eleven o'clock
Once the young aviators had engaged in a terrible conflict with those two mighty birds , on the crown of the mountain , where they had landed with their aeroplane , and been looked upon as intruders by the eagles , possibly under the belief that they entertained hostile intentions toward the fledglings in their nest that was built amidst the crags , close to the tip of the lofty peak . Frank and Andy often spoke of that thrilling episode , but never without some sort of little shiver , because it had been a serious time with them since one blow from those powerful wings might have toppled them over the edge of the dizzy height , and sent them to their deaths . But they had succeeded in beating their feather antagonists off by the aid of clubs which they wielded with vigor ; and after the eagles learned that no harm was intended to their young by these bold navigators of the upper air currents , they came to have more respect for the strange winged thing that came humming up from the earth on more than one occasion . When eleven o'clock came around , the boys were off again , and headed toward the northern end of the lake . Of course they kept close down to the treetops , because , once they discovered the opening , they would wish to drop into it as easily as possible . Suddenly Andy , who was on the lookout , while Frank paid more attention to the easy working of the motor , and the steering of the hydroplane , uttered an exclamation of satisfaction . `` I see it , dead ahead ! ''