"What do you suppose is the reason?"
"It must be that the cave is a little larger than it seems to be. It seemed to be getting bigger and bigger as I went further into it. If that is so, it accounts for the fact that the air supply has not yet begun to be vitiated."
"But mayn't there be any other reason?" she asked.
"I can't think of any other," he answered. Then as a thought suddenly struck him, he jumped as though he had been shot.
"Why didn't I think of that before?" he fairly shouted. "There may be another entrance!"
CHAPTER XXIV
THE ALARM
Unaware of the possible tragedy that was being developed within a few hundred yards of them, Tyke and Captain Hamilton had kept on digging in the excavation. For Tyke had refused to be kept out of the work of recovering the treasure, and when Drew had strolled off with the intention of discovering what had frightened Ruth and had been followed shortly after by the latter, the old man had seized Drew's abandoned shovel and had gone lustily to work.
"Too much of a strain on that game leg of yours to be heaving up those shovelfuls," the captain protested.