Rollo lay down upon the bridge, and looked into the water. There were some skippers and some whirlabouts upon the water. The skippers were long-legged insects, shaped somewhat like a cricket; and they stood tiptoe upon the surface of the water. Rollo wondered how they could keep up. Their feet did not sink into the water at all, and every now and then they would give a sort of leap, and away they would shoot over the surface, as if it had been ice. Rollo reached his hand down and tried to catch one, to examine his feet; but he could not succeed. They were too nimble for him. He thought that, if he could only catch one, and have an opportunity to examine his feet, he could see how it was that he could stand so upon the water. Rollo was considering whether it was possible or not, that Jonas might make something, like the skippers' feet, for _him_, to put upon his feet, so that _he_ might walk on the water, when suddenly he heard a bubbling sound in the brook, near the shore. He looked there, and saw some bubbles of air coming up out of the bottom, and rising to the top of the water. He thought this was very singular. It was not strange that the air should come up through the water to the top, for air is much lighter than water; the wonder was, how the air could ever get down there. From wondering at this extraordinary phenomenon, Rollo began to wonder at another quite different question; that is, where all the water in the brook could come from. He looked at a little cascade just above the bridge, where the water rushed through a narrow place between two rocks, and watched it a few minutes, wondering that it should continue running so all the time, forever; and surprised also that he had never wondered at it before. He looked into the clear, transparent current, which poured steadily down between the rocks, and said to himself, "Strange! There it runs and runs, all the time--all day, and all night; all summer, and all winter; all this year, and all last year, and every year. Where can all the water come from?" Then he thought that he should like to follow the brook up, and find where it came from; but he concluded that it must be a great way to go, through bushes, and rocks, and marshes; and he saw at once that the expedition was out of the question for him. Just then he heard another gurgling in the water near him, and, looking down, he saw more bubbles coming up to the surface, very near where they had come up before. Rollo thought he would get a stick, and see if he could not poke up the mud, and find out what there was down there, to make such a bubbling. He thought that perhaps it might be some sort of animal blowing. He went off of the bridge, therefore, and began to look about for a stick. He had just found one, when all at once he heard a noise in the bushes. He looked up suddenly, not knowing what was coming, but in a moment saw Jonas walking along towards him. "Ah, Jonas," said Rollo, "are you going home?"