At the same instant Ben emerged, but immediately turned and went back into the cave.
"Hurry, Rufe!" we heard him call out.

"What's the matter?
Hurry, or it will go off!" Consternation fell on us, and some of us started for the mouth of the cave; but before we had gone more than five paces Ben sprang forth.

He had not dared to remain an instant longer--and, indeed, he was scarcely outside when the explosion came.

It sounded like a heavy jolt deep inside the mountain.
To our horror a huge slab of rock, thirty or forty feet up the side of the Fall-off, started to slide with a great crunching and grinding; then, gathering momentum, it plunged down between us and the mouth of the cave and completely shut the opening from view.

Powder smoke floated up from behind the slab.
There was something so terrible in the suddenness of the catastrophe that the whole party seemed crazed.