Volume 1

Chambers's Information for the people / edited by William and Robert Chambers.

Date:
1848-1849
Catalogue details

Licence: Public Domain Mark

Credit: Chambers's Information for the people / edited by William and Robert Chambers. Source: Wellcome Collection.

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    from west to cast. These are denominated revolution- ary 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. Besides this motion of revolution, 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 those attending on Uranus, and overlooking that of Neptune, as yet unascertained, move on their axes in the same direction as the revo- lutionary 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 sur- rounded with a border of less dark appearance; some of which spots have been calculated to be no Icsh than 45,000 miles in breadth, or nearly twice as much as the circumference of the earth. The region of the 6un’s body on which the spots appear, is confined to a broad space engirdling his centre. They are sometimes ob- served to come into sight at his western limb, to pass across his body in the course of twelve or thirteen days, and then disappear. At other times they are observed to contract with great rapidity, and disappear like some- thing melted and absorbed into a boiling fluid. Upon the bright parts of the sun’s body there are also some- times 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 adapted 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 fourth of the density or compactness of that of our planet, or little more than the density of water. Diameters of Planets in English Miles. The Sun, 882,000 Mercury, - - 3,140 Venus, - 7,800 Earth, - 7,912 Mars, 4,189 The Asteroids, - * J upiter, - - 89,170 Saturn, 79,012 Uranus, - - 3.5,112 Neptune, - 50,000 Densities of Planets, that of the Earth being considered as 1. The Sun, - - 0-26 Mercury, - - 2-95 Venus, - - 099 Earth, - - 1' Mars, - - - 0-79 The Asteroids, Jupiter, - - 0 25 Batum, - - Oil Uranus, - - 0’2G Neptune, - - —1 Distances of Planets from the Sun. Mercury, - 37,000,000 Venus, - 68,000,000 Earth, - 95,000 000 Mars, - 144,000,000 The Asteroids, * Jupiter, - 490.000,000 Saturn, - 906,000,000 Uranus, 1,823,000,000 Neptune, 2,9UO,000,000 Periods of Devolution round the Sun. Mercury, • 880 Venus, - 225 Earth, 365$ Mars, - 687 The Asteroids, * Jupiter, - 4,330-J Saturn, 10,7465 Uranus, 30 681 Neptune, 60,936 The Solar System, to the orbit of Uranus. The sun is surrounded to a great distance by a faint eht or luminous matter of extreme thinness, shaped ke a lens or magnifying-glass, the body of the sun eiim in the centre, and the luminous matter extending i the plane of the planetary revolutions, till it termi- ates in a point. At particular seasons, and in favour- ble states of the atmosphere, it may be observed, before an rise or after sunset, in the form ol a cone pointing bliquely above the place where the sun is either about o appear, or which he has just left. It is termed the 'odiacal Light. , , , Mercury, the nearest planet to the sun, is a globe f about 3140 miles in diameter, rotating on its axis in 4 hours and 5k minutes, and revolving round the entral luminary, at a distance of 37,000,000 of miles, a 88 days. From the earth it can only be seen oc- asionally in the morning or evening, as it never rises efore, or sets after the sun, at a greater distance ot ime than 1 hour and 50 minutes. It appears to the aked eye as a small and brilliant star, but when ob- erved through a telescope, is horned like the moon, ecause we only see a part of the surface which the un is illuminating. Mountains of great height have 2 been observed on the surface of this planet, particularly in its lower or southern hemisphere. One has been calculated at lOf miles in height, being about eight times higher, in proportion to the bulk of the planet, than the loftiest mountains upon the earth. The mat- ter of Mercury is of much greater density than that of the earth, equalling lead in weight. 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
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