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                  [Illustration: The land is at rest]




                                  The
                            "LOOK ABOUT YOU"
                           Nature Study Books


                                BOOK II.


                                   BY
                            THOMAS W. HOARE

                        TEACHER OF NATURE STUDY
      to the Falkirk School Board and Stirlingshire County Council

                    [Illustration: Publisher's Logo]

                    LONDON: T. C. & E. C. JACK, Ltd.
                        35 PATERNOSTER ROW, E.C.
                             AND EDINBURGH




                                PREFACE.


This little book should be used as a simple guide to the practical study
of Nature rather than as a mere reader.

Every lesson herein set down has, during the author's many years'
experience in teaching Nature Study, been taught by observation and
practice again and again; and each time with satisfactory result. The
materials required for the lessons are within everybody's reach.

There is nothing that appeals to the heart of the ordinary child like
_living things_, be they animal or vegetable, and there is no branch of
education at the present day that bears, in the young mind, such
excellent fruit as the study of the simple, living things around us.

Your child is nothing if not curious. He wants to understand everything
that lives in his bright little world.

Nature Study involves so many ingenious little deductions, that the
reasoning powers are almost constantly employed, and intelligence grows
proportionately. The child's powers of observation are stimulated, and
his memory is cultivated in the way most pleasing to his inquiring
nature. By drawing his specimens, no matter how roughly or rapidly, his
eye is trained more thoroughly than any amount of enforced copying of
stiff, uninteresting models of prisms, cones, etc., ever could train it.

The love of flowers and animals is one of the most commendable traits in
the disposition of the wondering child, and ought to be encouraged above
all others. A few lessons on Nature Phenomena are added.

It is the author's fondest and most sanguine hope that his little pupils
may study further the great book of Nature, whose broad pages are ever
open to us, and whose silent answers to our manifold questions are never
very difficult to read.

                                                                T. W. H.




                                CONTENTS


LESSON                                                               PAGE
       I. How Plants take Food from the Soil (1)                        5
      II. How Plants take Food from the Soil (2)                       13
     III. The Weasel and the Otter                                     20
      IV. Dwellers in the Corn Field                                   27
       V. Harvest Time                                                 33
      VI. The Squirrel                                                 40
     VII. How the Fire Burns                                           48
    VIII. The Fire-Balloon                                             55
      IX. The Gull                                                     61
       X. Dew, Frost, Rain                                             68




                           "LOOK ABOUT YOU."
                                BOOK II.




              I.--HOW PLANTS TAKE FOOD FROM THE SOIL (1).


Uncle George had taught his little friends many things from what he
called the Book of Nature, and what they had learnt made them eager to
know more.

One day as Dolly, the boys, and Uncle George were in the garden they saw
that a tulip, which the day before was in full bloom and strong, was now
lying dead on the ground.

"Poor little tulip!" said Dolly. Both the boys were sorry too. They had
watched it come through the ground like a blade of grass, open out its
bud, and expand its bloom. Now all was over. The little flower would no
longer enjoy the bright sunshine or the rain. It would no longer send
forth its rootlets in search of the food it so much liked.

"Have you ever thought, Dolly, how the tulip, and indeed all plants,
take their food from the soil?" asked Uncle George.

"I know they _must_ feed in some way," said Dolly, "or they would not
grow. But I do not know how they do it."

"Should you like to know, Dolly?" asked Uncle George.

"Indeed I should," said the little girl.

The boys were just as eager as Dolly to know about this, so Uncle George
and the children went indoors for a lesson.

"I cannot tell you how plants take their food from the soil without
first of all showing you what happens when water and soil are mixed
together in a tumbler," said Uncle George. "Tom will fetch me a tumbler,
and you, Frank, bring me a little water."

When these were brought, Uncle George put a spoonful of soil into the
tumbler, and then poured some water on it.

"Stir it up, please, Dolly," said Uncle George, "and you may pretend you
are going to make a pudding."

Dolly did so.

"Now let us put it aside for a few minutes, while we place the flowers
we have gathered into the vases," said Uncle George. "Then we will look
at our tumbler of muddy water."

How pretty the flowers were made to look! How fresh they were! and how
pleasant was their scent! The children hardly thought of the tumbler,
but Uncle George was ready now for the lesson.

