period alone being fixed. Observations of these spots have led to some modifications as to the notions entertained respecting the nature of the body of the Sun. The antients thought it a body of fire; and some a body of gold in a state of fusion. Laplace imagines that the Sun is a mass of fire, subject to immense eruptions, after the manner of our volcanoes; on which hypothesis the spots would be vast cavities: from these, torrents of lava are thrown at intervals. Herschel, on the other hand, conceives that the Sun, so far from being fire, is a habitable body, like the earth, surrounded by an atmosphere almost entirely occupied by luminous clouds; and that these occasionally, when disturbed by winds, or other causes, permit the dark nucleus of the Sun to be seen through them, thus forming the solar spots. These spots are almost all comprised in a zone of the Sun's surface, whose breadth, measured on a solar meridian, never goes farther than about 30" from its equator. Bouquer satisfied himself, by many careful observations, that the light emitted by the Sun comes with more intenseness from the centre than from near the edge of the disk; and as this effect is contrary to that which ought to result from the spherical shape of the luminary, it is manifest that for some reason the light near the edges must be in part extinct. This suggests to some a reason for concluding that the Sun is surrounded by an immense atmosphere, which in some measure enfeebles its native light, but more towards the edges, where it is traversed obliquely by the rays just as our atmosphere diminishes the brilliancy of the stars, and especially about their rising and setting. This solar atmosphere has been proposed again as a mean for explaining that beautiful white light which is seen a little before the Sun's rising, and a little after its setting, and which is called the zodiacal light. Its translucency is such, that very small stars may be seen through it. Laplace, contemplating the lenticular form of this phenomenon, and its extent, thinks that it may, without hesitation, be ascribed to the solar atmosphere. His explication may be seen in his Système du Mond, liv. iv, chap. 9. It would not consist with our purpose, or our limits, to detail it here. The Naturalist's Diary. Now January o'er the northern world WINTER, to an inattentive eye, presents nothing, as it were, but the creation in distress: the orchards are stripped of their golden fruit; and harmony is extinct in the groves, now bending with the snow, 'their beauty withered, and their verdure lost.' Yet, when we explore these dreary scenes, the mind is amply gratified in the contemplation of the various phenomena peculiar to this inclement season. Winter, ushered into existence by the howling of storms and the rushing of torrents, manifests, not less than the more pleasing seasons of the year, the wisdom and goodness of the great Creator. Were there no winter, neither the spring, nor summer, nor autumn, would display such a variety of beauties; for the earth itself would lose those rich stores of nourishment and fertility, to which even the winter so copiously-contributes. |