They went on again, following up the river for an hour or two. In the meanwhile the mist melted, and Frank could see the endless ranks of mighty trees stretch away before him until they merged into a blurred columnar mass. At last the cañon, which was growing shallower, forked off into two branches, and they followed one branch until a broken rocky slope led them down to the water. It was a dull greenish color and foamed furiously past them among great stones. There was no means of ascertaining how deep it was and the boys looked at each other dubiously for a moment or two. Then Harry made a little gesture. "We have to get across," he said. Frank, without waiting for his resolution to fail him, plunged in on the instant, and a couple of steps took him well above his knees. The water seemed icy cold. As a matter of fact, it was mostly melted snow, and the drainage from the glaciers had given it the curious green color. The gravel commenced to slide away beneath Frank's feet, and by the time the foam was swirling round his waist he was gasping and struggling savagely. There was a big, eddying pool not far away and, though he could swim a little, he had no desire to be swept into it. A moment or two later he was driven against a rock with a violence that shook all the breath out of him. He clung to it desperately until Harry came floundering by and held out his hand. They made a yard or two together and then Harry slipped suddenly, jerking Frank off his feet as he rolled over in the flood. Frank went down overhead and as he felt himself being swept along toward the eddy he exerted all his energy in a struggle to regain his footing. He clutched at a rock, but the swirling waters only carried him past. Half dazed and breathless he was flung against another rock. This time, with a great effort, he managed to hold on, and when he stood up, gasping, he found that the water now reached only to his knees. In another minute he and Harry were safe on dry land. Half an hour later they crossed the other creek, and soon afterward Frank sat down limply in the warm sunlight, which at last came filtering between the thinner trees. "I must have a rest," he gasped. "There's just this trouble," Harry pointed out. "If you rest any time you won't want to get up again." "If I go on now I'll drop in another few hundred yards," declared Frank.