The light in the west grew rapidly. The lightning became less frequent. The thunder rolled farther and farther away. The rain fell less and less heavily. The weather vane that had pointed to the northeast began to waver, and then turned toward the southwest again. It rained steadily but more gently as the clouds rolled away eastward. And then the sun, lower now by two hours than when it was first hidden by the cloud, shone out clear and bright. Instantly everything glistened as with millions of diamonds. Even the air seemed to be filled with them, as though each raindrop was turned into a jewel as it fell. Uncle Robert went to the front of the house and looked toward the dark cloud that was now piled up in the eastern sky. "Come and see the rainbow!" he called. As they looked at the bright and perfect arch that lay against the dark mass of clouds, Susie asked, "What makes rainbows, uncle?" "It is the sun shining on the rain," replied Uncle Robert "This beautiful sunlight is made up of many, many rays. These rays fly from the sun as straight as arrows from a bow, unless something comes in their way to stop them. It seems as though such sharp little arrows of light would go right through raindrops. But they don't. They glance off the little round balls of water and bound up again like rubber balls. "Now you know if you throw a ball straight down at your feet it bounds back into your hands. If you throw it from you, when it strikes the ground it bounds farther away. It is just so with these little arrows of light that we call rays. If the sun is high, as it is at noon, the rays are thrown back to it again. That is why we never have rainbows at noon. But when the sun is low, as it is now, instead of going back to the place they came from, they bound up against that cloud, and so make the wonderful rainbow." "But, uncle," asked Donald, "why do we see so many colors in the rainbow? They are not in the sunlight." "Oh, yes, they are," was the answer. "These rays of light are of the same colors that we see in the rainbow. It takes all of them mixed together to make the clear white light which we call sunlight, and without which nothing could live or grow. "As the raindrops throw them up against that cloud, they are separated again, because some colors are more easily bent than others. The red, you see, is the highest and the violet the lowest in the bow. The raindrops make a prism. You have seen a prism. But through the prism the colors are turned the other way; the red is lowest and the violet highest." "How fast the rainbow is fading away!" said Susie. "I wish it would stay." "The rain is over," announced Donald, leaving them and walking out toward the garden. "The sky is quite clear." "It is getting warm again," said Frank, looking at the thermometer, "but it does not feel hot as it did before the rain." "The barometer is just where it was this morning," said Susie, coming from the dining-room.