Rollo's Philosophy. [Air]. Abbott Jacob

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      "There," said he to the boys, "you see I have nailed the leather, so that, when it lies down in its place, it covers the hole completely; and yet I can push it up a little with my fingers, so that there will be an opening."

      Then Jonas cut a small leather strap, and nailed one end of it down upon one side of the clapper, and the other end upon the other side of the clapper. He put one little carpet nail into each end of the strap. The strap, when it was nailed, passed directly across the clapper or valve. It was not drawn tight across, but it lay upon the clapper loosely. The ends were nailed tight, but the middle rested loosely upon the clapper.

      "Now," said Jonas, "I can push the clapper up a little way, but I can't push it far. The strap keeps it from coming up far."

      "But why," said Nathan, "do you want it to go up at all?"

      "To let the air in," said Jonas. "When I get the leather all nailed on again, I'll show you the whole operation of it."

      "And you can be telling us about it in the mean time," said Rollo.

      "Well, then," said Jonas, "when I lift up the upper side of the bellows by the handle, to blow, the air comes in by the hole. The clapper lifts up a little way, and lets it in. Then, when I press down the handle again, it presses the air out through the nose, because it can't go back through the valve hole."

      "Why not?" said Nathan.

      "Because," said Jonas, "the valve falls down over the hole, and stops it up. It is made so as to lift up easily, and then to fall down and cover the hole exactly, and prevent the air going out the same way it came in. So, as it cannot get out by the valve, it has all to go out through the nose. If the nose were stopped up, it could not get out at all."

      "And what then?" said Rollo.

      "Why, then," replied Jonas, "you could not bring the two sides of the bellows together again. The air between would keep them apart."

      "I should like to try," said Rollo.

      "Well," said Jonas; "and there are some other experiments you may perform with it too."

      At length, Jonas said that he had got the leather all nailed on, and they might try the experiment. He took hold of the nose of the bellows, and held his thumb near the end of it, ready to stop up the hole.

      "Now, Nathan, you may take hold of the handles, and pull them apart as if you were going to blow."

      Nathan did so. He pulled the handles apart, and held them open.

      "Now," said Jonas, "I will stop up the nose, and the valve will close itself; and then you will find that you cannot bring the sides together again."

      So Jonas put his thumb over the hole, and told Nathan to blow.

      Nathan pressed hard, and the sides came together again, about as easily as usual.

      "What!" exclaimed Jonas with surprise. He did not know what to make of the failure of his experiment.

      "There must be a leak somewhere," said he. And he took the bellows out of Nathan's hand to look for it.

      He found there was a corner, on the side opposite to the one where he had been working, where the leather was open, he having forgotten to nail it down.

      "Ah!" said he, "here is the difficulty. When I have nailed this down, we will try again."

      "Is that a leak?" said Nathan.

      "Yes," said Jonas. "When you worked the bellows, you pressed the air all out through there. I did not know that that was open. Let me nail this down, and then we will begin our experiment regularly."

      QUESTIONS

      What was Jonas doing in the shop, when Rollo and Nathan went out to find him? What part of the bellows was out of order? How did he make a new valve? How did he fasten it to its place? Did he nail down only one edge, or both edges? Why did he want the other edge to be left at liberty? How did he prevent its lifting up too far? What was the first experiment which he performed with the bellows, after he had finished the mending? Did it succeed at first? Why not? In working a pair of bellows, where does the air come in? Where does it go out? Why cannot the air escape through the valve where it comes in?

      CHAPTER IV.

      EXPERIMENTS

      When Jonas had finished nailing down the corner, he said, "Now there are several experiments, which we can perform with the bellows. I will be the professor, and you two shall be my class in philosophy, and I will direct you how to make the experiments.

      "First," said Jonas, "you, Rollo, may take hold of the nose of the bellows with your hand, in such a way as to put your thumb over the end of it, to stop it up, and then let Nathan try to blow."

      Rollo did so, and Nathan tried to blow. He found that he could open the bellows very easily; but when he attempted to press the sides together again, he could not. He crowded the handle belonging to the upper side down, as hard as he could, but it would not move.

      "What makes it do so?" said Nathan.

      "The air inside," said Jonas. "We have stopped up all the places, where it could get out. The valve stops itself. Rollo stops the nose with his thumb, and I have nailed the leather down close, about all the sides. And so the air can't get out, and that keeps you from bringing the sides together again."

      Nathan tried again with all his strength. The sides came together very slowly.

      "They're coming," said he.

      "Yes," said Jonas. "They come a little, just as fast as the air can leak out through the little leaks all around."

      "I thought you stopped all the leaks," said Nathan.

      "Yes," replied Jonas, "I stopped all the real leaks, but still I can't make it perfectly tight. Some air can escape between the leather and the nails all around, and just as fast as it can get out, so fast you can press the sides together, and no faster."

      Here Nathan tried again with all his strength; but he could only bring the sides together very slowly.

      "Now comes the second experiment," said Jonas. "While Nathan is trying to press the two handles together, you, Rollo, may run your finger into the hole, and push up the valve a little."

      Rollo did so. He pushed up the valve a little with his finger, and that allowed the air to escape through the opening. The consequence was, that the bellows collapsed at once under the pressure which Nathan was exerting upon them.