"No. Nothing. But I think it won't hurt to explore it. By the force of the cold air rushing down through here I think it must lead to the top."
"I'm coming up."
Joe disappeared up into the tunnel and Frank, putting his flashlight into his pocket, scrambled up to the shelf of rock. There he knelt and turned on the light again.
He could see Joe ahead of him, crawling on up through the narrow passage. The tunnel in the rock was just as Joe had described it, a long, narrow shaft that led upward at a steep slope. It was not so steep that they would not be able to clamber on up to wherever it might lead.
"Go ahead," he called out. "I'll follow you."
"I hope it doesn't get narrower up ahead."
"We'll go as far as the tunnel lets us."
The two boys began crawling up the rocky shaft. Joe called back:
"It's widening out!"
And, truly, the shaft became gradually wider until the boys could almost stand upright in it. The draft of cold air blew against them with great force and roared and whistled down the tunnel. Suddenly Joe stopped and waved the flashlight back and forth.