He is accomplished in the use of arms and hands. With hands he is able to hold sticks and handle them with great dexterity. Like any clawing animal he uses his hands or fore paws, to dig holes or tunnels and to excavate burrows and water-basins. His hind feet are the chief propelling power in swimming, although the tail, which may be turned almost on edge and is capable of diagonal movement, is sometimes brought into play as a scull when the beaver is at his swiftest. In the water beaver move about freely and apparently with the greatest enjoyment. They are delightfully swift and agile swimmers, in decided contrast with their awkward slowness upon the ground. They can swim two hundred yards under water without once coming to the surface, and have the ability to remain under water from five to ten minutes. On one occasion a beaver remained under water longer than eleven minutes, and came to the top none the worse, apparently, for this long period of suspended breathing. It is in standing erect that the beaver is at his best. In this attitude the awkwardness and the dull appearance of all-fours are absent, and he is a statue of alertness. With feet parallel and in line, tail at right angles to the body and resting horizontally on the ground, and hands held against the breast, he has the happy and childish eagerness of a standing chipmunk, and the alert and capable attitude of an erect and listening grizzly bear. [Illustration: A YOUNG BEAVER ON THE SIDE OF A BEAVER HOUSE] The beaver is larger than most people imagine. Mature male specimens are about thirty-eight inches in length and weigh about thirty-eight pounds, but occasionally one is found that weighs seventy or more pounds. Ten mature males which I measured in the Rocky Mountains showed an average length of forty inches, with an average weight of forty-seven pounds. The tails of these ten averaged ten inches in length, four and a half inches in width across the centre, and one inch in thickness. Behind the shoulders the average circumference was twenty-one inches, and around the abdomen twenty-eight. Ten mature females which I measured were only a trifle smaller. There are twenty teeth; in each jaw there are eight molars and two incisors. The four front teeth of the beaver are large, orange-colored, strong, and have a self-sharpening edge of enamel. The ears are very short and rounded. The sense of smell appears to be the most highly developed of the beaver's senses. Next to this, that of hearing appears to be the most informational. The eyes are weak. The hind feet are large and webbed, and resemble those of a goose. The second claw of each hind foot is double, and is used in combing the fur and in dislodging the parasites from the skin. The fore paws of the beaver are handlike, and have long, strong claws. They are used very much after the fashion in which monkeys use their hands, and serve a number of purposes.