CHAPTER II. DESCRIPTION OF THE SOLAR SYSTEM. In order to appreciate the force of the argument for a plurality of worlds, derived from the similarity of our earth to the other planets of the Solar system, we must call the attention of the reader to a popular description of the magnitudes, distances, and general phenomena of the different bodies that compose it. In making this survey, the first and the grandest object which arrests our attention is the glorious SUN,-the centre and soul of our system,—the lamp that lights it, the fire that heats it, the magnet that guides and controls it, the fountain of colour which gives its azure to the sky, its verdure to the fields, its rainbow hues to the gay world of flowers, and the "purple light of love" to the marble cheek of youth and beauty. This globe, probably of burning gas, enveloping a solid nucleus, is nearly 900,000 miles in diameter, above a hundred times the diameter of our globe, and five hundred times larger in bulk than all the planets put together! It revolves upon its axis in twenty-five days, and throws off its light with the velocity of 192,000 miles in a second. Sometimes by the naked eye, but frequently even by small telescopes, large black spots, many thousand miles in diameter, are seen upon its surface, and are evidently openings in the luminous atmosphere, through which we see the opaque solid nucleus, or the real body of the sun. Around, and nearest the sun, at a distance of thirty-six millions of miles, revolves the planet MERCURY, with a day of twenty-four hours, and a year of eighty-eight days; and he receives from the sun nearly seven times as much light and heat as the earth. Through the telescope some astronomers have observed spots on its surface, and mountains several miles in height. Next to Mercury the planet VENUS revolves at the distance of sixty-eight millions of miles, with a day of nearly twenty-four hours, and a year of 224 days. Her diameter is 7700 miles, a little less than that of the earth. She changes her phases like the moon, exhibits spots on her surface, and, according to Schroeter, has mountains nearly twenty miles in height. The light and heat which she receives from the sun is about double of that which is received by the earth.1 The next body of the Solar system is our own EARTH-our birthplace, and soon to be our grave. Its distance from the sun is ninety-six millions of miles; its diameter nearly 8000; its year 365 days, and its day twenty-four hours. The form of the Earth is that of an oblate spheroid, or of a sphere flattened at the poles like an orange. Its superficies is divided into continents and seas, the continents occupying one-third, and the seas two-thirds of its whole surface. The land, sometimes level and sometimes undulating, occasionally rises into groups and ranges of mountains, the highest of which does not exceed five miles. The Earth is sur 1 From the rare appearance and want of permanence in the spots of Mercury and Venus, Sir John Herschel is of opinion, " that we do not see as in the moon the real surface of these planets, but only their atmospheres, much loaded with clouds, and which may serve to mitigate the otherwise intense glare of their sunshine."-Outlines of Astronomy, § 509. rounded with an aerial envelope or atmosphere, which is computed to be about forty-five miles in height, though the region of clouds does not reach much above the summits of the highest mountains. The Earth is accompanied by a Moon or satellite, whose distance is 237,000 miles, and diameter 2160. Her surface is composed of hill and dale, of rocks and mountains nearly two miles high, and of circular cavities, sometimes five miles in depth, and forty in diameter, which are believed to be the remains of extinct volcanoes. She possesses neither lakes nor seas; and we cannot discover with the telescope any traces of living beings, or any monuments of their hands, though we hope it will be done with some magnificent telescope which may yet be constructed. Viewing the Earth as the third planet in order from the sun, can we doubt that it is a globe like the rest, poised in ether like them, and, like them, moving round the central luminary ? Next, beyond the Earth, is the red-coloured planet MARS, with a day of about twenty-five hours, and revolving round the sun in 687 days, at the distance of one hundred and forty-two millions of miles. His diameter is 4100 miles, and his surface exhibits spots of different hues, -the seas, according to Sir John Herschel, being green, and the land red. The spots which have been seen on this planet by several astronomers, are not always equally distinct, but when seen 66 they offer," as Sir John Herschel observes," the appearance of forms, considerably definite and highly characteristic, brought successively into view by the rotation of the planet, from the assiduous observation of which it has even been found practicable to construct a rude chart of the surface of the planet. The variety in the spots may arise from the planet not being destitute of atmosphere and cloud; and what adds greatly to the probability of this, is the appearance of brilliant white spots at its poles, which have been conjectured, with some probability, to be snow, as they disappear when they have been long exposed to the sun, and are greatest when just emerging from the long night of their polar winter, the snow line then extending to about six degrees from the pole." 1 Outlines of Astronomy, § 510. |