                [Illustration: Glass of Mud and Water.]

"Look! look, at the tumbler," said he. "Do you see a change?"

"Indeed we do," said all the children in one voice.

"The mud has sunk to the bottom of the glass," added Tom, "and the water
on the top is clear."

Uncle George poured some of the clear water into a clean flat dish. Then
he took a spirit-lamp from a little cabinet, and heated the water in the
dish with it.

The children watched to see what would happen. Soon a cloud was seen
over the dish, and by and by all the water had gone.

"But what is that at the bottom of the dish?" asked Uncle George.

"It looks like powder," said Frank.

"And it must have been in the water all the time," added Tom.

                [Illustration: Evaporating Salt Water.]

"And yet the water was clear," said Uncle George. "Look once more."

As he spoke, Uncle George took a glass of clean water from the tap. He
put two large spoonfuls of salt in, and stirred it up.

"You see," he said, "the salt has gone from sight. Still the water is
clear. Where has it gone?"

"Into the water," said Tom.

Uncle George put more salt in the water, and stirred it up. He kept on
doing this until the water would take up no more salt, no matter how
much it was stirred. This he called _brine_.

"Now, Frank, please go and ask mother for a fresh egg," he said, "and
you, Tom, please bring me some fresh water in another glass."

              [Illustration: Egg floating in Salt Water.]

Uncle George placed the egg in the glass in which the salt had been put,
and it floated in it. He then placed the egg in the glass of fresh
water, and it at once sank to the bottom.

"Can you explain this!" he said.

"The salt water is heavier and thicker than the fresh water. That is why
it bears up the egg," said Frank.

"That is very good indeed, Frank. That is just the reason. The salt
water or brine is _denser_, or heavier, than the other."

Uncle George next took a glass tube with a thistle-shaped bulb at the
end of it. Frank kept his finger on the small end, while his uncle
poured some of the brine into the bulb. He next tied a piece of bladder
skin over the bulb, and placed it in a glass of fresh water, so that the
salt water in the tube was at the same level as the fresh water in the
glass.

Then he took two small glass bottles. He filled one with fresh water and
the other with brine, and tied a piece of bladder skin over the mouth of
each. The one which was filled with brine he placed in a larger dish of
fresh water. The other, that is the one filled with fresh water, he
placed in a dish of brine.

"Now, children, we will go and have tea," he said, "and when we come
back we will see if any change has taken place."

About an hour later Uncle George, Dolly, and the boys came back.

"Oh," said Frank, "look, Uncle George! The water has risen up in the
thistle tube."

"Yes, how do you account for that, Frank?"

"Some of the fresh water has passed through the skin," Frank answered.

"Now taste the water in the glass outside the skin," said Uncle George.
"It was fresh water when we put it in, wasn't it?"

Frank did so. Tom tasted it too. Both boys declared that it was now
salt.

"Where did the salt taste come from?" their uncle asked.

"It must have come through the skin," said Tom.

"Then some of the salt water in the thistle tube has passed through the
skin into the glass; and some of the fresh water in the glass has passed
through the skin into the thistle tube. Can you tell me any more?"

Frank thought for a little while and then said, "Oh yes, more fresh
water than salt water has passed through the skin, because the salt
water is now far up the tube."

"Quite right, my boy. Now let us look at the small bottles. The skin on
the one filled with brine is swollen out like a ball, while the water in
the dish tastes salt. The skin of the other is drawn far in, showing us
that much of the fresh water which it contained has passed out. If you
taste the water in this bottle, you will find that a very little of the
brine in the dish has passed into it through the skin.

"Now what we learn from these things is really this--that when two
liquids, a heavy and a light one, are separated by a thin skin, they
_both_ pass through the skin. The heavy liquid passes through slowly,
and the light liquid passes through quickly."

Uncle George then placed some small seeds on a piece of wet
blotting-paper. He turned a glass tumbler upside down, and placed it
over them.

"We will leave these for a few days," he said.


                        Questions and Exercises.

