p south.

"Surrender!" cried Frank, believing that the very sound of his voice
would do much toward frightening the would-be traitor.

But he hardly expected such a tremendous upheaval as followed. The man,
believing that possibly the "devil-bird" had broken out of its cage and
was about to carry him off in its gigantic beak, gave a shrill scream of
terror, and bouncing up, broke the slender hold Frank had secured upon
his person.

Not to be outdone, Frank, recovering, chased after him. He believed it
his duty to at least learn the identity of the rogue, so that he might
understand just how deeply the conspiracy had taken root in the crew.

Between himself and the hanging lantern he could make out the fleeing
figure of the fellow, and hot in pursuit he followed as fast as his feet
would let him. The man undoubtedly heard him coming, for, if anything,
his fright increased. Out upon the open deck they flew, Frank just a few
feet in the rear. He had even stretched out his arm and touched the
garments of the runner, when with a screech the fellow made a furious
plunge straight over the side of the boat.

He evidently chose to take chances in the swift current of the Magdalena
rather than trust himself in the power of the unknown pursuer, which
doubtless he believed to be the dreaded "devil-bird" that had been
confined in the box cage!

CHAPTER XIV.

THE AIRSHIP LAUNCHED AT LAST.

Frank came near following after the unknown member of the crew, when the
other made that flying leap over the side of the boat. Not that he
wanted to take a bath just then, but his forward progress had been
rapid, and he only saved himself by banging up against the taffrail,
which was unusually high for so small a vessel, and holding on sturdily.

He had heard the splash as the fellow reached the water. Doubtless he
was a good swimmer, as about all these natives seemed to be, and barring
his falling a prey to some loitering alligator or other reptile, he
would be able to gain the neighboring shore further down.

At any rate it was folly to think of looking for him.

"What's all the row?" cried Andy, as he came plunging forth from his
stateroom.

Some of the crew were even then looking over the side, and Frank
imagined they could give a pretty good guess as to what it meant. But
he heard not a word from even old Quito, and while the absence of a man
must be noticed in the morning, there would probably be no complaint.

When A