Frank's observations that day showed that they could not be far from the spot from where the Bolo had been left, but eager scrutiny failed to reveal her till almost sundown, when Ben's sharp eyes spied her—little more than a tiny black object on the horizon.
"There she is," he hailed.
Frank's binoculars soon confirmed the good tidings.
But as they neared the Bolo an astonishing thing happened.
Through the glasses they saw a form they recognized as Bluewater Bill's come out on the deck and gaze at them in amazement, to judge from the way he threw his arms about.
Presently he was joined by two other figures that the boys recognized as Billy Barnes and Lathrop.
Harry impetuously rushed to the rail, oblivious of the fact that at that distance the boys could not hear him, and shouted at the top of his voice.
"Hullo, Billy, hullo, Lathrop, hullo, Bill!"
It was then that the surprise was sprung. Frank through the glasses saw Bluewater Bill raise a rifle to his shoulder, and take deliberate aim at the dirigible. The bullet sang by the pilot-house chipping off a bit of molding.
"What on earth is the matter with them, have they gone crazy?" exclaimed Harry.