ere's nothing
very wonderful about getting back to it, either. It's just a matter of
minding your P's and Q's, and remembering a thing or two. We couldn't
take the car through the gap, but I believe we can make it with these
machines. We'll go around the hills instead of over them."

Then began a sinuous weaving back and forth, following the seams in the
uplifts and mounting steadily toward the narrow gap. The pace was slow
and labored, but Frank unerringly traced the way until the motor-cyle
lamps flung their round, yellow eyes squarely into the fissure of the
mountain wall.

"Maybe there isn't anything wonderful about this," called Clancy, as
Frank led the way into the narrow passage, "but--well, it gets my goat.
Poor old Pink is missing the time of his life. Now, if we can find
Borrodaile, and jog him into a realization of where he is and what he
has done, we'll just about make a good night's work of it. It's a relief
to know that the prof hasn't been in danger of being bunkoed out of his
gold mine."

"We don't know that yet," Frank called back over his shoulder. "Don't
take too much for granted, Red. This move on Happenchance may be putting
us clear off the scent."

"I'll bet something it isn't," said Clancy, with supreme conviction.

Emerging from the pass, the boys descended into a circular valley, in
whose center shapeless ruins covered all the old-time glories--such as
they were--of a once bustling mining camp.

The searchlights pierced the vast heap of debris, and revealed the
cluttered lane which had once been the town's main street. Carefully
Frank steered through the passage and came at last to a halt in front of
the only four walls in the place that remained standing. Here was the
building in which they had discovered Professor Phineas Borrodaile,
living alone in primitive surroundings and trying to imagine him self a
troglodyte.

"Hello, professor!" shouted Clancy.

His voice echoed back and forth between the cliffs that rimmed the
valley, but brought no answer.

"Not here!" he exclaimed, in a voice of profound disappointment.

"You really expected that yell would bring him?" Frank asked.

"I really did. Hang the luck! Say, Chip, I guess the theory won't hold
water. The prof is still mysteriously absent, after all."

Merry had removed the lamp from his machine, and was standing in front
of the old door. It was swinging by one rusty hinge, and he pushed it
wide open.

"Look out for snakes,