"And very soon they were gliding smoothly along out of the cove."—Page 167.
After some inquiry, they found a boat, at a little distance out of the village, in a sort of cove, where there was a fine, sandy beach. The boat was of very good size, and it had in it two oars and a paddle. Jonas looked out upon the water, and up to the sky, and he listened to hear the moaning of the wind upon the tops of the trees. He wanted very much to persevere in his effort to find the carpenter; but then, on the other hand, he was not sure that it was quite safe to take Rollo out upon the water at such a time.He sat upon a log upon the shore a few minutes, and seemed lost in thought.
At last he said,—
"Well, Rollo, I believe we'll go. The worst that will happen will be, that you may get frightened a little. We can't get hurt."
"Why can't we get hurt?" said Rollo.
"Why, even if it comes on to blow hard, it will probably be a steady gale, and I can run before it, if I can't do anything else. And there can't be much of a sea in this pond."
Rollo did not know what Jonas meant by much of a sea in the pond; but, as Jonas immediately went to work taking the horse out of the wagon, Rollo did not ask any questions. The boys unharnessed the horse, for Jonas said he would stand easier out of harness, and they might be gone more than an hour. They fastened him then to a tree, and poured the oats down before him upon the ground. Then Jonas helped Rollo into the boat, and put in the tin pail containing their luncheon, and also the umbrella; though he said he did not think it would rain before they got back. Then he shoved off the boat, and jumped in himself;and very soon theywere gliding smoothly along out of the cove.
Rollo wanted to row; and so Jonas let him take one oar, while he himself sat in the stern with the paddle. Rollo soon learned the proper motion, so that his efforts assisted considerably in propelling the boat. They found, when they were out at a little distance upon the water, that the wind blew much harder than Rollo had expected.
"Jonas," said he, "the wind blows more here than it did upon the shore."
"No," said Jonas, "only we feel it more here than when we were under the lee of the land."
"What do you mean by the lee of the land?" said Rollo.
"I mean the shelter of it," replied Jonas. "Whenever a ship at sea is sheltered by anything, they say the ship is under its lee."
The boys went on, Rollo rowing, and Jonas paddling behind, until at length Rollo got tired. Jonas then told him to spread the umbrella, and hold it up for a sail. Rollo did so. The wind was blowing pretty nearly in the direction in which they weregoing, and, by its impulse upon the umbrella, it caused it to pull very hard. Rollo rested the middle of the handle of the umbrella upon his shoulder, holding the crook in his hand, turning it in such a position as to present the open part of the umbrella fairly to the wind. Jonas continued to paddle, and so they went on very prosperously until they had got two thirds across the pond, when Jonas ordered Rollo to take in sail.
"Why," said Rollo, "we have not got across yet."
"No," replied Jonas, "but the wind is taking us out of our course."
Rollo drew down the umbrella, and looked around. They were still at a considerable distance from the shore. Jonas extended his paddle out into the water as far as he could reach, and then drew it in towards him with several quick and strong strokes, as if he were endeavoring to pull the stern of the boat, in which he was sitting, round.
"What are you doing so for?" said Rollo.
"I am trying to bring her up into the wind," replied Jonas.
"What is that for?" asked Rollo.
"Why, we've drifted to leeward," saidJonas, "and I must bring herup; for we want to land around behind that point on the starboard bow."
Rollo did not understand Jonas's technical language very well. He particularly did not know what Jonas meant by bringing herup, for it seemed to him that the pond was perfectly level, so that there was no up or down either way. He did not know that, in sea language,againstthe wind was alwaysup, andwiththe wind,down.
Jonas found it hard to bring the boat up into the wind. The waves had begun to be pretty large, and they beat against the bows of the boat, and some of the water dashed over upon Rollo. The wind blew quite heavily, too; and now that they had changed their direction so as to bring the wind upon their side, it embarrassed, if it did not absolutely retard their progress. Some drops of rain also began to fall.
However, by hard and persevering exertion, Jonas at length succeeded in urging the boat forward until he began to draw nigh to the point of land; and soon afterwards they came under the shelter of it, where the water was smooth, and the air comparativelystill. Here Rollo put in his oar again, and they passed along close under a high shore, for some distance, until they came to the landing. Here they fastened the boat, and then began to walk along up the road.
