twelve o'clock
`` We must continue our voyage . '' They were soon on the _ Porpoise _ and steaming away from the strange island , the inventor deciding to get far off out of the influence of the terrible waterfall . The night was , as usual , spent with the ship slowly steaming ahead on the surface of the water . It was getting on toward twelve o'clock and Washington had the watch . He was to be relieved by Jack . The latter had been awakened by the alarm clock at the head of his bed , which time-piece he had set to arouse him so that he might take Washington 's place . Jack was just getting the sleep from his eyes by a vigorous rubbing when he heard a loud yell .