  1. Boil some river-water in a flat dish until all the water is gone.
          Do the same with some sea-water, or, if this is not at hand,
          make some brine. Examine the two dishes, and tell what you
          see.
  2. Take a glass gas chimney, and tie a piece of bladder, or parchment,
          over one end of it. Half fill it with sugar and water. Now
          place it with its tied-up end bottommost in a tumbler of clear
          cold water. After an hour or so taste the water in the
          tumbler. What have you to say about it?
  3. What takes place when brine and clear water are separated from one
          another by a piece of skin (parchment)?

                [Illustration: A Box of Mustard Seeds.]




              II.--HOW PLANTS TAKE FOOD FROM THE SOIL (2).


A whole week went by before Uncle George was ready for the next lesson.

At last he called the children and said to them--"Tom, will you please
fetch me the seeds which we put on the wet blotting-paper under the
tumbler? Frank, bring me two leafy branches from a rose-bush in the
garden; and, Dolly, please fetch two glasses from the kitchen."

Now there was nothing the children liked better than to help their Uncle
George, and all three rushed off at once to do his bidding.

While they were away Uncle George himself went into the garden, dug up
two young plants, and brought them to the children in the study.

               [Illustration: Sun-flower Plant in Water.]

"Now, children," said Uncle George, "we are ready to begin our lesson.
Fill one of the glasses with water, Frank, and put one of your leafy
rose branches in each glass--one branch in water and the other in a dry
glass. Can you tell me what will happen to the branches?"

The children had many times seen what had happened to flowers when the
maid had forgotten to put water in the vases, so that Tom readily said,
"Yes, the one in the dry glass will wither, while the one in the water
will keep fresh for some time."

"How do you know that?"

"Because it always happens, Uncle," said Frank. "Why, sometimes the
flowers we gather in the wood are faded before we get home. They often
come back to life when put in water."

"You are quite right, Frank," Uncle George replied. "See, here are two
young sun-flower plants, which I brought in from the garden. I placed
one in water. The other I left lying on the table. The one on the table
is dead. What does this show us?"

                 [Illustration: The Sun-flower, faded.]

"That plants require water," said Tom. "That whenever you cut off their
water supply they die."

"Quite right, Tom. We shall see by and by that plants are always giving
off a great deal of water to the air from their leaves.[1] Where do they
get this water from?"

"It must be from the soil," said Frank.

"It must be," said Uncle George. "If we keep a plant in a pot without
watering it, it soon dies. All the water it contains will by and by
travel up to the leaves. It passes out through tiny pores in the leaves
into the air. If no more water comes up from the soil, the plant withers
and dies. The roots of plants search the soil in all directions for
water. And in this water there is but little plant-food. We saw this
when we boiled away the clear water which covered the soil in the glass.

"If we boil away some water from the tap, we shall find some solid
matter left behind in the dish. Thus we see that in order to get a
_small_ quantity of food, plants take up a _great_ quantity of water
from the soil. Most of the water is sent into the air from the leaves.
But the food stuff remains in the plant, just as it did in the dish.

"Now I am going to show you how this water gets into the plant. Look at
these little seeds on the damp blotting-paper!

"Each seed has a small plant with a long root, and small, stout green
leaves. Look at the roots and tell me what you see?"

"They are covered with silky stuff," said Frank.

"Yes. Now take this glass, which will make things look bigger than they
really are, and look at the roots once more."

"The silky stuff is a number of fine hairs," said Frank.

                       [Illustration: THE OTTER]

                       [Illustration: FIELD-MICE]

"That is quite right, Frank," said Uncle George. "These are the
_root-hairs_. Each of these hairs is a long bag or sac, of very thin
skin. It is filled with a liquid called _sap_, which is slightly denser,
or heavier, than the water in the blotting-paper. Now, do you see how a
plant takes food from the soil, when it is growing in the garden or in a
field?"

"Yes, I think I do," said Frank. "The water in the soil contains very
little plant-food. The water inside the tiny sac contains very much."

"And what have you to say, Tom?"

"One of these liquids is denser than the other," said Tom. "Both are
separated by a thin skin. The lighter liquid outside the sac will pass
into it quickly, while the heavier liquid will pass out slowly."

"Bravo! Tom!" said Uncle George. "I couldn't have given a better reply
myself. The water from the soil passes in quickly. The sap from the
inside of each root-hair passes out slowly. If they were both of the
same density, neither would pass through the skin. If the water in the
soil were the denser, then the sap would pass out so quickly that the
plant would soon be robbed of its water.

