On the Earth it is very different. Here we can commonly see only a few miles off. Not because our eyes are not strong enough: but because the Earth’s rounded surface soon dips away, and all beyond that dip is cut off from us by the solid body of the Earth. On a flat plain, or close to the surface of the sea, our view is very narrow. If we climb a hill we get a wider landscape, because we can see farther over the “dip,” and from a mountain-top the view is very greatly increased. [Illustration: _Sunset._] Still, no matter how high we go, the Earth’s surface always stretches away to north and south, to east and west. It always _seems_ to rise and meet the sky, making our horizon-line. If we could get very, very far off indeed, into the sky, we should then see our Earth floating, like an enormous ball--a huge round solid globe. But this we are never able to do. We know our Earth to be a round ball: but we cannot stand apart and see her to be such. Did you ever notice a ship “hull-down” on the horizon?--that is, with its masts standing up above the horizon, and its body hidden? This again was caused by the shape of the earth: the hull of the ship having dipped down below the horizon, while the masts still stood up within sight. When we see the Sun in the sky, he is always a round body. But when he sinks at night below the horizon part of the round surface is hidden first, and then the whole. Hidden in the same way: by the Earth’s rounded surface coming between him and our eyes. At the moment when the Sun is all but gone, only one glimmer being visible, you might say of him too, as of the ship, that he is “hull-down.” QUESTIONS. 1. What is a Sphere? A body in the shape of a rounded ball or globe. 2. What shape is our Earth? The Earth is a sphere in shape: but not a perfect sphere, because flattened at the north and south poles. 3. What is a hemisphere? A hemisphere is a half-sphere. 4. Describe the two hemispheres of the Earth, commonly so called? The northern hemisphere is the whole of the Earth north of the equator; and the southern hemisphere is the whole of the Earth south of the equator. 5. What is the Equator? A line supposed to be drawn round the whole earth, exactly half-way between the north and south poles. 6. What is the horizon? The horizon is that line in the distance where the sky and earth seem to meet. 7. What hides all below the horizon? The solid body of our Earth. 8. How far can a man see on the Earth? A few miles, usually. On a hill he has a much wider view. 9. How far can a man see in the sky? He can see stars millions and billions of miles away. 10. What is meant by a ship “hull-down?” A ship “hull-down” is partly above and partly below the horizon. 11. What becomes of the Sun when he sets? He goes down below the horizon. 12. Is the Sun then too far off for us to see him? No: he is only hidden from us after sunset by the solid body of the Earth coming between him and our eyes.