“It’s pretty firm,” said Doctor Dan, trying it. “I feel more worried about the rope. Lay hold here, boys, we will unwind it and tie one end to the post. Leave the knots to me. I’ll fix them so that two P. D.’s could not unloose them, but I don’t want to guarantee that the rope won’t break.” It took half an hour of good hard work to get everything in readiness and during all that time old P. D. had never moved. As there would be no chance to lasso him until he did, Dick and Charley undertook to stir the monster up by throwing big stones into the pool. Meanwhile Clara had taken her place at the top of the ridge behind the hut, rather a dangerous spot, too, for behind her there was a sheer descent down over the cliffs of several hundred feet to a narrow ledge below. “Give him another, Dick,” cried Charley. “I’m sure my last one hit him, but he never budged.” Dick let another stone fly and with such good effect that it struck the Plesiosaurus square on the back. Immediately the monster threw up its head and the water began to boil. Up came the long neck and the head was thrust angrily out of the pool. Doctor Dan, with a peculiar cry, flung his huge lasso and it dropped down over the monster’s head. “Pull! Pull!” shouted the Indian. “We have got him if we can only hold him!” Dick and Charley were at the other end of the rope and they pulled with all their strength, old P. D. giving out his frightful cry as the rope tightened about his neck. Suddenly his whole huge body rose to the surface and he darted forward toward the shore. The rope flew taut and snapped short off close to the post with a suddenness and a force which threw down Dick, Charley and Doctor Dan. Clara screamed and once more the Plesiosaurus gave its dreadful bellow. Its huge webbed feet were on the shore now and it darted its head, with open jaws, straight down toward Doctor Dan, who was trying to regain his feet. CHAPTER XXII. MUDD ON TOP AGAIN. Dick and Charley fully realized Dr. Dan’s danger, but what could they do? The dangerous attempt to snare the Plesiosaurus had not only been a complete failure, but a fearful mistake, for a few seconds later it looked as if Dr. Dan was doomed. The Plesiosaurus caught him just as it had caught Dick. It did not bite the Indian, nor even seize him in its terrible jaws, as one might have expected, but with lightning quickness it ran its head under Dr. Dan, and the next Dick and Charley knew it had him twisted in a fold of its long neck, and went waddling off toward the steep, slippery trail down the mountain. “Fire at him, boys! Fire! Save me if you can!” shouted the unfortunate guide. Until then the boys had just stood there dumb with the horror of the situation. How could they fire? Dick’s revolver had been taken from him by Martin Mudd. Charley had lost his coming down through the Boiling Pot. Dr. Dan himself was the only man who was armed.