So Cold blew again, on the great white clouds of steam that came rolling up from the hot Earth, and his icy breath cooled the steam and turned it into Rain, just as the steam from a teakettle will turn to little drops of water if you cool it suddenly. And the Rain fell back on the Earth, year after year, until at last it filled up the great wide plains and valleys between the hills and turned them into rivers, and lakes and oceans. But they were boiling hot. "How do you like it now, Mother Nature?" asked Cold. "It still isn't fit for anything to live on," said Mother Nature. "You must cool it some more. And tell Rain to make some earth for things to grow in. They can't grow in solid rock." So Cold blew again, harder than ever, and as the cool Rain fell he said: "Rain, will you please make some earth for things to grow in?" "Very well," said Rain. "I will." So Rain fell for days and months and years on the hot rocks, and cracked and softened them, and each little raindrop as it rushed down the sides of the mountains, carried a bit of soft, crumbling rock down into the valleys, and after a very long time, all these bits of rock-dust which Rain had washed down from the hills formed great wide beds of mud covering the rocky surface of the plains many feet deep. At the same time that Rain was washing the soft rock down into the valleys to form mud, he also carried down many bits of harder rock, yellow and white, and other colours, like glass. These rocks would not form mud, because they were too hard, but instead they became smooth round pebbles of all sizes, with millions of tiny bits, called sand, and the rivers carried them down to the ocean, and made beautiful clean beaches, as you can see whenever you go to the seashore. And Rain washed many other things out of the rocks and carried them down into the ocean, such as salt. There are great beds of rock-salt all over the Earth, and Rain melted them, and washed the salt into the ocean, and that is why the ocean is salt. When Mother Nature, who was very busy, came to look at the Earth she smiled, because it pleased her. "You have done very well, Cold and Rain," she said. "All the rivers and lakes and oceans are full of nice warm water, and all the valleys and plains are covered with soft warm mud, ready for things to grow in. I think I had better speak to the Sun." So Mother Nature said to the Sun: "Sun, the Earth is ready for you now. Please make something grow." Then she went away to look after some other worlds she was fixing up. The Sun looked down at the Earth and smiled as he saw the nice rich beds of mud, and the great wide Ocean. "Are you ready, Ocean?" he asked. "Yes," said the Ocean. "I am warm and salt and full of Rain." "Good. We shall need plenty of Rain," said the Sun. Then he turned to the Air. "Are you moist and warm, Air?" he asked. "Yes," said the Air. "I am very moist and warm." "Good," said the Sun. Then he turned to the beds of mud.