"Here are two young plants, each growing in a small pot. I want you to
water them, Tom. Water one with salt and water (brine), the other with
tap-water."

Tom did as he was asked.

       [Illustration: Plants watered with Fresh and Salt Water.]

"See," said Uncle George, "the one which you watered with brine is
drooping. It is bending over the pot. That is because the water outside
its root-hairs is denser than that which is inside the plant."

"How does the water get up from the roots to the leaves?" Frank asked.

"Just in the same way as the oil travels up the wick of the lamp. Water
will always travel up through small spaces."

Uncle George poured some red ink into a saucer, and dipped the corner of
a lump of sugar into it. The red ink ran up into the sugar until it was
red all over. Next he took a bundle of very small glass tubes, and
dipped the ends of them in the ink. The ink ran up the tubes, filling
them to the top.

"Inside every plant," Uncle George went on, "there are thousands of long
tiny tubes, up which the water travels. In fact the _veins_ of a leaf
are just bundles of tubes, something like the bundle I hold in my hand."


                        Questions and Exercises.

  1. Why do branches wither quickly when cut from the tree? How would
          you keep them from withering quickly?
  2. Place two small panes of clean glass close together. Dip the corner
          of them in coloured water, and watch what happens.
  3. Why do we never see the silky _root-hairs_ when we dig or pull a
          plant out of the ground?




                    III.--THE WEASEL AND THE OTTER.


It was Frank who wanted to follow the stream far up towards the hills.
He wished to see where it began, for he had heard that its source was in
several small streams many miles away.

Uncle George agreed to take the children as far up the stream as they
could walk, without being tired. Soon they were far up above the wood,
and the fields, and the pond.

Frank was not in the least sorry when his uncle sat down on a large
stone by the side of the stream.

"We shall not go much farther," said Uncle George. "Some other day we
will. But tell me what you think of the country round about you."

"It is very wild and lonely," said Tom. "There are no fields of corn;
nothing but green hills and moorland. Yet it is very grand."

"The flowers and plants are not like those of the valley," said Tom.
"The stream, too, is different. Here it is a noisy, rushing course of
clear, lovely water. Down below it is a lazy-flowing stream."

"It is not always so clear," said Uncle George. "After heavy rains this
stream is swollen and brown."

"Look! look!" cried Dolly. "What is that on the other side of the
stream?"

Sure enough there was something moving about. Now it turned round and
opened its mouth, showing two rows of sharp, white teeth. Then, with a
harsh cry that could be heard above the noise of the water, it bolted
away.

There was just time for all to see the creature, which Tom at once
called a weasel.

"Yes, a weasel it is," said Uncle George; "it is one of the animals
which prey on rabbits and young hares. Look! there it is again."

The children looked, and saw it quite clearly. There it was, a pretty
little animal of a black and brown colour, with just a little white on
its breast. It sat up, and was holding something in its fore paws.

"Ah!" said Uncle George, "our little friend is a thief. He has found a
nest, and that is an egg he has stolen from it. Let us see what he will
do with it."

                  [Illustration: The Weasel at Home.]

In a moment or two Master Weasel tucked the egg under his chin and was
off once more.

"What a dear little thing, to be sure!" said Dolly. "How quaint to carry
an egg in that way!"

"It looks pretty, that is certain," said Uncle George, "but it is a
dreadful foe to the smaller animals of the field. There are other foes,
too, and I hope we may see some of them before we return."

The boys were glad to hear their uncle say this, and they asked him to
take them, now they were rested, a little farther up the stream.

All of them made a start.

By and by they came to a place where the stream made a kind of pool. The
pool was bounded on each side by high rocks. At the top end the water
came down with a rush from a great height.

It was a very lonely spot indeed; and, except for the noise of the
water, nothing could be heard.

On and on they went.

Uncle George told them of the stoat, the polecat, and the marten, all of
which, he said, were foes of the smaller animals.

Tom kept a sharp look out, and hoped he would see at least one of these.

As luck would have it, a dull splash was heard in the water a little way
in front of them. All of them looked towards the spot.

