Human workaholics who argue that it profits little to toil four days and take off Friday should look more closely at the beaver, which works less than half the time and enjoys long summer vacations. For Enos A. Mills, watching beavers was a lifelong preoccupation. From his arrival in Longs Peak Valley in 1884 until his death in 1922, the founder of Rocky Mountain National Park kept year-round vigil on the ponds nearby. With the kind of feeling generally reserved for more photogenic animals, Mills describes here the world of beavers, their unusual pacificism and vegetarianism, their engineering feats, their better-than-human conservation of natural resources. Mills estimates that there were as many as one hundred million beavers in North America at the beginning of the seventeenth century, just before the Hudson's Bay Company made capital of their pelts. He shows that no animal ever contributed more to civilization or was itself more civilized.