is dome-like, and it varies considerably in size.  The foundation is made on the bottom of the river, and the hut is built up like a mound, often twenty feet in diameter and projecting several feet above the surface of the water.  The walls of this structure are often five or six feet thick, and the roofs are all finished off with a thick layer of mud laid on with marvellous smoothness.  These huts form the winter habitations of the beavers, and as this compost of mud, grass and branches becomes congealed into a solid mass by the severe frosts of our northern winter, it can easily be seen that they afford a safe shelter against any intruder and particularly the wolverine, which is a most deadly enemy to the beaver.  So hard does this frozen mass become as to defy even the edges of iron tools, and the breaking open of the “Beaver houses” is at no time an easy task.  Beavers work almost entirely in the dark; and a pond which is calm and placid in the day time will be found in the night to be full of life and motion, and the squealing and splashing in the water will bear evidence of their industry.  Lest the beavers should not have a sufficient depth of water at all seasons, they are in the habit of constructing veritable dams to ensure that result.  These dams display a wonderful amount of reason and skill, and, together with the huts, have won for the beaver a reputation [Page 178] for engineering skill which the creature truly deserves.  In constructing these ingenious dams the beavers, by the aid of their powerful teeth, gnaw down trees sometimes of large size, and after cutting them into smaller pieces float them on the water to the spot selected for the embankment.  In swift streams this embankment is built so as to arch against the current, thus securing additional strength, and evincing an instinct on the part of the animal which amounts almost to reason.  In cutting down the trees the beaver gnaws a circular cut around the trunk, cutting deepest on the side toward the water, thus causing the trunk to fall into the stream.  The first step in constructing the embankment is to lay the logs down cautiously in the required line of the dam, afterwards weighting them with heavy stones, which the beavers by their united efforts roll upon them.  The foundation of the embankment is often ten feet in width, and is built up by continued heaping of branches, stones and mud, until it forms a barrier of immense strength and resisting power.  In many cases, through a lapse of years, and through a [Page 179] consequent accumulation of floating leaves, twigs, and seeds of plants, these embankments become thickly covered with vegetation, and, in many cases in the Hudson Bay country, have even been known to nurture trees of considerable dimensions.  The broad flat tail of the animal serves a most excellent purpose, in carrying the mud to the dams or huts, and in matting and smoothing it into a solidity.

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