"Down, boys, down! and keep quite still," said Uncle George. "Hide
behind these big stones. We shall have a treat."

Swimming on the surface of the water was an animal as large as a
good-sized dog. Now it dived to the bottom. The ripples on the water
showed that the animal was swimming underneath. The children held their
breaths and watched. Not in vain; for there, on the other side of the
stream, the animal came out of the water. It held a fish which it had
caught.

"Now," said Uncle George, "we have a fine chance to look at our new
friend. That animal is the otter. See! Its body is pretty flat; its legs
are short, and its toes are webbed like those of the duck. Look at its
round nose and its small ears. If we were closer to it we should see
that there is a fold of skin which can be turned over the ears while the
creature is in the water."

"How fierce it looks!" broke in Dolly, "and how its eyes gleam!"

"It is glad to have caught the fish, I should think," said Frank.

Uncle George raised his hand to hold the children in silence. Then he
went on in a soft voice. "Look at its flat tail, which is pointed at the
tip. The otter uses his tail as a rudder to guide him in the water. See
how sleek his dark brown skin is. It is now nearly dry, though he has
only just come out of the stream."

"Let us drive him away," said Dolly, who could not help but feel sorry
for the poor fish.

There was no need for this, however, as, just at that moment, the otter
turned towards the party, showing, as he did so, a lovely white throat.
He had heard them speaking, and was off like a flash, leaving the fish
on the rock.

The fish had an ugly bite in its back, and was quite dead.

"Poor, dear little thing!" cried Dolly. "What a shame to kill you!"

"It is the otter's nature," said Uncle George. "He does a great deal of
good, for he kills many water-voles, or rats, as they are sometimes
called, as well as frogs and water insects. Sometimes, however, he does
harm, for he catches salmon, trout, and wild-ducks. He seems to do this
more for sport than for food, for he only eats small portions of his
prey."


                        Questions and Exercises.

  1. Write down the names of some animals you would expect to find if
          you walked along the bank of a stream.
  2. Describe the Otter and the Weasel. Tell in what way they are like
          and unlike.

           [Illustration: Common and Ox-eye Daisy compared.]




                    IV.--DWELLERS IN THE CORN FIELD.


As Uncle George walked by the edge of the corn field, Dolly and her two
brothers ran up to him. Dolly carried a bunch of huge daisies in her
hand.

"We want you to tell us about these, Uncle George," she said. "Tom says
that these are the little field daisies grown up; and Frank says they
are not."

"Frank is right," said Uncle George, laughing. "This is not the common
field daisy. It is the _ox-eye_ daisy. You might bring me a common
daisy, Frank. I am sure there are many growing near. Ah, here is one at
our feet! Now let us hold them side by side.

"You can see that they are unlike one another in many ways. The _ox-eye_
daisy has much larger leaves and flowers. It bears its leaves and
flowers on tall, strong stalks. The leaves of the common daisy lie
almost flat on the ground, and there is only one little flower-head on
each stalk. When we get home we shall look at them both more closely."

"Oh, look at those big yellow daisies growing among the corn," said
Dolly.

"And I see some blue flowers near them," said Tom.

"The yellow flower is the _moon-daisy_. It is also called the
_corn-marigold_. It is a great deal like the two daisies we have just
been talking about. The other is the blue _cornflower_. It belongs to
the same great family as the daisies. Frank will go and fetch us some."

Frank gathered a bunch of both flowers. He was just reaching over for
some large red poppies when he saw a pair of small black cunning eyes
peering at him. Then a brown creature ran past him and went out of sight
among the long grass at the edge of the field.

"A rat! a rat! Uncle George!" he shouted.

"Yes, it is a rat, I saw it," said his uncle.

"But what is he doing out in the fields?" said Frank. "I always thought
that rats lived in houses."

"The brown rat lives where he can," said Uncle George. "Very likely this
one has come from the farm. Farm-yard rats often come out and live among
the long grass and reeds in summer-time. When the cold weather comes,
and the crops are gathered, they go back to the stables and barns. There
they rob the farmer. They are very cunning creatures. They steal eggs,
milk, grain, and even kill and carry away young chickens. The rat lives
by thieving. That is why he is killed whenever he shows his face.

