chunk: Jarvis and Tweel follow the cart creatures to their destination, a mound with a tunnel leading down below it. Jarvis soon becomes lost in the network of tunnels, and hours or days pass before he and Tweel find themselves in a domed chamber near the surface. There they find the cart creatures depositing their loads beneath a wheel that grinds the stones and plants into dust. Some of the cart creatures also step under the wheel themselves and are pulverized. Beyond the wheel is a shining crystal on a pedestal. When Jarvis approaches it he feels a tingling in his hands and face, and a wart on his left thumb dries up and falls off. He speculates that the crystal emits some form of radiation that destroys diseased tissue but leaves healthy tissue unharmed.