Читать книгу Rollo's Experiments - Abbott Jacob - Страница 1

One day, when Rollo was about seven years old, he was sitting upon the steps of the door, and he heard a noise in the street, as of some sort of carriage approaching. A moment afterwards, a carryall came in sight. It drove up to the front gate, and stopped. Rollo’s father and mother and his little brother Nathan got out. His father fastened the horse to the post, and came in.

When Rollo first heard the noise of the carryall, he was sitting still upon the steps of the door, thinking. He was thinking of something that Jonas, his father’s hired boy, had told him about the sun’s shining in at the barn door. There was a very large double door to Rollo’s father’s barn, and as this door opened towards the south, the sun used to shine in very warm, upon the barn floor, in the middle of the day.

Rollo and Jonas had been sitting there husking some corn,—for it was in the fall of the year;—and as it was rather a cool autumnal day, Rollo said it was lucky that the sun shone in, for it kept them warm.

“Yes,” said Jonas; “and what is remarkable, it always shines in farther in the winter than it does in the summer.”

“Does it?” said Rollo.

“Yes,” said Jonas.

“And what is the reason?” asked Rollo.

“I don’t know,” said Jonas, “unless it is because we want it in the barn more in the winter than we do in the summer.”

“Ho!” said Rollo; “I don’t believe that is the reason.”

“Why not?” said Jonas.

“O, I don’t believe the sun moves about in the heavens, to different places, only just to shine into barn doors.”

“Why, it keeps a great many farmers’ boys more comfortable,” said Jonas.

“Is it so in all barns?” asked Rollo.

“I suppose so,” said Jonas.

After some further conversation on the subject, the boys determined to watch the reflection of the sun’s beams upon the barn floor for a good many days, and to mark the place that it came in to, at noon every day, with a piece of chalk. It was only a few minutes before the carryall came up, that they had determined upon this, and had marked the place for that day; and then Rollo had come out of the barn, and was sitting upon the door step, thinking of the subject, when his reflections were interrupted in the manner already described.

So, when Rollo saw his father getting out of the carryall, he ran to meet him, and called out to him, talking very loud and rapidly,

“Father, Jonas says that the sun shines farther in, upon the barn floor, in winter than in summer;—does it, do you think?”

But this was not a proper time for Rollo to bring up his philosophical question. His father had a carpet bag and several packages in his hands, and he was also conducting Rollo’s mother in, and thinking about the horse and carryall. So he told Rollo that he must not speak to him then, for he could not attend to him.

Rollo then walked along back into the yard, and began to think of the subject of the sun’s shining in at the south door. He looked up towards the sun, and began to consider what sort of a change in its place, at noon, on different days, would be necessary in order to account for its shining in more at south doors and windows, on some days, than on others. He reflected that if the sun were exactly overhead, at noon, it could not shine in at any doors at all; for the rays would then strike perpendicularly down the sides of the houses. While he was standing thus, lost in thought, looking up to the sun, with his arm across his forehead, to shelter his eyes a little from the dazzling rays, he suddenly felt the pressure of two soft hands upon his ears, as of somebody who had come up behind him. He turned round, and found his cousin Lucy standing there.

Lucy asked him what he was thinking of, and he told her. He then took Lucy into the barn, and showed her the chalk mark upon the floor. She looked on with a good deal of interest, and said she thought it was an excellent plan; and she wished there was a great barn with a south floor at their house. Lucy knew more about the subject than Rollo did, and she gave him some explanations about it. “You see,” said she, “that the sun rises in the east every morning, and comes up higher and higher, every hour, till noon; and then it begins to go down again, and at last it sets in the west. But, at some times in the year, it comes up higher at noon than it does at other times, and so it does not shine so much into the door.”

“It shines more, you mean,” said Rollo.

“No,” said Lucy; “not so much. In the winter the sun moves around by the south, and keeps pretty low all day, and of course shines farther into doors and windows.”

Then, after a moment’s pause, she added,

“If we should mark the place on the floor all the year round, we should find what time the sun is farthest to the south.”

“So we should,” said Rollo.

“It would be in the winter,” said Lucy.

“Yes,” said Rollo; “in the middle of the winter exactly.”

“Yes,” said Lucy; “and in the middle of the summer it would be nearest overhead.”

“Jonas and I will try it,” said Rollo.

“I can try it in the house,” said Lucy, “where the sun shines in at my chamber window.”

“O no,” said Rollo; “that won’t do.”

“Why not?” said Lucy.

“Because the window does not come down to the floor, and so does not let the sun in enough.”

“O, that makes no difference,” said Lucy; “we have nothing to do with the bottom of the door; you only mark where it shines in the farthest, and that place is made by the top of the door, for it shines in farthest by the top of the door.”

“Well,” said Rollo, “I don’t know but that the house will do; but then you can’t chalk on the carpet.”

