so they continued on , soon leaving all signs of mining activity-holes drilled in the rock for dy***ite , rusted cans of black blasting powder , empty carbide kegs , strips of railroad track , drill steels , support timbers-and emerged into a natural cave , ceasing to follow the path of any particular tunnel , moving instead from room to room , some smaller than a closet , others larger than that first cavern , and the rock formations becoming more alien the deeper they ventured .