Yet presently Dick halted. Dave stopped beside him.

"We've passed him; he has doubled on us," uttered Darrin in a
tone of intense chagrin. "We belong in the primary class in wood
lore."

Then, suddenly, they heard a slight noise again. Forward they
dashed. Now they came out to a place where the ground was more
open. Before the two high school boys rose a great boulder of
rock, its front sloping backward, and running up to a height of
fifty feet or more. They had already seen this boulder from the
water.

"That fellow ran into the open, but he didn't have time to cross
it," announced Dick in a tone of conviction, as the pair halted
at the foot of the boulder. "He could have gone up this side;
there are crevices enough for foothold. But in that case we'd
have seen him."

Dave stood plucking absent-mindedly at the leaves of a bush in
a clump that grew at the foot of the boulder. Suddenly Dick glanced
down, noting that his feet were on boggy ground, though the surrounding
soil was firm enough.

"Is there a spring running out of the solid rock?" wondered Dick,
reaching out and pulling one of the bushes forward.

Then he gave a sudden shout of discovery:

"Look here, Dave! We're on the track of it! These bushes conceal