CHAMBERS'S INFORMATION FOR THE PEOPLE. NUMBER 1. CONDUCTED BY WILLIAM AND ROBERT CHAMBERS, EDITORS OF CHAMBERS'S called the Solar System-that is, the particular solar system to which our earth belongs. 1 THE SOLAR SYSTEM. ASTRONOMY (from the Greek, astron, a star, and nomos, | it can in none conceive. We begin with what is usually a law) is, comprehensively, that science which explains the nature and motions of the bodies filling infinite space, including our own globe in its character of a planet or member of the solar system. The science may be divided into two departments-1. Descriptive Astronomy, or an account of the systems of bodies occupying space; 2. Mechanical Astronomy, or an explanation of the physical laws which have produced and which sustain the arrangements of the heavenly bodies, and of all the various results of the arrangement and relations of these bodies. Uranography is a subordinate department of the science, presenting an account of the arrangements which have been made by astronomers for delineating the starry heavens, and working the many mathematical problems of which they are the subject. DESCRIPTIVE ASTRONOMY. The early ideas of mankind respecting the objects described by astronomy, proceeded upon appearances which the uninstructed eye placed before them, and were far from being true. It was supposed that the earth was, as it seems, a fixed plain, or, at the most, a fixed sphere, with an outer sphere, forming the heavens, revolving around it once in the twenty-four hours. Even philosophers deemed the earth the central and most important object in the system, and regarded the heavenly bodies, the sun, moon, planets, and stars, as comparatively small objects, fixed in different crystal spheres, each of which observed its own laws of revolution, according to the apparent motions of the bodies fixed in it. It was not till after much study and investigation that even the most enlightened minds arrived at a knowledge of the truth; nor was it for some time longer that the idea of the earth not being in the centre of the system, or any thing but a small and subordinate part of it, was generally admitted. There is no room here to trace all the steps by which the truth was ascertained, or to argue the uninstructed mind out of all its first and erroneous impressions. But it may be hoped that when the actual constitution of the heavens has been described, it will be possible to form some notion of how the objects in their real character and real arrangements come to appear as they do to our eyes. The field contemplated by the astronomer is no less than INFINITE SPACE. So, at least, he may well presume space to be, seeing that every fresh power which he adds to his telescope allows him to penetrate into remoter regions of it, and still there is no end. In this space, systems, consisting of suns and revolving planets, and other systems again, consisting of a numberless series of such lesser systems, are suspended by the influence of gravitation, operating from one to another, yet each body at such a distance from another, as, though the mind of man can in some instances measure, The solar system, so named from sol (Latin), the sun, consists of the sun in the centre, twenty-nine planets, and an unknown number of bodies named comets. The word planet is from the Greek, planao, to wander, because the few such bodies known to the ancients were chiefly remarkable in their eyes on account of their constantly shifting their places with reference to the other luminaries of the sky. Comets are so named from coma (Latin), a head of hair, because they seem to consist of one bright spot, and a long brush streaming from behind it. Planets.-Eleven of the planets are called primary, because they move directly around the sun, and eighteen secondary, because they move round primary planets. The secondary planets are also denominated satellites, from satelles (Latin), originally signifying a life-guardsman, but, by a wider application, one who follows and serves another. Only four of the primary planets have satellites. The primary planets are Mercury, Venus, the Earth, Mars, Vesta, Ceres, Pallas, Juno, Jupiter, Saturn, and Herschel, or Uranus. Most of these names are derived from the fabulous divinities of ancient Greece. The Earth has one satellite, the Moon; Jupiter has four; Saturn, seven; and Uranus is supposed to have six. The planets move round the sun on nearly one level or plane, corresponding with the centre of his body, and in one direction, from west to east. The secondary planets, in like manner, move in planes round the centres of their primaries, and in the same direction, from west to east. These are denominated revolutionary motions; and it is to be observed that they are double in the case of the satellites, which have at once a revolution round the primary, and a revolution, in company with the primary, round the sun. The path described by a planet in its revolution is called its orbit. Each planet, secondary as well as primary, and the sun also, has a motion in its own body, like that of a bobbin upon a spindle. An imaginary line, forming, as it were, the spindle of the sun or planet, is denominated the axis; and the two extremities of the axis are called the poles. The axes of the sun and planets are all nearly at a right angle with the plane of the revolutionary movements. The motion on the axis is called the rotatory motion, from rota, the Latin for a wheel. The sun, the primary planets, and the satellites, with the doubtful