Page:Eleven years in the Rocky Mountains and a life on the frontier.djvu/77

66 has attained the desired height. And not only is it made of the requisite height and strength, but its shape is suited exactly to the nature of the stream in which it is built. If the water is sluggish the dam is straight; if rapid and turbulent, the barrier is constructed of a convex form, the better to resist the action of the water.

When the beavers have once commenced a dam, its extent and thickness are continually augmented, not only by their labors, but by accidental accumulations; thus accommodating itself to the size of the growing community. At length, after a lapse of many years, the water being spread over a considerable tract, and filled up by yearly accumulations of drift-wood and earth, seeds take root in the new made ground, and the old beaver-dams become green meadows, or thickets of cotton-wood and willow.

The food on which the beaver subsists, is the bark of the young trees in its neighborhood; and when laying up a winter store, the whole community join in the labor of selecting, cutting up, and carrying the strips to their store-