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.