the leaf, and subsequent events confirmed his
reasonings."

The boys quickly learned their lessons. Each knew that every step
forward meant an entrance to an unknown world.

CHAPTER III

THE BEAR FIGHT

During the day, following the night when the mysterious lights appeared
in the lowland directly to the west and beyond the river, they passed
through several dense forests. George, who was in the lead at this time,
emerged from the thickest wood into a rather open plain. He saw the
river make a long circular sweep, and directly ahead noticed a coast
line of steep hills which marked the shore of the river on the opposite
side.

Harry and the Professor, who were behind with the team, had not yet
reached the clearing. As George passed into the open space he saw an
animal cross his path, and without waiting to inform the others, he
shot. This alarmed Harry, who was out of the wagon without waiting for
any word from the Professor. Immediately after George's shot was heard,
they plainly heard another from the direction of the river ahead of
them. The Professor, too, jumped from the wagon and followed Harry.
George fired a second time, and another shot came from the river. Harry
turned and looked back at the Professor in amazement.

"What can that mean? Did you hear four shots?"

"Yes; run ahead, and find George."

In a brief time both boys returned. "George says he did not hear the
shots from the river."

"They were as plain as your own."

George did not know how to explain it. The Professor moved forward. "Let
us get out into the opening."

As they reached the clearing beyond the wood, and the Professor saw the
steep bluffs beyond, he laughed, and looking at the hills, said:

"That is where the shots came from."

His amusing smile was reassuring, although his words were not.

"That bluff over there is about 2,000 feet from here. We had better find
out what he is doing there."

"Two thousand feet; and somebody there!"

"I did not say somebody was there, but that the noise of the shot came
from that place."

"Do you think it was simply an echo?"

"Undoubtedly; didn't you hear Baby's cries repeated?"

"But how do you know that the hills are 2,000 feet away?"

"Sound travels at the rate of 1,040 feet per second, and I made a mental
calculation that it took four seconds for Baby's cries to come back from
the hills. In that case the sound had to go to the hills and back again,
and it would, theref