The road lay through the woods, and among hills, so that it was sheltered; and the only indications of the wind which the boys noticed, was a distant roaring sound among the forests. They came at length to the bridge, where they found several workmen busily engaged in laying abutments of stone, but the carpenter himself was not there. The men told Jonas that he had gone about half a mile away, on a by-road, to select and cut some timber to be used in the construction of the bridge.
"How long will he be gone?" asked Jonas.
"He will be gone two or three hours," said a man with a stone hammer in his hand.
"What shall we do now?" asked Rollo, addressing Jonas, after a short pause.
"Keep on until we find him," replied Jonas. "But you may stay here and see them build the bridge, while I go after the carpenter."
Accordingly Jonas went on, leaving Rollo seated upon a bank watching the work. In about three quarters of an hour, he returned; and then he and Rollo went back to the boat. The wind had all this time continued to increase, though they were so much sheltered, that they did not notice it much.
Jonas, however, observed that some light, scudding clouds were flying across the sky, very low, being apparently far beneath the other clouds. When they reached the boat, Rollo proposed that they should stop and eat some luncheon; but Jonas said that he should eat his with a better appetite on the other side of the pond. So he hastened Rollo into the boat, and, talking his station in the stern, he began to ply his paddle with all his force, running the boat along under the shelter of the high shore.
"There isn't much wind, Jonas," said Rollo.
"We can tell better when we come round the point," replied Jonas.
Rollo observed that Jonas looked a little anxious, and he also seemed to be exerting himself so much in the long, steady strokes of his paddle, that it appeared to be rather aninterruption to him to hear and answer questions. Rollo therefore did not talk. He found, however, as he drew near the point, that the waves were running by it, with great speed and force, down the pond. As the boat shot out from the shelter of the point into this place of exposure, the storm struck them suddenly, with a blast which swept the bows of the boat at once round out of her course, and dashed the spray from the waves all over Rollo's face and shoulders. It was with great difficulty that Jonas could bring the boat to the wind again.
He succeeded, however, at length, and they went on, for some time, pitching and tossing, through the waves,—the wind pressing so hard upon the boat that it was very difficult for Jonas to make any headway. The wind had changed its direction, so that it blew now almost exactly across their course; and it required great exertion for Jonas to prevent being blown away down the pond, out of his track altogether.
In the mean time, the wind rather increased than diminished; and the water dashed in so much over the bows that Rollo had to dip it up with the cover of the tin pail, and pourit out over the side of the boat into the pond again. They were going on in this way, both toiling very laboriously, when suddenly they began to hear a sound like distant thunder, somewhat louder than the ordinary roaring of the wind. They both looked towards the shore in the direction from which the sound came. On the declivity of a range of hills covered with forests they saw an unusual commotion among the trees. The tops were bowed down with great force; the branches were broken off, and Jonas thought that he could see fragments of them flying in the air; and presently, farther down, he observed several tall pines bending over, and then sinking down till they disappeared.
"What is it?" said Rollo.
"A squall," said Jonas,—"and coming down directly upon us."
"What shall we do?" asked Rollo.
"Put the boat before the wind," replied Jonas, "and let her run: we must go where the squall carries us."
Jonas immediately began to pull the stern of the boat around with his paddle, so as to turn the head of it away from the quarterwhich the wind was blowing from; and then the wind drove the boat along very rapidly over the waves, which curled and foamed on each side, driving onward with great fury. When they looked around behind them, they saw that the pond, which was of a very dark color, though spotted with the white tips of the waves all over its surface, was almost black for a large space in the direction from which the squall was coming. It advanced with great rapidity, and at last struck the boat with a noise like thunder. The froth and foam flew over the surface of the water like tufts of cotton, and the boat seemed to fly along the water with almost as much speed as they; and the roaring of the winds and waves was so loud that Rollo had great difficulty in making Jonas hear what he had to say. After a few minutes, the violence of the wind somewhat abated; but it still blew a steady and furious gale, so that Jonas had to keep his boat directly before it. Thus they were driven on, wherever the wind chose to carry them, for more than half an hour.
Then they began to draw near the land, far, however, very far from the place wherethey had intended to go. Rollo observed that Jonas was looking out very eagerly towards the shore, and he asked him what he was looking for.
"Why, here we are," said Jonas, "on a lee shore, and I am looking out for a place to land."
