Astronomical Occurrences In April, 1830. "The Sun Starts forth, rejoicing in his strength, to run Of airy essences attended, take their way, As the northern declination of the Sun encreases, larger portions of the north frigid zone enjoy his enlivening beams; in climes south of the arctic circle, his powerful influence is marshalling in beautiful array the lovely and odorous train of Flora; some of these have already laid their blooming honors low, and disappeared; but the violet scents the vale, the starry primrose enlivens the sunny border, the harbingers of a more glorious succession of flowers of every shape and hue. Solar Phenomena. The Sun enters Taurus at 1 minute after 3 of the afternoon of the 20th of this month; he will also rise and set, during the month, as in the following Table of the Sun's rising and setting for every fifth day. April 1st, Sun rises 33 m. after 5, sets 27 m. after 6 To find the true time at any place, apply the following quantities to the time indicated by a good sun-dial, at the moment for which the time, as pointed out by a well-regulated clock, is required. TABLE. m. s. Thursday, Apr. 1st, to the time by the dial add 4 4 Tuesday, Sunday, 6th, 11th, 2 33 1 8 16th, from the time by the dial subtract 0 9 Wednesday.. 21st Monday, 1 17 2 15 LUNAR PHENOMENA. Phases of the Moon. 8th day at 29 m. past 7 in the morn. Full Moon Moon's Passage over the Meridian. The Moon's centre will pass the first meridian at the following times during this month: April 1st, at 21 m. after 7 in the evening. Eclipses of the Satellites of Jupiter. The following are such of the eclipses of the firstand second satellites of this planet as will be visible at the Royal Observatory this month. IMMERSIONS: Third Satellite, 13th day, 7 m. 21 s. after 4 in the morn... 29th 22.. 48 Second Satellite 10th .. 51 52. 2 Form of Saturn's Ring. April 1st.-Transverse axis = 3 1.000 Conjugate axis =-0.314 Conjunction of the Moon with the Planets and Apr. 5th, with ́ in Leo, at 6th, 8th, 18th, .... .... .... 9 in the even. 3 in the morn. 8 in the even. Other Phenomena. Jupiter will be in quadrature at 45 m. after 7 in the evening of the 6th. Saturn stationary on the 13th. Mercury in his superior conjunction at 45 m. after 7 in the morning of the 22nd. Mars and Uranus in conjunction at 5 in the morning of the 27th. The Asteriod Ceres is now visible in the zodiacal constellation Virgo, near the equinoctial colure. THE ASTEROIDS: (From the Literary Gazette.) Ceres is 163 miles in diameter, and appears of a ruddy colour, (which is also the prevailing hue of the others,) and shines with the brilliancy of a star. of the eighth magnitude: it is surrounded with an atmosphere 675 miles in height, which gives it very much the semblance of a small comet or nebulous star. Pallas, another of the asteroids, (80 miles in diameter,) has a similar nebulosity surrounding it, 468 miles in height. Juno and Vesta are destitute of this nebulous atmosphere, though the latter, which is the smallest of the four, (diameter 49 miles,) and subtending an angle not greater than one of the Saturnian satellites, or half a second, shines with a light so pure and distinct as to be visible to the naked eye, as a star of the fifth magnitude. Very considerable differences occur in the results obtained by Schroeter and Herschell in measuring the diameters of the asteroids. It is highly probable that the former included portions of their atmospheres in his measurements, while the latter (who is generally considered to be the most accurate,) measured only the nucleus or disc. The form and position of the orbits of the asteriods, and the physical changes observed in them, suggests the idea of their being a sort of connecting link, uniting the planetary and cometary bodies. The orbits of the old planets vary but slightly from circles; those of the new planets are considerably eccentric, though not so much as those of comets. The aphelion of Juno is double the distance of its perihelion; and the distance of the centre from the foci of its ellipse, 68,588,433 miles. It passes over that half of its orbit nearest the Sun in half the time occupied in traversing the other half; the major axis of its orbit little exceeding in length that of the comet of Encke; the former being 450,800,000 miles in length, and the latter 420,000,000 miles. The orbits of the asteroids make greater angles with the ecliptic than the planets, and in this respect resemble comets, some of which have their paths considerably inclined, and ascend or descend at right angles to the Earth's path. The least inclination of a planet's orbit to the ecliptic is that of Uranus, which is 46 min. 20 sec.; and the greatest that of Mercury, which is 7 deg. The inclination of the orbit of Vesta is 7 deg. 8 min. 9 sec.; and that of Pallas 34 deg. 50 min. 40 sec. The inclination of the orbits of the comets of Encke and Gambart or Biela are, respectively, 13 deg. 20 min. and 13 deg. 33 min.; and of one that appeared in 1818, the position of its path relative to the ecliptic was 89 dig. 47 min. More considerable and sudden changes are also observed in these small bodies than in the planets. Venus, it is supposed, has had an atmosphere generated about its orb since the commencement of the past century, which conceals those irregularities on the surface formerly so distinctly seen. Mars has a periodical change about its poles, supposed to arise from the melting of the snows when the planet is in certain parts of its orbit. Jupiter also has sudden changes in its belts, which are supposed to arise from its swift rotation. These changes in the planets are different to those observed in the visible hemispheres of Ceres and Pallas, which are sometimes pale, overclouded, or as if surrounded with a dense mist, and, at other seasons, suddenly shine forth and display well defined discs. Variations of a similar nature are also observed in the brilliancy of the other two. To account for these phenomena, so anomalous in the planetary system, some have supposed the asteroids to be fragments of an exploded planet, formerly moving between the orbits of Mars and Jupiter. Some curious coincidents occur to render such a theory plausible; for, on the supposition of such an explosion, the fragments ought to have two common points of reunion, through which they would all pass; and it is remarkable that the positions of the nodes of the asteroids favour the idea of their having diverged from the same place. The T |