Diagrams to explain the square-set timbering technique

While writing THE BONANZA KING, I became fascinated with the techniques and technology of Comstock mining. Here are some diagrams to help explain the square-set timbering technique invented in late 1860 by mining engineer Philipp Deidesheimer that made it possible to extract the Comstock Lode’s colossal ore bodies. (Clicking on the images should enlarge them...