Then, before the clattering had died away, came a sullen, hollow roar from higher up in the shaft. Timbers snapped and crackled. The old boards, long since rotting away, suddenly gave beneath the pressure of rocks and earth. An avalanche of stones descended into the shaft on top of the first downfall of rock. More followed, showers of earth came rushing down and a cloud of dust pervaded the cavern.
Joe leaped back.
Then, with a roar like thunder, the entire shaft caved in. Rocks and timbers came tumbling down with a terrific crash. The air was filled with the noise of smashing timbers and falling rock. The faint light from the shaft that had given some vague illumination to the cave, was blotted out. The mine reverberated with echoes and shook with the force of the crash.
Silence reigned. It was broken by the sharp sounds of falling pebbles that descended in the wake of the avalanche. Then those noises too died away. The cavern was filled with a choking cloud of dust.
Joe was almost stupefied by horror. He realized to the full the peril of the situation.
"The shaft has caved in," he thought. "We're trapped in the mine! We'll never get out alive!"
He turned his flashlight on the place where the shaft had been. The light revealed only a high, sloping hill of rocks and shattered timbers. The shaft was completely blocked. It would take an army of men to clear away the débris.
Joe realized that he and Frank would never be able to accomplish the task. And he knew there was no hope of assistance from outside, for no one knew where they were. It might be days before they were traced to the mine.