"Well, there isn't enough water here to float a log," said Lew, "though it's mighty wet and it looks as though the water was several inches deep a little farther on. Let's see if we can find a canal." They stripped off their shoes and stockings, and, rolling up their trousers, began to wade. Very soon they found the water nearly knee-deep. "There's more water here than there seems to be," admitted Lew. "There's so much marsh-grass and so many water-plants it fooled me." Cautiously they waded about. Suddenly Lew plunged forward, and only by grasping a bush did he save himself from getting completely wet. As it was, he found himself standing upright in three feet of water. After he recovered from his surprise, he felt about with his feet. "This is their canal all right enough," he said. "It's very narrow, but it will float anything that grows in this forest." He scrambled out and the two boys made their way back to dry ground. "How are you going to get dry?" asked Charley. "I don't want to make a fire unless it is absolutely necessary." "Never mind about me. I'll dry off soon enough. Let's find their dam." They made their way toward the run and soon discovered the dam. It was a great pile of branches, stones, moss, grass, mud, bark, etc., that had been built across the stream and extended for rods on either side. It looked very solid, yet the water did not pour over it, but filtered through it. "Think of all the work it took to make that," cried Lew. "Why, every stick in it had to be gnawed down and floated here, and all the bark and grass and roots had to be pulled and brought here and the stones collected. And say! How in the world do you suppose they ever handled those stones? And how do you suppose they ever anchored the stuff when they began building? I should think the current would have swept everything away at first. That's a pretty swift stream." "I read that they start their dams with saplings, which they anchor across the current with stones. They are much like squirrels, you know, and can use their fore paws about as well as we can use our hands. I suppose the stones lose weight by displacing water, but if I hadn't seen these rocks, I'd never have believed that such big stones could be handled by animals no larger than beavers." "See here," said Lew. "These willow branches must have taken root, for they seem to be growing right up out of the top of the dam. And there's a birch that's surely growing. You know the branches of some trees will root if you put them in water, especially willows. Why, if they continue to grow and take more root, there'll be a hedge of living trees right across this brook. The dam will become so dense that it will back up a great quantity of water. I reckon this bottom will just naturally turn into a swamp after a time."