Ten feet in front of it the engineer paused, and pointed to the ground.

Up out of the earth came two wires, which led away from the mouth of the cavern.
"Those wires go down to the explosives," he explained.

"They're battery wires half a mile long.

But we don't attach the battery until the final moment, as you saw last night.

There might be an accident." He bent his tall body and entered the mouth of the cavern, leading his wife by the hand.