Owing to the fact that the cross-pieces were above and close to their heads, the boys could not peer over the edge of the flume. The water filled it to within a foot and a half of the edge, and they had to keep their heads well down. "Try and grab a cross-piece," said Jack. The sticks were about six feet apart. Nat cautiously raised his hand. His fingers brushed under the sides of several braces, but he had to move his arm up very slowly as a sudden contact with them would have broken his wrist. Jack was doing the same thing. The roar was growing louder now, and the water could be heard tumbling and crashing down. "The flume must be broken just below here!" cried Jack. "We must stop or we'll be killed!" He made a desperate effort to grasp a brace. He got his fingers on one. Then came a sudden rush of water, caused by a sharp decline in the level of the sluiceway, and Jack was torn from the cross-piece. At the same time his plank was swept from under him, and he was buried in an overwhelming rush of water. Over and over he was rolled along the bottom of the flume. Then he was tossed to the surface. For an instant he had a glimpse of Nat also struggling in the murky flood, on which the moon shone brilliantly. [Illustration: JACK WAS SHOT FORWARD AS THOUGH FROM A CATAPULT.] The next instant Jack was shot forward as though from a catapult, feet foremost, and, as he fought and struggled to get his breath, he saw that he was in the midst of a giant waterspout, as it leaped from the end of the broken flume and plunged, like a stream from an immense hose, into a swirling pool which the freed sluice water had dug in the soft soil. Forward and down went Jack, and, though it seemed like an hour while he was being shot out with the water as it spurted from where the flume was raised on a high trestle, it was only a second or two before he was plunged into the pool. As he sank down and down the lad was aware of a splash close beside him, and he dimly thought it must be Nat. And so it proved. Nat, also, had been spouted from the flume into the pool, and, when Jack, after a fierce fight with the bubbling water came to the surface and began swimming, he saw Nat bob up a moment later. Both boys worked to get away from the plunging stream. "Are--you--hurt?" asked Jack, pantingly. "No--are--you?" inquired Nat. "Nope! Wonder--what--sort of--a place--this--is." "Kind--of--wet," remarked Nat, and, in spite of his peril Jack could not help smiling. When the water had cleared from their eyes the boys saw they were in the midst of a miniature lake. It was formed of the water that escaped from the broken pool, and had filled a big hole, a sort of basin on a ledge of the mountain. They struck out for the nearest shore, reaching it after some little difficulty, for their wet clothing hampered them.