Questions and Exercises.

“Oh, what a lovely little animal,” said Dolly; “and what pretty eyes he has. They are just like a pair of bright, black beads.”

“I think Tom ought to have the glasses now,” said Uncle George. “He has been very patient indeed. Come Tom, tell us what the squirrel is like.”

Tom took the glasses and looked through them for a long time. Then he said, “He is a very pretty creature, as Dolly has said. His colour is rich brown all over, except the front part of his body, which is a very light brown, changing almost to white. His tail is very large and bushy, and his ears are upright and tufted with brown hair. His fore-paws are just like little hands. He holds the nut in them and nibbles it just like a little monkey. His head is not unlike the rabbit’s head. His teeth are almost exactly like rabbit’s teeth. They are chisel-shaped, and seem to be very sharp.”

“Splendid, Tom,” said his uncle, patting him on the back, “I don’t think you have left anything out. Now, let me look.”

“Oh, there is another one. There are now two of them,” said Frank.

“Where did that one come from?” askedhis uncle, looking through the glasses. “It seemed to come out of the tree, did it not?”

“I thought you children would leave me nothing to find out; but I see something which you have missed. Here, Frank, take the glasses and see if you can find it. Look at the fork of the tree just below where the squirrels are.”

“I see something like a nest,” said Frank. “I noticed that before, but I thought it was a rook’s nest.”

“Nay,” said his uncle, “it is a squirrel’s nest. Rooks build on the very top branches of trees, and you never see one rook’s nest without a lot of others near it. Besides, the rook’s nest is a rough flat nest, while this is a round one with a roof on it, and a hole in the side to let the squirrels out and in.”

“Then that other squirrel must have come out of the nest,” said Frank.

“Just so,” said Uncle George. “That is Mrs Squirrel. She has come out to get some food, and her little husband will look after the family while she is away hunting for nuts and buds and soft green bark.

“If we could get up to that nest, we should find it to be built of twigs and moss cleverly woven together.

“The inside is lined with soft warm moss and dry leaves. We should, most likely, find four or more tiny squirrels cuddled up together inside. Blind, naked, helpless things they are at first. But they soon grow up, and their long bare tails become bushy. Then the little mother teaches them to climb and find food for themselves. Should one of them fall, she springs down and carries it up to the nest in her mouth, just as a cat carries her kittens.

“By autumn these young squirrels will be quite as clever as their parents. Autumn is the squirrel’s busy time. He has to prepare for the long winter, for no nuts are to be found then. So the squirrel gathers in his harvest of nuts. These he hides in secret places buried in the ground. He usually has more than one storing-place. In fact, he sometimes has so many that he forgets about some of them.”

“We never see squirrels in winter,” said Tom.

“No, because the squirrel sleeps the wholewinter through. After he has gathered his harvest, he looks for a snug hole deep under an old tree-stump. This he lines with dry leaves and pieces of bark. When the weather becomes very cold he seeks his winter nest, coils his body up so that his great tail is folded almost right round him, and falls fast asleep. Cold makes him drowsy, but warmth wakes him up. On a mild winter’s day he wakes up, crawls out of his hole, and visits his store of nuts. After he has made a good meal of them, he goes back to his bed again, and sleeps on until hunger and mild weather wake him up.

“During autumn the squirrel’s coat is very pretty. It is of a deep, rich brown colour, and very thick. His tail is then very large and bushy, and he is quite fat and sleek.

“When he comes out of his sleeping quarters in spring he is thin and hungry. His coat is then a very pale brown.”

“What does he do for food in spring?” asked Tom. “There are no nuts to be found then.”

“Alas, no, Tom. In spring he robs birds’ nests of their eggs, and that is why thepretty little squirrel is hunted and shot by the game-keeper. In spring, too, he feeds on the tender buds, and so does much damage to trees and shrubs; that is, if his winter stores are used up.”

“I should think,” said Frank, “that such a large tail would be very much in the squirrel’s way when climbing and leaping from branch to branch.”

“Not at all,” said his uncle, “his huge tail is of the greatest use to him in guiding his body. Without it he could not take such flying leaps among the tree-tops.

“Besides this, it often enables him to escape from his enemies. Many a time the game-keeper’s bullets pass harmlessly through his fluffy tail, while Mr Squirrel scampers safely up the tree; and many a time he escapes from the cat by leaving the tip of his brush in pussy’s claws.

