He was gone the best part of half an hour, when he returned in considerable excitement. "The haythins have tracked us to the waterfall!" he whispered. "An' wan av thim--Chief Walru--is thinkin' av thryin' to git behind th' water into the cave!" CHAPTER XVI THE ESCAPE TO THE COAST The announcement that the savages were trying to get into the cave under the waterfall filled Dave and his friends with new alarm. "You are sure of this, Stoodles?" questioned Captain Broadbeam, as he leaped to his feet. "I am," was the Irishman's answer. "We ought to be able to hold them back," put in the doctor. "Can't we hurl them into the stream as fast as they appear?" "That's the talk," came from Bob. "Let us line up just this side of the waterfall." "Perhaps we can scare them," suggested Dave. "I know all savages are very superstitious." All made their way to the edge of the waterfall, and Pat Stoodles showed them a crack in the rocks, at the side of the falls. Here they could see the savages lined up outside, with Chief Walru at their head. Several were talking excitedly, and the chief was wading in the water at the very foot of the falls. Now the chief took up a rock and hurled it into the waterfall. It whizzed past Doctor Barrell and struck the flooring some distance to the rear of the cave. Dave saw the movement, and of a sudden a strange idea came into his head. He would scare the savages if he could. Filling his lungs with air, he let out a most blood-curdling scream, followed by a series of wild and unearthly groans and a long hiss. The savages were thunderstruck, and those on the bank of the stream took to their heels with all possible speed, while Chief Walru tumbled backward and then began to scramble over the rocks for dear life. Again Dave let out a scream, and then groans which were more dreadful than the others. In less than three minutes not a savage was to be seen. "They have gone!" said Bob. "If only they don't come back," returned Captain Broadbeam. "I have an idea," said the young diver. "Why can't we pile up some stones in front of that opening? Then if the savages try to get through the waterfall they will get badly left." "That's the talk!" came from Bob. "Are there stones handy, Stoodles?" "Sure, plinty of thim." And the Irishman showed the way to where lay a quantity of stones, large and small. With the doctor holding a torch to light them, all hands began to haul stones to the opening. Those that were flat were placed on the bottom and soon the opening was filled up to within two feet of the top. Other stones were piled up behind, so that those in front might not be shoved back. "Now we are safe--at least for the time being," said Captain Broadbeam. "But the next question is, how are we to escape and get on board of the _Swallow_?" "Isn't there another exit from the cave?" asked the doctor. Pat Stoodles shook his head.