TASKS.
A few days after this, there commenced a long storm of rain. Rollo and
Nathan were glad to see it on one account, for their mother told them it
would melt away the snow, and bring on the spring. The first day, they
amused themselves pretty well, during their play hours, in the shed and
in the garret; but on the second day, they began to be tired. Nathan
came two or three times to his mother, to ask her what he should do; and
Rollo himself, though, being older, his resources might naturally be
expected to be greater, seemed to be out of employment.
At last, their mother proposed that they should come and sit down by
her, and she would tell them something more about the air. "How should
you like that, Rollo?" said she.
"Why, pretty well," said Rollo; but he spoke in an indifferent and
hesitating manner, which showed that he did not feel much interest in
his mother's proposal.
"_I_ can't understand very well about the air," said Nathan.
Their mother, finding that the boys did not wish much to hear any
conversation about the air, said nothing more about it just then, and
Rollo and Nathan got some books, and began to read; but somehow or
other, they did not find the books very interesting, and Rollo, after
reading a little while, put down his book, and went to the window,
saying that he wished it would stop raining. Nathan followed him, and
they both looked out of the window with a weary and disconsolate air.
Their mother looked at them, and then said to herself, "They have not
energy and decision enough to set themselves about something useful, and
in fact I ought not to expect that they should have. I must supply the
want, by my energy and decision."
Then she said aloud to Rollo and Nathan,--
"I want you, boys, to go up into the garret, and under the sky-light you
will see a large box. Open this box, and you will find it filled with
feathers. Select from these feathers three or four which are the most
downy and soft about the stem, and bring them down to me."
"What are they for?" said Rollo.
"I will tell you," replied his mother, "when you have brought them to
me."
So Rollo and Nathan went up into the garret, and brought the feathers.
They carried them to their mother. She said that they would answer very
well, and she laid them gently down upon the table.
Then she took up her scissors, and began to cut off some of the lightest
down, saying, at the same time,--
"Now, children, I am going to give you some writing to do, about _the
air_."
"Writing?" said Rollo.
"Yes," said his mother. "I am going to explain to you something about
the air, and then you must write down what I tell you."
"But I can't write," said Nathan.
"No," said his mother, "but you can tell Rollo what you would wish to
say, and he will write it for you."
"Why, mother," said Rollo, "I don't think that that will be very good
play."
"No," replied his mother, "I don't give it to you for play. It will be
quite hard work. I hope you will take hold of it energetically, and do
it well.
"First," said she, "I am going to perform some experiments for you,
before I tell you what I want you to write."
By this time, she had cut off the downy part of several feathers, and
had laid them together in a little heap. Then she took a fine thread,
and tied this little tuft of down to the end of it. Then she took up the
thread by the other end, and handed it to Rollo.
"There, Rollo," said she. "Now, do you remember what your father told
you, the other day, about the effect of heat upon air?"
"It makes it light," said Rollo.
"And why does it make it light?" asked his mother.
"Why, I don't exactly recollect," said Rollo.
"Because it swells it; it makes it expand; so that the same quantity of
air spreads over a greater space; and this makes it lighter, But cool
or cold air is heavier, because it is more condensed.
"Now, wherever there is heat," continued his mother, "the air is made
lighter, and the cool and heavy air around presses in under it, and
buoys it up. This produces currents of air. You recollect, don't you,
that your father explained all this to you the other day?"
"Yes," said Rollo, "I remember it."
"Well," said his mother, "now you and Nathan may take this little tuft,
and carry it about to various places, and hold it up by its thread, and
it will show you the way the air is moving; and then you may come to me,
and I will explain to you why it moves that way."
"Well," said Rollo, "come, Nathan, let us go. First we will hold it at
the key-hole of the door."
Rollo held the end of the thread up opposite to the door, in such a way,
that the tuft was exactly before the key-hole. The tuft was at once
blown out into the room.
"O, see, Nathan, how it blows out. The air is coming in through the
key-hole."
"Yes," said his mother; "when there is a fire in the room, and none in
the entry, then the cold air in the entry runs down through the
key-hole into the room."
"It don't run down, mother," said Rollo; "it blows right in straight."
"Perhaps I ought to have said it spouts in," said his mother, "just as
the water did from the hole in your dam. And, now," she continued, "come
and hold the tuft near the chimney."
Rollo did so; and he found that it was carried in, proving, as their
father had showed them before, that the heavy, cold air, pressing into
the room, crowded the warm, light air up the chimney.
"Now, should you think," said their mother, "that the cold air could
come in through the key-hole, as fast as it goes up the chimney?"
Both Rollo and Nathan thought that it could not.
"Then go all around the room," said she, "and see if you can find any
other place, where it comes in. For it is plain, you see, that the light
air cannot be driven up chimney any faster than cold and heavy air comes
in to drive it up and take its place."
So Rollo and Nathan went around the room, holding their tuft at all the
places they could find, where they supposed there could be openings for
the cold air to press in. They found currents coming in around the
windows, and by the hinges of the doors; and at length Rollo said, he
meant to open the window a little way, and see if the cold air from out
of doors would not press in there too. He did so, and the tuft was blown
in very far, showing that the cold air from out of doors pressed in very
strongly.