“A great many of our trees have been planted by squirrels. Many a stately oak and beech tree has sprung from the squirrel’s buried store of acorns and beech nuts. For, as I have already told you, sometimes he forgets where he has buried them, or perhaps fails to find them when the forest is whitewith snow. So, you see, the little animal is of some use after all.”

It was a cold wet day—so cold and wet that neither Dolly nor her brothers could venture out. They had grown tired of reading books and drawing pictures, and were indeed feeling very dull. They sat looking at the bright fire. Uncle George laid down his paper and said:

“Come, let us have a lesson. What shall it be? The rain? The cat? Or shall it be the cosy fireside?”

“The fire,” said Frank. “Tell us why the fire burns, Uncle George!”

“I will,” said cheery Uncle George. “Just wait until I get some things from the kitchen. Come along, boys.”

When Uncle George and the boys came back to the room, they brought a lot of curious articles with them. These were an empty pickle-bottle, a small saucer, a glass bell-jar, a large dish, a piece of candle, some tacks, and a taper.

A Baby Cloud

THE BALLOON

“Now,” said Uncle George, “we are ready to begin.”

He first lighted the piece of candle and lowered it into the bottle. It burned for a short time, then it went out.

“Can you tell me why it goes out?” he asked.

“Want of air,” said Tom and Frank at the same time.

“But there is air in the bottle,” said Uncle George.

“Yes, but not the kind of air the candle wants,” said Frank.

Candle burning in Open Jar.

“That is a queer answer, Frank. The candle burned for a time in the bottle before it went out.”

“Because it used up that part of the air which makes things burn,” said Frank.

“That isverygood,” said Uncle George.

Uncle George then poured some water into the large dish. He fixed the candle on a big cork, lighted it and set it floating on the water. Then he placed the glassbell-jar over it. But first of all he marked the level of the water on the outside of the bell-jar.

Very soon the flame of the candle became small, and at last went out. Just then the water inside the bell-jar rose far up above Uncle George’s mark. He marked this new level, and asked the boys if they could tell him why the water rose in the jar.

Both Frank and Tom shook their heads sadly.

Candle in Stoppered Jar—burning.

“Then I must explain,” said Uncle George.

“Some of the air has gone,” said Tom.

“Yes,” said Uncle George. “How much of the air has gone?”

Frank pointed to the space between the two marks.

“That is right,” said Uncle George. “The water has risen up in the bell-jar to take the place of the air that has been used up by the burning of the candle. Where has this used-up air gone?”

“It must have gone into the water,” said Tom.

“Why did it not go into the water before the candle burned?”

“Perhaps the burning of the candle haschangedthis part of the air,” said Frank.

“Very good, Frank. You are right again. The burning of the candle has changed a certain part of the air. It has, indeed, so changed it that it can dissolve in water just as if it were sugar or salt.”

Uncle George now poured water into the outer dish until it was level with the water inside the bell-jar. Then he took out the stopper and pushed a lighted taper into the bell-jar. The taper at once went out.

Candle in Stoppered Jar—gone out.

“This shows us,” he said, “that a part of the air causes things to burn. The other part of the air does not. It puts burning things out. If we blow the fire with a bellows orfan, it burns more brightly and quickly. Why? Just because we are forcing a stream of air upon it, and a part of that stream of air is changed by the burning.”

Uncle George next put some bright iron tacks in a small dish. He poured some water out of the large dish, and placed the bell-jar in the dish. After that he added water until it was just up to his first mark on the bell-jar.

Then he floated the dish with the tacks on the water. Next he wetted the tacks with water, and then placed the bell-jar over them and put in the stopper.

“Now,” he said, “we will leave this just as it is for a few days.”

The boys watched the bell-jar every day, and this is what they saw. The water rose slowly in the bell-jar. As it rose the bright tacks turned red with rust. The water rose higher and the tacks turned redder every day.

At length it rose to Uncle George’s second mark. It rose no farther, although left for a whole week.

Then Uncle George called the boys andasked them what had taken place in the bell-jar.

“The tacks have rusted, and some of the air in the jar has been used up,” said Frank.

“How much air has been used up?” Uncle George asked.

“Just exactly the same as was used up when we burned the candle,” said Tom, pointing to the top mark.

“Let us see, then,” said Uncle George, “what part of the air has gone.”

