"We'll float down the sluiceway to freedom!" he cried, as he placed the plank on the edge of the flume. Nat did likewise, and, when Jack climbed over into the big oblong box, his companion followed. They had entered the sluiceway at a place where there was scarcely any current. Then they moved forward, crouching to avoid the cross pieces. "Here we go!" whispered Jack, throwing himself on the plank, an example which Nat followed. The next instant the two boys were being whirled down the sluiceway on top of the water at a swift pace. And, as they shot ahead they, heard a voice calling: "The kids have got away!" CHAPTER XXXIII DOWN THE SLUICEWAY Almost with the speed of an arrow from the bow the two boys flew forward on the swiftly-moving water in the sluiceway. The planks were submerged only a few inches, so great was the force of the current, and Jack and Nat, crouching on them as a boy goes sliding down hill on his sled, with his head between the points of the runners, felt themselves propelled forward with an irresistible power. At first it was so dark in the big box they could see nothing. Then, as their eyes grew accustomed to the gloom, they could note the sides of the flume slipping past them. A glance over their heads showed them the stars, and there was a confused blurr of the many cross- pieces. "Are you all right, Nat?" called Jack. "Sure," was the reply. "Say, it took my breath away at first, but it's all right now. This is going some!" Faster and faster the boys were whirled along. The water was beginning to chill them now, and they were wet through. Once or twice a sudden change in the direction of the sluiceway nearly brought them to grief, and on one occasion Nat slipped off his plank. It was floating away from him, but his cry warned Jack, who managed to stop it, while Nat struggled forward, stooping to avoid the braces, and secured it again. This occurred in a comparatively level place, where the current, after a quick descent, was not so rapid, otherwise there might have been a different ending to this story. For a mile farther the two boys floated along at an easy pace. "I guess we've left 'em behind," Nat observed. He was riding his plank alongside of Jack now, as the flume was broad enough to permit this. "Yes, but they're not going to give up so easily," Jack rejoined. "There's too much at stake. They'll chase us, but it's another thing to catch us. Hark! What's that?" From down below in the moonlit valley, into which the flume dipped there came a roaring sound. It was like a mighty wind blowing, and, as the boys were carried on and on, it increased in intensity. "Sounds like a waterfall," observed Nat. "So it does. I hope this flume doesn't do any stunts like that. We'll be dashed to pieces." "Maybe we'd better stop now, and get out," said Nat. "I wonder where we are?" "Haven't the least idea. We must have come about three miles though. Let's see if we can stop ourselves,"