exception of two attending on Uranus, move on their axes in the same direction as the revolutionary movements, from west to east. The Sun is a sphere or globe, of 882,000 miles in diameter, or 1,384,472 times the bulk of the earth, moving round its axis in 25 days. When viewed through a telescope, the surface appears intensely bright and luminous, as if giving out both heat and light to the surrounding planets. But on this surface there occasionally appear dark spots, generally surrounded with a border of less dark appearance; some of which spots have been calculated to be no less than 45,000 miles in breadth, or nearly twice as much as the circumference of the earth. The region of the sun's body on which the spots appear, is confined to a broad space engirdling his centre. They are sometimes observed to come into sight at his western limb, to pass across his body in the course of twelve or thirteen days, and then disappear. They are sometimes observed to contract with great rapidity, and disappear like something melted and absorbed into a boiling fluid. Upon the bright parts of the sun's body there are also sometimes observed streaks of unusual brightness, as if produced by the ridges of an agitated and luminous fluid. It has been surmised, that the sun is a dark body, enveloped in an atmosphere calculated for giving out heat and light, and that the spots are produced by slight breaks or openings in that atmosphere, showing the dark mass within. Though so much larger than the earth, the matter of the sun is of only about a third of the density or compactness of that of our planet, or little more than the density of water. The sun is surrounded to a great distance by a faint light, or luminous matter of extreme thinness, shaped like a lens or magnifying-glass, the body of the sun being in the centre, and the luminous matter extending in the plane of the planetary revolutions, till it terminates in a point. At particular seasons, and in favourable states of the atmosphere, it may be observed, before sunrise or after sunset, in the form of a cone pointing obliquely above the place where the sun is either about to appear or which he has just left. It is termed the Zodiacal Light. Saturn Mercury, 1796 Venus, - 1334 Inclinations of Orbits to Venus, Mars, 1° 51' 6" 2. Vesta, 7° 8' 9" 0. Juno, 13° 4' 9" 7. Ceres, 10° 37′ 26′′ 2. Pallas, 34° 34' 55" 0. Jupiter, 1° 18′ 51′′ 3. Saturn, 2° 29′ 35′′ 7. Uranus, 0° 46′ 29′′ 4. The Solar System. Mercury, the nearest planet to the sun, is a globe of about 3140 miles in diameter, rotating on its axis in 24 hours and 5 minutes, and revolving round the central luminary, at a distance of 37,000,000 of miles, in 88 days. From the earth it can only be seen occasionally in the morning or evening, as it never rises before, or sets after the sun, at a greater distance of time than 1 hour and 50 minutes. It appears to the naked eye as a small and brilliant star, but when observed through a telescope, is horned like the moon, because we only see a part of the surface which the sun is illuminating. Mountains of great height have been observed on the surface of this planet, particularly in its lower or southern hemisphere. One has been calculated at 10 miles in height, being about eight times higher, in proportion to the bulk of the planet, than the loftiest mountains upon earth. The matter of Mercury is of much greater density than that of the earth, equalling lead in weight; so that a human being placed upon its surface would be so strongly drawn towards the ground as scarcely to be able to crawl. Venus is a globe of about 7800 miles in diameter, or nearly the size of the earth, rotating on its axis in 23 hours, 21 minutes, and 19 seconds, and revolving round the sun, at the distance of 68,000,000 of miles, in 225 days. Like Mercury, it is visible to an observer on the earth only in the morning and evening, but for a greater space of time before sunrise and after sunset. It appears to us the most brilliant and beautiful of all the planetary | and stellar bodies, occasionally giving so much light as to produce a sensible shadow. Observed through a telescope, it appears horned, on account of our seeing only a part of its luminous surface. The illuminated part of Venus occasionally presents slight spots. It has been ascertained that its surface is very unequal, the greatest mountains being in the southern hemisphere, as in the case of both Mercury and the Earth. The higher mountains in Venus range between 10 and 22 miles in altitude. The planet is also enveloped in an atmosphere like that by which animal and vegetable life is supported on earth; and it has consequently a twilight. Venus performs its revolution round the sun in 225 days. Mercury and Venus have been termed the Inferior Planets, as being placed within the orbit of the Earth. The Earth, the third planet in order, and one of the smaller size, though not the smallest, is important to us, as the theatre on which our race have been placed to "live, move, and have their being." It is 7902 miles in mean diameter, rotating on its axis in 24 hours, at a mean distance of 95,000,000 of miles from the sun, round which it revolves in 365 days, 5 hours, 56 minutes, and 57 seconds. As a planet viewed from another of the planets, suppose the moon, "it would present a pretty, variegated, and sometimes a mottled appearance. The distinction between its seas, oceans, continents, and islands, would be clearly marked; they would appear like brighter and darker spots upon its |