He poured water into the large dish until it was level with the water inside the bell-jar. Then he put a lighted taper into the bell-jar as before. It went out at once.

“It is the same part of the air as the burning candle used up,” said Frank.

“Then we have found out,” said Uncle George, “that when a thing burns it uses up a certain part of the air; and that when iron rusts, exactly the same part of the air is used up.

“In the first case, the burning of the candle changed part of the air into a gas which dissolved in the water. In this case, that same part of the air has joined up to part ofthe iron tacks to form that red powder which we callrust.”

One day Uncle George made the children a fire-balloon. He took twelve strips of tissue-paper shaped as you see in the picture. These he pasted neatly together at the edges so as to form a kind of bag with a round opening at the bottom. A ring of wire was then fixed at the bottom to keep it firm, and across the ring was stretched another piece of wire. This was to hold a dry sponge by and by.

Uncle George swung the balloon till it was filled with air. He told Frank to hold it by the ring while he heated the air inside the balloon.

This was done by holding the mouth of the balloon over a piece of rag which had been dipped in spirits and set on fire.

Strip for Balloon.

Soon Frank felt the balloon rising. He lifted it up away from the flame, while Uncle George moved the little sponge along the wire to the middle of the ring. Then he soaked the sponge with spirits and set fire to it.

“Let go!” said Uncle George; and away went the balloon, soaring up towards the sky. Higher and higher it rose, moving with the wind. The children watched it until at last it seemed a mere dot in the sky, and then it went quite out of sight.

“What makes the balloon rise up?” Dolly asked, as they returned to the house.

For answer Uncle George took a cork and held it under a trough of water. When he let it go, the cork at once rose to the top of the water.

“What makes the cork rise up?” he asked.

“Because it is lighter than the water,” said Tom.

“For just the same reason the balloon rises in the air,” said Uncle George. “Our balloon is only a bag filled with air.”

“Then the air inside the balloon is lighter than that outside,” said Frank.

“Yes,” said his uncle. “What did we do to it to make it lighter?”

“We heated it,” said Tom.

“And what has this taught you?” asked Uncle George.

“It has taught us,” said Frank, “that if we heat air we make it lighter.”

“What takes place is this,” said Uncle George. “When a small quantity of air is heated it swells out and fills a much larger space than before. It therefore becomes much lighter than the air round about it, and rises up through it. Come into the house and let us take another lesson from the fire.

Strips pasted together.

“We have already learned that the fire in burning uses up part of the air. After using up this part of the air, how is it that the fire does not go out?”

“Because there is always a fresh supply of air coming into the grate!” said Frank.

“Quite right. If we stand between thedoor and the fire we can feel this stream of air. Something else is taking place in the grate besides the burning of coal. What is it, Tom?”

“Air is being heated!”

“Very good, Tom, and what becomes of the heated air?”

“It rises up the chimney, carrying the smoke with it; just as the heated air in our balloon rose up, carrying the paper bag with it,” said Frank.

“That is really a clever answer, Frank. Now, can you tell me what makes this constant stream of cold air from the door to the fireplace?”

“It is the cold air rushing in to take the place of the heated air that has gone up the chimney,” said Frank.

“Very good indeed, Frank,” said Uncle George. “And now I am going to show you something which will prove all this very nicely.”

He then took a saucer and poured some water into it. He placed a piece of lighted candle in the middle of the dish and put a lamp chimney over it. The candle burned for a few seconds and then went out.

“Why does the candle go out?” he asked.

“Because it has used up that part of the air which makes things burn,” said Tom.

“That is right,” said Uncle George, and he began to cut a piece of stout card, shaped like the letterT, but broader every way. The upright part fitted into the top of the lamp chimney.

“We are now going to give the candle flame a stream of fresh air,” he said, as he fitted the piece of card into the chimney.

The candle was again lit and the chimney placed over it. This time it did not go out. It burned brightly, and the flame seemed to be blown from side to side.

“That is very strange,” said Frank.

Draught in Chimney Glass.

Uncle George lit a piece of brown paper. “You will understand it now,” he said, as he held smoking paper near the top of the chimney.

Then the boys saw a stream of smoke godown one side of the card and come up the other side.

“Oh, I see it now,” said Tom. “The card divides the chimney into two. The air, heated by the candle flame, rises up one side of the card, and the cold air goes down the other side to supply its place, drawing the smoke with it. The candle does not go out now, because it gets a constant stream of fresh air.”

