The clockwork rocks

The clockwork rocks

In the woods, there is a small clearing of sorts. In it is a large slab of stoned, with a dozen round rocks of spherical form upon it, all slightly different size. You can easily tell that the smaller rocks are moving. Getting closer, you can see groves in the stone slab, no doubt made by or for the moving rocks. If one were to wait long enough, you would notice that the larger rocks are moving too, if at a much slower, almost glacial pace. In the center of the concentric grooves is a small panel, about 3 inches from the ground. Upon it is a multitude of dial, made of transparent crystal, perhaps of some value . Do you dare turn one and see what it does, or simply pry one of the crystal off and sell it to the highest bidder?