"Rats are sometimes useful, though. They swarm in ship docks and places
where stuff is left about. They eat up what would rot and poison the
air. They thus help to keep down disease.

"Now, boys, before we go home I am going to show you something. I found
it the other day when taking a walk."

Uncle George led the children to the end of the field, and pointed to a
strange object among the corn. It was a nest of some sort. It was made
of dried grass, and hung from five or six wheat stalks. It was round
like a cricket-ball, and just about as big.

"It is the nest of the harvest-mouse," said Uncle George in a low voice.
"Keep still, and perhaps we shall see Mistress Mousie."

The children waited a long time looking at the curious little object. At
last a tiny brown creature ran up one of the wheat stalks and went into
the nest. It seemed to go right through the wall of its little house.
There was no hole to be seen where it went in. Then Uncle George clapped
his hands. At once two wee brown mice came out.

They slid down the corn stalks and were out of sight in a moment.

"Ha! Mr and Mrs Mousie, we have disturbed you," said Uncle George. "We
will now go nearer and see your nest."

"I can't see where they came out," said Tom. "There is no hole to be
seen."

Uncle George pointed out to the children how the nest was woven together
and fixed to the wheat stalks. He then took a pencil from his pocket and
moved aside some of the dried grass. The children looked in and saw a
family of naked little mice cuddled up together. They could not tell how
many there were; but Uncle George said that there were eight or nine
young ones as a rule in a harvest-mouse's nest.

"What will become of these wee mice when the corn is ripe?" Tom asked.

"They will perhaps be grown up and able to take care of themselves by
that time, Tom," said Uncle George.

"The harvest-mouse stores up corn in its nest. Before winter comes it
makes a hole in the ground. Here it sleeps through most of the winter
and spring. It wakes up from time to time and feeds upon its store of
grains."

"It is much smaller and browner than our house-mouse," said Frank.

"Yes, Frank, it is our smallest four-footed animal. We have many kinds
of mice in this country. The brown rat is the largest and the
harvest-mouse is the smallest of our mouse family."

"How does it manage to slide down the wheat stalk so quickly without
falling off?" Tom asked.

"It can use its long tail as well as its feet for climbing," his uncle
answered.

"When it wishes to get to the ground it just coils its little tail round
the stalk and slides down."


                        Questions and Exercises.

  1. Name some flowers that grow among the corn in summer and in autumn.
  2. Describe the Rat.
  3. Do you know any other animals that have teeth like the rat?
  4. What other animals, besides the harvest-mouse, store up food for
          the winter?

                      [Illustration: HARVEST TIME]

                      [Illustration: THE SQUIRREL]




                           V.--HARVEST TIME.


"They are very busy here," said Uncle George, as he went into the field
with Frank, Tom, and Dolly.

And well might he say so, for the _whirr_ of the reaping-machine could
be heard far away. Round the field it went, sweeping down the golden
wheat. Following behind it were several girls, who twisted bands of
straw and laid them on the ground. Behind these came women who quickly
gathered up the cut wheat and placed it in bundles upon the bands. Then
came men who bound these bundles into sheaves and tossed them aside.
After these, again, came men who caught up the sheaves and placed them
upright in bunches of six or eight. These bunches of sheaves they called
"_stooks_." Last of all came a huge rake drawn by horses, gathering up
all the straws that were left. Every now and then the man that guided
the rake pressed an iron bar, and, whenever he did so, all the teeth of
the rake rose up at once, and left a row of gathered straw on the field.
Then a man came and bound them into rough sheaves as before.

All was work and bustle and noise. What with the whirr of the
reaping-machine, the girls singing as they worked, the larks singing in
the sky, and the glorious autumn sun, the children thought the
harvest-field was the most cheerful place they had ever seen.

"Why do you do that?" Frank asked a man who was fixing up the stooks.
"Would it not be just as well if you left the sheaves lying on the
ground until you cart them away?"

"Ah, no, Master Frank," said the man, who knew him well, "that would
never do. We must allow the corn time to get dry, so we place the
sheaves upright that the sun and wind may dry them; and so that any rain
that falls may run down the stalks to the ground. When the sheaves are
quite dry, we take them home to the stack-yard."

"How long does that take?" Frank asked.

