ng in the surface
opening, the boys stopped once more for consultation.

While they stood on the edge of the chasm considering the situation, a
bright blaze leaped up some distance to the north.

"Some one's burning green boughs!" exclaimed Tommy.

"How do you know that?" asked Sam.

"Look at the white smoke!" answered Tommy. "I guess if you had made and
answered as many Boy Scout smoke signals as I have, you'd know how to
make a smudge."

"It's so bloomin' dark I couldn't tell whether the smoke is while or
black!" declared Sam. "I can see only the bulk of it."

"If it was good and black," Tommy answered, "we couldn't see it so
plainly. And, come to think about it," he added, laying a hand excitedly
on Frank's shoulder, "there are two columns of smoke."

"I see the two now," Frank answered. "One column has just begun to show.
You know what that means, of course!"

"It means a Boy Scout signal for assistance," replied Tommy.

Doctor Pelton turned to the boys with an anxious face.

"Do you really mean that?" he asked.

"Sure we do!" replied Tommy. "Two columns of smoke ask for help."

"Then there must be Boy Scouts in trouble on the other side of the
chasm!" the doctor concluded.

"That's about the size of it!" Frank exclaimed.

"Look here," Tommy declared, "we've just got to get across that crack! I
wonder if it would be possible to find walls so slanting that we could
pass down this side and up the other."

"Well, even if we did," Sam argued, "there's a rush of water at the
bottom. I don't see how we could get across that."

"I know how we can get across it if we find the walls accommodating,"
Tommy exclaimed. "You saw how the trees tumbled into the chasm, didn't
you? Well, if we can find a place where the moraine was heavily wooded,
we'll find a bridge of tree trunks across any water there may be at the
bottom! And the bridge may not be very far down, either!"

"Great head, little man!" laughed Frank.

"You ought to consider the matter very seriously before entering the
chasm at all," suggested the doctor. "Remember that it is uncertain as
to size and that the walls are liable to crumble."

"But see here," exclaimed Tommy, "there's a Boy Scout signal for help on
the other side, and we've just got to get across! For all we know, the
cabin may have been wrecked by the earthquake, and the boys may have
been injured in some way!"

"I'm game to go!" shouted Sam.

"Of course I'll go with you," the d