"Now, if all these openings were to be stopped," said their mother,
"then no cold air could crowd into the room; and of course the hot air
could not be buoyed up into the chimney, and a great deal of the hot air
and smoke would come into the room. This very often happens when houses
are first built, and the rooms are very tight.
"But now, Rollo," she continued, "suppose that the door was opened wide;
then should not you think that _more_ cold and heavy air would press in,
than could go up the chimney?"
"Yes, mother, a great deal more," said Rollo.
"Try it," said his mother.
So Rollo opened the door, and held his tuft in the passage-way; and he
found that the air was pressing in very strongly through the open space.
Wherever he held it, it was blown into the room a great deal, showing
that the heavy air pressed in, in a torrent.
"Now, as much warm air must go out," said she, "as there is cold air
coming in; but I don't believe that you and Rollo can find out where it
goes out."
Rollo looked all around the room, but he could not see any opening,
except the chimney and the door, and the little crevices, which he had
observed about the finishing of the room. He said he could not find any
place.
His mother then told him to hold his tuft down near the bottom of the
door-way. He did so, and found that the current of air was there very
strong. The tuft swung into the room very far.
"Now hold it up a little higher," said his mother.
Rollo obeyed, and he found that it was still pressed in, but not so
hard.
"Higher," said his mother.
Rollo raised it as high as he could reach. The thread was of such a
length, that the tuft hung about opposite to his shoulder. The tuft was
still pressed in, but not nearly as far as before.
"So you see," said his mother, "that the air pours in the fastest at the
lowest point, where the weight and pressure of the air above it are the
greatest; just as, in your dam, the water from the lowest holes spouted
out the farthest."
"Yes," said Rollo, "it is very much like that."
"Now," continued his mother, "you see that a great deal of air comes in,
and if you look up chimney, you will see that there is scarcely room for
so much to go up there;--and yet just as much must go out as comes in.
"Get the step-ladder," said his mother, "and stand up upon it, and so
hold your tuft in the upper part of the door-way."
There was in the china closet a small piece of furniture, very
convenient about a house, called a step-ladder. It consisted of two
wooden steps, and was made and kept there to stand upon, in order to
reach the high shelves. Rollo brought out the step-ladder, and placed it
in the door-way, and then ascended it. From the top he could reach
nearly to the top of the door; but then, as his tuft was at the end of
the thread, it hung down, of course, some little distance below his
head.
"Why, mother," said Rollo, "it goes _out_."
"Yes," repeated Nathan, "it goes out."
In fact, Rollo found that the tuft, instead of swinging into the room,
was carried out towards the entry.
"You have found out, then," said his mother, "where the hot air of the
room goes to, to make room for the cold air, that comes in from the
entry."
"Yes, out into the entry," said Rollo.
"Through the upper part of the door," said his mother. "Suppose the
entry were full of water, and the parlor full of air, and the door was
shut, and the door and the walls were water-tight. Now, if you were to
open the door, you see that the water, being heavier, would flow in,
through the lower part of the door-way, into the parlor, and the air
from the parlor would flow out, through the upper part of the door-way,
into the entry. The water would settle down in the entry, until it was
level in both rooms, and then the lower parts of both rooms would be
filled with water, and the upper parts with air."
"Yes, mother," said Rollo.
"And it is just so with warm and cold air. If the parlor is filled with
warm air, made so by the fire, and the entry with cold air, and you open
the door, then the cold air, being heavier, will sink down, and spread
over the floor of both rooms; and the warm air, being light, will spread
around over the upper parts of both rooms; and this will make a current
of air, in at the bottom of the door-way, and out at the top.
"Now," continued his mother, "let me recapitulate what I have taught
you."
"What do you mean by _recapitulating_ it?" said Nathan.
"Why, tell you the substance of it, so that you can write it down
easier."
"O, I can write it now," said Rollo; "I remember it all."
"Can you remember it, Nathan?" said his mother.
"Perhaps I can remember some of it," said Nathan.
So Rollo and Nathan went out into another room, where Rollo kept his
desk, and they remained there half an hour. When they returned, they
brought their mother two papers.
Their mother opened the largest paper, and read as follows:--
"We took a tuft of down, tied to a thread, and held it in the
cracks and places that the air came in at, to see which way it
went. We held it at the window, and it blew _in_ very strong. At
the bottom of the door, it blew _in_ very strong too; but at the
top, it blew _out_, into the entry. So, when the entry is full
of cold air, and this room full of warm, the cold air will press
in and drive out some of the warm air, into the entry.
ROLLO."
The other paper was also in Rollo's handwriting, and was as follows:--
"If the entry was full of water, and the parlor full of air, and
the walls were water-tight, and you were to open the door
between the two rooms, the water would flow into the parlor down
below, and the air would flow into the entry up above. We tried
it with a tuft.
NATHAN."
QUESTIONS.
Why were Rollo and Nathan at first glad to see the rain? What
did their mother say to herself on the second day, when she
observed their weary and listless appearance? What did she at
first direct them to do? How did she prepare the downy tuft?
What experiments did they perform with it? Where did they find
that the air came in which crowded the warm air up the chimney?
What experiments did they perform when the door was opened?
Which way did they find that the current of air was setting at
the lower part of the door-way? Which way did the current set at
the upper part of the door-way? What did Rollo write in his
exercise? What was written in Nathan's exercise?