"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?
CHAPTER IX.
BURNING.
After the snow had all gone off, and the ground was dry, Jonas piled up a heap of stumps, roots, and decayed logs, in a field, not far from the brook, and one sunny afternoon he and Rollo went down to set the heaps on fire.
Jonas set one on fire, and then he told Rollo that he might set another on fire. After this, Jonas employed himself in gathering up sticks, bushes, roots, and other such things that lay scattered about the field, and putting them upon the fires, while Rollo amused himself in any way he pleased.
After a time, Rollo found, on the margin of the field, near the edge of a wood, an old stump, taller than he was, much decayed. There was a hole in the top. Rollo climbed up so that he could put a stick in, and run it down, to see how far down the hole extended. He found that it extended down very near to the bottom.
Then Rollo called out to Jonas, with a loud voice, saying,--
"Jonas, I have found a hollow stump here. It is hollow away down to the bottom. May I build a fire in it?"
"Yes," said Jonas, "if you can."
Rollo accordingly went to the nearest fire, and got a quant.i.ty of birch bark, which he had collected there to aid him in kindling his fires. He lighted one piece, and put it upon the end of a stick, and carried it to the stump, with the rest of the birch bark in the other hand.
Rollo then spent some time in fruitless attempts to make some lighted birch bark go down into the stump, and burn there. He succeeded very well in getting pieces completely on fire; but, after they were dropped into the hole, they would not burn. Rollo could not think what the reason could be.
At last he called Jonas to come and help him set the stump on fire.
Jonas said that he did not think that it could be set on fire.
[Ill.u.s.tration: ""Jonas, I have found a hollow stump here," said Rollo, calling with a loud voice."--Page 122.]
"Why not?" said Rollo.
"Because," said Jonas, "it is so wet."
"Yes, but, Jonas," replied Rollo, "your brush heaps burn, and why should not this stump?"
"Because," said Jonas, "the stump is more solid, and the water soaks into it more in the winter and early in the spring; and it takes it much longer to dry, than it does brush and small roots, which lie open and exposed to the air."
"Well, then," replied Rollo, "why does not my birch bark burn? that is dry; but as soon as I drop it down into the stump, it goes out."
Jonas looked into the stump, and down around the bottom of it, and said,--
"Because there is no air."