"All horizontal or subhorizontal development openings made in a mine have the generic name of drift. These are simply tunnels made in the rock, with a size and shape depending on their use—for example, haulage, ventilation, or exploration." -- Encyclopedia Brittannica This drift is at the 16 level in the Gilman mine and has been abandoned. Water dripping through the ceiling carries minerals, forming stalagtites and stalagmites.