cording to Schröter, they are still higher than those of the moon; and there is one which surpasses Chimborazo, in South America, by twenty-four thousand feet! The whole height of Chimborazo is less than twenty-two thousand! I will tell you more about the mountains, upon Venus, upon the moon, and upon the earth; in my Tales about Mountains, Rocks, Caverns, Grottoes, Lakes, Rivers, Wells, Fountains, Aqueducts, and Baths, and Springs. CHAP. XXXIX. ABOUT THE EARTH. ABOUT THE ARMILLARY SPHERE. THE next planet to Venus is the earth. It is eighty-two millions of miles from the sun, and travels round him in three hundred and sixtyfive days, five hours, and forty-nine minutes. The earth has a diurnal motion, by which the inhabitants at the equator are carried at the rate of one thousand and forty-two miles in an hour. The surface of the earth contains in all about one hundred and sixty millions five hundred and twenty-two thousand and twenty-six square miles; nearly three-fourths of which are covered with water. I shall tell you much more. about the earth hereafter. The earth, by its revolution about the sun in three hundred and sixty-five days, five hours, and forty-nine minutes, measures out that space of time which we call a year; and the line described by this annual revolution about the sun is called the ecliptic. This line is always laid down on the artificial globes, divided into twelve distinct portions, each containing thirty degrees, and marked with the twelve signs of the zodiac. The ecliptic, which, as you have before seen reason to understand, is an imaginary line, drawn. through the middle of the equally imaginary belt of the zodiac, is represented, and marked with its degrees, in my figure of an Armillary Sphere; where, also, you see the earth, and the various other imaginary circles and points (as those of the tropics, the meridian, and the zenith and nadir) which astronomers and geographers describe about it, in order to assist our knowledge of its phenomena. The armillary sphere revolves upon an axis within a silvered horizon, which is divided into degrees, and moveable every way upon a brass supporter. In Pembroke Hall, Cambridge, there is an armillary sphere constructed by Dr. Long, which is eighteen feet in diameter, and will contain more than thirty persons sitting within it, to view, as from a centre, the representation of the celestial spheres. CHAP. XL. ABOUT MARS. MARS is one hundred and forty-four millions of miles from the sun. It turns round on its axis once in twenty-five hours. Of course, its days and nights are a little longer than ours. It revolves round the sun once in about two years. It travels in its orbit at the rate of fifty-five thousand miles an hour. It is supposed to be much darker, and twice as cold, in this planet, than on the earth. Mars may be seen with the naked eye. It is of a remarkably red colour. When How far is Mars from the sun? How long is it turning on its axis? At what rate does Mars travel in its orbit? What of its light and heat? Can it be seen by the naked eye? What colour is it? |