John Muir is one of the most important figures in the history of the American conservation movement. A self-styled "poetico-trampo-geologist-bot. and ornith-natural, etc!-!-!," he remains a strong influence on environmentalists, and except for the influence of literary figures such as Henry David Thoreau and poet Gary Snyder, the regard of environmentalists for Muir is unrivaled. He is most often associated with the Yosemite Valley and the mountains of California; Muir joyfully describes these places and his adventures in them. In a passage that bestows on the Sierra Nevada a nickname still widely used, Muir writes with an enthusiasm for the natural world that is as luminous as the mountains he describes: "After ten years spent in the heart of it, rejoicing and wondering, bathing in its glorious floods of light, seeing the sunbursts of morning among the icy peaks, the noonday radiance on the trees and...