“Chalk on the carpet?” said Lucy.

“Yes, to mark the place.”

“No,” said Lucy, thinking; “but I can mark it some other way.”

“How?” asked Rollo.

“Why, I can put a pin in,” said Lucy.

“O dear,” said Rollo, with a laugh, “put a pin in! That’s no way to mark a shadow.”

“It isn’t a shadow,” said Lucy.

“Yes, it is,” said Rollo.

“No,” said Lucy; “a shadow is dark, and this is bright.”

“Yes,” said Rollo, “this is a bright shadow; some shadows are bright, and some are dark.”

“O Rollo!” said Lucy; and she turned away from him, a little out of humor.

The truth was, that Rollo and Lucy were getting decidedly into a dispute. From the sublime heights of practical astronomy, they had fallen, by a sad and very rapid descent, to a childish altercation. Rollo had a very high idea of the superior facilities afforded by Jonas’s barn floor for observing the daily changes in the sun’s meridian altitude, and he did not like the idea of Lucy’s finding that she had equally good opportunities for observation at her home. Lucy was a little fretted at Rollo’s captious spirit; but then her mind soon became unruffled again, and she turned back towards Rollo, and said, as they walked along the yard,

“I don’t think the sunshine on the floor is a shadow, Rollo; but then I don’t see why a shadow would not do, just as well.”

“How?” said Rollo.

“Why, look there at the shadow of that post,—that would do.”

She pointed to a post with a rounded top upon it, which stood by the side of the garden gate. The shadow, clear, distinct, and well defined, was projected upon the walk; and Lucy told Rollo that they might mark the place where the top of that shadow came every day, and that that would do just as well.

“But how could we mark it?” said Rollo.

“Why, we could drive a little stake unto the ground.”

“O, that would not do,” said Rollo. “People would trip over them, and break them down. They would be exactly in the walk.”

Lucy saw that this would be a difficulty, and, for a moment, seemed to be at a loss. At length, she said,

“We might go somewhere else, then, where the people would not come.”

“But what should we do for a post?” said Rollo.

“Could not we get Jonas to drive a tall stake down?” said Lucy.

“Yes,” said Rollo; “I suppose so.”

The children went out into the garden to find a good smooth place, and while they were walking about there, Rollo’s mother came out, and they told her the whole story. She seemed quite interested in the plan, and told them of a better way than any that they had thought of.

“You see,” said she, “that the height of the stake or pole that makes the shadow is not material; for the shadow of a small one will vary just as much, in proportion to its length, as that of a long one will. So, instead of taking a wooden stake, out of doors, you might take a large pin, and drive it down a little way into the window sill, in the house. Then you can mark the shadow with a pen, very exactly.”

“So we can,” said Lucy, clapping her hands.

“And you might put a piece of white paper, or a card down first,” continued Rollo’s mother, “and drive the pin through that, and then mark the places where the end of the shadow comes every day, directly on the card, with a fine pen. Thus you could be a great deal more exact than you can in chalking upon a barn floor.”

Rollo asked his mother if she would not be kind enough to help them fix their apparatus; but she said she would give them particular directions, though she should prefer letting them do the whole themselves, and then, if they met with any difficulties, they might come and report them to her, and she would tell them how to surmount them. So she recommended to them to go and find a blank card, or piece of white pasteboard, or of stiff white paper, as big as a common card. “Then,” said she, “choose some window where the sun shines in at noon, and put the card down upon the sill, and drive the pin down through it. But you must not drive the pin through the middle of the card, for the shadow will always be off to the north of the pin, and therefore the pin may be pretty near the south end of the card. Then the shadow will be more likely to come wholly upon the card, even when it is longest. You had better place the card in such a position, too, that its sides shall lie in the direction of north and south. Then the shadow at noon will lie along exactly in the middle of it. You must get a large and stout pin, too; and drive it in firmly, a little way, with a small hammer. It will be well, too, to drive another smaller pin into the other end of the card, so as to keep it fixed in its north and south position.”

“How can we know when it is north and south, exactly?” said Lucy.

“You cannot do it exactly,” said Rollo’s mother; “but you can get it pretty near. One way is to borrow father’s little compass, and adjust it by that. Another way is to see when it is exactly twelve o’clock by the clock, and then the shadow of the pin will of itself be about north.

“Then you might move the north end of the card until the shadow is brought exactly into the middle of the card, and then put the other pin in, and fix it in that place. Then if you make a mark along where the shadow comes, that mark will be a north and south line, and you can mark the place where the shadow of the pin’s head crosses that line, when it crosses it every day at noon.”

The children said that they believed they understood the directions, and they determined to try the plan. They thought they would fix two cards, one at Rollo’s house, and one at Lucy’s; and they immediately went off in pursuit of blank cards and big pins.