"The mills!" said Susie. "Where are the mills?"

"I know one," said Donald. "The river is a great mill. Don't you remember about the pebbles?"

"And the glaciers are mills, too," said Frank.



"Yes, the rivers, the ice rivers or glaciers, the wind, the frost, heat and cold, all grind masses of rock into bowlders, pebbles, and sand."

"The rock has been ground so long I should think there would be nothing left but soil," said Frank.

"You saw the limestone down by the spring?" asked Uncle Robert.

"Yes," the children said together.

"That limestone was once soft mud spread out upon the bottom of the ocean in shallow water."

"How do you know that is so, uncle?" questioned Frank.



"There are many proofs, but the best proof is that in the limestone are found shells of animals that live in the sea," said Uncle Robert.

"Fossils," said Mrs. Leonard.

"Yes, fossils. They are the remains of plants and animals that lived a very long time ago. Many rocks are almost entirely made of fossils. Fish and shells also have been covered with soft clay and left their imprints. Great beasts have walked in the mud, and we now find their footprints in the hard stone. Coral—you have seen coral?—is often found in limestone. It is made of the shells of little animals, called the polyp, which live in the sea."



"So you see that the firm ground under foot is made of rock, some of which has been ground up over and over again. But there is something else besides rock that makes the world"

"Water," said Donald promptly as he looked down upon the river.

"Yes, the water is just as much a part of our world as the solid rock and the soil. There is water in the soil and in the solid rock, too. It comes out to us in——"

"Springs," said Donald.

"Water fills hollows in the earth——"

"Ponds and lakes," said Frank.

"Water runs down the slopes—"

"Streams," said Frank.

"Rivers," said Donald.

"There is water in the air—mist, fogs, and clouds—and there is much water in the air which we can not see."

"Vapor?" asked Frank.

"Sometimes water is so thin we can not see it, and again it is so thick and hard that we may walk over it."

"Ice," said Susie.

"Tiny bits of vapor come together until they become so heavy that they fall to the ground."

"Raindrops," said Donald.

"Water is sometimes frozen in the clouds in beautiful white crystals, and then they sail down to the earth."

"Snowflakes," said Susie.

"Sometimes drops start from the clouds and go through very cold air. The cold air freezes them quickly, and then they rattle on the roof and dash on the ground. They cut the corn leaves and destroy the crops."

"Hailstones," said Donald.

"Oh," said Susie, "I saw a hailstone once as big as an egg."

"The lakes are hollows in the ground filled with water. There are many small hollows, and some big ones, but there is one so great that we may call it immense. It is the largest hollow in the world—so large that it occupies three-fourths of the earth's surface."



"The ocean," said Frank.

"Yes, the ocean is only a great big hollow filled with water."

"How deep is the ocean?" asked Frank.

"Very deep in some places—deeper than the height of the highest mountains. In others it is very shallow. In some places bits and masses of land rise out of the ocean."

"Islands?" asked Donald.

"Four great masses of land rise above the ocean level. These immense rock masses are called—"

"Continents," said Frank.

"Yes," said Uncle Robert. "We live on one of them."

"The continent of North America," said Donald.

"Our island rises right out of the river," said Susie.

"Rock and water make only a part of our world. We live on the firm earth. But we live in something. Indeed, we live at the bottom of a great, deep ocean, deeper than the water ocean, and broader than the rock and water surface taken all together."

"We live at the bottom of an ocean!" said Donald in surprise.

"Now you are joking, Uncle Robert," said Susie. "If we lived on the bottom of an ocean we should all drown."

"Fish live in the ocean, and we live in an ocean, too—a very deep one, how deep no one really knows. It may be a hundred, or hundreds of miles deep. We see a part of the surface of the earth and of the water, but no one has ever seen the surface of the mighty ocean in which we live."

Susie and Donald were puzzled. Frank's face lighted up as he said:

"I think you mean the air, Uncle Robert."

"You are right, Frank. The great ocean in which we live is the air, or, as it is called, the atmosphere. The atmosphere is just as much a part of our world as the rock and the water. The rock we may call solid, the water fluid, and the air gaseous. Solid, fluid, gas."

"How do we know that the atmosphere is so deep?" asked Frank.

"We do not know exactly, but there are ways of proving that it is very, very deep. When people began to study the atmosphere they thought it extended about fifty miles from the surface of the earth. Now they are sure that it is much deeper. We know that air has weight, like soil and water. It presses on us and everything else—"

"Fifteen pounds to the square inch," said Donald.

"We weigh the air with the—-"

"Barometer," said Susie.

"It is heavier at the ocean level than it is on the tops of mountains. We are sure that the higher we go up—-"

"The less the air weighs," said Frank.

"At the height of fifty miles it is thought to have little or no weight, and so people believed that was as far as it extended. But in time they discovered another way of measuring the atmosphere. You have seen falling stars, haven't you?" asked Uncle Robert.



"Oh, yes," said the three children together.

"I saw a star fall, so fast—just like a rocket. Then the light went out, and I wondered where it went," said Susie.

"Falling stars are not stars at all, though they look like them. They are pieces of rock that break off from other worlds and whiz through space."

"Oh!" said Susie.

"Outside of our atmosphere there may be nothing for these masses of rock to strike against, but just as soon as they come into the air, it tries to stop them. The air is not strong enough to stop them, but it grinds them up."

"Grinds them up!" exclaimed Donald. "Isn't that wonderful? But, uncle, what makes them look just like fire?"

"If you put an axe or scythe on a dry grindstone and turn the crank, what do you see?"

"Sparks of fire," said Frank.

"Why do you put grease or oil upon the axles of your buggy?"