“Are the balloons, which are large enough to carry people, fire-balloons?” asked Dolly.

“No, my dear,” replied Uncle George. “They are filled with a gas that is lighter—very much lighter—than the air. They rise up easily, and can carry quite a heavy load.”

Frank, Tom, and Dolly had never seen the sea. Long ago Uncle George had told them that he would take them, and at last the time came for them to go.

It was afternoon when they reached the little sea-side village where they were to spend a few days. The children were filled with wonder when they saw the great, restless ocean. They watched the waves breaking into white surf, and gathered sea-weeds and shells on the sandy beach.

By and by they all sat down to rest and to watch the gulls, for there were many here-about.

“We have seen birds like these before, have we not?” said Uncle George.

“Yes,” said Tom, “we see them at home in the fields at spring-time. But are these the same kind of gulls?”

“Yes, Tom, they are. There are severalkinds of gulls. Here we have just two kinds. Thecommon gulland thetern. You can tell the one from the other even in the distance by their mode of flying.

“Do you see that one flying rapidly over the sea? Every now and then he swoops down to the water and skims along, almost touching it with the tips of his long, pointed wings. Do you know any other bird that flies like that?”

Gull flying.

“The swallow flies over the lake at home something like that,” said Frank.

“That is so,” said Uncle George. “Thetern is very like the swallow both in shape and in his manner of flight. He differs, however, in size and colour. He is often called the ‘sea-swallow,’ and is the smallest of the gull family.

“Your swallows at home catch flies and other insects as they skim through the air. The ‘sea-swallows’ live on fish. Every time they dart down they seize and swallow a little fish. But it is done so quickly that you cannot see it.

“The gull’s flight is quite different. Sometimes he flies so lazily that he does not seem to move onwards at all. Then all of a sudden he darts down into the water to seize his prey. Sometimes he flaps his great white wings and wheels swiftly away, flying in great circles until he is a mere speck in the distance. The gull has a very sharp eye. Watch!”

Uncle George threw a piece of bread into the sea. At once about a score of gulls pounced upon it, screaming loudly. Uncle George waited until they flew away. Then he threw them a piece of wood. None of the gulls came near it.

“You see,” he went on, “they can tell apiece of bread from a piece of wood at a great distance.”

“Then they do not live entirely on fish,” said Frank, as his uncle threw them another piece of bread.

Gull feeding.

“Oh, no, Frank, the gull is by no means dainty about his food. Nor does he live all the year round at the sea. Great flocks of gulls fly inland in spring and autumn. Then they live on worms, grubs, and whatever else can be picked up in the fields.

SEA-GULLS AND TERN

“We have a fine chance now, boys, of watching the gull. See, there are some walking on the sand quite close to us, some are floating idly on the sea, some are flying all round us. They think, no doubt, we have lots of bread for them. Now then, boys, tell me about the common gull.”

Gull at rest on the water.

“He is a large bird,” said Tom. “His body is white in colour, all but his wings and back. These are of a pale bluish-grey.”

“Very good, Tom,” said Uncle George. “Come on, Frank.”

“He has a large, greyish-green bill. The tip of it is hooked in shape, and yellow. Hislegs are greenish-grey. The three front toes of his feet are webbed.”

“But,” said Tom, “I can see other gulls darker in colour. Their bodies are dark brown and grey above and light brown below. What are they?”

“They are the young gulls, Tom. They have not got rid of their nest feathers yet.”

“Where do they build their nests?” Dolly asked.

“High up on the cliffs, and on lonely rocky islands. Like the rooks, they all nest together. The gull’s nest is a very simple thing. It is just a hole scraped in the ground and covered with dried grass. Here two, or perhaps three, spotted eggs are laid. The gull is very fond of her young. She will not allow them to try to fly from the high cliff. She carries them one by one on her back down to the sea, and there teaches them to swim.

“Some gulls—theblack-headed gull, for example—go far inland to nest. These build their nests on the shores of small hill lakes. They return to the sea with their young ones in autumn.

“Gulls are clever birds. They are boldand active. The wild ocean is their home. Storms bring no fears for them.”

Engine puffing on a cold day.

“How is it, Uncle George, that there is always a clear space between the spout of the kettle and the puff of steam?”