"It all depends on the weather," the man replied. "If it keeps fine,
they will be dry within a week. In rainy weather, sometimes the sheaves
have to stand in the fields for some weeks. In the next field the crop
was cut a week ago. They are taking it home now."

                    [Illustration: The Stack-yard.]

"And you build the sheaves into great stacks there?" said Tom.

"Yes, it is kept in stacks until we are ready to thresh it. You must all
come over to the farm and see it being threshed into grain and straw
some day."

"But why do you build it into stacks?" asked Frank.

"So that we may keep it through the winter, and thresh a stack at a time
as we need it," the man replied. "It is threshed by passing it through a
mill. At our farm the mill is turned by horses. At some farms there are
mills turned by a great water-wheel. Sometimes a steam-engine comes and
threshes the whole crop in the fields."

"And what do you do with it when it is threshed?" Dolly asked.

"When the corn is passed through the mill, it is so shaken up that all
the grain is removed from the stalks. The grain comes out at one side of
the mill and falls into sacks. The straw is tossed out at another part.
We use the straw for bedding for horses and cows, and some kinds of
straw we use for feeding them. The grain goes to the miller, who grinds
it into flour. The flour goes to the baker, who bakes it into bread."

"Come along, boys!" Uncle George shouted from the next field. "We are
going over to the farmyard to see the stacks made."

In the next field the farmer's men were loading a waggon with sheaves of
corn. The sheaves were caught up by long pitch-forks and tossed on to
the waggon. Here a man put them into a great square load. When this was
done, the men lifted Dolly up, and she rode up to the farmyard on the
top of the great load of sheaves.

In the stack-yard a large round stack was being built. A wooden frame
was in the middle, and round this a man put the sheaves in a circle as
they were thrown to him from the waggon.

"Now, boys," said Uncle George, "Dolly wants to know why sheaves are
made with all the ears of corn at one end. Can you tell us?"

"Oh, that is easy," said Tom. "The sheaves have to stand in the field
for a long time to dry. They could not stand up so well if they were
made any other way. Besides, the ears of corn must be up from the
ground, or they would be broken off."

"There is another reason," said Uncle George. "Look how the stack is
being made. The top, or grain end of the sheaf is inside. The outside of
the stack is made up of the cut ends of the straws. Thus the grain is
kept secure from bad weather and thieving birds. Besides, the stack
could not be made round in shape if they were placed in any other way.
The bottom of the sheaf is much wider than the top."

In another part of the yard men were busy roofing the newly built stacks
with straw. The straw roof was tied down with many ropes, also made of
twisted straw, and then the stack was ready.

"What a lot of work there is in getting corn," said Frank.

"Ah, yes," said his uncle, "much more work than we have seen to-day.
Think of the work done in the fields in spring, getting the land ready
for seed--the work of ploughing, sowing, reaping, and threshing done by
the farmer's men and horses--the work done by the rain and sun in
growing and ripening the wheat--the work done by the miller and baker;
and all this, Frank, that we may have a loaf of bread."


                        Questions and Exercises.

  1. Tell the story of a wheat plant from the time it begins to grow
          from the seed until it is ready to be cut.
  2. Where does the making of a loaf of bread really begin? From what
          you have learnt in the lesson, trace the history of a loaf of
          bread.
  3. Make a list of crops grown on the farm, and tell the use of each.




                           VI.--THE SQUIRREL.


"Halloa! there he goes again," said Frank, as he watched a nimble little
animal leaping from branch to branch, and from tree-top to tree-top. "He
will fall if he does not take care."

"No fear of that," said Uncle George. "His home is among the tree-tops.
He never falls. That is a squirrel, and I should not be surprised if his
nest is somewhere near. Let us sit down on this bank and watch."

As he spoke, Uncle George took his pair of field-glasses out of the
leather case which he sometimes carried on a strap across his shoulder,
when he went out to watch the birds.

"Now, Mr Squirrel," he said, "we can watch your antics from a distance.
You are a very cunning and clever little chap, no doubt."

When Uncle George and Dolly and the two boys first saw the squirrel, the
little creature was on the ground, bobbing about among the ferns and the
grass. The moment it saw them, however, it bounded into a tree, going
swiftly up by jerk after jerk, and always keeping on the far side of the
trunk.

