"Then there is not much use in our going any farther, Jack?"
"No, not if we want to find Rollins and the rest."
"Suppose we take the widest passage, Jack!"
"Very well. Come ahead."
They went on for twenty feet, when the floor of the passage began to take a sudden decline which increased at every step.
"Hold on, Dick," said Jack, holding his light low and flashing it along the rough floor. "This thing may take a sudden drop and——"
"So it does!" gasped Percival, lying at full length on the floor and crawling carefully forward a pace or two. "It takes a drop for fair. It is a lucky thing you noticed it."
"Then we may as well go back, for I don't care to take a drop I don't know how deep."
"I'll see," muttered Percival, picking up a loose stone as big as his fist and tossing it ahead of him.
Not until several seconds had passed did the boys hear the sound of the stone falling into water, and Percival said with a sigh of relief: