A beaver appears awkward as he works on land. In use of arms and hands he reminds one of a monkey, while his clumsy and usually slow-moving body will often suggest the hippopotamus. By using head, hands, teeth, tail, and webbed feet the beaver accomplishes much. The tail of a beaver is a useful and much-used appendage; it serves as a rudder, a stool, and a ramming or signal club. The beaver _may_ use his tail for a trowel, but I have never seen him so use it. His four front teeth are excellent edge-tools for his logging and woodwork; his webbed feet are most useful in his deep-waterway transportation, and his hands in house-building and especially in dam-building. It is in dam-building that the beaver shows his greatest skill and his best headwork; for I confess to the belief that a beaver reasons. I have so often seen him change his plans so wisely and meet emergencies so promptly and well that I can think of him only as a reasoner. I have often wondered if beaver make a preliminary survey of a place before beginning to build a dam. I have seen them prowling suggestively along brooks just prior to beaver-dam building operations there, and circumstantial evidence would credit them with making preliminary surveys. But of this there is no proof. I have noticed a few things that seem to have been considered by beaver before beginning dam-building,--the supply of food and of dam-building material, for instance, and the location of the dam so as to require the minimum amount of material and insure the creation of the largest reservoir. In making the dam, the beaver usually takes advantage of boulders, willow-clumps, and surface irregularities. But he often makes errors of judgment. I have seen him abandon dams both before and after completion. The apparent reasons were that the dam either had failed or would fail to flood the area which he needed or desired flooded. His endeavors are not always successful. About twenty years ago, near Helena, Montana, a number of beaver made an audacious attempt to dam the Missouri River. After long and persistent effort, however, they gave it up. The beaver may be credited with errors, failures, and successes. He has forethought. If a colony of beaver be turned loose upon a three-mile tree-lined brook in the wilds and left undisturbed for a season, or until they have had time to select a site and locate themselves to best advantage, it is probable that the location chosen will indicate that they have examined the entire brook and then selected the best place. As soon as the beaver's brush dam is completed, it begins to accumulate trash and mud. In a little while, usually, it is covered with a mass of soil, shrubs of willow begin to grow upon it, and after a few years it is a strong, earthy, willow-covered dam. The dams vary in length from a few feet to several hundred feet. I measured one on the South Platte River that was eleven hundred feet long.