All this work had been done on an ascending grade, and the ascent was continued about 40 ft. farther in the clay. By this time a sufficient elevation was gained to pass over the underground stream, and the tunnel line was changed to head toward the lake shaft, and the grade reduced to a level. The underground stream was passed without trouble and the tunnel continued for a distance of 54 ft. without difficulty. On July 10 the clay in the heading suddenly softened, and before the miners could secure it by bracing, the water rushed in, followed by gravel, filling up solidly some 34 ft. of the tunnel before it was stopped by a timber bulkhead hastily built.
Longitudinal Section Showing Method of Construction in Rock Covered with Quicksand.
Sketch “a”.
Section A-B-C-D.
Sketch “c”.
Longitudinal Section of Tunnel.
Sketch “b”.