The victims that were tied in the chair by the savages must have been sitting looking at the audience, so that their backs were to the wall itself. That meant that when the rod was dropped to make contact between the wall and victim, the discharge only burned the sacrifice's head. Evidence of that was the fact that only skulls were stacked around the altar. The charred head was severed and the body carted outside to one destination or another. What puzzled Green was how the audience managed to escape the fury of the blast and of the dust, even if they stood at the farthest end of the big room. Determined to find out what happened at those times, he returned to the doorway. Just around its corner, in the second room, he discovered what he'd not noticed before, probably because it was placed so upright and so firmly against one side of the wall. And because its back, which was turned away from the wall, was also made of gray metal. When he switched it around so he could see its other side, he was staring into a mirror about six feet high and four feet wide. Now he could visualize the ceremony. The victim was strapped into the chair and a rope was tied around the rod. Everybody but the priestess, or whoever conducted the rites, retreated from the altar room. The conductor himself, or herself, then stood in the doorway and released the cord. Before the rod could make contact, the conductor had stepped around the corner. And there the audience saw in the mirror, placed in the doorway so it reflected the interior of the altar room, the ravening discharge of a tremendous electrostatic blast. And immediately afterward, no doubt, they saw nothing because of the dust that would fill the two rooms. Strange and strong magic to the savages. What myths they must have built about this room, what tales of horrible and powerful gods or demons imprisoned in that wall of dirt! Surely their old women must whisper to the wide-eyed children stories of how the Great Cat-Spirit had been caught by their legendary strong man and savior, some analog to Hercules or Gilgamesh or Thor, and how the Cat-Spirit was the tribe's to keep prisoner with their magic and to appease from time to time with human kills from other tribes lest it become so angry it burst through the wall of earth and devour everybody upon the floating island! Green knew that it was hopeless to try to dig through that wall, even if it would be safe for days. It might only be several feet thick, or it might be twenty or more.