It was a flat, nearly round stone, some fifteen inches in diameter.
"That stone looks like a lid, doesn't it ?" Dick asked.
"Cover to a gold mine," sneered Hen.
Dick did not answer, but stepped over, bent and began to pry at the edges of the stone.

It did not move easily.

Dan brought the crowbar and quietly handed it to his chum.
"What have you got ?" demanded Tom, glancing up from his book.
"Don't know yet," Dick laughed.
By the aid of the crowbar Dick pried the stone loose from its setting in the ground.
"There's a hole underneath, anyway," announced Dick.
"And--Geewhillikins! Fellows, drop everything but your good names, and come here--quick! Hustle!".