The natural home of the beaver is not a burrow like that of a water-rat, but a wigwam above ground, built of heaped-up poles, branches, and roots, filled in with short sticks, stones, and sods. The shape is that of a low dome-like brush heap. Inside the irregular dome which is some eight or nine feet in diameter, is a small room which is the living room of the beavers. Several of these huts are placed near together and each has but one compartment; the tales of homes of many rooms have arisen from finding the various separate homes of the colony resting against each other. In each of these huts from four to eight beavers live. In the sides of the room are the beds of leaves, each beaver having a bed of its own. The centre of the apartment where they gnaw the bark from the short sticks which they bring in serves as a dining-room. They are very cleanly, and carry out all rubbish and refuse. The beaver house has no opening above ground. The two doors to the wigwam are in the floor, opening into long underground galleries, one connecting with the piled-up store of food branches, the other leading out toward the bank. Thus there is no approach to the home of the beaver except by passing under the water, and it is to secure a depth of from twenty inches to three feet of water over the entrance passages that the beaver builds a dam. If the bank or island where the home is built is so placed that a proper current and depth of water over the passages to the food pile can always be had, the beaver builds no dam. If the water is likely to run low the dam is built. The dam is a loosely constructed barrier, seldom in water over three feet deep, and generally rising but little above the surface. As the parts of trees of which it is built are of kinds which easily take root from rods or wands, as willow, birch, and alder, these sometimes shoot up and spread, growing into a kind of hedge, which, catching débris coming down stream, constantly increases the strength and size of the structure. Slight and low as the beaver dam is, it is marvellous that a brute should construct it, and its size is by no means contemptible. One giant dam, seven feet high and a quarter of a mile long, is mentioned by H. P. Wells, an accurate observer. Especially is it marvellous that in the places where there is little current the dam is carried straight across the stream, while in those where the current is strong the structure has a deep curve down stream, and is thus capable of resisting the force of the water.