The truth was, that Rollo and Lucy were getting decidedly into a dispute. From the sublime heights of practical astronomy, they had fallen, by a sad and very rapid descent, to a childish altercation. Rollo had a very high idea of the superior facilities afforded by Jonas's barn floor for observing the daily changes in the sun's meridian altitude, and he did not like the idea of Lucy's finding that she had equally good opportunities for observation at her home. Lucy was a little fretted at Rollo's captious spirit; but then her mind soon became unruffled again, and she turned back towards Rollo, and said, as they walked along the yard, "I don't think the sunshine on the floor is a shadow, Rollo; but then I don't see why a shadow would not do, just as well." "How?" said Rollo. "Why, look there at the shadow of that post,--that would do." She pointed to a post with a rounded top upon it, which stood by the side of the garden gate. The shadow, clear, distinct, and well defined, was projected upon the walk; and Lucy told Rollo that they might mark the place where the top of that shadow came every day, and that that would do just as well. "But how could we mark it?" said Rollo. "Why, we could drive a little stake unto the ground." "O, that would not do," said Rollo. "People would trip over them, and break them down. They would be exactly in the walk." Lucy saw that this would be a difficulty, and, for a moment, seemed to be at a loss. At length, she said, "We might go somewhere else, then, where the people would not come." "But what should we do for a post?" said Rollo. "Could not we get Jonas to drive a tall stake down?" said Lucy. "Yes," said Rollo; "I suppose so." The children went out into the garden to find a good smooth place, and while they were walking about there, Rollo's mother came out, and they told her the whole story. She seemed quite interested in the plan, and told them of a better way than any that they had thought of. "You see," said she, "that the _height_ of the stake or pole that makes the shadow is not material; for the shadow of a small one will vary just as much, in proportion to its length, as that of a long one will. So, instead of taking a wooden stake, out of doors, you might take a large pin, and drive it down a little way into the window sill, in the house. Then you can mark the shadow with a pen, very exactly." "So we can," said Lucy, clapping her hands. "And you might put a piece of white paper, or a card down first," continued Rollo's mother, "and drive the pin through that, and then mark the places where the end of the shadow comes every day, directly on the card, with a fine pen. Thus you could be a great deal more exact than you can in chalking upon a barn floor."