That was Frank’s way; and just now Andy fully approved of it.  His heart was so set upon having a chance to use the monoplane in the endeavor to discover that strange cliff-enclosed valley, where his father was imprisoned, that he did not mean to take any chances of losing out through over confidence.

So he packed off to his berth, while Frank prepared for three hours of lonely vigil.  He expected to make the rounds just about once in so often, and have a few words with the man at the wheel.  Felipe had declared that it was his intention to keep busy himself through the night, since he dared not trust the wheel in the hands of an inexperienced pilot while darkness lasted.

In the morning he could give directions, and allow an assistant to do the work, while he secured some rest.

There was no moon after early in the evening, when the young queen of the night disappeared in the west, leaving the bright stars to control the skies.

The boat continued to make good headway against the current, though at this season of the year the Magdalena is bank full with the summer rains, which fall almost every afternoon in a deluge.

A searchlight sent a dazzling shaft of light far ahead on the troubled surface of the booming flood.  This was an absolute necessity, for otherwise it would have been too dangerous bucking against that tide; laden as the river was with floating tree trunks of gigantic size, that had been swept from their resting-places in the lowlands above.

Once Frank had seen a wild animal crouched on one of these great logs.  The boat passed so very close to the floating refuge of the beast that ere darkness claimed the strange craft with its stranger cargo, Frank had been able to see the tawny hide of the crouching beast, and note the quick, jerky motion of its long tail.

Upon hurrying to the pilot house and making inquiries of Felipe he learned that, just as he suspected, the animal was a jaguar, the most feared inhabitant of the tropical forests away off at the headwaters of the Magdalena and Orinoco rivers.

There was a spice of peril hovering over the progress of the little boat during every hour of that night.  It might come in the sudden leap of a wild animal, that judged any port would be better than a floating log.  Then there was a chance of their running afoul of a monster derelict, in the shape of a drifting snag, that might punch a hole in their bow, and bring about trouble.

On top of all was this unseen peril from the revolutionists, who were making the Magdalena country the center of their renewed activity, for some reason or other, and had their minds set on securing the first aeroplane ever known to be in Colombia.

The time passed away.  When three hours had really gone, and all seemed well, Frank awoke his chum.  Generous to a fault, he might have held out much longer, for he did not feel exhausted; but Andy, who knew him like a book, had made him promise faithfully, on his word of honor, that he would arouse him at exactly the time agreed upon.