"Why, yes," said his father, "worse disasters than these; but I do not know whether you would understand them, if I should explain them." "O, try," said Rollo; "I think we shall understand." "Well, let me think," said his father. "You have noticed how a chaise wheel, on a muddy road, in a wet day, holds the mud upon it, until when it is going very swiftly down a hill, and then the mud flies off in all directions." "Yes, sir," said all the children. "And if the mud did not stick to the wheel pretty tight, it would be thrown off at all times, even when the wheel was going slow. You understand this." "Yes, sir." "Well, now, this whole earth, you all know, is whirling around through space, and moving on also around the sun. And all the loose things upon the surface would be thrown off at once, if they were not held to it by a strong attraction. If this attraction were to cease suddenly,--whisk!--away we should all go in an instant--rocks, houses, men, animals, all in confusion." "O father!" exclaimed Rollo; "where should we go to,--off into the air?" "Not exactly into the air, for the air would all fly off, and be dissipated too; we should fly off into the sky somewhere, some in one direction, and some in another. You'd be a thousand miles off from the earth, almost before you would know it." "Would it kill us, father?" said Nathan. "Yes," said his father. "I don't know that there would be any shock that would hurt us, but we should have no air to breathe, and it would be dark and dismal." "Dark?" said Rollo. "There would be the sun." "Yes," said his father, "there would be the sun; and the sun would look bright enough when you looked directly towards it, but there would be no general light about you, unless there was air." The children all paused to reflect upon the strange results which their father had told them would ensue from a suspension of the earth's attractive force. Rollo began to think that he had been too hasty in his wish that there was no gravitation. "But, father," said he, "the houses would not go off, certainly;--only the loose things would go." "Very well; houses are loose." "O father! they are fastened down." "How are they fastened down?" asked his father. "O, they are nailed--and," "Not nailed to the ground, certainly," said his father. "No," said Rollo, laughing; "but then they are built with great stones and mortar." "Yes, but there is no mortar under the lowest stones. The foundations are simply laid upon the ground." "Well," rejoined Rollo, "I thought they were fastened somehow or other." "No," said his father; "they dig the cellar, and only just lay the foundations upon the ground, without any fastening. The earth holds them in place." "Well, father," said Rollo, "that is what I meant, when I said we could not stand up straight. I meant the houses. I read in a book that houses would be blown away, if the gravitation did not hold them down."