Andy looked at his chum admiringly.

“Blessed if you don’t just think of everything!” he said; “and get ready long before it happens.  However do you do it, Frank?”

“Oh, it’s easy, once you make up your mind,” laughed the other.  “I took to it long before this new Boy Scout movement started.  You know they’ve got as their leading motto the words:  ‘Be prepared.’  And there never was a better slogan ever given to boys.  Think how many things might be avoided if we were always prepared.”

“Yes, I’ve given the subject much thought,” grumbled Andy; “but somehow I seem to slip up when it comes to the critical time.  I stay awake eleven hours, and just when I doze off in the twelfth watch the blamed thing happens!  It’s always that way, seems to me.  How can a fellow stay awake all the time, tell me that?”

“Oh, rats!  There’s no need of that.  Just fix things so you’ll be aroused when it comes along, and be ready to turn the tables.”

So they talked away into the afternoon.  The engine seemed to be on its best behavior.  McClintock, the Scotch engineer, who was the only foreigner aboard besides the boys, reported that he was beginning to have more faith in the machinery.  The work of the last twenty odd hours had certainly been a pretty heavy tax on it and everything seemed to be going like clockwork.

“I only hope it’ll keep up, then,” said Andy.  “One more night is all I ask.  Then Felipe promises to have us at our journey’s end, when I can see and talk to the very man who picked up that wonderful little parachute, with its message from the unknown valley among the cliffs.  I wish the time was here right now.”

“Felipe, by the way, is taking his rest now,” said Frank, after a little time; “for he expects another night on duty.  We still meet many tree trunks sweeping down on the current.  The man at the wheel has to keep on guard constantly.  Look at that tremendous one, will you, Andy?  And just 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.”