Rollo looked, and saw that the waves were tumbling with great violence upon the rocks and gravelly beaches which lined the shore, and he was afraid that the boat would get dashed to pieces upon them. Jonas, however, observed a large tree, which originally stood upon the bank, but which had fallen over, and now lay with its top partly submerged. He thought that this might afford him some shelter, and so he made great exertions to guide the boat so as to bring it in to the shore around behind this tree. By means of great efforts he succeeded; and so he and Rollo both escaped safe to land.
The boys did not get home until late that night, for they were thrown upon the shore nearly two miles from the Mill village, and of course they had that distance to walk. Jonas was detained a little there, too, in making arrangements to send a boy for theboat after the storm had subsided. When they got home, Rollo's father said that he was sorry for their fatigues and exposures, but he was very glad that Jonas had persevered and found the carpenter; for the high wind had blown down the back chimney and broken the roof over the kitchen, and it was very necessary to have it repaired immediately.
What ismomentum? Has air momentum, when it is in motion, as well as water? At what time in the spring of the year does the sun rise at six o'clock? What did Rollo think was the prospect in respect to the weather? What did Jonas think? What is meant by being under theleeof a shore? What is asquall? What indications did Jonas observe of the approach of the squall? What course did he pursue in order to avoid the danger of it?
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A fewdays after the adventure described in the preceding chapter, Rollo heard his father proposing to his mother that they should take a walk the next morning before breakfast. Rollo wanted to go too. His father said that they should be very glad to have his company; and he promised to wake him in season.
Rollo felt rather sleepy, when his father called him the next morning; but he jumped up and dressed himself, and was ready first of all. It was a cool, but a very pleasant morning. The sun was just coming up. The ground in the path before the door was frozen a little, and the air seemed very still.
When Rollo's mother came out to the door, she said,—
"Well, husband, which way shall we go?"
"Up on the rocks," said Rollo; "let's go up on the rocks, mother. It will be beautiful there this morning."
"Well," replied his mother; "we'll go up on the rocks."
The place which Rollo called the rocks, was the summit of a rocky hill, which had a grassy slope upon one side, by which they could ascend, and a precipice of ragged rocks upon the other. There was a very pleasant prospect from the top of the rocks.
As they walked along, Rollo said that it was very different weather that still morning, from what it was the day that he and Jonas were out upon the pond.
"Yes," said his father, "you had an opportunity to see the effects of air in motion then."
"And nowair at rest," replied Rollo.
"Pretty nearly," said his father.
"Yes, sir,entirely," said Rollo; "there is no wind at all, this morning: hold up your hand, and you can feel."
So Rollo stopped a moment upon the grass, and held up his hand to see whether there was any wind.
"I know there is not any wind that you can perceive in that way," said his father.
"How can we perceive it, then?" said Rollo.
"I'll tell you," replied his father, "when we get to the top of the hill."
They reached the top of the hill soon after this, and sat down upon a smooth stone. There was a very wide prospect spread out before them,—fields, forests, hamlets, streams,—and here and there, scattered over the landscape, a little patch of snow. The sun was just up, and the whole scene was very bright and beautiful.
"Now, father," said Rollo, "tell me how you know that there is any wind at all."
"I did not say that there was anywind. I saidmotion of the air."
"Why, father," replied Rollo, "I thought that wind was motion of the air."
"So it is," said his father; "but all motion of the air is not wind. Wind is acurrentof air, that is, aprogressivemotion;—and in fact, there is, this morning, a slight current from the westward."
"How can you tell, father?" asked Rollo.
"By the smokes from the chimneys; don't you see that they all lean a little from the west towards the east?"
"Not but a little, father;—and there's one, from that red house, which goes up exactly straight."
"Yes," said his father, "there is one; but, in general, the columns of smoke lean; which is proof that there is a gentle current of air to the eastward."
"Westward, you said, father," rejoined Rollo.
"Yes,fromthe westward, buttothe eastward.
"That is what is called a progressive motion," continued Rollo's father; "that is, the whole body of air makes progress; it advances from west to east. But there is another kind of motion, called avibratorymotion."
"What kind of a motion is that, father?" asked Rollo.
"It is a very hard kind to describe, at any rate," said his father. "It is a kind of quivering, which begins in one place and spreads in every direction. Don't you hear a kind of a thumping sound?"
"Yes," said Rollo, "a great way off; what is it?"
"Look over across the pond there," said his father; "don't you see that man cutting wood?"
