"Why, the heat of the flame, when you first put the paper in," replied Miss Mary, "makes the air that is above it lighter; and the common air all around crowds in under it, in buoying it up; and by that means, if the flame is too large, common air is carried into the tumbler. You ought to make a very small flame, if you leave the top of the tumbler open." "How can we make a small flame?" said Rollo. "One good way," replied Miss Mary, "is to roll up some paper into a very small roll. I will show you how." So Miss Mary took a piece of paper, and cut it into the proper shape with her scissors, and then rolled it up into a long and very slender roll; one end of it was not much larger than a large knitting-needle. She gave this to Rollo, and told him that, if he tried the experiment again, he must light the small end, and it would make a flame not so big as a pea. Rollo explained to Jonas what Miss Mary had said, and they resolved on attempting the experiment again that evening. And they did so. Dorothy stood by watching the process, as she had done the evening before, but Rollo did not assert so confidently and positively what the result would be. He had learned moderation by the experience of the night before. When all was ready, Jonas lighted the end of the slender roll in the lamp, and plunged it carefully into the tumbler. It went out immediately. "There!" said Rollo, clapping his hands, "it goes out." "Why, it is only because the wind blew it out." "No, Dorothy," said Rollo, "there isn't any wind in the tumbler." "Yes," replied Dorothy, "when you push it down, it makes a little wind, just enough to blow it out." "Get another tumbler," said Jonas, "and let us see." So Dorothy brought another tumbler, and Jonas put the burning end of the paper down into it, with about as rapid a motion as that with which he had put it before into the tumbler he had at first. The paper continued to burn. "There," said he to Dorothy, "when I put it down into common air, it burns on the same as ever; so it can't be that the wind puts it out." Jonas repeated the experiment a number of times; the effect was always the same. Whenever he put it into the tumbler of common air, it burned on without any change; but whenever he put it into the choke damp, it immediately went out. Even Dorothy was satisfied that there was a difference in the kind of air contained in the two tumblers. That evening, when Rollo gave his mother a full account of their attempts,--describing particularly their failure at first, and their subsequent successes,--his mother seemed much interested. When he had finished, she said,-- "Well, Rollo, I don't see but that you have learned two lessons in philosophy." "Two lessons?" said Rollo. "Yes," replied his mother. "The first is, that fire will not burn in choke damp; and the second is, that it requires nice attention and care to verify philosophical truths by experiment."