he 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?"

"Yes," said Jonas, "unless you will go for me."

"Well," said Rollo, "what do you want me to get?"

"I want some fire, to burn up some brush. You can bring out the
lantern."

"Very well," said Rollo, "I will go; only I wish you would tell me where
these bubbles come from out of the bottom of the brook."

"What bubbles?" said Jonas.

So Rollo took his stick, and pushed the end