Vesta, the largest of them all, is perhaps over three hundred miles through, and three others come rather near Vesta in size. The greater number are under one hundred miles through; some being mere balls, about the size of Mars’ moons. QUESTIONS. 1. Which is the next planet outside Venus? The Earth on which we live. 2. How far is the Earth from the Sun? About 92 millions of miles. 3. How fast does our Earth travel? About 19 miles each second. 4. How long is the Earth’s year? About 365 days, or 12 months. 5. Which is the next planet outside the Earth? Mars. 6. What is the diameter of Mars? About 4,000 miles, or half that of our Earth. 7. How far is Mars from the Sun? About 140 millions of miles. 8. How long is Mars’ year? Nearly twice as long as our year. 9. Does Mars spin on his axis? He is believed to do so, in twenty-four hours and a half. 10. How near does Mars come to us? Never closer than 35 millions of miles off. 11. But how much nearer does the most powerful telescope seem to bring Mars? Perhaps to about 35 thousands of miles off. 12. Are air and water found on Mars? Some kind of air, and water also, and ice and snow. 13. Are there oceans on Mars? There are patches of color which may be continents and oceans. 14. Where are ice and snow perhaps seen on Mars? White caps are seen at the two poles. 15. Is Mars inhabited? Nobody can tell. It does not seem to be quite impossible, so far as we understand what Mars is like. 16. Which planet comes next after Mars? Hundreds of Planetoids come next. 17. Are they close to Mars? No; there is a great space between Mars’ pathway and Jupiter’s pathway; and the Ring of Planetoids lies somewhere about the middle of that great space. 18. What is the name of the biggest Planetoid? Vesta. CHAPTER XV. THE PLANET JUPITER. Now we pass on to JUPITER, chief in size of all the worlds in the kingdom of the Sun. The four inner planets are all small together. The four outer planets are all large together, Jupiter and Saturn being the twin giants of the Solar System. You now know that the distance of Mercury from the Sun is about 35 millions of miles, and that the distance of Mars is about _four_ times that of Mercury. But the distance of Jupiter from the Sun is nearly _fourteen_ times that of Mercury. Think what an enormous gap this means between the pathway of Mars and the pathway of Jupiter. And, distant as Jupiter is from the Sun, he is quite as far from his next neighbor on the other side, Saturn. So Jupiter lies just about half-way between the Sun and Saturn. Yet Saturn is nearer to Jupiter than to his other neighbor, Uranus. The gap between the pathway of Saturn and the pathway of Uranus is _twice_ as broad as the gap between Jupiter and Saturn. Outside Uranus stretches another vast empty space: and then we get to the last known planet, far-away Neptune!