"To keep them from becoming hot and dry," said Frank. "One time when father and I were on a train there was a hot box, and we had to stop to cool it."

"The heat and the sparks of fire are caused by one body rubbing against another. The faster they move, the greater the heat. This rubbing is called friction."

"There was a time," said Mr. Leonard, "when fires were started by rubbing two pieces of wood together. Some Indians do so now."

"Then the great pieces of rock rub against the air when they whiz through it, and that makes the sparks?" asked Frank.

"You are right. We can see the blaze of fire caused by the friction."

"I should think the rocks would fall on us and kill us," said Donald.

"Most of them are probably ground up into bits of dust before they reach the ground. Some of them, indeed, do strike the ground, and very large ones bury themselves deep in the earth. When we go to the Field Columbian Museum, in Chicago, we shall see these visitors from other worlds. They are called meteoric stones, or meteorites. When they are in the air we call them meteors."

"I am going to watch the next one I see," said Susie.

"They fly so fast that you hardly see them before they are gone," said Donald.

"Men who study the heavens tell of the depth of the atmosphere by the angle the meteor makes in falling, but perhaps you can not understand that now. So you see, children, we live on the bottom of a great ocean of air, and that air, or atmosphere, is a part of our world—the outside part."

"How plain it all is," said Mrs. Leonard, "when we think of it this way!"

"Now we have the land and the water," said Uncle Robert.

"And the atmosphere," put in Donald.

"And they are all right here close to us. Here is the land with its hollows, and there," pointing to the river glistening in the moonlight, "is the water, and—"

"You can't see the air," said Donald.

"We can feel it, anyway," said Susie.

"How large is the earth, uncle?" asked Frank.

"Eight thousand miles through it and twenty-five thousand miles around it," answered Uncle Robert.

"But, uncle, is it all solid rock for eight thousand miles?"

"No one knows. The rocky outside of the ball is called the crust of the earth. Miners have dug down nearly four thousand feet, and makers of artesian wells have bored still farther. They always find rock."

"I wonder how far four thousand feet would be," said Donald.

"A little over three quarters of a mile," said Mr. Leonard.

"The farther they go down into the crust of the earth, the warmer they find it. I have been down in a mine thirty-two hundred feet, and it was very hot. No one could have lived there if cool air had not been brought down from the surface.

"Some people have thought that inside the crust of the earth the rock is all a molten mass, like melted iron. You have read about volcanoes, and of the lava that is thrown out of them?"

"Does that come out of the inside of the earth?" asked Donald.



"It comes from somewhere in the earth. Some men give their whole lives to the study of these questions, but you know they can not see beneath the crust of the earth. It is thought by some that the weight of the crust would keep the center of the earth a solid mass. So you see there are still many questions unsettled. We know that the crust is moving up and down all the time."

"Oh, I hope the land won't rise here!" said Susie.

"You wouldn't know it, Susie, if it did," said Uncle Robert, laughing.

"Unless there was an earthquake," said Frank.

"Or a volcano," said Donald. "I'd like to see one."

"I would like to see the ocean," said Frank. "It must be grand to stand on the shore and look way off and not see anything but water."

"It is a grand sight, Frank. I have sat on the beach many a time and watched the waves roll in, and thought of the wonderful work the ocean is doing. You know it is the great reservoir that supplies all the land with water."



"The heat of the sun lifts the water up, or evaporates it. The vapor that makes the clouds rises into the air. The winds blow the vapor many long miles, and some of the clouds come right over our heads. The cold air draws the little bits of vapor together and makes the clouds heavy, and down they fall upon the earth as drops of rain.

"Some of the rain runs directly into the streams. Some of the rain water sinks down into the earth; in the gravel it sinks fast; in the sand it sinks slower; and in the loam, clay, and rock it sinks very slowly indeed. The water in the ground dissolves the rock or the loose earth into little particles so fine that the tiny roots, or root hairs, drink them up, and so the rock furnishes a part of the nourishment, or food, of plants.

"Without the water that the clouds bring no plant could grow. It gives life and growth to everything that lives, and then sinks deep into the earth. It comes out of the ground again in springs, and flows away in rivulets, brooks, creeks, and rivers—away, and away, back to the ocean again.

"On its way to the ocean it wears down the land, carries silt from place to place, spreads it out on beaches, sand bars, bottom lands, deltas, and on the bottom of shallow places in the ocean."

"Isn't it strange how everything changes, and how all the changes help us?" said Frank thoughtfully.

"Yes, Frank, it is wonderful how the Creator of all things is constantly moving earth, air, and water, and, as you say, making all these changes to help man."

"It is the Big Book that tells us of this marvelous world of ours and of other worlds as well. It lies open before us for us to read every day. God has created and is still creating our home, the dwelling place of His children. We must study Him, my dear children, in all He has made. We must learn of His works in order to use everything to make man happier, better, and more useful."

Mr. Leonard, who had been listening very attentively to the story, said, as his face lighted with a happy smile:

"I never thought of it all in that way before. Every day, in all our work on the farm and in the house—indeed, wherever we may be—we should learn new and beautiful revelations from our Heavenly Father; how much He is constantly giving us, and how thankful we should be."

The moon had risen to its full glory over the earth. The waters of the river glistened. The trees, cornfields, and meadows were peaceful and grand, as though they, too, felt the power of the glorious light.

Susie put her brown arms around her mother's neck and kissed her good-night.

"Oh, how I love the Big Book!" she said.

"I wish I could read it as all those great men have read it," said Frank.

"So do I," said Donald.

"'Day unto day uttereth speech, and night unto night sheweth knowledge,'" mused the mother as her loved ones went to bed with sweet thoughts of a beautiful world and a loving God.

THE END