He began to wish he could see the end of that gorge. But it grew narrower, and the shade changed to twilight, and there were no long, straight stretches. The river kept turning corners. Quick to note the slightest change in conditions, Ken felt a breeze, merely a zephyr, fan his hot face. The current had almost imperceptibly quickened. Yet it was still silent. Then on the gentle wind came a low murmur. Ken’s pulse beat fast. Turning his ear down-stream, he strained his hearing. The low murmur ceased. Perhaps he had imagined it. Still he kept listening. There! Again it came, low, far away, strange. It might have been the wind in the palms. But no, he could not possibly persuade himself it was wind. And as that faint breeze stopped he lost the sound once more. The river was silent, and the boat, and the boys--it was a silent ride. Ken divined that his companions were enraptured. But this ride had no beauty, no charm for him. There! Another faint puff of wind, and again the low murmur! He fancied it was louder. He was beginning to feel an icy dread when all was still once more. So the boat drifted swiftly on with never a gurgle of water about her gunwales. The river gleamed in brown shadows. Ken saw bubbles rise and break on the surface, and there was a slight rise or swell of the water toward the center of the channel. This bothered him. He could not understand it. But then there had been many other queer formations of rock and freaks of current along this river. The boat glided on and turned another corner, the sharpest one yet. A long, shadowy water-lane, walled in to the very sides, opened up to Ken’s keen gaze. The water here began to race onward, still wonderfully silent. And now the breeze carried a low roar. It was changeable yet persistent. It deepened. Once more Ken felt his hair rise under his hat. Cold sweat wet his skin. Despite the pounding of his heart and the throb of his veins, his blood seemed to clog, to freeze, to stand still. That roar was the roar of rapids. Impossible to go back! If there had been four sets of oars, Ken and his comrades could not row the heavy boat back up that swift, sliding river. They must go on. *X* *LOST!* “Ken, old man, do you hear that?” questioned Hal, waking from his trance. George likewise rose out of his lazy contentment. “Must be rapids,” he muttered. “If we strike rapids in this gorge it’s all day with us. What did I tell you!” Pepe’s dark, searching eyes rested on Ken. But Ken had no word for any of them. He was fighting an icy numbness, and the weakness of muscle and the whirl of his mind. It was thought of responsibility that saved him from collapse. “It’s up to you, old man,” said Hal, quietly. In a moment like this the boy could not wholly be deceived.