"Unless," said his father, "you had something above you, to push against, so as to push yourselves down. You would be just like a boy in a boat, off from the shore, and without any paddle or pole. He could not get back again." "We might tie a rope to something," said James, "before we went up, and so pull ourselves down." "Yes, that you might do." "And could not we flap our hands, like a bird, and so fly a little?" "Perhaps you could," said his father. Here the children all began to flap their hands, like young birds trying to fly; and Rollo said again, he wished, with all his heart, there was no gravitation; "for then," said he, "we should have strength enough to fly." "That would lead to serious consequences," said his father. "What consequences?" said James. "Much more serious than you would suppose." "Tell us what they would be, uncle," said James. "O, I know," said Rollo; "you could not stand up straight without gravitation." "O, we could, couldn't we, father?" said Nathan. "What makes you think, Rollo," said his father, without replying to James's question--"what makes you think that we could not stand up straight without gravitation?" "Why, you see," said Rollo.--Here he paused, and looked confused, and did not know what to say. He had an indistinct recollection of having read something about it in some book; but he could not tell what. "I don't see what should prevent any body's standing up straight, if the attraction of the earth should cease; in fact, if it made any difference, it would be rather easier to stand up straight." Here Rollo looked rather foolish, but he did not reply. The truth is, like almost all other children, who take an interest in reading, he was sometimes a little vain of his knowledge; and in this case, instead of listening attentively, and endeavoring to learn something new from his father's explanations, he seems to have thought it a good plan for him to help him elucidate the subject to James and Nathan. He exchanged the character of learner for teacher too soon. "Well, uncle," said James, "what would be the consequence if gravitation should cease?" "Why, in the first place," said Rollo's father, "all the streams in the world would stop running." "The streams!" said Rollo, astonished. "Yes," said his father, "every river, brook, and rill. The reason why the streams flow is, that the earth attracts the water from the mountains and hills, down into the valleys and towards the sea." "Well, sir, what else?" said Rollo. "Why, there would never be any more rain." "No more rain!" exclaimed all the children. "No," he replied. "The drops of rain fall only because the earth draws them down by its attraction; and, of course, if this attraction should cease, they would remain where they are." The children were musing a minute upon these strange effects, when Rollo asked if anything else would happen.