By degrees the bats vacated their sleeping chamber, and when quiet had been restored the boys looked for a promising place to lie down and sleep.
"We can take a closer survey after we wake up," suggested Frank, with a reason he did not care to explain just then. But as Lanky was dead for sleep and tired, he failed to ask questions, as was his custom.
They were not disturbed. If any of those fierce-looking winged denizens returned to their roost, neither of the boys knew of the fact, so deep was their slumber for some hours.
Frank felt confident that there was some opening not far away from this cave, because those hosts of bats could never have come from such a long distance as that crevice.
When Lanky opened his eyes he saw that Frank had lighted a torch and was coming toward him, bearing one in his hand.
"What time do you think it can be, Frank?" was his first question, and a very natural one too, since Frank carried a small wrist watch.
"About sunrise, I'd judge," Lanky was told. He noticed Frank looked unusually smiling, upon which he pointed a finger at him, and demanded:
"Here, what's all that grinning about? You've got something up your sleeve, Frank Allen, which you're meaning to tell me right off the handle. Go to it, now."
"For one thing," said the other impressively, "I noticed something before we lay down to sleep; but didn't mention it, because we were both tuckered out and needed rest most of all. Scramble up off your downy couch and come along with me."