eo's camp, first--flying very high. From there on
I'll direct you. Shall we start?"

"You're the doctor," grunted Johnny, not much pleased with Cliff's
habit of giving information a bit at a time as it was needed. It
seemed to betray a lack of confidence in him, a fear that he might tell
too much; though how Johnny could manage to divulge secrets while he
was flying a mile above the earth, Cliff had probably not attempted to
explain.

Because he was offended, Johnny gave Cliff what thrills he could during
that flight. He went as high as he dared, which was very high indeed,
and hoped that Cliff's ears roared and that he was thinking pleasant
thoughts such as the effect upon himself of dropping suddenly to that
sliding relief map away down below. He hoped that Cliff was afraid of
being lost, and of landing on some high mountain that stuck up like a
little hill above the general assembly of dimpled valleys and spiny
ridges and hills. But if Cliff were afraid he did not say so, and when
the double-pointed hill that Johnny had reason to remember slid toward
them, Cliff pointed ahead to another, turned his head and shouted.

"See that deep notch in the ridge away off there? Fly toward that
notch."

Johnny flew. The double-pointed hill drifted behind them, other hills
slid up until the two could gaze down upon their highest peaks.
Beyond, as Cliff's maps had told him, lay Mexico. At eight thousand
feet he shut off the motor and glided for the notched ridge. The
patrol who sighted the Thunder Bird at that height, with no motor hum
to call his attention upward, must have sharp eyes and a habit of
sky-gazing. Cliff, peering down over the edge of the cockpit, must
have thought so, for he laughed aloud triumphantly.

"Fine! I think we are putting one over on my friends, the guards," he
cried, with more animation than Johnny had yet observed in him.
Indeed, it occurred to Johnny quite suddenly that he had never heard
Cliff Lowell laugh heartily out loud before. "How far can you keep
this up--without the motor?"

"Till we hit the ground," drawled Johnny, who was enjoying his position
of captain of this cruise. He had been taking orders from Cliff for
about forty-eight hours now without respite save when he slept, and
even his sleep had been ordered by Cliff.

"I could make that twelve miles or so from here, though. Why?"

"In the twelve miles you would not be using gas--could you glide to the
ridge, circle a