Another of the series of articles that were later published together as the Birchbark Book. This recounts several years of the author's observations of a particular beaver nicknamed the Chief Engineer for his building prowess. It is noted how rapidly the beavers, which at the time of the writing, 1918. had only recently been reintroduced, were reclaiming their old range in the Adirondacks after having been virtually wiped out by hunting and trapping.