Now, if you have done all this faithfully, you have worked hard enough, and I will reward you with a story. Once upon a time there was a princess named Callisto, and the great god Jupiter fell in love with her. Naturally, Jupiter's wife, Juno, wasn't pleased, so she changed the princess into a bear. But before this happened, Callisto became the mother of a little boy named Arcas, who grew up to be a mighty hunter. One day he saw a bear and he was going to kill it, not knowing that the bear was really his own mother. Luckily Jupiter interfered and saved their lives. He changed Arcas into a bear and put both bears into the sky. Callisto is the Big Bear, and Arcas is the Little Bear. But Juno was angry at that, and so she went to the wife of the Ocean and said, "Please, never let these bears come to your home." So the wife of the Ocean said, "I will never let them sink beneath the waves." And that is why the Big and the Little Dipper never set. They always whirl around the Pole star. And that is why you can always see them, though some nights you would have to sit up very late. Is that a true story? No. But, I can tell you a true one that is even more wonderful. Once upon a time, before the bear story was invented and before people had tin dippers, they used to think of the Little Dipper as a little dog. And so they gave a funny name to the Pole star. They called it Cynosura, which means "the dog's tail." We sometimes say of a great man, "he was the cynosure of all eyes," meaning that everybody looked at him. But the original cynosure was and is the Pole star, because all the stars in the sky seem to revolve around it. The two Dippers chase round it once every twenty-four hours, as you can convince yourself some night when you stay up late. So that's all for to-night. What! You want another true story? Well, just one more. Once upon a time the Big Dipper was a perfect cross. That was about 50,000 years ago. Fifty thousand years from now the Big Dipper will look like a steamer chair. How do I know that? Because, the two stars at opposite ends of the Dipper are going in a direction different from the other five stars. How do I know that? Why, I don't know it. I just believe it. There are lots of things I don't know, and I'm not afraid to say so. I hope you will learn how to say "I don't know." It's infinitely better than guessing; it saves trouble, and people like you better, because they see you are honest. I don't know how the stars in the Big Dipper are moving, but the men who look through telescopes and study mathematics say the end stars do move in a direction opposite to the others, and they say the Dipper _must_ have looked like a cross, and will look like a dipper long, long after we are dead. And I believe them. CONSTELLATIONS YOU CAN ALWAYS SEE