This dam constitutes one bank of the stream which receives the valley waters, and is about thirty-eight feet high, and half a mile in length; the elevation, however, gradually diminishes from the centre to the extremities. The mineral waters of the valley contain, as we have intimated, an immense quantity of lime, which is deposited with astonishing rapidity in the state of a simple carbonate, (especially in those places where the water has much motion,) producing those mineral forms called _stalactites_ and _stalagmites_. With this knowledge it is easy to comprehend how these imperishable monuments of beaver labor and economy were produced.--For instance, these animals, according to their manner of building, felled trees across the mouth of the branch, and filled smaller interstices with brush, which would cause motion in the water and serve as nuclei for its mineral depositions. Consequently, in this dam may be seen immense incrustations of logs, brush, roots and moss. In many instances, the ligneous matter, not being able to resist the decomposing effects of time and moisture, is entirely removed, leaving petrous tubes, resembling, in the larger specimens, cannon barrels. These calcareous deposites not only cemented the timber together, but secured the entire work against the smallest percolation, prevented the escape of mountain _debris_, and rendered permanent a labor, which under other circumstances, would little more than have survived the duration of the timber, or the life of the industrious artificer. The outside of the dam is stalactical in its whole length, which resulted from the beaver's keeping its summit level, and thus causing the water to flow over every point of it. This circumstance, in connexion with the stream that washes its outer base, has caused large and over hanging projections of the stalactical deposites, and cavernous excavations; attached to the roofs of which is to be seen a great variety of small and beautiful spars. At the point over which the water at present is precipitated, the dam, is a bold and interesting spectacle. Add to this a large descending column of white spray, into which the water is converted by obstacles opposing its march over the dam, and the scene is rendered truly sublime. The soil of the several basins seems to rest on stalagmite, and the channel of the branch is worn out of it. In many places, far above the present level of the basins or dams, may be seen large rocks of this stalagmite: thus proving incontestibly, that this water occupied a position, two hundred feet at least above what it did at the time the beavers commenced their labor, and before the deep excavation was effected between the mountains.