“Wonder where the light comes from?” pondered Bob. “It’s from the outside, all right, but how does it get in?”
Dr. Rander bent over and pressed something in a crack in the floor, straightening up a moment later.
Again the youths were filled with amazement. A huge stone block swung away on unseen hinges, leaving an opening perhaps four feet in width.
“Now we must use flashlights,” Dr. Rander said, stepping inside. “There is no opening to the outside, apparently.”
The beams of the electric torches revealed the fact that they were in another cave.
“Over here,” explained the old man, “is a sort of bin cut out of the rock. It is covered with a stone that I cannot lift. But I feel sure that all three of us can.”
“Let’s have a look at it,” said Bob.
Together they heaved on the stone block with all their strength. Before long they saw that their efforts were not in vain. The stone was slowly slipping from the top of the bin. At length it fell to the floor with a dull thud.
The explorers turned the beams of the flashlights into the opening, looking about eagerly.