"Yes," said Rollo; "that's what makes the noise.—No, father," he continued, after a moment's pause, "that's not it. Look, father, and you'll see that the thumping sound comes when his axe is lifted up."
They all looked, and found that it was as Rollo had said. The strokes of the axe kept time, pretty well, with the sound of blows, which they heard, only the sounds did not correspond with the descent of the axe. When the axe appeared to strike the wood, they did not hear any sound, but they did hear one every time the axe was lifted up.
"So, you see," said Rollo, "it is not that man that we hear. There must be some other man cutting wood."
"We will wait a minute," said his father, "until he gets the log cut off, and then he will stop cutting; and we will see whether we cease to hear the sound."
So they sat still, and watched the man for a minute. Presently he stopped cutting,—and,to Rollo's great surprise, the sound stopped too.
"That's strange," said Rollo.
In a moment more, the man had rolled the log over, and commenced cutting upon the other side; and in an instant after he began to cut, Rollo began to hear the sound of strokes again.
"Yes," said Rollo, "it must be his cutting that we hear; but it is very strange that he makes a noise when he lifts up his axe, and no noise when it goes down."
"I'll tell you how it is," said his father. "He makes the noise when his axe goes down; but, then, it takes some little time for the sound to get here; and by the time the sound gets here, his axe is up."
"O," said Rollo, "is that it?"
"Yes," replied his father, "that is it."
Rollo watched the motion of the axe several minutes longer in silence, and then his attention was attracted by the singing of a bird upon a tree in his father's garden, at a short distance below him.
Pretty soon, however, his mother said that it was time for her to return; and they all,accordingly, arose from their seats, and rambled along together a short distance upon the brow of the hill, but towards home.
"Then the sound moves along through the air," said Rollo, "from the man to us."
"Yes," said his father; "that is, there is a vibratory motion of the air,—a kind of quivering,—which begins where the man is, and spreads all around in every direction, until it reaches us. But there is noprogressivemotion; that is, none of the air itself, where the man is at work, leaves him, and comes to us."
"But, husband," said Rollo's mother, "I don't see how anything can come from where the man is, to us, unless it is the air itself."
"It is rather hard to understand," said his father. "But I can make an experiment with a string, when we get home, that will show you something about it."
They rambled about among the rocks for a short time longer, and then they descended by a steep and crooked path, in a different place from where they had ascended. When they had got nearly home, Rollo said that hewould run forward and get his father's ball of twine and bring it out; and so have it all ready for the experiment.
Accordingly, when Rollo's father and mother arrived at the front door, they found Rollo ready there with a small ball of twine in his hand, about as large as an apple.
"Now, Rollo," said his father, "you may take hold of the end of the twine, and walk along out into the street, while I hold the ball, and let the string unwind."
Rollo did so. He drew out a long piece of twine, as long as the whole front of the house, and then he stopped to ask his father if that was enough.
"No," said his father; "walk along."
So Rollo walked on for some distance farther, until, at last, the ball was entirely unwound. Rollo had one end of it, and was standing at some distance down the road, while his father, with the other end, stood at the gate of the front yard. The middle of the string hung down pretty near to the ground.
"Draw tight, Rollo," said his father.
So Rollo pulled a little harder, and by that means drew the line straighter.
"Now," said his father, "walk along slowly."
So Rollo walked along, drawing the end of the line with him. His father followed with the other end. Thus they advanced several steps along the side of the road.
"There," said his father. "Stop. That, you see, was aprogressivemotion."
"Yes, sir," replied Rollo.
"The whole string advanced along the road," added his father. "It made progress, and so it was a progressive motion. Now, fasten your end of the string, Rollo, to that tree directly behind you."
Rollo looked behind him, and saw that he was standing near a small maple-tree, which had been planted, a few years before, by the side of the road.
"Tie it right around the stem of the tree," said his father, "about as high as your shoulder."
Rollo fastened the string as his father had directed. Then his father fastenedhisend, in the same way, to another tree, which was growing near where he was standing.
"Now," said he, "there can be no more progressive motion, but there can be a vibratoryone. Take hold of the string near where it is fastened to the tree."
Rollo took hold of it, as his father had directed, and then his father told him to shut his eyes. When his eyes were shut, so that he could not see, his father said that he was going to strike the string, at his end of it, with his pencil-case, and he asked Rollo to observe whether he could feel any motion.
