"This is strange," said Jack. "We dried our meat and ate our meal just about here, and the stone was not out of its place then."
"Perhaps our movements loosened it," replied his father. He spoke with the native woman for a little, then turned to his son. "It sank a moment back when she stepped on it," he said. "Just when she cried out. She feared she was going to fall through the floor."
Jack knelt down and pressed heavily on the stone. It slid away from his hands, and, had he not grasped the edge of the hole quickly, he would have rolled after it The stone vanished, and was heard to land with a heavy ringing crash on stone below.
"By Jove, I nearly went head first after it," said Jack. "It was as loose as possible. Where does this lead to?"
Mr. Haydon knelt down and looked carefully around the sides of the square hole left in the floor.
"It's a secret entrance to some place or other," he said. "See, Jack, the wooden bar on which this stone worked. It has rotted through, and the stone held its place, as you may say, by clinging to the neighbouring stones. But a slight weight was sufficient to start it moving."
"What's underneath, I wonder?" murmured Jack.
"Some chamber built in the thickness of the floor between this room and the vault below," replied his father.
"We ought to have a look into this," remarked Jack.
"We will," said his father; "but I hardly see how it will avail us. There might be a chance to make it useful if we could get the stone into place, but it is very heavy, and the machinery on which it worked has rotted away."