This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
Jack Frost is busy with you, too. He takes the vapor of your breath and per-spi-ra-tion, as you lie warm in bed, and makes pictures with it on the cold window pane. Such pretty pictures ! They are all mosses and ferns and grass spears, and spangles to trim fairy queen's dresses.
Cold is a wonderful artist with water. It makes snow crystals and hailstone pearls. Snow is made by rain drops falling through air that is at the freezing point. The drops burst, when they freeze. Now, when things burst they make noises. You know how it is when fire crackers ex-plode? And pop-corn? If you were away up in the clouds, when it was snowing, and you had the ears of a fairy, no doubt you could hear the tiny rain drops explode into snow.
The Indians called pop-corn the corn that flowers. So snow is rain that blossoms. The next time you see a quiet snow storm, when the snow falls in large soft flakes, ask your mother for a piece of black velvet or cloth. Put it out of doors to get cold, but keep it dry. Then catch some snow flakes on it and study them through your pocket microscope. Most of them will look like little broken feathers. But if you are patient, you will be sure to find some that are perfect, six-pointed stars. The points will be veined and fringed like the petals of a flower. All snow flakes should be six sided or pointed crystals. Most of them are torn by the wind, or get their points knocked off by falling against other flakes.
Hailstones are made in quite a different way from snow flakes. Snow falls only in the winter, but hail storms come in summer, on hot days. Weather men think that when rain drops are formed in clouds, and are all ready to fall, they are suddenly pulled up much higher, into freezing air. The rain drops freeze but do not burst. Then they fall through other rain clouds, and more water freezes on the balls of ice. They are tossed up and down until they become so heavy that they drop like bullets. They drop so fast that they pass through the warm air near the earth without melting. Sometimes they are as big as pigeon's eggs. Find a very big one, some day, and ask papa to cut it across quickly, with his strong knife. You will find that the hailstone was made in layer rings like a lily bulb. The oyster makes the beautiful pearl in the same way. Around a hard center it puts layers of the pearl with which it lines its shell house. The hailstone pearl is just as beautiful as the shell pearl, but it melts so fast it is hard to study it.
But you can study larger pieces of ice. On very cold mornings you sometimes find a glass of water frozen. The water did not fill the glass, and was level. But the ice is pushed to the top, and into a little mound in the middle. When water freezes into ice it takes more room. Big people say it expands. In reading about land you learned that rocks are split by water freezing and expanding in the cracks. If water freezes in water pipes in a house, the pipes burst. Then a plumber has to come to mend them. Running water does not freeze as easily as still water. So, on cold nights, it would be a good thing to leave a faucet a little open, to keep the water flowing through the pipes.
Ice is lighter than water, that is, it fills more space for its weight, so it floats on water. It forms on top of water first, and freezes downward. You never can tell just how thick it is from the top. Before you try to slide or skate on a pond or river, you should take a hot poker and melt a hole through the ice to see how thick it is. And when ice is ready to break up, it gets "rotten" or spongy, first. You must always obey a "danger" sign that grown people put up on ice.
It is fine to see ice break up in a river. But keep off the bridges. The big blocks of ice crash against timbers and stone piers, and sometimes destroy the bridges. Sometimes, in fogs, icebergs crash into ships and sink them. When you crossed the ocean you may have seen icebergs as big as hills, floating in the sea. If you did you wondered how they were made.
Do you remember the ice rivers, or glaciers, in the high valleys of the Alps mountains? Away up north, where the Esquimos live, all the rivers are frozen. They melt a little in the summer, but more snow falls every year than is melted. The new snow presses on the old below, and squeezes it into ice, or very hard water rock, just as sea water presses sand into stone. This ice is pushed down the river beds by the weight above. The ice rivers reach the sea just as all other rivers do. In the summer the ice that is near the sea melts, or it becomes "rotten" and breaks off in large chunks. Those chunks are icebergs. They float into warmer water and melt.
It may have been a hundred years since the icebergs you saw were fleecy vapor clouds, riding on the wind-horses, in the blue sky. But there they were at last, in their old home in the ocean. Soon the berg will melt. Then the sun will turn it into vapor again, to begin another journey. (See Water, Ocean, Sea, Glacier, Waterpower, etc.)