“Come, let’s go home!” exclaimed Andy.  “I’m sure Colonel Josiah will be tremendously interested in what we’ve learned.  He’ll be the most disappointed man in the whole U.S. just because he’s so crippled that he can’t go along.  For many years he’s traveled in every country under the sun.  Perhaps he might tell us more about the interior of Colombia than we know right now.”

Accordingly they hurried away.  Frank came near forgetting the news he had been bearing at the time he met his cousin.  But then, that was hardly to be wondered at.  The capture of the escaped robber was of minor importance when compared with this wonderful business connected with Professor Bird.

And just as Andy had said, Colonel Josiah was tremendously interested when he heard about it, and with his own eyes looked upon the letter that had come from a living tomb.

“Somebody pinch me,” he said, looking at the boys almost helplessly.  “I surely must be asleep, and dreaming this.  It seems too strange to be true.  Philip alive all these months, and in that terrible situation, while we were enjoying the good things of the world up here.  It is monstrous!  You must go down there with as little delay as possible, Andrew.  Who knows but what it may be your blessed good fortune to rescue your dear father, and bring him back with you.  Money—­all you need; and the prayers of an old man go with you.”

“But think,” said Andy, uneasily, “this was written three months ago.  What may not have happened in all that time?  There must be beasts in that sunken valley, and doubtless many poisonous reptiles.  Perhaps—­”

“Hold on!” cried Frank, interrupting him, “don’t you go to imagining all sorts of terrible things.  He had been there at least nine months already.  Nothing had happened to injure him.  He does not even hint at such a thing; but says he means to sustain his life as long as he retains his proper mind.  Your father was not in the least like you, Andy.  He possessed a wonderfully well-poised mind, and laid out his plans with deliberation.  Believe me, the chances are ten to one he is still there, and waiting.  We are going to find him.  Don’t allow any other idea to take possession of your head.  Find him, do you hear?”

Of course that sort of talk had its effect on Andy, and he braced up.  They began to make preparations and plans without delay.  The monoplane was taken apart, and carefully crated.  Then Frank ran down to the city and returned with several duplicate parts, secured at an aeroplane agency he knew of, and which would come in handy in case of an accident in that strange country, where they must depend entirely on themselves.

For two days there was a tremendous lot of bustle around both homes.  Dr. Bird had no longer any valid excuse for refusing Frank permission to go, since it was a mission of mercy that beckoned the boys on to that South American mountainous region.  Besides, he had always been very fond of his elder brother, who had done so much to make the name of Bird famous, in college and out; even though the professor had thought best to make his old friend, Colonel Josiah, his boy’s guardian instead of the physician.