time that it employs in describing the other half, which is further from the Sun; from the same cause its greatest distance from the Sun is double the least. The difference between the two being about 127 millions of miles. Its mean distance from the Sun is computed at 252 millions of miles, and performs its tropical revolution in 4 years and 128 days. Its diameter is estimated at 1,425 miles, and its apparent diameter as seen from the Earth, three seconds of a degree, and its inclination of orbit twenty-one degrees. ON CERES. The planet Ceres was discovered at Palermo, in Sicily, on the first of January, 1801, by M. Riazzi, an ingenious observer, who has since distinguished himself by his Astronomical labors. It was however again discovered by Dr. Olders, on the first of January, 1807, nearly in the same place where it was expected from the calculations of Baron Zach. The planet Ceres is of a ruddy color, and appears about the size of a star of the 8th magnitude. It seems to be surrounded with a large dense atmosphere of 675 miles high, according to the calculations of Schroeter, and plainly exhibits a disk, when examined, with a magnifying power of 200. Ceres is situated between the orbits of Mars and Jupiter. She performs her revolution round the Sun in four years, 7 months and ten days; and her mean distance is estimated at 263 millions of miles from that luminary. The observations which have been hitherto made upon this celestial body, do not appear sufficiently correct to determine its magnitude with any degree of accuracy. ON PALLAS. The planet Pallas was discovered at Bremen, in Lower Saxony, on the evening of the 28th of March, 1802, by Doctor Olders, the same active Astronomer, who re-discovered Ceres. It is situated between the orbits of Mars and Jupiter, and is nearly of the same magnitude and distance with Ceres, but of a less ruddy color. It is seen surrounded with a nebulosity of almost the same extent, and performs its annual revolution in nearly the same period. The planet Pallas however is distinguished in a very remarkable manner from Ceres, and all the primary planets, by the immense inclination of its orbit. While these bodies are revolving round the Sun in almost circular paths, rising only a few degrees above the plane of the ecliptic; Pallas ascends above this plane, at an angle of about 35 degrees, which is nearly five times greater than the inclination of Mercury. From the eccentricity of Pallas being greater than that of Ceres, or from a difference of position in the line of their apsides, where their mean distances are nearly equal, the orbits of these two planets mutually intersect each other; a phenomenon which is altogether anomalous in the Solar System. Pallas performs its tropical revolution in four years 7 months and 11 days. The distance of this planet, from D the Sun, is estimated at 265 millions of miles. It is surrounded with an atmosphere 468 miles high. OF JUPITER. Jupiter, the largest of all the planets, is still higher in the Solar System, being four hundred and ninety millions of miles from the Sun, and by performing his annual revolution round the Sun in eleven years, 314 days, 20 hours and 27 minutes, he moves in his orbit at the rate of 29,000 miles in an hour. The diameter of this planet is estimated at 89,170 miles, and performs a revolution on its own axis in nine hours, 55 minutes and 37 seconds; which is more than 28,000 miles every hour, at his equator, the velocity of motion on his axis being nearly equal to the velocity with which he moves in his annual orbit. This planet is surrounded by faint substances called belts, in which so many changes appear, that they have been regarded by some, as clouds or openings in the atmosphere of the planet; while others imagine that they are of a more permanent nature, and are the marks of great physical revolutions which are perpetually changing the surface of the planet. The axis of Jupiter is so nearly perpendicular to his orbit, that he has no sensible change of seasons, which is a great advantage, and wisely ordered by the Author of nature; for if the axis of this planet were inclined any considerable number of degrees, just so many degrees round each pole would in their turn, be almost six of our years together in darkness, and, as each degree of a great circle on Jupiter contains 778 of our miles at a mean rate; judge ye what vast tracts of lands would be rendered uninhabitable by any considerable inclination of his axis. The difference between the equatorial and polar diameters of this oblate spheroid is computed at 6,230 miles; for his equatorial diameter is to his polar, as13 is to 12; consequently his poles are 3,115 miles nearer his centre than his equator. This results from his rapid motion round his axis, for the fluids together with the light particles which they can carry, or wash away with them, recede from the poles, which are at rest towards the equator, where the motion is more rapid, until there be a sufficient number of such particles accumulated to make up the deficiency of gravity occasioned by the centrifugal force, which arises from a quick motion round an axis; and when the deficiency of weight or gravity of the particles is made up by a sufficient accumulation, the equilibrium is restored, and the equatorial parts rise no higher. The orbit of Jupiter is inclined to the ecliptic one degree and 20 minutes. His north node is in the 7th degree of Cancer, and his south node in the 7th degree of Capricorn. His mean apparent diameter as seen from the earth is 39 seconds, and as seen from the Sun, 37 seconds of a degree. This planet being situated at so great a distance from the Sun, does not enjoy that degree of light emanating from his rays, which is enjoyed by the earth. To supply this deficiency, the great Author of our existence has provided 4 satellites, or Moons to be his constant attendants, which revolve around him, in such manner, that scarcely any part of this large planet but is enlightened during the whole night, by one or more of these Moons, except at his poles, where only the farthest Moons can be seen; there, however this light is not wanted; because the Sun constantly circulates in or near the horizon, and is very probably kept in view of both poles by the refraction of his atmosphere. The first Moon, or that nearest to Jupiter performs a revolution around him in one day, 18 hours and 36 minutes of our time, and is 229 thousand miles distant from his centre: the second performs his revolution in 3 days 13 hours and 15 minutes at a distance of 364 thousand miles: the third in seven days, three hours and 59 minutes, at the distance of 580 thousand miles, and the fourth, or farthest. from his centre in 16 days, 18 hours, and 30 minutes, at the distance of one million of miles from his centre. The angles under which these satellites are seen from the earth, at its mean distance from Jupiter, are as follows:- The first three minutes and 55 seconds: the second six minutes and 15 seconds: the third 9 minutes and 58 seconds, and the fourth 17 minutes and 30 seconds. This planet when seen from its nearest Moon, must appear more than one thousand times as large as our Moon does to us. The three nearest Moons to Jupiter, pass through his shadow, and are eclipsed by him, in every revolution, but the orbit of the fourth is so much inclined, that it passes by its opposition to Jupiter without entering his shadow, |