Muir traveled the world, and Thoreau stayed pretty much within New England, but one would be hard-pressed to decide which of the two has had more of an impact on our understanding of the relationship between humans and nature. Two biographies of Thoreau are Walter Harding’s The Days of Henry Thoreau: A Biography and Michael Sims’s The Adventures of Henry Thoreau: A Young Man’s Unlikely Path to Walden Pond. A Historical Guide to Henry David Thoreau, edited by William Cain, provides another approach to the man. One thinks of Thoreau first as an essayist or a naturalist, but in Walden’s Shore: Henry David Thoreau and Nineteenth-Century Science, Robert Thorson details how Thoreau used Walden and its environs as a scientific laboratory. Richard Premack brings Thoreau into the modern world with his Walden Warming: Climate Change Comes to Thoreau’s Woods. He uses Thoreau’s records concerning first flowering and first observations of breeding birds as compared with those of his research team to determine the extent of climate change in the Boston area.