They could just see its bushy tail, first at one side of the trunk and
then, much higher up, at the other side. When it reached the top part of
the tree, it leapt from branch to branch in the most daring manner.

"We have alarmed the creature," said Uncle George. "But if we sit here
quite still for a little while, Mr Squirrel will get over his fright.
Ah, there he is."

Uncle George handed the glasses to Frank.

"Now, tell us what you see," he said, "and then Tom and Dolly shall each
take a look."

"He is sitting up on his hind legs," said Frank. "His great, bushy tail
is bent right over his head. He is holding a little green thing in his
fore-paws. Ah, he is eating it. Look Dolly!" and Frank handed the
glasses to his little sister.

"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?" asked his 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 whole winter 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 the pretty 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 white with snow. So, you see, the little animal is of some use
after all."


                        Questions and Exercises.

  1. The squirrel has chisel-shaped teeth suited for gnawing. Name other
          animals of the same kind.
  2. The squirrel's bushy tail is of great use to him. Why?
  3. Make a list of our wild animals (1) which sleep through the winter,
          and (2) which store up food for winter.




                       VII.--HOW THE FIRE BURNS.


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.

                      [Illustration: A Baby Cloud]

                      [Illustration: 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.

              [Illustration: 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 is _very_ good," 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 glass bell-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.

           [Illustration: 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 has _changed_ this 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.

           [Illustration: 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 or fan, 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 and asked 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 of the iron tacks to form that red powder
which we call _rust_."


                        Questions and Exercises.

  1. How is rust formed?
  2. Explain why things which are made of iron should be painted.
  3. A grate full of coals burns away and only a small quantity of ash
          is left in the grate. What has become of the coals?




                        VIII.--THE FIRE-BALLOON.


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.

                   [Illustration: 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.

                [Illustration: 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 the door 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 letter T, 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.

               [Illustration: 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 go down 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."


                        Questions and Exercises.

  1. Take an empty bottle and heat it gently. Now turn it upside down,
          and place the neck of it in cold water. Why does the water
          rise in the bottle?
  2. How is a _draught_ caused?
  3. Why does a fire burn more brightly on a cold, frosty day, than on a
          warm summer's day?




                             IX.--THE GULL.


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 several kinds of gulls. Here we have just
two kinds. The _common gull_ and the _tern_. 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?"

                      [Illustration: Gull flying.]

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

"That is so," said Uncle George. "The tern 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 a piece 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.

                     [Illustration: 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.

                   [Illustration: 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."

               [Illustration: 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. His legs 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--the _black-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 bold and active. The wild ocean is
their home. Storms bring no fears for them."


                        Exercises and Questions.

  1. Tell the life-story of the common gull.
  2. Make a list of all the sea birds you know.
  3. The common gull has very large wings, curious beak and feet. Can
          you explain what these are for?

             [Illustration: Engine puffing on a cold day.]




                         X.--DEW, FROST, RAIN.


"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 and the puff of
steam is not always of the same size."

              [Illustration: 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 call
_steam_ is 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 made up 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 come _through_
the 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 the glass 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 have _frost_."

"Oh, that is why we have frost on the _inside_ of 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 call _clouds_. 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 as _rain_."

                     [Illustration: A Showery Day.]


                        Questions and Exercises.

  1. If you place a saucer full of water outside on a hot day in the
          morning, and go back to it in the evening, you will find the
          saucer dry. Where has the water gone?
  2. Fill a tin can with a mixture of salt and snow (or chopped ice).
          Place it in a warm room. _Frost_ comes on the outside of the
          tin. Place a glass jug of water in the same room. _Dew_ is
          formed on the outside of the jug. Can you explain this?
  3. Let the steam puff of the kettle strike against a cold sheet of
          glass or metal, or a slab of stone. What is formed?




                               Footnotes


[1]See Lesson I., Book IV.

[2]See lesson "The Fire-Balloon."


        PRINTED IN GREAT BRITAIN AT THE PRESS OF THE PUBLISHERS.




                          Transcriber's Notes


--Retained publication information from the printed exemplar (this eBook
  is in the public domain in the country of publication.)

--Only in the text versions, delimited italicized text with
  _underscores_.

--Silently corrected several typos.