Venus is very nearly the same size as our Earth. She lies farther from the Sun than Mercury, and nearer the Earth. This means that she has more light and more heat than we have, but less light and less heat than Mercury has. From Venus the Sun looks very much larger and more brilliant than we see him, yet much smaller and less brilliant than as seen from Mercury. Also, the Sun pulls Venus more strongly than he pulls the Earth, but less strongly than he pulls Mercury. Venus does not journey so fast as Mercury, but she goes farther than our Earth goes. You see how perfectly these things are all planned, so as just to fit in one with another. We may well talk of our Sun’s kingdom in the sky as a _System_, when we find its wonderful arrangements and note the order and beauty of the whole. The two inner worlds, Mercury and Venus, are called “Inferior Planets,” because they lie between the Earth and the Sun. All other worlds, having pathways outside our Earth’s pathway, are called “Superior Planets.” The next oval hoop which surrounds the pathway of Venus is that of THE EARTH. Outside the pathway of our Earth lies that of MARS: another world, a good deal smaller than the Earth or Venus, but larger than Mercury. Both Mercury and Venus can only be seen in the sky near to the Sun, either a short time before he rises in the morning, or not long after he sets in the evening--either towards the east in the morning, or towards the west in the evening. But Mars and all the other outer planets may be seen in various parts of the sky at different times. Of these four small Worlds our Earth is the largest, being nearly 8,000 miles straight through from side to side. Venus is the next in size, being nearly as large as Earth. Mars is the next, being about 4,000 miles through. Mercury is the smallest, being less than 3,000 miles through. And our Moon, as you know, is smaller still, being only 2,000 miles through. Suppose we look upon these worlds, as we have done earlier, in a lessened size; letting one inch stand for 2,000 miles. Then to picture our Moon we should want a very large grape, or a small walnut, one inch through. Our Earth would be a very big apple, or a small cocoa-nut, four inches through. Venus would be another big apple, almost as large as the Earth. Mars might be a small orange, two inches through. Mercury might be a crab-apple, only one inch and a half straight through. If you can manage to find five balls of the right sizes, and put them all in a row, you will get a very fair idea of the sizes of these worlds, as _compared_ one with another. Try also to fix the names firmly in your memory, by saying them often over and over--“Mercury, Venus, Earth, Mars.” Remember that “Earth” is the name of our world, just as “Venus” is the name of another world. All the planets are “worlds,” but only one of them is “Earth.”