Another thing: The lake-dwellers had plenty of water to build in; plenty, but not too much. The beavers don't have this advantage. They usually build in the water of flowing streams, and they have to make their _own_ lakes. How would you do it; even if you had tools? But remember, being a beaver, you've got nothing to use but two honest paws and a set of teeth. It was with these Mr. Beaver did it all--with his teeth, his paws, and his head; the inside of his head, I mean--his brain. Take the matter of water arrangements. He gets the water to lie quietly and at just the right depth by building his dam across the stream. This dam not only provides him with water of just the right depth to protect his front door from enemies and to keep rushing torrents from carrying his house away, but the spreading out of the original stream bed into a pond helps in gathering the Fall harvest of trees, since it brings the trees nearer to the water's edge, and water transportation among beavers, as among men, is always cheapest. Although dams are usually built of trees which the beavers cut down themselves, they also use cobblestones where trees are scarce; for Mr. Beaver is a very thrifty soul; he doesn't waste material nor time nor effort. Many books about beavers say they cut the trees so they will fall across the stream, but Mills says, in his book on the beaver, written after many years of patient observation, that beavers don't seem to care how the tree falls, just so it doesn't fall on _them_! Not but what they _could_ cut trees to fall in the water if they thought best; for just watch them build a dam and see how clever they are; cleverer, possibly, than some of us. [Illustration: BEAVERS AT WORK ON A DAM See how many of the features of the building of a beaver dam, as described in our story of these wise little people, you can make out in this picture.] Let's see. Say you've got your trees up to where the dam is to be; now how are you going to set them in building the dam? SEE IF YOU'RE AS CLEVER AS MR. BEAVER "Right across the dam," you would say, wouldn't you? That is what most people have said when I have asked them that question; for that is the way men do it. But remember, if you built the dam as men build dams you would have to drive stakes or do something to keep the logs from washing away. Years ago, when writers used to theorize a great deal on how things were done, instead of getting outdoors and watching patiently to see how they actually _were_ done, it was said that Mr. Beaver in building his dam did really drive stakes and that he did it with that big tail of his. But what Mr. Mills found was that the beaver lays his trees lengthwise of the stream. You see why that is, don't you? When the trees are laid lengthwise, the water, instead of striking them broadside, strikes only the end and so there is less likelihood of their being carried away. Another thing, two things, about the trees in the dam--in fact four: