Jupiter whirls with such speed upon his axis, that it takes him less than ten hours to spin once round. A day of only five hours, and a night of only five hours! How should we like that? But with the short day he has a very long year. Jupiter gets once round the Sun in twelve of our earthly years. So a man who on Earth is nearly forty years old would on Jupiter be just over three years old: and an old Earthly gentleman of seventy would there be under the age of six. Our little boys and girls would hardly like only one birthday in twelve years. We have seen how, with greater distance from the Sun, each planet goes more and more slowly, as the Sun’s pulling becomes weaker. Jupiter rolls through the skies at a rate of only about eight miles each second. A beautiful world is Jupiter, looked upon from the Earth: the brightest in our sky after Venus. No other planet, except Venus, and no Star in the heavens can outshine Jupiter. This is because of two things--his great size and his nearness to us. Not nearness compared with that of the smaller worlds, but nearness compared with that of Saturn and Uranus and Neptune. Saturn, though almost as big as Jupiter, is very much farther off. And while Jupiter can hardly be so bright actually as Mars, because very much farther from the Sun, yet his huge size makes him greatly outshine Mars, which is so much nearer to us than he is. Seen through a pretty good telescope, Jupiter grows into a broad, soft, moon-like world, very flat at the north and south poles, with colored bands round him, on and near his equator. Four small bright moons are also to be noticed. Sometimes all four can be seen at once; sometimes one or two are hidden behind him, or the shadow of one creeps like a black dot over his face. The fifth little moon, found lately, can seldom be seen. Through a bigger telescope, Jupiter shows exquisite colors--rich reds, and browns, and greens, and purples. But these markings do not mean continents and oceans, as they perhaps mean on Mars. They are believed to belong to a very stormy Cloudland. Jupiter seems to be wrapped in thick masses of clouds; and these clouds are ever on the move, always changing their shapes. It may be that we now and then get a tiny glimpse through them of the more solid world within, but this we cannot be sure of. It _may_ be that the clouds never part so far as to let us see through. It _may_ be that there is nothing solid within at all. Anyhow, the solid part is very much smaller than the size of the Jupiter we see. For, like other planets, Jupiter has been weighed, and he is found to be very light in make. He is not nearly so heavy as one would expect with a globe of that size. The inner part may or may not be solid; some say it is most likely _not_. At any rate, it is enfolded by an enormous thickness of heated and tempestuous clouds.