One of the most interesting of all the rodent animals is the beaver, which is found in the northern parts of Europe, Asia, and America. It spends a great part of its life in the water, and no doubt you have heard of the wonderful dams which it makes in order to prevent the rivers from drying up during the summer months. When the animals want to construct one of these dams, the first thing they do is to fell a number of trees which stand near the banks of the river. They do this by gnawing through the stems quite close to the ground, and they are able easily to cut through trunks ten or even twelve inches in diameter. Most likely one of the trees falls across the stream. In that case they leave it as it is. Then they strip off the bark from the others, and cut up both the trunks and the larger branches into logs about four or five feet long. These logs they arrange most carefully in position, piling them upon one another, and keeping them in their places by heaping stones and mud upon them. They also fill up all the gaps between them with mud, and so hard do they work that by the time the dam is finished it is often two hundred yards long, fifteen or even twenty feet thick at the bottom, and six or eight feet high. And when the river runs swiftly, they are clever enough to make their dam in the form of a curve, so that it may be better able to resist the force of the current. This dam causes the river to swell out into a broad shallow pool, and in districts where beavers are plentiful the whole course of a stream is sometimes converted into a series of pools, made in this curious manner. After a time peat is formed round the edges, and gradually spreads, and then the marshy ground round the pool is called a beaver-meadow. But beavers do not only make dams. They construct what are called lodges as well, to serve as dwelling-places. These are made by piling up a number of logs, mingled with clods of earth, stones, and clay, and digging out the soil from underneath so as to form a sort of hut. These lodges are oven-shaped, and are from twelve to twenty feet in diameter, the inside chamber being about seven feet wide. So, you see, they have very thick walls. And they are generally entered by at least two underground passages, all of which open in the river-bank below the surface of the water, so that the animals can go straight from their lodge into the river without showing themselves above ground at all. Inside each lodge is a bed of soft warm grasses and woodchips, on which the animals sleep; and it is even said by some hunters that each beaver has his own bed! At any rate, several animals of various ages live together in each lodge. Then near the lodge these wonderful creatures make a ditch or hole, which is so deep that even in the hardest winter the water in it never freezes quite to the bottom; and in this deep place they pile up a great quantity of logs and branches, so that in winter they may have as much bark as they require to eat.