Elsewhere the same authority says: “Whilst watching upon their dams at night I have been startled by this tremendous stroke, which, in the stillness of the hour, seemed like a pistol-shot. I have heard it distinctly for half a mile, and think it can be heard twice or three times that distance, under favourable conditions.” That must have been a splendid thing to hear—that sudden, startling blow—in the dead silence of the night, and in the loneliness of the North American wilderness; in the Hudson’s Bay territories perhaps—the headquarters of the beaver—where, for hundreds of miles around, there would be no other white man, or even, perhaps, an Indian, within a very great distance. Any other beaver that happened to be about at the time—at any rate, all those that were living in the same pond—when they heard that sound of alarm would go down too in the same way, so that there would be cracks like pistol-shots all about. That would be a concert worth listening to. But now, what is this pond of the beavers which is referred to by Mr. Morgan in the above passage of his book, _The American Beaver and his Works_—a most interesting work, which should be read by anyone who wants to know all about beavers? It is made, or rather caused, by the beavers themselves, and this brings us to the dam, which is their principal work, and which they construct for the express purpose of having this pond to live in. They are animals who simply cannot do without water, and as the streams on which they take up their abode are often small and shallow, it is of the greatest consequence to them that they should never run dry—which in a drought or dry summer they might easily do. To prevent this, having first selected a part of the stream where the water is not more than two or three feet deep, they bring earth from the adjacent banks and lay it down in mid-stream. Soft earth of a clayey consistency is preferred, for this, penetrated as it is, and partially held together, by roots and other vegetable fibres, is not at once washed away by the force of the water. The beavers have thus time to add to and strengthen the dam, and the better to effect this object they lay sticks and brushwood upon it, which they then press down into the mud with their feet. To these stones are added, and then more earth and sticks, till at last the crest of the dam appears above the surface of the water, and begins to rise higher and higher. It may attain, at last, to a height of six feet, or even more, above the level of the stream, whilst the length of some dams is as much as two hundred, or even three hundred feet. The stream itself, at the point where the dam intersects it, may only be a few yards in breadth, but as the mass of the flowing water cannot penetrate the solid embankment of mud and sticks which the beavers have made, it broadens out and begins to make a way on either side of it. The beavers, however, to prevent this, keep lengthening the dam, and in