It was Frank that asked the question. He had been watching the kettle boiling for a long time.

“It is the same with the railway engine,” said Tom. “There is always a big space between the funnel and the puff.”

“That is so,” said Uncle George. “But if you watch carefully, you will notice that the space between the funnel of the engine andthe puff of steam is not always of the same size.”

Engine puffing on a hot day.

“No,” said Frank, “I have noticed that the white puff is farther away from the funnel on a hot day than on a cold day.”

“That is true,” said his uncle. “Perhaps you have also noticed that, as the engine rushes along, it leaves a long white cloud trailing in the air behind it. Sooner or later this long white cloud melts away from sight. It melts away sooner on a hot day than on a cold day. Where does it go?”

“It goes into the air,” said Frank; “just as the cloud from this kettle goes into the air of the room.”

“Very good,” said Uncle George. “Tom, will you please fetch me a tumbler full of cold water, and see that the outside of the glass is quite dry?”

When Tom came back with the glass of cold water, Uncle George wiped it outside with a clean dry cloth. When he was sure that the outside of it was dry, he placed the tumbler of water on the table in the middle of the warm room.

“Now,” he said, “let us try to answer Frank’s question about the clear space between the spout of the kettle and the puff of steam.

“The fact is,” Uncle George went on, “the white puff which we callsteamis not steam at all. We might just as well call it ‘water-dust.’ For it is made up of tiny droplets of water—so tiny that they float in air. Steam is water in the form of gas. Like the air we breathe, it cannot be seen. In fact, this water-gas forms part of the air around us. The clear space between the spout of the kettle and the puff is madeup of hot steam. We cannot see it. As it comes out into the colder air, it is cooled into the tiny droplets which form the puff. It is only when cooled into tiny droplets that we can see it.

“If you hold any cold object, such as a knife, in the puff, these water particles run together and form large drops upon it. The cloud of water-dust melts away in the room, as Frank told us. What takes place is this. The tiny droplets, when spread out into the warm air, become real steam, or ‘water-gas,’ again.

“The outside of this tumbler of cold water was quite dry when I placed it on the table. Run your finger along it and tell me what you find.”

Frank did so, and said, “Why, it is quite wet now.”

“Yes,” said Uncle George, “it is covered all over with very small drops of water. Where did this water come from. It could not comethroughthe glass.”

“It is like dew,” said Tom.

“It is dew—real dew,” said Uncle George. “The water in the glass is much colder than the air around it. The film of air next theglass is cooled, and the ‘water-gas’ which this film of air contains is changed into water drops.

“The earth is heated during the day by the sun, and the layer of air next to it becomes filled with water-gas. At night the earth gets cold. The water-gas, if the night is calm, comes out of the film of air next to the earth. It settles in the form of tiny drops on everything around.

“When the earth gets very cold, the water freezes as it changes from gas to water, and instead of dew we havefrost.”

“Oh, that is why we have frost on theinsideof the window panes in winter,” said Frank.

“That is so,” said his uncle. “The frost on your window pane is the water-gas of the warm room changed into particles of ice. But let us come back to our steam puff. We spoke about the long white streak of water-dust which the engine leaves behind it. Do you know of anything else like that outside?”

“Oh yes,” said Tom, “the clouds far up in the sky are very like it.”

“They are,” said Uncle George. “In fact, the clouds in the sky and the cloud behind the engine are just the same kind of thing. They are both made up of tiny particles of water.

“We have learnt that the streak of cloud left by the steam-engine melts away quickly on a hot day, also that the puff is farther from the funnel on a hot day. This shows us that the warmer the air is, the more water can it take up and hold. We have also learnt that warm air is light and rises up.[2]

“What happens when warm air, which holds much water-gas, rises up to the higher and colder parts of the sky?”

“It gets cooled,” answered Frank.

“Yes, and its water-gas gets cooled too. Then we can see it as great masses of water-dust. These masses we callclouds. If these masses of cloud get further cooled, the tiny water particles run together to form great drops—as they did on the cold knife. They are now too large and heavy to float in the air, so they fall to the earth asrain.”

A Showery Day.

[1]See Lesson I., Book IV.[2]See lesson “The Fire-Balloon.”

[1]See Lesson I., Book IV.

[2]See lesson “The Fire-Balloon.”

PRINTED IN GREAT BRITAIN AT THE PRESS OF THE PUBLISHERS.

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