They came to the cement wall that barred further progress along the passage.
“First to see if it’s solid rock,” Cora suggested.
“How?” asked Belle.
“By tapping. I brought along a hammer.” With this implement Cora gave several blows against the obstruction. An unmistakable hollow sound resulted.
“I believe it’s only a wooden door, covered over with cement stucco,” Cora said. “Now to find the secret catch.”
With their flash lamps the girls went over every inch of the surface of the door. At first it all looked alike, dull, gray, smooth cement. Then Cora’s light lingered a moment on a certain place.
“Girls, watch!” she said suddenly.
With her thumb she pressed on the spot where it seemed the cement was worn smoother than elsewhere. And then, to the surprise of even Cora herself, the cement door swung slowly back, revealing a dark passage beyond.
“We’ve discovered it!” cried Cora. “No need to tear the door down. Just as I suspected, it’s on hinges. Come on, girls!”
Hardly realizing what they were doing, the others followed, their torches illuminating the plank sides of the underground tunnel.