Read the passage from Part 1 of “To Build a Fire.” He knew that at fifty below spittle crackled on the snow, but this spittle had crackled in the air. Undoubtedly it was colder than fifty below—how much colder he did not know. But the temperature did not matter. He was bound for the old claim on the left fork of Henderson Creek, where the boys were already. They had come over across the divide from the Indian Creek country, while he had come the roundabout way to take a look at the possibility of getting out logs in the spring from the islands in the Yukon. What excerpt from the passage reveals the environment of the story?