"Because, if there were any, they would immediately rise from the earth, and float upwards, till they got up where the air was so light and thin, that they could not go up any higher."
"And so," said Rollo, "we should lose them."
"That would not be all," said his father. "They would float about, above us, and, if there were enough of them, they would form a perpetual cloud over our heads, to keep out the sun, and to make the world dark and gloomy. There seems to have been no way to keep all the solid and visible substances of the earth down upon its surface, but to make them all heavier than the air.
"And thus," continued his father, "all solid substances being heavier than the air, they sink in it, like stones or iron in water. Only those that are very much expanded in surface, sink very slowly, and sometimes almost seem to float."
"What do you mean by expanded, father?" said Nathan.
"Spread out," said his father. "An umbrella, for example, when it is spread out, is said to be expanded; other things are expanded in a little different way. A feather is expanded, that is, it is spread out in fine filaments, which extend, in every direction, into the air, all around the stem of it. Things that are expanded take a great deal of air with them when they descend, and so can only descend slowly."
"And water is expanded in a soap bubble," said Rollo.
"Yes," replied his father, "and there is a great deal of air included in it, which all has to be brought down when the bubble itself descends. And thus, you see, the bubble must descend slowly. Water is expanded, too, in clouds; for, in that case, it is divided into millions of small particles, by which it is spread out over a great deal of air, and cannot descend without bringing a large portion of the air with it. Men have contrived, on this principle, to make an apparatus to prevent being hurt by falling from great heights."
"What is it?" said Rollo.
"Why, it is called a parachute. It is a sort of umbrella; in fact, it is an umbrella, only made very large. It is folded up, and fastened under a balloon, just over the car, which the man is in. Then, if the balloon bursts, or any other accident happens to it, and the man begins to fall, the parachute opens and spreads, and then the man falls very slowly. The reason is, that the parachute takes hold of a large mass of air, and brings it down with it; and so it cannot descend very fast."
* * * * *
A few days after this, Nathan said to Rollo, as they were playing in the yard, that he wished that he had a parachute.
"I know where there is one," said Rollo.
"A parachute," said Nathan; "a real parachute?"
"Yes," said Rollo, "or, what is the same thing, a great umbrella."
"Is that just the same?" said Nathan.
"Yes," said Rollo; "for father said that a parachute was in fact only a large umbrella; and father has got a large umbrella in the closet, and I have a great mind to go and get it for a parachute."
"But you haven't got any balloon," said Nathan.
"O, no matter for that," said Rollo.
"Then how are you going to get up into the air?" asked Nathan.
"Why, I can climb up on the shed, and jump off that, and hold the umbrella over my head."
Just at this moment, Rollo's cousin James came into the yard, and Rollo ran to him, to explain to him about the parachute. After describing to him the construction of it, and its use by men who go up in balloons, he said he was going to get his father's umbrella, which would make an excellent parachute.
"And then," continued he, "I am going to get upon some high place, and jump off, and hold the parachute over my head, and then I shall come down as light as a feather."
"O Rollo," said James, "I don't believe you will."
"Yes I shall," said Rollo: "you see the parachute is expanded, and so brings down a great deal of air with it, and this makes it come very slowly. Air is a real thing, James, and it keeps the parachute back a great deal."
[Illustration: "James and Nathan both ran towards him, thinking that he must be hurt."-Page 37.]
So Rollo ran off after the umbrella, very much interested in proving to James, by actual experiment, that the air was a real thing. When he came with it, he was himself inclined to make the first experiment from the low side of the shed. He could climb up, by means of a fence at the corner. James advised him, however, to try it first from the end of a woodpile, which was pretty high, but yet not so high as the shed. James was not quite sure that the experiment would succeed, and he was afraid that Rollo might get hurt.
Rollo said that he was not afraid to jump off the shed. He knew the parachute would bear him up. He did not believe but that he could jump off the house with it; and, at any rate, he could jump off the shed, he knew. He accordingly clambered up, and, taking his station upon the eaves, he spread the umbrella over his head, and then jumped off.
Down he came with great violence; his cap flew off in one direction, and his umbrella rolled away in another, as he had to put out both his hands, to save himself, when he reached the ground. As it was, he came down upon all fours, and in such a way, that James and Nathan both ran towards him, thinking that he must be hurt.
"Did you hurt yourself, Rollo?" said James.
"No," said Rollo, "not much."
"I don't think the umbrella did you much good."
"No," said Rollo, as he got up rubbing his elbows, "it didn't, and I don't see what the reason is."
"You came down just as hard as you would without it."
"Yes," said Nathan, "and he almost broke his back; I don't believe the air is any real thing at all."
The fact was, that the umbrella did do some good. Rollo did not come down quite so hard as he would have done without it. It retarded his descent a little. But it was not large enough to enable him to descend in safety. When his father said that a parachute was in fact only a large umbrella, he meant a great deal larger than Rollo had supposed. A parachute, such as is used with balloons, is a great deal larger than any umbrella that ever was made.
QUESTIONS.
What was Nathan's wish, after he had read his father something
out of his book? Did he think that he could fly if he had
wings? Did his father think so? What deficiency did his father
think was even more important than that of wings? Did Nathan
think that a boy was stronger than a bird? Is a boy absolutely
stronger than a bird? Is he relatively stronger? What is the
meaning of relatively stronger? Would a man be strong enough
to work wings that were sufficiently large to bear him up into
the air? Would there be any great difficulty in constructing
wings for him if he were strong enough?
Is any visible substance lighter than air? What would be the
consequence if any of the loose substances about the earth's
surface were light enough? What are clouds composed of? What
difficulty did Rollo's father point out, in regard to their
floating in the air? What is a parachute? Describe Rollo's
experiment with the umbrella.
CHAPTER III. VALVE MAKING.
One morning, when Rollo awaked, he heard a sharp clicking against the window.
"Nathan," said he, "Nathan, I believe there is a snow-storm."
But Nathan was too sleepy to hear or understand.
Rollo looked up, but there was a curtain against the window, and he could not see very well. He listened. He heard a low, moaning sound made by the wind, and a continuance of the sharp clicking which he had heard at first.
When he had got up, and dressed himself, he found that there was a violent snow-storm. At first he was glad of it, for he liked snow-storms. But then, pretty soon, he was sorry, for it had been winter a long time, and he was impatient for the spring.
After breakfast, he and Nathan read and studied for two hours, under their mother's direction. When they were released from these duties, Rollo proposed to Nathan that they should go out into the shed, and see how the storm came on. There was a large door in the shed, opening towards the street, where they could stand, protected from the wind, and see the drifts of snow.