Eclipse of the Moon. The Moon will be eclipsed on the 20th of this month, but the eclipse will be invisible in this country, as it will take place under the following circumstances: viz. Digits eclipsed 4° 5' on the Moon's southern limb, or from the northern side of the earth's shadow. Moon's Passage over the Meridian. The following passages of the Moon over the first meridian will afford opportunities of observation, if the weather prove favourable at the several times. If the place of observation be distant from the first meridian, the times specified will require a corresponding correction, which is to be made as already directed. March 10th, at 29 m. past 4 in the afternoon PHENOMENA PLANETARUM. Phases of Venus. This beautiful planet now begins to resemble the full Moon in appearance; but as her distance from the earth is greatly increased, her brightness is diminished in proportion. March 1st {Dluminated part = 11-24178 Dark part...... 0.75822 Eclipses of Jupiter's Satellites. The following are such of the eclipses of the first and second of these small bodies as are visible this month. They are recorded in mean time at the Royal Observatory. Immersions. First Satellite... 9th day, at 35 m. 48 s. after 4 in the morning 25th ...... 51.. 9 16 39 Emersion. 2 ...... ...... 5 ........ Second Satellite, 8th day, at 8 m. 56 s. after 5 in the morning Conjunction of the Moon with the Planets and Stars. March 2d, with 8 in Capricorn, at 4 in the afternoon ....10 at night ..... 2 in the morning 2 Mercury ..... 8 .... .10 y.. Libra......10 at night 30th B.. Capricorn... 1 in the morning. .... Other Phenomena. Jupiter will be in quadrature at 30 m. past 9 in the evening of the 4th of this month. Mercury will be stationary on the 13th, and attain his greatest elongation on the 27th. Saturn will be stationary on the 28th, and Jupiter on the 31st. THE COMET. [Concluded from page 71.] It is scarcely possible for us, at this period, to conceive of the terror and dismay which pervaded all ranks throughout the world during the transit of the comet of 1680: some idea might be formed of its tremendous appearance, if we could fancy the nucleus, or more brilliant part of it, in the zenith of any place, and the tail extending thence to the horizon: this was somewhat of its appearance, as observed at Paris, but more especially so at Constantinople; while coruscations were continually rushing through the whole length of its projecting luminosity, so as to give the awful phenomenon-not the appearance of a tranquil body passing on in its harmless course-but a wrathful messenger, charged with vengeance and destruction. On November 12th, 1 h. 6 min. it was only the semi-diameter of the Sun from the northern part of the Earth's orbit, and approached within a sixty-sixth part of the Earth's distance from the Sun. It is at this time urging on its rapid course, and will not attain its greatest distance from the Sun till the year 1967, and again visit the fountain of light in the year 2255. It must be confessed, that the chances against the meeting of a comet with this earth are so numerous, that we may consider our earth as tolerably safe from such an occurrence; the probability is some millions to one against such a contact: even the tail of a comet cannot come near our atmosphere, unless the comet be at its inferior conjunction very nearly at the time it is in a node. The nature of the improbability of such an event may be more easily understood from an instance in the planet Venus, which moves in a plane not much inclined to that of the Earth's orbit (3 deg. 23 min. 25 sec.), and yet the Earth and Venus are in the same plane with the Sun at the time of inferior conjunction only thirty-five times in 2100 years, though this planet passes between the Earth and Sun, during this long period, upwards of 3360 times. The safety of the planetary bodies from the concussion of these wandering stars is principally owing to the nature of their respective orbits. The orbits of the planets are nearly circular; those of comets are very elliptical: planets move nearly in the same plane; comets descend into the solar system, making every possible angle with the ecliptic: planets move all the same way; comets move in every direction,— both contrary to, and in the order of, the signs. Now, if these bodies moved in the same plane with the planets, the probability would be increased in an astonishing proportion. But there is another circum stance which is calculated to diminish apprehension: there is every reason for supposing comets to have very little density, and to be mere collections of vapours condensed about the centres of each; so that their power to produce any deviation in the planetary bodies must be very inconsiderable. One that passed very near to Jupiter had no sensible effect on that planet or his satellites, which would have been the case had the comet contained matter in proportion to its bulk. The solid part of the nucleus of some comets has been proved to be not much larger than many mountains on our Earth's surface, such as Dhawala-giri, the highest mountain of the Himmalayan chain, to the north of Hindostan. 000 The comet of 1770 made a closer approximation to our earth than any that has visited this part of the solar system: had it been equal in magnitude and density to our planet, it would have shortened the length of our year 2 hours 40 minutes. It is certain that no perceptible diminution did occur; whence it is inferred, that the mass of the comet was less than 30th of the mass of the Earth. It was the comet of 1770 that passed through the system of Jupiter without deranging the motions of the satellites; but though these small bodies were not affected by its. close approach, there is every reason to believe that the path of the comet was altered by its proximity to the vast body of Jupiter: this may account for its non-appearance since 1770. It was calculated that the comet would again be in conjunction with Jupiter on August 23d, 1779, when its distance from that planet would be onlyth of its distance from the Sun: the attraction of Jupiter on the comet would, in this case, have been 224 times greater than that of the Sun; which must have so altered all the elements of its orbit, as to render it perfectly impossible to identify it as the same at any subsequent return. Should a comet approach so near the earth as to be more attracted by it than by the Sun, the course of its revolution would be altered; and, instead of revolving about the Sun as an independent body, it would describe an orbit round our Earth, as a Moon, and would possibly be hailed as a valuable auxiliary, instead of being dreaded as the messenger of destruction to this terrestrial orb and its teeming inhabitants, which may be more speedily brought about than by a concussion with these celestial agents. A single principle of motion annihilated, evaporation suspended, or a component part of the atmosphere abstracted, and final ruin would drive her ploughshare o'er creation.' Universal conflagration would instantly ensue, from the separation of the oxygen from the nitrogen of the atmosphere: the former exerting its native energies without control wherever it extends, solid rocks, ponderous marble, metals, and even water itself, would burst into an intensity of flame, and change the aspect of all sublunary objects. But all these vast bodies of the universe are doubtless 'kept in their prescribed limits, as with so many reins and bridles;' and when this Earth has completed its destined circles, and fulfilled the purposes for which it was called out of nothing, it will need but the command of the glorious Creator, who at first spoke this beautiful frame into being, bliss, and light, to return it to its primeval gloom, or bid it shine forth with new resplendent beauty and lustre. |