"Now that's interesting," suggested Charley. "You know the Bible tells us the world was made in six days; but it seems to me it isn't finished yet. Every rain washes down soil from the hills and helps to fill up the valleys and the river-bottoms, and the floods scour out the watercourses and carry earth and stones down to the ocean. And here we see a piece of land that used to be fine, dry bottom, now becoming a swamp. It looks to me as though the earth is changing every day." They examined the dam more critically. "It's two hundred feet wide if it's an inch," said Lew, "though the brook isn't more than fifteen or twenty. You see, it extends on each side of the brook to land that is a little higher than the level of the stream bank. That's what makes this big head of water. At the least there are several acres of it." "There's one thing that we haven't seen yet," added Charley, "and that's their houses. They ought to be some distance above the dam." "I wonder if those are beaver lodges," said Lew, pointing to some bulky heaps of brush at a little distance up-stream. "That's exactly what they are. They don't look much like houses, do they? But I guess they're pretty snug inside. The entrances are deep under water, you know, so that the ice can't clog them in winter, and so that the beavers can get to their food all right." "What do they eat, Charley? Do you know?" "Sure. They eat roots, and tender plants, but mostly bark from certain trees. I believe these are willow, poplar, birch, and some others. They cut down the wood in summer and pile it under water in front of their huts and hold it down with stones." "Well, what do you think of that!" cried Lew. "They eat a pile of it, too. I don't remember how many trees that article said a colony of beavers would eat in a winter, but I'm sure it was up in the hundreds. I remember how astonished I was when I read about it." "No wonder they clear the forest so fast. I wonder if we ought to tell Mr. Marlin. Maybe he doesn't know about these beavers. They might begin to cut down his virgin pines. I'm sure he wouldn't want that to happen." Charley laughed. "I'd bet my last dollar that Mr. Marlin knows all about these beavers. You can bank on it that he knows all there is to know about the territory he has charge of. And as for the beavers eating the pines, it seems to me that I read that they never touch evergreens." A ray of sun slipped through the leaves above them and fell directly upon Charley's face. He glanced up and was surprised to note how high the sun had climbed. Then he looked at his watch. "Gee whiz!" he cried. "We must have been fooling around this beaver dam for more than an hour. We must be about our business. We'll go on and locate the boundary line." "I wish we could get a glimpse of a beaver," sighed Lew.