The story of Amos F. Clough, a pioneering photographer of the White Mountains, has rested in obscurity for a century and a half. Born and raised before the Civil War in the rural New Hampshire town of Warren, Clough began his career in photography early in the 1860s, seeking out what he called 'gems' from the natural world. Using a special camera with two lenses side-by-side, he took stereoscopic photographs. The most spectacular of them came from...