They found a place where saltpeter was very thinly and erratically distributed. They scraped off all the films of it that were visible and procured a small amount. They completed their circuit and reached the foot of the long, steep slope of the Craigs without finding anything more.

It was an awesome climb that lay before them; up a grade so steep and barred with so many low ledges that when their legs refused to carry them farther they crawled. The heat was still very serious and there would be no water until they came to the spring beyond the mountain’s summit. A burning wind, born on the blazing floor of the chasm, followed them up the mountain all day. Their leather canteens were almost dry when night came and they were no more than a third of the way to the top.

The mockers had become silent as the elevation increased and when they stopped for the night Humbolt saw that they would never live to cross the mountain. They were breathing fast, their hearts racing, as they tried to extract enough oxygen from the thin air. They drank a few drops of water but they would not touch the corn he offered them.

The white mocker died at midmorning the next day as they stopped for a rest. The yellow one crawled feebly to her side and died a few minutes later.

“So that’s that,” Humbolt said, looking down at them. “The only things on Ragnarok that ever trusted us and wanted to be our friends⁠—and we killed them.”

They drank the last of their water and went on. They made dry camp that night and dreams of cold streams of water tormented their exhausted sleep. The next day was a hellish eternity in which they walked and fell and crawled and walked and fell again.

Barber weakened steadily, his breathing growing to a rattling panting. He spoke once that afternoon, to try to smile with dry, swollen lips and say between his panting gasps, “It would be hell⁠—to have to die⁠—so thirsty like this.”