Rollo held very still, while his father struck the string; and immediately afterwards he called out, "Yes, sir." Then his father struck the string again, several times, and every time Rollo could feel a distinct vibratory or quivering motion, which was transmitted very rapidly through the string, from one end to the other; although, as the string was fastened by both ends to the trees, it was evident that there could be no progressive motion.
Rollo's mother had been standing all this time at the step of the door, watching the progress of the experiment; and, when she saw the expression of satisfaction upon Rollo's countenance, while he was standing, with his eyes shut, holding the end of thestring, she wanted to come and take hold of it herself, so as to see what sort of a sensation the vibratory motion of the string produced.
So she came out through the gate, and asked Mr. Holiday to wait a moment while she went to where Rollo was standing, and took hold of the string. But he said that it would not be necessary for her to go there, as she could take hold of his end of the line just as well, and let Rollo strike the other end.
They accordingly performed the experiment in that way, and Rollo's mother could feel the vibrations very distinctly.
"One thing you must observe," said Mr. Holiday; "and that is, that the vibrations pass along from one end of the line to the other very quick indeed. We feel them at one end almost at the same instant that the other end is struck."
"Exactlyat the same instant, sir," said Rollo.
"No," replied his father, "not exactly at the same instant, though it is very nearly the same."
"I did not see any difference," said Rollo.
"No," replied his father, "you cannot perceive any difference in so short a string, but if we had a string, or a wire, a mile long, I presume that we should find that it would require a sensible period of time to transmit the vibrations from one end to the other."
"What do you mean by a sensible period of time, father?" asked Rollo.
"Why, a length of time that you could perceive," said his father; "just as it was with the man cutting wood. We could see that some time elapsed between the striking of the blow, and our hearing the sound."
"Yes," said Rollo, "just as long as it took him to lift up his axe."
"That is not certain," replied his father, "because the sound that we heard might have belonged to a blow made before. That is, it might be that, when he had struck one blow, he had time to raise his axe and strike another, and then raise his axe again, before the sound of the first blow came to us."
"Yes, sir," said Rollo, "I understand."
Mr. Holiday then told Rollo that he might unfasten the string from the trees, and wind it up again into a ball, and bring it in.Then he and Rollo's mother went into the house, to see if breakfast was not almost ready.
That morning, after they were all seated at the breakfast table, Rollo said to his father that he did not exactly understand what sort of a motion the vibratory motion of the air was, after all.
"No," said his father, "I suppose you do not. And, in fact, I do not understand it very perfectly myself. I only know that the philosophers say, that, when a man strikes a blow with an axe upon a log of wood, it produces a little quivering motion of the air, which spreads all around, darting off in every direction very swiftly. If a boy strikes a tin pail with a drum-stick, it makes another kind of quivering or vibration, which is different from that which is made by the axe; but I don't know precisely how it differs. So, when the air is full of sounds, on a still morning, it is full of these little vibrations, like a string which trembles from end to end, though its ends are fastened so that it cannot move away."
"Then the air is never at rest," said Rollo's mother.
"No; certainly not, when any sound is to be heard; and it is never perfectly silent."
"There is one thing very extraordinary," said Mrs. Holiday.
"What is it?" asked Rollo's father.
"Why, that, when a great many sounds are made at the same time," she replied,—"as, for example, when we are upon the top of a hill, on a still morning, and hear a great many separate sounds, as a man cutting wood, birds singing, a bell ringing, and perhaps a man shouting to his oxen,—all those tremblings or vibrations, being in the air together, do not interfere with one another."
"Yes," said Mr. Holiday, "it is very extraordinary indeed. They do not seem to interfere at all. When there are too many sounds, or if there is a wind with them, they do interfere; but, in a calm morning, like this, when the air is at rest, you can hear a great many distant sounds very distinctly."
"Yes," said Rollo, "and I mean to go up to the top of the rocks again after breakfast, and listen."
What time of the year was it when Rollo took this walk? How did Rollo satisfy himself that there was no wind at all? How did his father prove that there was a little wind? Is all motion of the air wind? What two kinds of motion are mentioned? What sound did they hear? What made Rollo think the sound was not made by the man whom they saw cutting wood? How did his father explain this phenomenon? What experiment did they try with the string? Were the vibrations transmitted slowly or rapidly through the string? Did Rollo think that he understood perfectly the nature of the vibrations? What extraordinary circumstance did Rollo's mother mention at the breakfast table?
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