The number of asteroids composing this belt of miniature worlds cannot be correctly fixed, but it has been calculated from mathematical reasoning that it must be about 150,000. Possibly this may be too high. 13. JUPITER. The largest of all the planets, Jupiter, next meets us in our progress through the awful spaces of the heavens, but before we reach it we must have passed through nearly 500,000,000 miles from the sun, a distance which is more than five times that of the earth from that orb. In this inconceivable remoteness, which is yet the very threshold, as it were, of the dominions of the Eternal, Jupiter revolves in an orbit which bears it, when at its aphelion, 520,000,000 miles from the central orb, and leads it back, at its near sweep, to within 472,000,000 miles of it. Its course round this immense ellipse requires 12 years, at 30,000 miles an hour, which is eighty times more than the swiftness of a cannon ball. At its greater distance from the earth, an expanse of 617,000,000 of miles separates us from this planet. In size it is stupendous, for it is 1,400 times larger than our world, which we think so immense. If it were as near us as the moon is, this vast bulk would make a disk 1,200 times as large as that of our moon at its full. 14. Jupiter revolves on itself in about 10 hours, so that its day and night are less than half as long as ours, but as its poles are nearly at right angles to the line of its path, there is little difference of length in day and night over the greater part of its surface throughout its long year. At the poles, alternately, the sun is visible for nearly six years, and hidden for an equal period. Summer reigns through the whole year in the regions near its equator; its temperate zones rejoice in a perpetual spring, and its poles suffer a continual winter. The heat and light received by Jupiter from the sun can be but little at such a distance compared with the amount received by our earth, but it may be that the internal heat of the planet itself, and special characteristics of its clouds or soil may make up the deficiency. The year of Jupiter, as we have seen, is equal to 12 of ours. 15. One of the greatest peculiarities of this planet are the belts or patches that stretch across it—some greyish, others rose coloured-some darker some lighter. There are also spots of various sizes and forms here and there over the huge disk. These phenomena are regarded as resulting from the movements of great bodies of clouds in the atmosphere of Jupiter, and seem to indicate, by the changes seen in them, the prevalence of light winds, like our trade winds. but blowing in the opposite direction. Although Jupiter is so much larger than our world it is much lighter, weighing less, bulk for bulk, than a quarter as much as our earth does. 16. Jupiter has four moons which move round it as our moon moves round our earth, but they move more rapidly than our moon. Their distances are far greater, for the most part, from the planet they attend, than our moon is from us, for, while the nearest is 278,000 miles off, the others are respectively 443,000 707,000, and 1,243,000 miles away. Thus the most remote of the four revolves in an orbit of nearly 2 millions of miles in diameter! Their size is in proportion to the mighty orb they serve. One is 39 miles more in diameter than our moon, a second 387 miles more; a third 1,426 miles more, and the fourth 909 miles more. The first and second are of a bluish colour; the third is yellow, and the fourth reddish. 17. SATURN. We next come to Saturn, which has eight moons for Jupiter's four, and has besides a system of rings which no other planetary body exhibits. Some of these shine with a golden light, others are transparent. (Fig. 73.) When farthest distant from the sun, Saturn is 960,000,000 of miles off in the immensities of space, but the sun is more than 100,000,000 miles nearer one end of the ellipse of its orbit than the other, so that when in perihelion it is about 858,000,000 miles from the central light. To travel this tremendous sweep takes the planet 29 years and 167 days, which is the length of its year. It speeds on in this path at the rate of 22,000 miles an hour. At its farthest from our earth it is 1,057,000,000 miles from us, and at its nearest to us 761,000,000 miles. Its diameter through its equator is 75,100 miles, or 9 times that of our earth, but it is so flattened at its poles that its diameter through them is only 68,270 miles or 8 times that of the earth. Thus, to travel round their gigantic world, the inhabitants of Saturn, if there be any, have to go 214,000 miles the one way, or 236,000 the other. Its size, however, is no index to its solidity, for it is composed of matter seven times lighter than our earth. It revolves on its axis in 10 hours, day and night succeeding each other at an interval of about five hours. 