notice how dense the forest is ashore around here. How any one can get
around at all beats me. I should think they'd have to keep their
machetes busy all the time cutting the matted vines away."

"I understand they do," the other went on. "And I rather guess that
there's hardly a country under the sun where an aeroplane would be of
more real benefit than right here in the tropics. Think of avoiding all
that tangle--of floating along, a mile a minute if you wanted, far above
the tree tops and away from all such a muss."

"You're right," agreed Frank, fervently. "And it's the only way any one
could ever hope to discover this strange prison of your father. From a
distance of a thousand feet we can have a big range of vision. With our
good glass it will not be hard to discover the cliffs, if only we figure
out in which direction we can have the best chance. And I think I've got
a scheme ready to manage that."

"I depend on you to do it," said Andy. "Alone by myself I would simply
despair of ever learning anything worth while. But while you are along I
just feel that we're going to succeed."

"I ought to thank you for saying that, but I won't," Frank
declared. "Because it makes me tremble for my reputation as a prophet."

"But you have seen nothing to make you less confident, I hope?" cried
the other.

"To be sure I haven't," replied Frank, readily enough. "On the other
hand, I ought to feel better satisfied than ever, because we've managed
to outwit every cause for trouble that has cropped up this far. We'll