bottom
of the window; so that Rollo could easily get upon it to descend. The
wind and storm, which raged with great violence, were somewhat
terrifying; but he knew that the ladder was secure, the upper part being
confined in the window; and so he resolutely descended. When he had
fairly reached the ground, he looked up, with an expression of great
satisfaction upon his countenance, and said,--

"There! now, Nathan, for your turn."

But Nathan was afraid to venture; and Rollo himself was half afraid to
have him make the attempt. While they were standing in this perplexity,
Rollo heard a voice behind him, calling out,--

"Rollo."

Rollo turned, and saw Dorothy standing by the door.

"What are you doing, Rollo?" said Dorothy.

"I am trying to get Nathan out of the barn," said Rollo.

"How came he in the barn?" said Dorothy.

"Why, Jonas locked us in, and I had to come down the ladder; but Nathan
is afraid, and I can't get him out."

"Why don't you go to the door, and let him right out?"

"O," said Rollo, laughing, "I never thought of that. Go down, Nathan,"
he continued, "to the door, and I will go round and knock out the fid."

So Nathan went down, and Rollo, meeting him there, knocked out the fid,
and released him from his imprisonment.

QUESTIONS.

What was the first experiment with the bellows, described in
this chapter? Why could not Nathan press the two sides of the
bellows together, while the nose was stopped? What was the
second experiment? What was the effect produced by turning the
bellows bottom upwards, as in the third experiment? What was the
fourth experiment? What was the use of the smoke of the paper?
How were the experiments interrupted? What evidence did Rollo
and Nathan have that the air was a real substance, when in the
barn chamber?

CHAPTER V.

PRESSURE.

One evening, just after tea, Rollo came to his father, who was sitting
by the side of the fire, and said,--

"Father, I wish we could see the air, as we can the water, and then
perhaps we could try experiments with it."

"O, we can try experiments with the air as it is," said his father.

"Can we?" said Rollo; "I don't see how."

"We cannot see the air, it is true; but then we can see its effects, and
so we can experiment upon it."

"Well, at any rate," said Rollo, "we can't build a dam, and make it
spout through a hole, like water."

"No," said his father, "not exactly.