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
circumstances 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 shore 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."
"What is the equinoctial storm?" said Rollo.
"O, it is a great storm, which comes generally about this time of year.
I shouldn't wonder if it should come on to-morrow. But it may not come
for a week; and so I hope we shall have time to get the roof mended
first."
"Does it look like a storm to-night?" said Rollo.
"No, not much," replied Jonas. "It is a little hazy in the south-west.
However, if it looks like a storm in the morning, you need not go,
unless you choose; though I shall."
"I wish you'd wait till the storm is over," said Rollo.
"No," said Jonas, "I had rather go in the storm than not."
"Why?" said Rollo.
"Because," said Jonas, "I like to be out in storms. Sometimes it is very
grand."
The next morning, when Rollo awoke, he found that it was light, but not
yet sunrise. He arose, and looked out of the window to see if it was
pleasant. The sky was somewhat overcast, but there was a little blue to
be seen, and Rollo thought that it would be pleasant. He heard a noise
in the barn-yard, and, looking in that direction, he saw Jonas just
leading the horse out of the stable. So he dressed himself soon, and
went down.
When he got ready, he went down into the yard, and found that Jonas had
got the horse harnessed, and everything prepared. There was a little bag
of oats in the back part of the wagon, and also a tin pail, with a
cover, which contained a luncheon. Jonas fastened the horse to a post,
and said,--
"Now, Rollo, we'll go in and get some breakfast."
"I thought that luncheon was for breakfast," said Rollo.
"No," said Jonas, "that is for dinner."
"Shall we be gone all the day?" said Rollo.
"We may be gone till after dinner," said Jonas, "and so I thought I
would be sure."
The two boys went into the house, and there they found that Dorothy had
got some breakfast ready for them upon the kitchen table. After eating
their breakfast, they got into the wagon, and set out. Jonas first put
in a large umbrella. Just as they were driving out of the yard, the
first beams of the morning sun shone in under the branches of a great
tree in the yard, and brightened up the tips of the horses' ears and the
boys' faces. At the same time, a rude gust of wind came around the
corners of the house, and slammed to the gate of the front yard.
"It's going to be pleasant," said Rollo; "the sun is coming out."
"I'm not very sure of that," said Jonas; "the wind is rising."
"We start just at sunrise," said Rollo.
"Yes," replied Jonas, "the sun always rises at six o'clock at this time
of the year."
The boys rode along for about three hours, before they came to the
carpenter's. They were obliged to travel very slow, for the roads were
not good. It is true that the snow was all gone, and the frost was
nearly out of the ground; but there were many deep ruts, and in some
places it was muddy. The sun went into a cloud soon after they set out,
and it continued overcast all the morning. There was some wind too, but,
as it was behind them, and as the road lay through woods and among
sheltered hills, they did not observe it much. Jonas said that there was
a storm coming on, but he thought it was coming slowly.
They arrived at length at the pond. There was a little village there,
upon the shore of the pond. The reason why there happened to be a
village there, was this: A stream of water, which came down from among
the mountains, emptied into the pond here, and, very near where it
emptied, it fell over a ledge of rocks, making a waterfall, where the
people had built some mills. Now, where there are mills, there must
generally be a blacksmith's shop, to mend the iron work when it gets
broken, and to repair tools. There is often a tavern, also, for the
people who come to the mills; and then there is generally a store or
two; for wherever people have to come together, for any business, there
is a good place to open a store, to sell them what they want to buy.
Thus there was a little village about these mills, which was generally
called the Mill village.
Jonas inquired where the carpenter lived, and then drove directly to his
house. He found that he was not at home. He had gone across the pond, to
mend a bridge, which had been in part carried away by the floods made
when the snow went off. Rollo sat in the wagon in the yard by the side
of the carpenter's house, while Jonas stood at the door, making
inquiries and getting this information.
"If you want to see him very much," said the carpenter's wife, "I
presume you can get a boat down in the village, and go across the pond."
"How far is he from the other side of the pond?"
"O, close by the upper landing," said she; "not a quarter of a mile
from the shore, right up the road."
Jonas thanked the woman for her information, and got into the wagon.
"Let us get a boat and go over, Jonas," said Rollo, as they were turning
the wagon round.
"I should," said Jonas, "if there was not such a threatening of a
storm."
"It does not blow much," said Rollo.
"No," said Jonas, "not much now, but the wind may rise before we get
back. However, we'll go and see if we can get a boat."
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.
[Illustration: "And very soon they were gliding smoothly along out of
the cove."--Page 167.]
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
they were 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 were going, 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," said Jonas, "and I must bring her
_up_; 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 her _up_, 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, _against_ the
wind was always _up_, and _with_ the 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 comparatively still. 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 an interruption 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 pour it 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 quarter which 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 where they 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 the boat 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.
QUESTIONS.
What is _momentum_? 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 the _lee_ of a shore? What is a _squall_? What
indications did Jonas observe of the approach of the squall?
What course did he pursue in order to avoid the danger of it?