Rollo's Philosophy Part 19

"Why, in the first place," said Rollo's father, "all the streams in the world would stop running."

"The streams!" said Rollo, astonished.

"Yes," said his father, "every river, brook, and rill. The reason why the streams flow is, that the earth attracts the water from the mountains and hills, down into the valleys and towards the sea."

"Well, sir, what else?" said Rollo.

"Why, there would never be any more rain."

"No more rain!" exclaimed all the children.

"No," he replied. "The drops of rain fall only because the earth draws them down by its attraction; and, of course, if this attraction should cease, they would remain where they are."

The children were musing a minute upon these strange effects, when Rollo asked if anything else would happen.

"Why, yes," said his father, "worse disasters than these; but I do not know whether you would understand them, if I should explain them."

"O, try," said Rollo; "I think we shall understand."

"Well, let me think," said his father. "You have noticed how a chaise wheel, on a muddy road, in a wet day, holds the mud upon it, until when it is going very swiftly down a hill, and then the mud flies off in all directions."

"Yes, sir," said all the children.

"And if the mud did not stick to the wheel pretty tight, it would be thrown off at all times, even when the wheel was going slow. You understand this."

"Yes, sir."

"Well, now, this whole earth, you all know, is whirling around through s.p.a.ce, and moving on also around the sun. And all the loose things upon the surface would be thrown off at once, if they were not held to it by a strong attraction. If this attraction were to cease suddenly,--whisk!--away we should all go in an instant--rocks, houses, men, animals, all in confusion."

"O father!" exclaimed Rollo; "where should we go to,--off into the air?"

"Not exactly into the air, for the air would all fly off, and be dissipated too; we should fly off into the sky somewhere, some in one direction, and some in another. You'd be a thousand miles off from the earth, almost before you would know it."

"Would it kill us, father?" said Nathan.

"Yes," said his father. "I don't know that there would be any shock that would hurt us, but we should have no air to breathe, and it would be dark and dismal."

"Dark?" said Rollo. "There would be the sun."

"Yes," said his father, "there would be the sun; and the sun would look bright enough when you looked directly towards it, but there would be no general light about you, unless there was air."

The children all paused to reflect upon the strange results which their father had told them would ensue from a suspension of the earth's attractive force. Rollo began to think that he had been too hasty in his wish that there was no gravitation.

"But, father," said he, "the houses would not go off, certainly;--only the loose things would go."

"Very well; houses are loose."

"O father! they are fastened down."

"How are they fastened down?" asked his father.

"O, they are nailed--and,"

"Not nailed to the ground, certainly," said his father.

"No," said Rollo, laughing; "but then they are built with great stones and mortar."

"Yes, but there is no mortar under the lowest stones. The foundations are simply laid upon the ground."

"Well," rejoined Rollo, "I thought they were fastened somehow or other."

"No," said his father; "they dig the cellar, and only just lay the foundations upon the ground, without any fastening. The earth holds them in place."

"Well, father," said Rollo, "that is what I meant, when I said we could not stand up straight. I meant the houses. I read in a book that houses would be blown away, if the gravitation did not hold them down."

Here Rollo's father had a hearty laugh; and he told Rollo that he thought that was rather wide shooting. Rollo wanted to know what he was laughing at; and Nathan asked him what he meant by wide shooting.

"Why," said he, "Rollo, you undertook to explain to us, from your stores of knowledge, what the effects of a suspension of gravitation would be; and, in attempting to tell that houses would be in danger of being blown away, you came no nearer than to tell us that boys could not stand up straight; and that is what I call pretty wide shooting."

So saying, he rose from his seat, and walked away, appearing to be very much amused. James laughed too, and even Rollo could not help smiling at the ridiculous figure which his display of his learning made. As for Nathan, he continued to look grave; and said he did not see that it was any shooting at all.

After a short pause, Rollo's mother said, "So you see, children, the cause of all the pressure, both of air and of water, and all the effects produced by them, are the results of their gravitation towards the earth."

"Yes," said Rollo, "I believe I understand it now."

After this, Rollo took James and Nathan out into the yard, to see if some beans had come up, which he had been planting in a sunny corner of the garden the day before.

QUESTIONS.

What was Mr. Holiday's apostrophe to the earth? What is the cause of weight? Why did the boys wish that there was no gravitation? What was the first evil consequence which their father said would ensue, if there was no gravitation? What was the second evil consequence? What did their mother say after the conversation with their father was closed?

CHAPTER XI.

AIR IN MOTION.

Rollo's dam, which he had made when he was studying the philosophy of water, and which was at first undermined by the pressure of the water, was afterwards carried away by its momentum. Rollo learned, at that time, that water moving rapidly had a great momentum; and about this time he had an opportunity of learning that air, when in motion, had a momentum too, capable of producing very powerful effects. The circ.u.mstances of the case were as follows:--

One morning, towards the latter part of March, Jonas, being out in the barn, observed some indications that the roof wanted repairs. It had been strained and weakened by the heavy snows in the winter. He reported the fact to Rollo's father, who said that he might go, the next day, and get the carpenter to come and repair it. The carpenter lived ten miles distant, near the sh.o.r.e of a long pond.

When Rollo heard of this proposed expedition, he wanted to go too; and his father gave him permission. Jonas was going in the wagon. He told Rollo, the evening before, that he meant to set out at six o'clock.

"But suppose it looks like a storm," said Rollo.

"Then there will be more need of going," said Jonas; "for if the equinoctial storm comes on before the roof is strengthened, it may get carried away."