“Yes, something o’ the sort,” Phil replied, smiling. “Jab the pick into that crack there and see if you can’t pry some of those bricks loose.”

Winslow did as directed, and was astonished on discovering with what ease half a dozen of the bricks came out.

“Fine!” exclaimed Phil gleefully. “Now, try some of that solid wall.”

Winslow did as directed. He was a powerful fellow—Phil had selected him as an aid for this reason. The pick stood the test and the wall fell away in bits. In less than an hour—estimated—a section of the wall three feet wide and nearly six feet high had been broken away, and the first candle was still burning.

“Everything’s going great,” said the young engineer of the enterprise. “The candles are going to last longer than I thought.”

“Shan’t we light two of them?” Dan suggested. “We can work faster, maybe.”

“No, not yet,” Sergeant Speed replied quickly. “We’ll have two or three of them going after we get the tunnel started a few feet.”

“Stick ’em on our hats?” inquired Winslow.

“No, we haven’t any way that I know of to fasten them to our hats. We’ll cut niches in the wall and set the candles in there. By the way, I’m going upstairs and get a couple more fellows down here to help.”

“We’ll have to have some fresh air before long,” said Dan. “First thing we know we’ll be asphyxiated—carbon-dioxidized, as it were. That fresh air upstairs won’t come down here unless forced down with a fan, or we manage to effect some kind of open-air vent through these walls.”