Lying at the heart of Franconia Notch State Park, the Flume has enthralled travelers since the first decades of the nineteenth century. Early tourists like Emerson and Thoreau were awed by the gorge's wild grandeur and spectacular granite walls rising nearly ninety feet overhead. Railroads in the 1850s brought a flood of visitors, including artists, poets, scientists and photographers, who richly documented the natural splendor of the Flume. Since...