in the late afternoon, after a long period of inactivity
and silence, that an inspiration came to Kendric. Meantime they had
poked into every crack and cranny, they had scraped at any loose dirt
on the ground, they had gone back and forth and up and down over every
square inch of the place repeatedly. And Kendric thought that he had
given up when the last idea came to him. He went quickly back to the
boulder. Betty watched him interestedly.

"I thought we'd given that up," she said.

He had both hands on the boulder, his fingers gripping the edge of the
baffling hole, and was seeking to shake the big block of rock. Betty
came to his side.

"You think that it was made as a hand-hole? That you can turn the rock
over?"

"It does move--just a little," he said. He put all of his strength
into a fresh attack. The boulder trembled slightly--that was all.

"I'll bet you my half of the loot that I've got the hang of it, Miss
Betty," he announced triumphantly.

"Wait and see."

He began looking about him for something.

"If I only dared slip outside for a minute," he said. Then his eye
fell on the rifle. "We'll have to make this do. I run a risk of
jamming the front sight but I guess we can fix that."

He protected the sight as well as he could by wrapping his handkerchief
about it. The muzzle of the gun he thrust down into the hole in the
rock.

"Get it now?" he asked. "If that hole wasn't made to allow a lever to
be inserted, then tell me what it _was_ made for. And here's even the
place to stand while a man uses it! I'll double the bet!"

That excitement which always gets into any man's blood when he believes
that he is on the threshold of a golden discovery, already shone in his
eyes. He stepped to a sort of shelf in the cavern wall close to the
boulder, so that now his feet were on a level with the top of the rock
he meant to move. So he could just reach out and grasp the butt of the
rifle. Betty stood by, watching with an eagerness no less than his
own. Gradually he set his force at work on his lever, trying this way
and that. And then--

"It's moving!" cried Betty. "The rock is turning!"

And now it turned readily, his leverage being ample to the task.

"Look under the rock as it tips back," he told Betty. "See if there
isn't a hole under it. Big enough for a man to go through!"

"Yes!" answered Betty after a breathless fashion. "Yes. A little
more. Oh, come see. It looks almos