18. Like that of the earth, Saturn's axis shows a striking inclination from the path of its orbit; and hence its seasons vary on different parts of it. Each of them lasts more than seven of our years, and there is an interval of nearly fifteen years between the autumn and spring equinoxes, and between the summer and winter solstices. The rings round Saturn may be broadly distinguished into three; an outer one of a grayish tint, 10,000 miles broad. Then, at an interval of 1,750 miles comes the middle one, which is more luminous than the planet itself. Its breadth is 18,300 miles. A third, dark, almost purplish, ring, comes next, joining the middle ring. It is 9,000 miles broad, and its inner edge is 10,150 miles from the body of the planet. The entire breadth of the ring system is thus over 39,000 miles, but its thickness is probably not more than 100 miles. Fig. 74. RELATIVE SIZES OF THE LARGER PLANETS. 1. The Earth. 2. Jupiter. 3. Saturn. 4. Uranus. 5. Neptune. This wondrous system of rings is thought by the latest observers to be nothing less than a vast stream of satellites, countless as the sands on the sea shore for multitude, forming a luminous girdle round the planet. 19. The eight moons of Saturn revolve round it at distances ranging from 119,000 to 2,292,000 miles-four of them being nearer to it than our moon is to us, while the farthest off is ten times farther from it than it is from our earth to the moon. The seasons of Saturn are no less strange than its structure. During fifteen of our years the sun does not leave its north pole, and during these years a night equally long rests on its south pole, after which the case is reversed for the same period. What must be the cold of regions thus deprived of light and heat so long! As in the case of Jupiter, the body of the planet is marked by great belts, which are probably the reflection of light from vast masses of cloud. 20. URANUS. The planet Uranus was discovered by Sir William Herschel in 1781, and is still deeper and deeper in the recesses of space than Saturn. Its distance from the sun varies between 1,743,000,000 and 1,913,000,000 miles, and in round numbers it is 2,000,000,000 of miles from our earth! Uranus is 82 times larger than our earth, and, like Saturn, it has eight moons, the nearest of which goes round it in two days, while the farthest off takes 108. From Uranus the sun looks only the 370th part as large as it does to us, and the heat and light received from it by the planet are in the same proportion. Perhaps the eight moons help to brighten its gloomy nights. It takes 84 years for Uranus to revolve round the sun, so that that is the length of one of its years. The matter of which it is composed is only, bulk for bulk, a sixth part as heavy as the matter of our globe. 21. NEPTUNE. Neptune, the most remote of the known planets of our system, revolves in its orbit round the sun, at a distance from that body of 2,862,000,000! It takes 165 of our years to make one of its, for so long is it in going round its orbit, though it moves onward night and day, for ever, at a speed of 12,400 miles an hour. The light and heat received by it from the sun are little more than the thousandth part of that which is received by us. The density of the matter of Neptune is less than a fourth of that of the matter of our earth. Only one moon has yet been discovered attending it. NOTE.-The exquisite lines on the next page are a translation from the Spanish of Lopez de Vega (1562-1635), by Henry Richard, third Lord Holland, husband of the celebrated Lady Holland, friend of Sydney Smith, Macaulay, and many other distinguished men. He died in 1840, while a member of Lord Melbourne's Cabinet, as Chancellor of the Duchy of Lancaster, and is buried in Westminster Abbey. Lopez wrote no fewer than 497 plays, twenty-one religious poems, and a great number of minor pieces. R THE STARRY FIRMAMENT.-Lord Holland. I GAZE upon your orbs of light, The countless stars that gem the sky; Temple of light and loveliness, And throne of grandeur !—can it be That souls whose kindred loftiness Nature hath framed to rise to thee What madness from the path of right Awake, ye mortals! raise your eyes With all its pomps and vanities, With all its hopes and all its fears. Who can look forth upon this blaze Of heavenly lamps, so brightly shining Yet in harmonious concord joining; Who sees the silver chariot move, Of the bright moon, and, gliding slow, |
