Lake examined the sheets of mica. “We could make windows for the outer caves of these,” he said. “Have them double thickness with a wide air space between, for insulation. As for the quartz crystals.⁠ ⁠…”

“Optical instruments,” Craig said. “Binoculars, microscopes⁠—it would take us a long time to learn how to make glass as clear and flawless as those crystals. But we have no way of cutting and grinding them.”

Craig went to the east that fall and to the west the next spring. He returned from the trip to the west with a twisted knee that would never let him go prospecting again.

“It will take years to find the metals we need,” he said. “The indications are that we never will but I wanted to keep on trying. Now, my damned knee has me chained to these caves.⁠ ⁠…”

He reconciled himself to his lameness and confinement as best he could and finished his textbook: Geology and Mineral Identification .

He also taught a geology class during the winters. It was in the winter of the year four on Ragnarok that a nine-year-old boy entered his class; the silent, scar-faced Billy Humbolt.

He was by far the youngest of Craig’s students, and the most attentive. Lake was present one day when Craig asked, curiously:

“It’s not often a boy your age is so interested in mineralogy and geology, Billy. Is there something more than just interest?”

“I have to learn all about minerals,” Billy said with matter-of-fact seriousness, “so that when I’m grown I can find the metals for us to make a ship.”

“And then?” Craig asked.

“And then we’d go to Athena, to kill the Gerns who caused my mother to die, and my grandfather, and Julia, and all the others. And to free my father and the other slaves if they’re still alive.”