"Well, I wish you would explain, Hugh," said Jack, "for I want to understand about this."
"Well, now," Hugh went on, "let's suppose you've got a little creek coming down from the mountains where no beaver have ever been, and a couple that have left some colony where they belonged go off and find this little creek, and think it's a pretty good place to stop. Maybe the creek is shallow, and, if it is, about the first thing they do is to build two or three low dams across it, so as to give them deep water for safety. Then from one of these little ponds where the water is deep, they'll dig a tunnel off at right angles to the stream, pretty well under the ground, about on a level, and when they get thirty or forty feet from the creek they'll enlarge it and make a room, and there is where they'll live for a little while. In the bottom of the tunnel there is water for quite a little way, but when they have dug up and made a room it's pretty dry there, except for the water that they pack in on their fur. Maybe they'll stay there for quite a while, but after a little while they dig upward and come out to daylight--on top of the ground in the stream bottom, I mean.
"Now, like enough they go off and begin to cut willows or cottonwood or aspen and bring it down close to the hole that they have in the ground, and very likely they'll pile sticks over that hole, possibly, at first, with the idea of hiding it. They drag down more and more sticks and make the hole from the tunnel bigger, and, presently, they begin to cut out the sticks that were first piled on top of the hole, so that, finally, they have their nest in the lower portion of this pile of sticks. Meantime, very likely, they have been working, more or less, on the dam on the creek below the house, and have raised the water still more, so that perhaps the tunnel is now full of water, and then, instead of using this tunnel to get out of, they'll gnaw a hole through the sticks of the house, making a passage-way from the room they occupy down to beneath the surface of the water. They still keep working at the dam, raising it and making it level, so that the pond gets bigger and bigger all the time.
"Perhaps the water is raised, so that it begins to come into the room in the house that they occupy; the place is getting too wet for them. Then it's quite possible that they will start down at the very edge of the water and gnaw a tunnel upward, in a slanting direction, perhaps quite close to the covering of the house, and, finally, when they get up near the top of the house, they'll gnaw out another room, almost above the two they had occupied before. All this time they're working at the dam and raising the water, and all this time, too, they are packing sticks up on top of the house, raising it higher and higher, and perhaps bringing mud, which they get along the bank, and putting this among the sticks on top of the house so as to bind the whole together and make it tight and warm for winter. If you study some old beaver pond, as I have, you will find that all along the edge of the pond, under the bank, but above the water, but, of course, below the grass-roots, the beaver have tunneled out roads partly hidden by the overhanging sod and grass. They take this mud, as I have told you, and use it on the houses and on the dams, and these hidden ways under the bank enable them to go quietly from one place in the pond to another without ever being seen."