Page:Popular Science Monthly Volume 25.djvu/24

16 ground, a distance easily reached while sitting upon the tail and haunches, the tree is gouged around in a complete circle, equally on all sides, but gradually growing deeper and deeper with each circuit, forming, as it were, two cones whose points meet at a common center. When the space chipped out proves too narrow to admit the head, the teeth are applied above and below, as the woodman plies his axe, until the desired result is obtained. Steadily and faithfully he labors, rarely resting, and then but to take a refreshing bath in the nearest pool. At the last he frequently pauses, and, erecting himself upon his hind-legs, feels the trunk with his paws, as if to determine which way it shall fall, or whether it shows any signs of yielding; finally, when perhaps but an inch or two of the heart remain uncut, he gnaws vigorously upon the side toward which he desires it to fall, and, as the warning crack is heard, whips himself with great celerity and adroitness to the opposite side to avoid being crushed in its descent. Next the trunk is divided into lengths, and dragged by aid of teeth, paws, and chin to the water, where it is floated to the dam or storehouse. When large trees are chosen, they almost invariably stand upon the margin of the water, into which they are made to fall; but small growths are frequently sought at considerable distances, and regular paths or "runways" are beaten in the tall grass and ferns where such have been transported. The number of trees felled by one small colony is surprising, and the regularity of the stumps left might lead one unacquainted with the cause to believe them the result of human industry.

When the beaver selects a home on the bank of lake, pond, or stream whose waters are both deep and abundant, dams are rendered unnecessary, and even houses are not always constructed, but instead dwellings are hollowed out from the banks. But on shallow, narrow waters, dams are indispensable in order to secure sufficient depth to allow of concealment and free movement beneath the surface, as well as to prevent obstruction by ice: the entrance to the dwelling or storehouse is always beneath the water, which acts not only as a doorway, but as a safeguard from predatory enemies.

In the building of a dam considerable engineering qualities are developed. It is seldom seen as a mere straight embankment, but goes winding across the stream in graceful curves, bending hither and thither to present its convexity toward the swifter flowing current or deeper waters, taking advantage at the same time of all natural inequalities, now a rock, here an islet, and there a hillock. Trunks of trees are carefully intermingled with clods of earth, stones, and twigs, and every crevice is carefully stopped with mud or clay for greater security; and, when all is finished, the whole presents a structure of almost incredible solidity and compactness, frequently increased by the roots of willow and larch which spring up with all the regularity of a hedge. In the neighborhood of Washington Mine, Lake Superior, may be seen a dam with a total length of fifteen hundred and thirty