“All this time I have sustained life by means of fruits that grow in abundance in this tropical valley.  In the hope that I may manage to communicate my horrible condition to the outside world I have made scores of small parachutes, and when the breeze at the top of the cliffs appeared favorable, send them up by means of hot air, each carrying a message to my son.  God in His infinite wisdom only knows if one of these will ever reach him.  I shall continue to have hope, and sustain life as long as my mind remains—­

“Professor Philip B——­”

When he had finished this astonishing document Frank turned to his chum.

“Oh! what a remarkable thing!  I never heard its equal in all my life.  To think that your father has been alive all these months, though a prisoner in that cliff-bordered valley!  But Andy, don’t you see that now nothing is going to keep us from going down there, and finding him?  Here is the clue you wanted, only instead of discovering his sad fate you are going to rescue him, and bring him home again!”

They reached out and gripped hands.  There was something in that act to stamp the more than brotherly feeling existing between them.

“Do you think we could do it, Frank?” exclaimed Andy, more than ever willing that his clear-eyed chum should take the lead in this most eventful moment of his whole young life.

“Sure I do,” answered the comforter, readily.  “Didn’t we conquer one battery of cliffs that were said to be insurmountable, when we sailed in our dandy little monoplane up to the crown of Old Thunder Top, and snatched that silver cup for a prize?  Make up your mind, my boy, that that was just meant to get us in practice for better things.  The time’s come for us to show what we’re made of.  And instead of a silver cup, the prize this time will be—­”

“My father’s life!” murmured Andy, tears in his eyes, as he again squeezed that faithful hand which held his so firmly.

“That’s right,” Frank continued.  “We can go straight to this fine Spanish gentleman, Senor Almirez, and get all the points he knows.  From there we’ll get up-river to this valley town and visit Carlos Mendozo on his cocoa plantation.  Depend on it he’ll be able to set us on the track, somehow or other.”

“Oh! it seems like a strange dream,” said Andy, as he raised the piece of bark to his young lips, and passionately kissed it, regardless of the fact that some one passing the post office might notice him.

“Well, you want to wake up right away then,” remarked Frank, smiling, “because we’ve just got to get a hustle on us, if we’re going to start on this wonderful trip.  Here’s where our aeroplane is going to help us out.  Just imagine how we can pass over regions where it would be next to impossible for us to navigate on foot—­mountainous country, tropical valleys where wild beasts roam and poisonous snakes abound; and jungles where the natives have to cut a passage foot by foot, I understand, with their machetes.  And to think that we can sail freely over it all, looking for that spot where that bark letter came from.”