“It isn’t more than four feet from the surface,” answered Frank. “It runs in the wall.”
“You can see it, can you?” asked Jack.
“Plainly,” was the reply. “It’s as large as a church door.”
“It wouldn’t be safe to dive in there and swim through, would it?”
“I should say not!” replied Frank. “The passage is entirely filled by the current and you couldn’t breathe in there more than half a minute. Besides all that, the swiftness of the current shows a steep fall and you’d probably bump your head against a rock before you went a hundred feet. Nothing doing in that line, kid!”
Again and again the boys tramped around the edge of the pool, stopping whenever they came to Harry’s side to speak words of encouragement, but all they discovered in the way of an exit was a crevice which might at one time have furnished an exit for the waters.
The wash from the rocks, brought down, undoubtedly, by water from the melting snows, had apparently lifted the margin of the pool at least a yard above the mouth of the old crevice, which was something like a foot in width. This accumulation of pulverized rock formed a perfect and complete dam across the mouth of the opening.
“Here’s a dry exit,” Frank exclaimed with a grim smile. “If we could just whittle off a few pounds of fat, we might be able to get through there!”
“It dips down pretty fast,” Jack answered. “The chances are that we’d get about such a bump as Harry received before we found the sunshine again. Well, it’s not large enough anyway,” he added, “so we may as well look for some other means of egress.”
While the boy was still standing by the crevice looking about with hopeful eyes, Frank caught sight of a moving object on the rim above.