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."